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IRLF

MEMCAL

Medical Library Exchange

Library of the

Medical College of Vir-
ginia.

THE

PHYSIOLOGY OF MAN;

DESIGNED TO REPRESENT

THE EXISTING STATE OF PHYSIOLOGICAL
SCIENCE,

AS APPLIED

TO THE FUNCTIONS OF THE HUMAN BODY.

AUSTIN FLINT, JR., M. D.,

PROFESSOE OF PHYSIOLOGY AND MICEOSCOPY IN THE BELLEVUE HOSPITAL MEDICAL COLLEGE,

NEW YOBK ; FELLOW OF THE NEW YORK ACADEMY OF MEDICINE ; MEMBER OF THE

MEDICAL SOCIETY OF THE COUNTY OF NEW YORK ; RESIDENT MEMBER OF THE

LYCEUM OF NATURAL HISTORY IN THE CITY OF NEW YOEK, ETC., ETC.

SECRETION; EXCRETION; DUCTLESS GLANDS; NUTRITION;
ANIMAL HEAT ; MOVEMENTS ; VOICE AND SPEECH.

XEW:
D. ^PPLKTOX5:

90, 92 & 94 GRAND STREET.
1870.

EOTERED, according to Act of Congress, in the year 1869, by

D. APPLETON & CO.,

In the Clerk's Office of the District Court of the United States for the Southern
District of New York.

PEE FAG E.

WITH the completion of this volume, all of the subjects
belonging to human physiology, that are usually taught in
medical schools or are treated of in systematic works, have
been carefully considered, except the functions of the ner-
vous system and the processes of generation and development.
The first volume, published in 1866, treated of the blood,
circulation, and respiration ; and the second volume, pub-
lished in 1867, was upon the subjects of alimentation, diges-
tion, absorption, and the lymph and chyle.

The original plan of the work has been adhered to in the
preparation of these three volumes, as each one constitutes a
separate and distinct treatise, being complete in itself, while
the full series is intended to cover the entire subject of
human physiology. In recording the success of the parts
already published, the author feels that his labors have been
more than appreciated; and the friendly and encouraging
criticism that the work has thus far received has stimulated
him to increased efforts in the preparation of the present
volume.

Some of the subjects taken up in this volume have an
especial interest to the author, from the fact that he has

4: PREFACE.

investigated them by original experiments, and has suc-
ceeded in developing new facts of a certain degree of value ;
but it has been his endeavor not to give to these questions
undue prominence, to the prejudice of other subjects of equal
importance to the physiological student. The most promi-
nent points developed by original investigation in the present
volume are, the discovery of an excretory function of the
liver, that had never before been described, and the mechan-
ism of glycogenesis, a question that seems now to be defini-
tively settled, notwithstanding the apparently opposite
results obtained by different experimenters.

Since the chapter on the glycogenic function of the liver
has been printed, the author has seen an analysis of a series
of observations on this subject, in which his conclusions with
regard to the mechanism of the formation of sugar in the
economy have been fully confirmed. The views embodied
in this chapter, however, are entirely original, and were
published in the New York Medical Journal in January,
1869.1 The confirmatory observations, by Tieffenbach, are
also original, as far as any knowledge of this publication is
concerned, and were published in the form of an Inaugural
Dissertation, later in the same year.3 In laying claim to
priority of publication, the author fully appreciates the im-
portance of these independent experiments, by which the
accuracy of his own researches have been so fully confirmed.

1 FLINT, Jr., Experiments undertaken for the Purpose of reconciling some of
the Discordant Observations upon the Glycogenic Function of the Liver. — New
York Medical Journal, Jan., 1869, p. 373.

2 TIEFFENBACH, Ueber die Existenz der glycogenen Function der Leber, Disser-
tation, Konigsberg, 1869. — Zeitschrift fur rationelle Medidn, Leipzig u. Heidel-
berg, 1869, Dritte Reihe, Bd. xxxv., S. 210.

PREFACE. 5

"\Vith regard to the general mechanism of secretion, it
has seemed important to the author to draw as closely as
possible, the line of distinction between secretions proper
and excretions; and our information with regard to the
mode of formation of the secretions, and the production of
excrementitious principles and their separation from the
blood, is now of so positive a character, that we are able to
subject these processes to pretty definite generalization.

If we comprehend fully the mechanism of secretion and
excretion, it is evident that our knowledge of particular
fluids must be to a great extent based upon accurate proxi-
mate analyses. The author has taken the greatest care in
compiling the tables of composition of the various secretions
and excretions, particularly with regard to the urine, having
endeavored to make the table of its composition repre-
sent as closely as possible the general process of disassimila-
tion and its variations under physiological conditions.

The author cannot but regard the description of the
excretory function of the liver, with the discovery of the
physiological relations of cholesterine, as of very great im-
portance, in its relations to pathology as well as physiology.
This subject has been elaborately considered in the chapter
treating of the excretory function of the liver, and the views
therein presented are put forward with more confidence,
since they have been honored with a favorable report by a
committee from the French Academy of Sciences? As the
result of the author's investigations on this subject, it seems
to be conclusively proven that cholesterine, under certain

1 ST. LAUGIER, Academic des sciences. Hole de la cholesterine dans Torganixme ;
recherche* de M. AUSTIN' FLINT (fils). — Revue des cours scientifgues, Paris, 1868-
1869, tome vi., p. 495, and Comptes rendus, Paris, 1869, tome Ixviii., p. 1371.

6 PREFACE.

pathological conditions, bears the same relation to disorgan-
izing diseases of the liver that urea does to corresponding
conditions of the kidneys. The experiments by which these
facts have been developed are so repulsive and difficult that
there is little likelihood of their being extensively verified ;
and while the author confidently awaits the time when the
results of his investigations will be generally admitted, he is
satisfied at present with the acknowledgment that they are
entirely original.

Within a short time, several mooted points of great
importance with regard to the physiological anatomy of the
liver and the kidneys have been definitively settled. It is
hoped that the chapters in which these anatomical questions
have been considered will be found to represent the latest
and most reliable views ; and it does not seem now that the
conclusions will be materially altered by future researches.

The author feels that he has no apology to make for the
apparent delay in the issue of the present volume. His
labor upon it has been almost unremitting since the issue of
the volume on alimentation, digestion, and absorption;
and his chief endeavor has been to make it represent faith-
fully the existing state of the science, without sparing time
or pains. All he can promise is, that the remainder of the
work will be prepared with equal care, and, it is hoped,
within a shorter interval.

NEW YORK, September, 1869.

0 O3STTEJST TS.

CHAPTER I.

SECRETION IN GENERAL.

General considerations — Relations of the secretions to nutrition — General
mechanism of secretion — Differences between the secretions and fluids
containing formed anatomical elements — Division of secretions — Mechan-
ism of the production of the true secretions — Mechanism of the production
of the excretions — Influence of the composition and pressure of the blood
upon secretion — Influence of the nervous system on secretion — Excito-
secretory system of nerves — General structure of secreting organs — Ana-
tomical classification of glandular organs — Secreting membranes — Fol-
licular glands — Racemose glands — Tubular glands — Ductless, or blood-
glands — Classification of the secreted fluids — Secretions proper (perma-
nent fluids; transitory fluids) — Excretions — Fluids containing formed
anatomical elements, Page 13

CHAPTER II.

SEROUS AND STNOVIAL FLUIDS — MUCUS — SEBACEOUS FLUIDS.

Physiological anatomy of the serous and synovial membranes — Synovial fringes
— Bursse — Synovial sheaths — Pericardial, peritoneal, and pleural secre-
tions— Quantity of the serous secretions — Synovial fluid — Mucus — Mucous
membranes — Mucous membranes covered with pavement-epithelium — Mu-
cous membranes covered with columnar epithelium — Mucous membranes
covered with mixed epithelium — Mechanism of the secretion of mucus —
Composition and varieties of mu9us — Microscopical characters of mucus
— Nasal mucus — Bronchial and pulmonary mucus — Mucus secreted by the
lining membrane of the alimentary canal — Mucus of the urinary passages
— Mucus of the generative passages — Conjunctival mucus — General func-
tion of mucus — Xon-absorption of certain soluble substances, particularly
venoms, by mucous membranes — Sebaceous fluids — Physiological anatomy

3 CONTENTS.

of the sebaceous, ceruminous, and Meibomian glands — Ordinary sebaceous
matter — Smegma of the prepuce and of the labia minora — Vernix
caseosa — Cerumen — Meibomian secretion — Function of the Meibomian
secretion, Page 39

CHAPTER III.

MAMMAEY SECKETION.

Physiological anatomy of the mammary glands — Condition of the mammary
glands during the intervals of lactation — Structure of the mammary glands
during lactation — Mechanism of the secretion of milk — Conditions which
modify the lacteal secretion — Influence of diet — Influence of liquid ingesta —
Influence of alcoholic beverages — Influence of mental emotions — Quantity
of milk — Properties and composition of milk — Specific gravity of milk —
Coagulation of milk — Microscopical characters of milk — Composition of
milk — Nitrogenized constituents of milk — Non-nitrogenized constituents
of milk — Inorganic constituents of milk — Variations in the composition
of milk — Colostrum — Composition of colostrum — Lacteal secretion in the
newly-born — Composition of the milk of the infant, . . . .72

CHAPTER IV.

EXCKETION — ACTION OF THE SKIN.

Differences between the secretions proper and the excretions — Composition of
the excretions — Mode of production of the excretions — Discharge of the
excretions — Physiological anatomy of the skin — Extent and thickness of
the skin — Layers of the skin — The corium, or true skin — The epidermis
and its appendages — Desquamation of the epidermis — Physiological anat-
omy and uses of the nails and hair — Development and growth of the nails
— Varieties of hair — Number of the hairs — Roots of the hairs, and hair-fol-
licles— Structure of the hairs — Sudden blanching of the hair — Uses of the
hairs — Perspiration — Sudoriparous glands — Mechanism of the secretion of
sweat — Quantity of cutaneous exhalation — Properties and composition of
the sweat — Peculiarities of the sweat in certain parts, . . .108

CHAPTER V.

PHYSIOLOGICAL ANATOMY OF THE KIDNEYS.

CONTENTS. 9

tubes — Xarrow tubes of Henle — Intermediate tubes — Distribution of blood-
vessels in the kidney — Vessels of the Malpighian bodies — Plexus around
the convoluted tubes — Veins of the kidney — Stars of Verheyen — Lym-
phatics and nerves of the kidney — Summary of the physiological anatomy
of the kidney, Page 144

CHAPTER VI.

MECHANISM OF THE FORMATION AND DISCHAEGE OF FEINE.

Formation of the excrementitious constituents of the urine in the tissues,
absorption of these principles by the blood, and separation of them from
the blood by the kidneys — Effects of removal of both kidneys from a liv-
ing animal — Effects of tying the urelers in a living animal — Extirpation of
one kidney — Influence of blood-pressure, the nervous system, etc., upon
the secretion of urine — Effects of the destruction of all the nerves going
to the kidneys — Alternation in the action of the kidneys upon the two
sides — Changes in the composition of the blood in passing through the
kidneys — Physiological anatomy of the urinary passages — Mechanism of
the discharge of urine, 162

CHAPTER VII.

PROPERTIES AND COMPOSITION OF THE UEINE.

General physical properties of the urine — Quantity, specific gravity, and reaction
— Composition of the urine — Urea — Origin of urea — Compounds of uric
acid — Hippurates and lactates — Creatine and creatinine — Oxalate of lime —
Xanthine — Fatty matters — Inorganic constituents of the urine — Chlorides
— Sulphates — Phosphates — Coloring matter and mucus - — Gases of the
urine — Variations in the composition of the urine — Variations with age and
sex — Variations at different seasons and at different periods of the day —
Variations produced by food — Urina potus, urina cibi, and urina sanguinis
— Influence of muscular exercise — Influence of mental exertion, . 186

CHAPTER VIII.

PHYSIOLOGICAL ANATOMY OF THE LIVEE.

Coverings and ligaments of the liver — Capsule of Glisson — Lobules — Branches
of the portal vein, the hepatic artery and duct — Interlobular vessels — Lob-
ular vessels — Origin and course of the hepatic veins — Interlobular veins —
Structure of a lobule of the liver — Hepatic cells — Arrangement of the
bile-ducts in the lobules — Anatomy of the excretory biliary passages —
Vasa aberrantia — Gall-bladder — Hepatic, cystic, and common ducts —

10 CONTENTS.

Nerves and lymphatics of the liver — Mechanism of the secretion and dis-
charge of bile — Secretion of bile from venous or arterial blood — Quantity
of bile— Variations in the flow of the bile — Influence of the nervous system
on the secretion of bile — Discharge of bile from the gall-bladder, Page 232

CHAPTER IX.

EXCEETOEY FUNCTION OF THE LIVEE.

General properties of the bile — Composition of the bile — Biliary salts — Tauro-
cholate of soda — Glycocholate of soda — Origin of the biliary salts — Choles-
terine — Process for the extraction of cholesterine — Biliverdine — Tests for
bile — Test for biliverdine — Test for the biliary salts — Pettenkofer's test
— Excretory function of the liver — Origin of cholesterine — Experiments
showing the passage of cholesterine into the blood as it circulates through
the brain — Analyses of venous blood from the two sides of the body in
cases of hemiplegia — Elimination of cholesterine by the liver — Analyses
showing accumulation of cholesterine in the blood in certain cases of
organic disease of the liver — Cholestersemia, 258

CHAPTER X.

PEODTTCTION OF 8UGAE IN THE LIYEE.

Evidences of a glycogenic function in the liver — Processes for the determination
of sugar — Fehling's test for sugar — Examination of the blood of the portal
system for sugar — Inosite — Examination of the blood of the hepatic veins
for sugar — Does the liver contain sugar during life ? — Characteristics of
liver-sugar — Mechanism of the production of sugar by the liver — Glyco-
genic matter — Process for the extraction of glycogenic matter — Variations
in the glycogenic function — Production of sugar in foetal life — Influence of
digestion and of different kinds of food on glycogenesis — Influence of the
nervous system, etc., on glycogenesis — Artificial diabetes — Influence of the
inhalation of anaesthetics and irritating vapors on glycogenesis — Destina-
tion of sugar — Alleged production of fat by the liver — Changes in the
albuminoid and the corpuscular elements of the blood in their passage
through the liver, 295

CHAPTER XL

THE DUCTLE8S GLANDS.

CONTENTS. 11

spleen — State of our knowledge concerning the functions of the spleen —
Variations in the volume of the spleen during life — Extirpation of the
spleen — Anatomy of the suprarenal capsules — Cortical substance — Medul-
lary substance — Vessels and nerves — Chemical reactions of the suprarenal
capsules — State of our knowledge concerning the functions of the supra-
renal capsules — Extirpation of the suprarenal capsules — Addison's disease
— Anatomy of the thyroid gland — State of our knowledge concerning the
functions of the thyroid gland — Anatomy of the thymus — Pituitary body
and pineal gland, .... .... Page 331

CHAPTER XII.

NUTRITION.

Nature of the forces involved in nutrition — Protoplasm — Definition of vital
properties — Life, as represented in development and nutrition — Principles
which pass through the organism — Principles consumed in the organism —
Xitrogenized principles — Development of power and endurance by exercise
(Training) — Xon-nitrogenized principles — Formation and deposition of fat
— Conditions under which fat exists in the organism — Physiological anatomy
of adipose tissue — Conditions which influence nutrition — Products of dis-
assimilation, 366

CHAPTER XIII.

ANIMAL HEAT.

General considerations — Limits of variation in the normal temperature in man
—Variations with external temperature — Variations in different parts of
the body — Variations at different periods of life — Diurnal variations — Rela-
tions of animal heat to digestion — Influence of defective nutrition and in-
anition— Influence of exercise, mental exertion, and the nervous system,
upon the heat of the body, 394

CHAPTER XIV.

SOURCES OF ANIMAL HEAT.

Connection of the production of heat with nutrition — Seat of the production of
animal heat — Relations of animal heat to the different processes of nutri-
tion— Relations of animal heat to respiration — The consumption of oxygen
and the production of carbonic acid in connection with the evolution of
heat — Exaggeration of the animal temperature in particular parts after
division of the sympathetic nerve and in inflammation — Intimate nature of
the calorific processes — Equalization of the annual temperature, . 418

12 CONTENTS.

CHAPTER XY.

MOVEMENTS — GENEBAL PEOPEETIES OF CONTKACTILE TISSUES.

Amorphous contractile substance — Ciliary movements — Movements due to elas-
ticity— Varieties of elastic tissue — Muscular movements — Physiological
anatomy of the involuntary muscles — Mode of contraction of the involun-
tary muscular tissue — Physiological anatomy of the voluntary muscles —
Primitive fasciculi — Sarcolemma — Fibrillse — Fibrous and adipose tissue in
the voluntary muscles — Connective tissue — Blood-vessels and lymphatics
of the muscular tissue — Connection of the muscles with the tendons —
Chemical composition of the muscles — Physiological properties of the mus-
cles— Elasticity — Muscular tonicity — Sensibility of the muscles — Muscular
contractility, or irritability, Page 436

CHAPTER XYI.

MUSCTJLAE CONTRACTION — PASSIVE OKGANS OF LOCOMOTION.

Changes in the form of the muscular fibres during contraction — Secousse,
Zuckung, or spasm — Spasm produced by artificial excitation — Mechanism
of prolonged muscular contraction — Tetanus — Electric phenomena in the
muscles — Muscular effort — Passive organs of locomotion — Physiological
anatomy of the bones — Fundamental substance — Haversian rods — Haver-
sian canals — Lacunae — Canaliculi — Bone-cells, or corpuscles — Marrow of
the bones — Medullocells — Myeloplaxes — Periosteum — Physiological anat-
omy of cartilage — Cartilage-cavities — Cartilage-cells — Fibro-cartilage, 468

CHAPTER XVII.

VOICE AND SPEECH.

Sketch of the physiological anatomy of the vocal organs — Vocal chords — Mus-
cles of the larynx — Crico-thyroid muscles — Arytenoid muscle — Lateral
cricc-arytenoid muscles — Thyro-arytenoid muscles — Mechanism of the pro-
duction of the voice — Appearance of the glottis during ordinary respira-
tion— Movements of the glottis during phonation — Variations in the quah'ty
of the voice, depending upon differences in the size and form of the larynx
and the vocal chords — Action of the intrinsic muscles of the larynx in
phonation — Action of the accessory vocal organs — Mechanism of the dif-
ferent vocal registers — Mechanism of speech, 490

PHYSIOLOGY OF MAN,

CHAPTER I.

SECRETION IX GENERAL.

THE phenomena classed by physiologists under the
head of secretion are intimately connected with the gen-
eral process of nutrition. In the sense in which the term
secretion is usually received, it embraces most of the pro-
cesses in which there is a separation of material from the
blood or a formation of a new fluid out of matters fur-
nished by the blood. The blood itself, with the lymph
and the chyle, are no longer regarded as secretions. These
fluids, like the tissues, are permanent constituents of the
organism, undergoing those changes only that are neces-
sary to their proper regeneration. They are likewise char-
acterized by the presence of certain formed anatomical ele-

14 SECRETION.

ments, which themselves undergo the processes of molecular
destruction and regeneration. These characters are not pos-
sessed by the secretions. As a rule, the latter are homoge-
neous fluids, without formed anatomical elements, except as
accidental constituents; such as the desquamated epithe-
lium in mucous or sebaceous matter. The secretions are not
permanent, self-regenerating fluids, except when they per-
form simply a mechanical function, as the humors of the
eye, or the liquids in serous and synovial cavities. They
are either discharged from the body, when they are called
excretions, or, after having performed their proper function
as secretions, are taken up again in a more or less modified
form by the blood.

With the exception of those fluids which have a function
almost entirely mechanical, the relations of the secretions to
nutrition are so close, that the production of many of them
forms almost a part of this great function. It is impossible,
for example, to conceive of nutrition without the formation
of the characteristic constituents of the urine, the bile, and
the perspiration ; and it is impossible, indeed, to study satis-
factorily the phenomena of nutrition without considering
fully the various excrementitious principles, such as urea,
cholesterine, creatine, creatinine, etc. ; for the constant forma-
tion and discharge of these principles by disassimilation
create the necessity for the deposition of new matter in
nutrition. Again, the most important of the secretions, as
contradistinguished from the excretions, are concerned in the
preparation of food by digestion, for the regeneration of the
great nutritive fluid.

As would naturally be supposed, the general mechanism
of secretion was very imperfectly understood early in the
history of physiology, when little was known of the circula-
tion, the functions of the digestive fluids, and particularly of
nutrition. From its etymology, the term should signify
separation ; but it is now known that many of the secreted
fluids are formed in the glands, and are not simply sepa-

DIVISION OF SECRETIONS. 15

rated, or filtered from the blood. Physiologists now regard
secretion as the act by which fluids, holding certain solid
principles in solution, and sometimes containing liquid nitro-
genized principles, but not necessarily possessing formed
anatomical elements, are separated from the blood, or are
manufactured by special organs out of materials furnished
by the blood. These organs may be membranes, follicles,
or collections of follicles or tubes, when they are called
glands. The liquids thus formed are called secretions;
and they may be destined to perform some function con-
nected with nutrition, or may be simply discharged from the
organism.

It is not strictly correct to speak of formed anatomical
elements as the results of secretion, except, perhaps, in the
case of the fatty particles in the milk. The leucocytes
found in pus, the spermatozoids of the seminal fluid,
and the ovum, which are sometimes spoken of as products
of secretion, are real anatomical elements developed in the
way in which these structures are ordinarily formed. It has
been conclusively demonstrated, for example, that leucocytes,
or pus-corpuscles, are developed in a clear blastema, without
the intervention of any special secreting organ ; l and that
spermatozoids and ova are generated by a true development
in the testicles and the ovaries, by a process entirely differ-
ent from ordinary secretion. It is important to recognize
these facts in studying the mechanism by which the secre-
tions are produced. It is true that in some of the secretions,
as the sebaceous matter, a certain quantity of epithelium,
more or less disintegrated, is found, but this is to be regarded
as an accidental admixture of desquamated matter, and not
as a product of secretion.

Division of Secretions. — The secretions are capable of a
physiological division, dependent upon differences in their
functions and the mechanism of their production. Investi

1 See vol. i., Blood, p. 124, and voL ii., Absorption, p. 523.

16 SECRETION.

gations within the past few years have shown that these
differences are very distinct.

Certain of the fluids are formed by special organs, and
have important functions to perform, which do not involve
their discharge from the organism. These may be classed
as the true secretions ; and the most striking examples of
them are the digestive fluids. Each one of these fluids is
formed by a special gland or set of glands, which generally
has no other function ; and they are never produced by any
other part. It is the gland which produces the characteris-
tic element or elements of the true secretions out of materials
furnished by the blood ; and the principles thus formed never
preexist in the circulating fluid. The function which these
fluids have to perform is generally intermittent ; and when
this is the case, the flow of the secretion is intermittent, tak-
ing place only when its action is required. "When the parts
which produce one of the true secretions are destroyed, as
may be sometimes done in experiments upon living animals,
the characteristic elements of this particular secretion never
accumulate in the blood, nor are they formed vicariously
by other organs. The simple effect of such an experiment
is absence of the secretion, and the disturbances consequent
upon the loss of its function.

Certain other of the fluids are composed of water, holding
one or more characteristic principles in solution, which re-
sult from the physiological waste of the tissues. These prin-
ciples have no function to perform in the animal economy,
and are simply separated from the blood to be discharged
from the body. These may be classed as excretions ; the
urine being the type of fluids of this kind. The characteristic
principles of the excrementitious fluids are formed in the tis-
sues, as one of the results of the constant nutritive changes
going on in all organized living structures. They are not pro-
duced in the glands by which they are eliminated, but ap-
pear in the secretion as the result of a sort of elective filtra-
tion from the blood. They always preexist in the circulating

DIVISION OF SECRETIONS. IT

fluid, and may be eliminated, either constantly or occasion-
all v, by a number of organs. As they are produced con-
tinually in the substance of the tissues and taken up by
the blood, they are constantly discharged into the substance
of the proper eliminating organs. "When the glands which
thus eliminate these principles are destroyed, or their func-
tion seriously impaired, the excrementitious matters may
accumulate in the blood, and give rise to certain toxic
phenomena. These effects, however, are often retarded
by the vicarious discharge of such principles by other
organs.

There are some fluids, as the bile, which perform impor-
tant functions as secretions, and which nevertheless contain
certain excrementitious matters. In these instances it is
only the excrementitious matters that are discharged from
the organism.

In the serous sacs, the sheaths of tendons and of muscles,
the substance of muscles, and some other situations, are found
fluids which simply moisten the parts, and which contain
very little organic matter and but a small proportion of in-
organic salts. Although these are frequently spoken of as
secretions, they are produced generally by a simple mechan-
ical transudation of certain of the constituents of the blood
through the walls of the blood-vessels.1 Still, it is difficult
to draw a line rigorously between transudation and some of
the phenomena of secretion ; particularly as late experiments
upon dialysis have shown that simple osmotic membranes are
capable of separating complex solutions, allowing certain con-
stituents to pass much more freely than others.3 This fact ex-
plains why the transuded fluids do not contain all the soluble
principles of the blood in the proportions which exist in the
plasma. All the secreted fluids, both the true secretions and
the excretions, contain many of the inorganic salts of the
blood-plasma.

1 See vol. ii., Absorption, p. 505. 8 Ibid., p. 477.

18 SECRETION.

Mechanism of the Production of the true Secretions. —
Although the characteristic elements of the true secretions
are not to be found in the blood or in any other of the
animal fluids, they can generally be extracted in quantity
from the glands, particularly during their intervals of repose.
This fact has been repeatedly demonstrated with regard to
many of the digestive fluids, as the saliva, the gastric juice,
and the pancreatic juice ; and artificial fluids, possessing
many of the physiological properties of the natural secre-
tions, have been prepared by simply infusing the glandular
tissue in water. There can be no doubt, therefore, that even
during the periods when the secretions are not discharged,
the glands are taking from the blood matters which are to
be transformed into principles characteristic of the individual
secretions, and that this process is constant. Extending our
inquiries into the nature of the process by which these pecu-
liar principles are formed, it is found to bear a close resem-
blance to the general act of nutrition. There are certain
anatomical elements in the glands which have the power
of selecting the proper material from the blood and causing
them to undergo a catalytic transformation ; as the muscu-
lar tissue takes from the great nutritive fluid the albumen,
fibrin, etc., and transforms them into its own substance. The
exact nature of this property is unexplained ; it belongs to
the class of phenomena observed in living structures only,
and is sometimes called vital.

In all of the secreting organs a variety of epithelium is
found, called glandular, which seems to possess the power
of forming the peculiar elements of the different secretions.
Inasmuch as the epithelial cells lining the tubes or follicles
of the glands constitute the only peculiar structures of these
parts, the rest being made up of basement-membrane, con-
nective tissue, blood-vessels, nerves, and other structures
which are distributed generally in the economy, we should
expect that these alone would contain the elements of the
secretions. In all probability this is the fact ; and with re-

MECHANISM OF SECRETION. 19

gard to some of the glands, this has been satisfactorily de-
monstrated. It has been found, for example, that the liver-
cells contain the glycogenic matter formed by the liver ; 1 and
it has been further shown that when the cellular structures
of the pancreas have been destroyed, the secretion is no
longer produced.2 There can be hardly any doubt with re-
gard to the application of this principle to the glands gener-
ally, both secretory and excretory. Indeed, it is well known
to pathologists, that when the tubes of the kidney have be-
come denuded of their epithelium, they are no longer capable
of separating from the blood the peculiar constituents of the
urine.

"With regard to the origin of the principles peculiar to
the true secretions, it is impossible to entertain any other
view than that they are produced in the epithelial structures
of the glands ; and the old idea that they exist ready-formed
in the blood, though adopted by some physiologists of the
present day,8 cannot be maintained. While the secretions
contain inorganic salts transuded in solution from the blood,
the organic constituents, such as pepsin, ptyaline, pancrea-
tine, etc., are readily distinguished from all other albuminoid
principles by their peculiar physiological properties ; al-
though some of them are apparently identical with albumen
in their ultimate composition and in most of their chemical
reactions.

It may be stated, then, as a general proposition, that the
characteristic elements of the true secretions, as contradistin-
guished from the excretions, are formed de novo by the epi-
thelial structures of the glands, out of material furnished by
the blood ; and that their formation is by no means confined
to what is usually termed the period of functional activity
of the glands, or the time when the secretions are poured out,

1 SCHIFF, De la nature des granulations qui remplissent les cellules hepatiques :
Amidon animale. — Comptes rendus, Paris, 1859, tome xlviii., p. 880.

2 BERNARD, Memoire sur le pancreas, Paris, 1856, pp. 17 and 69.

3 MILNE-EDWARDS, Lecons sur la physiologie^ Paris, 1862, tome vii., p. 282.

20 SECRETION.

but takes place more or less constantly when no fluid is dis-
charged.

It is more than probable that the formation of the ele-
ments of the secretions takes place with fully as much activ-
ity in the intervals of secretion as during the discharge of
fluid ; and most of the glands connected with the digestive
system seem to require certain intervals of repose, and are
capable of discharging their secretions for a limited time
only.

When a secreting organ is called into functional activity —
like the gastric mucous membrane, or the pancreas, upon the
introduction of food into the alimentary canal — a marked
change takes place. The circulation in the part is then very
much increased in activity ; thus furnishing the water and
the inorganic elements of the secretion. This difference in
the vascularity of the glands during their activity is very
marked when the organs are exposed in a living animal, and
is one of the important facts bearing upon the mechanism
of secretion. Beaumont observed this in his experiments
on St. Martin, and was the first to show conclusively that
the gastric juice is secreted only when food is taken into the
stomach, or some stimulation is applied to its mucous mem-
brane.1 Bernard, in his experiments on the pancreas, noted
the pale appearance of the gland during the intervals of
digestion, and its reddened and congested condition when
the secretion flowed from the duct ; a and these observations
have been confirmed by all who have experimented upon the
glands in living animals.

In later experiments upon the circulation in the salivary
glands and its relation to secretion, Bernard has investigated
this subject fully, with the most definite and satisfactory re-
sults.3 His observations were made chiefly on the submaxil-

1 BEAUMONT, Experiments and Observations on the Gastric Juice, and the
Physiology of Digestion, Plattsburg, 1833, p. 103.

2 BERNARD, Memoire sur le pancreas, Paris, 1856, p. 43.

3 BERNARD, Lecons sur les proprietes physiologiques et les alterations patho-

MECHANISM OF SECRETION. 21

lary gland in dogs ; and lie has shown that during the func-
tional activity of this organ, if a tube be introduced into the
vein, the quantity of blood which may be collected in a given
time is four or five times that which is discharged in the in-
tervals of secretion.1 It was ascertained, also, that the venous
blood coming from the gland contained much less water
than the arterial blood ; and on comparing the quantity of
water lost by the blood in its passage through the gland in
a gh»en time with the quantity discharged in the saliva, they
were found to exactly correspond.11

The differences in the quantity and the composition of
the blood coming from the glands during their repose and
their activity have an important bearing upon the mechan-
ism of secretion. As far as the composition is concerned,
these differences appear to be mainly dependent upon the
modifications in the circulation. When the gland is in re-
pose, the blood coming from it has the usual dark, venous
hue and contains the ordinary proportion of carbonic acid ;
but during secretion, when the quantity of blood passing
through the organ is increased, the color is nearly as bright
as that of arterial blood, and the proportion of carbonic acid
is very small. At this time, also, the blood is frequently
discharged from the vein pulsatim to the distance of several
inches.3 The cause of this difference in color is very easily
understood. During the intervals of secretion, the blood is
sent to the gland for the purposes of nutrition and the man-
ufacture of the elements of the secretion. It then passes

logiques des liquides de Vorganisme, Paris, 1859, tome ii., p. 272, et seq. ; Du
role des actions reflexes paralysantes dans le phenomene des secretions.— Journal de
Vanatomie et de la physiologie, Paris, 1864, tome i., p. 507, et seq. ; Lecons sur les
proprietes des tissus vivants, Paris, 1866, p. 400, et seq.

1 Unpublished lectures delivered by Bernard at the College of France in the
summer of 1861.

2 Unpublished lectures, 1861 ; Journal at tanatomie et de la physiologic,
Paris, 1864, tome i., p. 513 ; and Lemons sur Ifs proprietes des tissits vivants,
Paris, 1866, p. 401.

3 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 296.

22 SECRETION.

through the part in moderate quantity and undergoes the usu-
al change from arterial to venous, in which a great part of the
oxygen disappears and carbonic acid is formed ; but, when
secretion commences, the ordinary nutritive changes are not
sufficient to deoxidize the increased quantity of blood, and
the venous character of the blood coming from the part is
very much less marked.1

These facts enable us to form a pretty clear idea of the
mechanism of secretion; though the exact nature of the
forces which effect the changes of the organic princi-
ples of the blood into the characteristic elements of the
secretions is not understood. Experiments, however, have
shown that in the act of secretion there are two tolerably
distinct processes :

1. It may be assumed that at all times the peculiar se-
creting cells of the glands are forming, more or less actively,
the elements of the secretions, which may be washed out of
the part or extracted by maceration ; but during the inter-
vals of secretion, the quantity of blood received by the
glands is relatively small.

2. In obedience to the proper stimulus, when a gland
takes on secretion, the quantity of blood which it receives
is four or five times greater than it is during repose. At
that time, water, with certain of the salts of the blood in
solution, passes into the secreting structure, takes up the
characteristic elements of the secretion, and fluid is dis-
charged by the duct.

In all the secretions proper, there are intervals, either of
complete repose, as is the case with the gastric juice or the
pancreatic juice, or periods when the activity of the secretion
is very greatly diminished, as in the saliva. These periods
of repose seem to be necessary to the proper performance of
the function of the secreting glands ; forming a marked con-
trast with the constant action of the organs of excretion. It

1 This subject is more fully discussed in vol. i., Blood, p. 106, under the
head of " Color of the Blood."

MECHANISM OF SECRETION. 23

is well known, for example, that the function of digestion is
seriously disturbed when the act is too prolonged, from the
habitual ingestion of an excessive quantity of food. With
regard to the pancreas this fact has been demonstrated in
the most satisfactory manner. The experiments of Bernard
and others have shown that this organ is peculiarly suscep-
tible to irritation ; and when a tube is fixed in its duct, after
a time the flow of the secretion may become constant, leav-
ing no intervals for repose of the gland. "WTien this occurs,
the fluid discharged loses the character of the normal secre-
tion and is found to possess none of its peculiar diges-
tive properties.1 In one or two instances in which the irrita-
tion of the tube introduced into the pancreatic duct did not
produce a constant secretion, the fluid, which was discharged
intermittently in the normal way, possessed all its physio-
logical properties.2

From the considerations already mentioned, it is evident
that the secretions, as the rule, are formed by the epithelial
structures of the glands. There has been a great deal of
speculation with regard to the mechanism of this action of the
cells. As we before remarked, this question cannot be con-
sidered as settled. It does not seem probable that the cells
are ruptured during secretion and discharge their contents
into the ducts, for under these circumstances we should
expect to find some of their structure in the secreted fluid ;
whereas, aside from accidental constituents, the secretions
are homogeneous, and do not contain any formed anatomical
elements. There is no good reason for supposing that this
action takes place, and that more or less of the glandular
epithelium is destroyed whenever secretion occurs ; and, in
the present state of our knowledge, we can only assume that
the secreting cells induce catalytic transformations in the
organic elements of the blood and modify transudation, with-
out pretending to understand the exact nature of this process.

1 See vol. ii., Digestion, p. 337.

2 BERNARD, Memoire sur le pancreas, Paris, 1856, p. 46.

24: SECRETION.

The theory that the discharge of the secretions is due
simply to mechanical causes, and is attributable solely to the
increase in the pressure of blood, cannot be sustained.
Pressure undoubtedly has considerable influence upon the
activity of secretion ; but the flow will not always take place
in obedience to simple pressure, and secretion may be in-
duced for a limited time without any increase in the quan-
tity of blood circulating in the gland. In the numerous ex-
periments by Bernard upon the influence of the circulation
upon secretion in the submaxillary gland of the dog, these
facts are very clearly shown. By very powerful galvaniza-
tion of what he termed the motor nerve of the gland (the
chorda tympani), secretion was excited, but the circulation
was reduced ; and again, after ligation of the vein, by which
the gland was engorged with blood and the circulation could
not be modified, galvanization of the nerve was nevertheless
followed by an increase in the secretion. A slight secretion
was also produced by galvanization of the nerve after the
artery supplying the gland had been tied. These experi-
ments are made with great facility upon the submaxillary
gland of the dog, for the reason that the parts may be ex-
posed and operated upon without interrupting the secretory
function, and the nerves and vessels communicating with the
gland can be easily isolated. The function of most of the
glands, however, becomes so much disturbed by exposure,
that the influence of the nerves upon their action is observed
with great difficulty.

From the experiments just cited, Bernard concludes that
the glands possess a peculiar irritability, which is manifested
by their action in response to proper stimulation. During
their secretion, they generally receive an increased quantity
of blood ; but this is not indispensable, and secretion may be
excited without any modification of the circulation. This
irritability will disappear when the artery supplying the part
with blood is ligated for a number of hours ; and secretion
cannot then be excited, even when the motor nerve is stimu-

MECHANISM OF EXCKETIOX. ZO

lated and the blood is again allowed to circulate. If the gland
be not deprived of blood too long, the irritability is soon re-
stored ; but it may be permanently destroyed by depriving the
part of blood for a long time.1 These observations are very
striking, and show a certain similarity between glandular
and muscular irritability, though their properties are mani-
fested in very different ways.

Mechanism of the Production of the Excretions. — Certain
of the glands have the function of separating from, the blood
excrementitious matters, which are of no use in the economy,
and are simply to be discharged from the system. These
matters, which will be fully considered, both in connection
with the fluids of which they form a part, and under the
head of nutrition, are entirely different in their mode of pro-
duction from the characteristic elements of the secretions.
Our definite information concerning the mechanism of ex-
cretion dates from the researches of Prevost and Dumas, who
discovered urea in the blood of dogs after its elimination had
been arrested by extirpation of the kidneys.2 These experi-
ments were confirmed by Segalas and Yauquelin ; 3 but at
that time the means of analysis of the animal fluids were not
sufficiently delicate to enable chemists to detect urea in
healthy blood. The later observations of Marchand, how-
ever, demonstrated its constant presence in very small
quantity in the blood.* These analyses have been repeated-
ly confirmed, and it is now generally believed that all the
excrementitious principles exist in greater or less quantity

1 Unpublished lectures delivered by Bernard at the College of France in the
summer of 1861.

2 PREVOST ET DUMAS, Examin du sang et de son action dans les divers plie-
nomenes de la vie.—Annales de ckimie et de physique, Paris, 1821, tome xviii., p.
280.

3 SEGALAS, Sur des nouvelles experiences relatives aux propriete* medicamen-
teuscs de Turce, etc. — Journal de physiologic, Paris, 1822, tome ii., p. 354.

4 MARCHAND, Sur la presence de Turee dans le sang. — Annales des sciences
naturelles, Paris, 1838, 2me serie, tome x., p. 46.

26 SECEETION.

in the circulating fluid.1 That urea is actually separated
from the blood by the kidneys is further confirmed by recent
observations, showing that in the renal artery the proportion
of this principle is about twice as great as in the renal vein.3

Adopting this view, we have nothing to do at present
with the formation of excrementitious principles. This takes
place in the tissues and is connected with the general process
of nutrition ; and in the excreting glands there is simply a
separation of matters already formed. The action of the ex-
creting organs being constant, there is not that regular peri-
odic increase in the activity of the circulation which is
observed in secreting organs ; but it has been observed that
the blood that comes from the kidneys is nearly as red as
arterial blood, showing that the quantity of blood which this
organ receives is greater than is required for mere nutrition,
the excess, as in the secreting organs, furnishing the water
and inorganic salts that are found in the urine. It has also
been shown that when the secretion of urine is interrupted,
the blood of the renal veins becomes dark like the blood in
the general venous system.3

The function of excretion is not, under all conditions,
confined to the ordinary excretory organs. When their func-
tion is disturbed, certain of the secreting glands, as the folli-
cles of the stomach and intestine, may for a time eliminate
excrementitious matters ; but this action is abnormal, and is

1 In a recent work on the urine (ROBERTS, A Practical Treatise on Urinary
and Renal Diseases, Philadelphia, 1866, p. 359), it is stated on the authority
of observations and analyses by Oppler, Schottin, Perls, and Zalesky, that urea
and uric acid are actually produced in the kidneys. These statements, which
will be discussed more fully hereafter, are in direct opposition to facts that
have been regarded as settled by accurate analyses of the blood, and cannot
be accepted without confirmation. It is supposed, however, that urea and the
urates are the result of transformation of other excrementitious principles
existing in the blood, and are not formed de novo, like the elements of the true
secretions.

2 ROBIN, Lecons sur les humeurs normales et morbides dw corps de rhomme^
Paris, 1867, p. 89.

3 BERNARD, Liquides de Torganisme, Paris, 1859, tome i., pp. 257 and 297.

MODIFICATIONS OF SECRETION. 27

analogous to the elimination of foreign matters from the blood
by the glands.

Influence of the Composition and Pressure of the Blood
upon Secretion. — Under normal conditions the composition
of the blood has little to do with the action of the secreting
organs, as it simply furnishes the material out of which the
characteristic principles of the secretion are formed ; ' but
when certain foreign matters are taken into the system or
are injected into the blood-vessels, they are eliminated by the
different glands, both secretory and excretory. These organs
seem to possess a power of selection in the elimination of
different substances. Thus, sugar, ferrocyanide of potas-
sium, and the salts of iron, are eliminated in greatest quantity
by the kidneys ; the salts of iron by the kidneys and the
gastric tubules ; and iodine by the salivary glands.

The act of secretion is almost always accompanied with
increase in the pressure of blood in the vessels supplying the
glands ; and it has been shown, on the other hand, that an
exaggeration in the pressure, if the nerves of the glands do
not exert an opposing influence, increases the activity of se-
cretion. The experiments of Bernard on this point show the
influence of pressure on the salivary and the renal secretion,
particularly the latter. After inserting a tube into one of
the ureters of a living animal, so that the activity of the
renal secretion could be accurately observed, the pressure in
the renal artery was increased by tying the crural and the
brachial. It was then found that the flow of urine was
markedly increased. The pressure was afterward dimin-
ished by the abstraction of blood, which was followed by a
corresponding diminution in the quantity of urine.1 The
same phenomena were observed in analogous experiments on
the submaxillary secretion.

These striking facts, as we have already seen, do not de-
monstrate that secretion is due simply to an increase in the

1 BERNARD, Liquids de rorganisme, Paris, 1859, tome ii., p. 155, et seq.

250 SECRETION.

pressure of blood in the glands, though this undoubtedly
exerts an important influence. It is necessary that every
condition should be favorable to the act of secretion, for this
influence to be effective. Experiments have shown that
pain is capable of completely arresting the secretion of urine ;
operating undoubtedly through the nervous system. If, now,
the flow of urine be arrested by pain, an increase in the
pressure of blood in the part fails to influence the secretion.
To illustrate this fact more fully, Bernard divided the nerves
on one side, through which the reflex nervous action was
communicated to the kidney, leaving the other side intact.
He then found that increase in the arterial pressure, accom-
panied with pain, diminished the flow of urine on the sound
side, through which the nervous action could operate, and
increased it upon the other.1 We have already alluded to
the experiments in which secretion was excited through the
nervous system, when the arterial pressure had been con-
siderably diminished.

The influence of pressure of blood upon secretion may,
then, be summed up in a few words : There is always an in-
crease in the activity of secretion when the pressure of blood
in the glands is increased, and a diminution when the pres-
sure is reduced ; except when there is some modifying influ-
ence operating through the nervous system.

Influence of the Nervous System on Secretion. — The fact
that the secretions are generally intermittent in their flow,
being discharged in obedience to impressions which are made
only when there is a demand for the exercise of their func-
tions, would naturally lead to the supposition that they are
regulated, to a great extent, through the nervous system ;
particularly as it is now well established that the nerves are
capable of modifying and regulating local circulations. The
same facts apply, to a certain extent, to the excretions, which

1 These experiments were detailed by Bernard in his lectures at the College
of France in the summer of 1861.

MODIFICATIONS OF SECRETION. 29

are also subject to considerable modifications. A few years
ago, indeed, there was considerable discussion regarding a
subdivision of the reflex system of nerves, which was supposed
to preside over secretion, and was called the excito-secretory
system. The facts which led to the description of this sys-
tem of nerves had long been observed ; and they simply il-
lustrated the production of secretion in response to irritation.
Dr. H. F. Campbell, of Augusta, Georgia, published, in
185T, an essay on the excito-secretory system of nerves,
which received the prize of the American Medical Associa-
tion for that year ; 1 and a few months later, the same idea
was put into shape by Dr. Marshall Hall, who, however, yield-
ed the priority to Dr. Campbell. To Dr. Campbell certainly
belongs the credit of proposing the theory that the sympa-
thetic system presides over secretion ; but in this he only rea-
soned from the old experiments of Pourfour du Petit and
others, and failed to give any satisfactory physiological de-
monstration of his views.

In 1852, five years before the publication of Dr. Camp-
bell's essay, in the course of his researches on the secretions
of the different salivary glands, Bernard pointed out the
reflex character of the act of secretion, and demonstrated
experimentally the influence of certain nerves upon the dis-
charge of fluid from the duct of the submaxillary. These
experiments were the first to give a clear idea of the action
of the nervous system upon secretion, and they have been

1 CAMPBELL, Essays on the Secretory and the Excito-secretory System of Nerves
in their ^Relations to Physiology and Pathology, Philadelphia, 1857 ; also, Trans-
actions of the American Medical Association for 1857.

In 1850, Dr. Campbell published in the Southern Medical and Surgical Jour-
nal an Essay on the Influence of Dentition in producing Disease ; in which he re-
marked the fact, that during dentition, the irritation in the mouth frequently in-
duced, in addition to the usual increase hi the salivary secretions, an increased
action of the kidneys and the mucous membrane of the intestinal canal. He
states that " this increase and change in the secretion are effected by the agency
of the altered function of the nerve upon the arteries from which these secre-
tions are eliminated." Dr. Campbell supposed that the nerves through which
these operations took place belonged to the sympathetic system.

30 SECRETION.

confirmed and extended by the subsequent observations of
Bernard and other physiologists. The following are the
most important facts, taken from Bernard, bearing upon the
question under consideration : l

" Introducing into the mouth of a dog, in which the three
salivary ducts have been isolated, a very sapid substance,
such as vinegar, for example, it is found that the duct of the
submaxillary discharges saliva in very great abundance.
But, by operating directly upon the nerve of taste itself, I
have been enabled to act solely upon the special secretion,
and to demonstrate directly this intimate relation between
the secretion of the submaxillary saliva and the sense of gus-
tation.

" When we divide in a dog the lingual nerve opposite the
middle of the horizontal process of the lower jaw, and pinch
the central end, which is connected with the encephalon, we
immediately see the duct of the submaxillary excrete saliva
with great activity, while the ducts of the parotid and sub-
lingual, which are not connected with the sense of gustation,
remain perfectly dry. This sort of functional reaction, which
irritation of the central end determines exclusively, in the
submaxillary gland, is explained, for in operating thus we
produce in the nervous centre the impression of exaggerated
gustatory sensation, which immediately provokes, by an ac-
tion called reflex !, the salivary secretion destined physiologi-
cally to allay and diminish the too acute impression of sapid
substances."

These experiments clearly demonstrated the importance
of the nervous influence in the production of the secretions ;
but the more recent observations of Bernard show that the
effects are produced mainly by increasing the activity of the
circulation in the glands. This takes place in greatest part
through filaments from the sympathetic system, which are

1 BERNARD, Recherches cTanatomie et de physiologie comparee sur ies ylandes soli-
vaircs chez Thomme et Ies animaux vertebres. — Comptes rendus, Paris, 1852, tome
xxxiv., p. 239.

MODIFICATIONS OF SECRETION. 31

distributed to the muscular coats of the arteries of supply.
When these filaments are divided, the circulation is increased
here, as in other situations, and secretion is the result ; and,
if the extremity of the nerve connected with the gland be
galvanized, contraction of the vessels follows, and the secre-
tion is arrested.1

With regard to many of the glands, Bernard has shown
that the influence of the sympathetic is antagonized by nerves
derived from the cerebro-spinal system, which he calls the
motor nerves of the glands. The motor nerve of the sub-
maxillary is the chorda tympani ; and as both this nerve
and the sympathetic, together with the excretory duct of the
gland, can be easily exposed and operated upon in a living
animal, most of the experiments of Bernard have been per-
formed upon this gland. When all these parts are exposed
and a tube introduced into the salivary duct, division of the
sympathetic induces secretion, with an increase in the circu-
lation in the gland, the blood in the vein becoming red. On
the other hand, division of the chorda tympani, the sympa-
thetic being intact, arrests secretion, and the venous blood
coming from the gland becomes dark. If the nerves be now
galvanized alternately, it will be found that galvanization
of the sympathetic produces contraction of the vessels of the
gland and arrests secretion, while the stimulus applied to
the chorda tympani increases the circulation and excites se-
cretion.3

These experiments show that the submaxillary gland has
distributed to it a special nerve which is capable of exciting
its functional activity, the sympathetic ramifying upon
the walls of the blood-vessels in this, as in other situa-
tions ; and it remains to see whether other glands are like-
wise supplied with motor nerves. In his lectures, delivered
in 1861, Bernard announced that he had demonstrated the
existence of such nerves for the other salivary glands.

1 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 270.
8 Op. cit., p. 267, et seq.

32 SECEETION.

The motor nerve of the parotid is derived from the auri-
culo-temporal branch of the submaxillary division of the
fifth pair ; and the nerve of the sublingual, from the
lingual branch of the fifth. He found, however, that
neither the. parotid nor the sublingual was so easily ex-
cited to secretion by galvanization of the nerves as the
submaxillary. With regard to other glands, the condi-
tions for experimentation are so difficult, and some of them,
as the pancreas, are so sensitive to irritation, that it is impos-
sible to repeat on them the experiments made upon the sali-
vary glands. Enough is known, however, of the nervous
influences which modify secretion, to admit of the inference
that all the glands are possessed of nerves through which
reflex phenomena, affecting their secretions, take place. It
is the motor, or functional nerve of the gland through which
the reflex action takes place ; the influence of the sympa-
thetic being constant, and the same as in other parts where
it is distributed to blood-vessels.

As reflex phenomena involve the action of a nervous
centre, it becomes an interesting question to determine
whether any particular parts of the central nervous system
preside over the various secretions. ' We must refer again to
the experiments of Bernard for an elucidation of this ques-
tion. If a puncture be made in the space included between
the origin of the pneumogastrics and the auditory nerves in
the floor of the fourth ventricle, there is an increase in the
discharge of urine, and an excretion of sugar, from an ex-
aggeration in the sugar-producing function of the liver.
Irritation applied a little higher, toward the pons varolii, just
posterior to the origin of the fifth pair of nerves, is followed
by a great increase in the activity of the salivary secretion.1

1 BERNARD, Lemons sur la physiologic et la pathologic du systeme nervcux, Paris,
1858, tome i., pp. 898-399.

This operation is easily performed upon the rabbit, by passing an instrument
directly through the occipital bone, entering just behind the protuberance, and
through the cerebellum to the medulla oblongata. These experiments will be
more fully described in connection with the nervous system.

STRUCTURE OF SECRETING ORGANS. 33

Mental emotions, pain, and various circumstances, the
influence of which upon secretion has long been observed,
operate through the nervous system. Numerous familiar
instances of this kind are quoted in works on physiology :
such as the secretion of tears ; arrest or production of the sali-
vary secretions ; sudden arrest of the secretion of the mam-
mary glands, from violent emotion ; increase in the secretion
of the kidneys or of the intestinal tract, from fear or anxiety ;
with other examples which it is unnecessary to ennumerate.

The effects, upon some of the secretory organs, of de-
struction of the nerves distributed to their parenchyma
are very curious and interesting. Miiller and Peipers
destroyed the nerves distributed to the kidney, and found
that not only was the secretion arrested in the great ma-
jority of instances, but that the tissue of the kidneys be-
came softened and broken down.1 These experiments have
been lately repeated by Bernard. He found that animals
operated upon in this way died, and that the tissue of the
kidney was broken down into a fetid, semifluid mass. After
division of the nerves of the salivary glands, the organs be-
came atrophied, but did not undergo the peculiar putrefac-
tive change which was observed in the kidneys. The same
effect was produced when the nerve was paralyzed by in-
troducing a few drops of a solution of woorara at the origin
of the little artery which is distributed to the submaxillary
gland.3

General Structure of Secreting Organs. — In treating of
the mechanism of secretion and excretion, it has been evi-
dent that all glandular organs must be supplied with blood
to furnish the materials for secretion, and be provided with
epithelium, which changes these matters into the characteris-
tic elements of the secretions. We can understand how cer-

1 MUELLER, Manuel de physiologic, Paris, 1851, tome i.,p. 391.
8 BERNARD, Lefonssur les proprietes des tissus vivant*, Paris, 1866, p. 399.
• 3

34 SECRETION.

tain of tlia liquid and saline constituents of the blood can
escape by exosmosis through the homogeneous walls of the
capillaries,1 but the more complex fluids require for their
formation a different kind of action ; although, in the act
of secretion, there is considerable transudation of liquid and
saline matters, which take up in their course the peculiar
principles formed by the cells.

Though it is somewhat difficult to draw a line between
transudation and the simplest forms of secretion, it may be
assumed, in general terms, that fluids which are exhaled
directly from the blood-vessels, without the intervention of
glandular apparatus or of a secreting membrane, are transu-
dations ; while all fluids produced by simple membranes, by
follicles, or discharged from the ducts of glands, are secre-
tions. This division places the intermuscular fluid and the
fluid found in all soft tissues among the transudations, and
the serous and synovial fluids among the secretions.

The serous and synovial membranes present the simplest
form of a secreting apparatus. Blood is supplied to them
in small quantity, and on their free surfaces are arranged
one or two layers of epithelial cells which effect the slight
changes that take place in the transuded fluids. In some
of the serous membranes, as the pleura and peritoneum, the
amount of secretion is very small, being hardly more than a
vaporous exhalation ; but others, like the serous pericardium
and the synovial membranes, secrete a considerable quantity
of fluid. The action of all of these membranes may become
exaggerated, as a pathological condition, and the amount of
their secretions is then very large.

Anatomists have now a pretty clear idea of the structure
of what are called the glandular organs ; and it will be seen
that they simply present an arrangement by which the se-
creting surface is increased, and at the same time compressed,
as it were, into a comparatively small space. The mucous
follicles, for example, are simple inversions of a portion of

1 See vol. ii., Absorption, p. 505.

CLASSIFICATION OF GLANDS. 35

the mucous membrane ; while the ordinary racemose glands
are nothing more than collections of follicles around the ex-
tremities of excretory ducts. These ideas concerning the
general anatomy of the glands date from the observations
of Malpighi,1 who was the first to correct the old notion
that the secretions were discharged into the glandular organs
through openings in the blood-vessels. It is evident that
nothing could have been known of the mechanism of Secre-
tion before the connection between the arteries and veins
had been ascertained, which, it will be remembered, was also
discovered by Malpighi. Although the ideas of Malpighi
were not at first generally received, more recent observations
with the microscope have shown that they were in the main
correct ; though, from the imperfection of his optical instru-
ments, Malpighi was unable to investigate the minute struc-
ture of the glands very thoroughly.

Anatomical Classification of Glandular Organs. — The
organs which produce the different secretions are susceptible
of a classification according to their anatomical peculiarities,
which greatly facilitates their study. They may be divided
as follows :

1. Secreting membranes. — Examples of these are the se-
rous and synovial membranes.

2. Follicular glands. — Examples of these are the simple
mucous follicles, the follicles of the stomach, the follicles of
Lieberkiihn, and the uterine follicles.

3. Tubular glands. — Examples of these are the cerumi-
nous glands, the sudoriparous glands, and the kidneys.

4. Racemose glands, simple and compound. — Examples
of the simple racemose glands are the sebaceous and Meibo-
mian glands, the tracheal glands, and the glands of Brunn.
Examples of the compound racemose glands are the salivary

1 MALPIGHI, Exercitationes A natomicce de Structura Vlscerum. — Opera Omnia,
Ludg. Batav., 1687, tomus ii., p. 257.

36 SECRETION.

glands, the pancreas, the lachrymal glands, and the mam-
mary glands.

5. Ductless , or Hood-glands. — Examples of these are the
thymus, the thyroid, the supra-renal capsules, and the spleen.

The liver is a glandular organ which cannot be placed in
any one of the above subdivisions, as we shall see when we
treat specially of its anatomy. The lymphatic glands and
other parts connected with the lymphatic and the lacteal
system are not embraced in the above classification.1 These
are sometimes called conglobate glands.

The general structure of secreting membranes and the
follicular glands is very simple. The secreting parts consist
of a membrane, generally homogeneous, on the secreting sur-
face of which are found epithelial cells, either tesselated
or of the variety called glandular. Beneath this mem-
brane ramify the blood-vessels which furnish the elements
of the secretions. The follicles are simply digital inversions
of this structure, with rounded, blind extremities, the glan-
dular epithelium lining the tube.

The tubular glands have essentially the same structure
as the follicles, except that the tubes are long and more or
less convoluted. The more complex of these organs contain
connective tissue, blood-vessels, nerves, and lymphatics.

The compound racemose glands are composed of branch-
ing ducts, around the extremities of which are arranged
collections of rounded follicles, like bunches of grapes. In
addition to the epithelium, basement-membrane, and blood-
vessels, these organs contain connective tissue, fibro-plastic
elements, lymphatics, involuntary muscular fibres, and nerves.
In the simple racemose glands the excretory duct does not
branch.

The ductless glands contain blood-vessels, lymphatics,
nerves, sometimes involuntary muscular fibres, fibro-plastic
elements, and a peculiar structure called pulp, which is com-

1 For the anatomy of the lymphatic system, see vol. ii., Absorption, p. 439,
et seq.

CLASSIFICATION OF SECRETIONS. 37

posed of fluid with cells and occasionally closed vesicles.
These are sometimes called blood-glands, because they are
supposed to modify the blood as it passes through their
substance.

The testicles and the ovaries are not simple glandular
organs; for in addition to the production of mucous or
watery secretions, their principal function is to develop cer-
tain anatomical elements, the spermatozoids and the ova.
The physiology of these organs will be considered in connec-
tion with the subject of generation.

Classification of the Secreted Fluids. — The products of
the various glands may be divided, according to their function,
into secretions and excretions. The secreted fluids may be
subdivided into the permanent secretions, which have a more
or less mechanical function, and transitory secretions ; some
of the latter, like mucus, are thrown off in small quantity,
without being actually excrementitious ; others, like most
of the digestive fluids, are produced intermittently and
rapidly, and finally undergo resorption.

Tabular View of the Secreted Fluids.

SECRETIONS PBOPEB.

Permanent Fluids.
Serous fluids.
Synovial fluid.
Aqueous humor of the eye.
Vitreous humor of the eye.
Fluid of the labyrinth of the internal ear.
Cephalo-rachidian, or subarachnoid fluid.

Transitory Fluids.
Mucus, in many varieties.
Sebaceous matter.

Cerumen, the waxy secretion of the external meatus.
Meibomian fluid.
Milk and colostrum.
Tears.
Saliva.

38 SECRETION.

Gastric juice.

Pancreatic juice.

Secretion of the glands of Brunn.

Secretion of the follicles of Lieberkiihn.

Secretion of the follicles of the large intestine.

Bile (also an excretion).

EXCRETIONS.

Perspiration, and the secretion of the axillary glands.

Urine.

Bile (also a secretion).

FLUIDS CONTAINING FORMED ANATOMICAL ELEMENTS.

Seminal fluid, containing, besides spermatozoids, the secretions of a number of

glandular structures.
Fluid of the Graafian follicles.

CHAPTEK II.

SEKOUS AND SYNOVIAL FLUIDS MUCUS SEBACEOUS FLUIDS.

Physiological anatomy of the serous and synovial membranes — Synovial fringes
— Bursse — Synovial sheaths — Pericardial, peritoneal, and pleural secre-
tions— Quantity of the serous secretions — Synovial fluid — Mucus — Mucous
membranes — Mucous membranes covered with pavement-epithelium — Mu-
cous membranes covered with columnar epithelium — Mucous membranes
covered with mixed epithelium — Mechanism of the secretion of mucus —
Composition and varieties of mucus — Microscopical characters of mucus
— Xasal mucus — Bronchial and pulmonary mucus — Mucus secreted by the
lining membrane of the alimentary canal — Mucus of the urinary passages
— Mucus of the generative passages — Conjunctival mucus — General func-
tion of mucus — Xon-absorption of certain soluble substances, particularly
venoms, by mucous membranes — Sebaceous fluids — Physiological anatomy
of the sebaceous, ceruminous, and Meibomian glands — Ordinary sebaceous
matter — Smegma of the prepuce and of the labia miuora — Yernix
caseosa — Cerumen — Meibomian secretion — Function of the Meibomian
secretion.

Physiological Anatomy of the Serous and Synovial
Membranes.

THE serous and synovial membranes, which are fre-
quently classed together by anatomists, present several well-
marked points of distinction, both as regards their structure
and the products of their secretion. The serous membranes
are the arachnoid, pleura, pericardium, peritonaeum, and
tunica vaginalis testis. The synovial membranes are found
around all the movable articulations. They also form elon-
gated sacs enveloping many of the long tendons, and exist
in various parts of the body in the form of shut sacs, when
they are called bursae.

40 SECRETION.

Serous Membranes. — The structure of the serous mem-
branes is very simple. They consist of a dense tissue of
fibres, which is frequently quite closely adherent to the sub-
jacent parts, and covered by a single layer of pavement, or
tesselated epithelium. The fibres are mainly of the inelastic
variety arranged in bundles, interlacing each other in the
form of a close net-work, and mingled with small, wavy
fibres of elastic tissue and numerous blood-vessels. It has
not been satisfactorily demonstrated that the serous mem-
branes contain nerves and lymphatics, though the latter are
generally quite abundant in the subjacent parts, particularly
beneath the visceral layers.1 The capillary blood-vessels are
in the form of a close, polygonal net-work, with sharp angles.

The epithelium of the serous membranes is pale, regular,
with rather large nuclei, and is easily detached after death.
Todd and Bowman describe a delicate basement -membrane
between the fibrous structure and the layer of epithelium,2
but others have not been able to distinguish it, and the ex-
istence of such a membrane is considered doubtful.3

These membranes, as a rule, form closed sacs, with their
opposing or free surfaces nearly in apposition. The secre-
tion, which is generally very small in quantity, is contained
in their cavity. The exceptions to this are the arachnoid
membrane, the surfaces of which are exactly in apposition,
the fluid being situated beneath both layers,4 and the perito-
neum of the female, which has an opening on either said for
the Fallopian tubes.

Synovial Membranes. — The true synovial membranes are
found in the diarthrodial, or movable articulations ; but in

1 See vol. ii., Absorption, p. 433.

2 TODD AND BOWMAN, Physiological Anatomy and Physiology of Man, Lon-
don, 1845, vol. i., p. 130.

3 BRINTON, Serous and Synovial Membranes. — Cyclopedia of Anatomy and
Physiology, London, 1847-1849, vol. iv., part i., p. 514.

* MAGENDIE, Memoire sur un liquide qui se trouve dans le crane et le canal
vertebral de Vhomme et des animaux mammiferes. — Journal de physiologic, Paris,
1825, tome v., p. 36.

SYNOVIA^ MEMBRANES. 41

various parts of the body are found closed sacs, sheaths, etc.,
which resemble synovial membranes both in structure and
function. Every movable joint is enveloped in a capsule
which is closely adherent to the edges of the articulating
cartilage and is even reflected upon its surface for a short
distance. It was formerly thought that these membranes,
like the serous sacs, were closed bags, with one layer
attached to the cartilage, and the other passing between
the bones so as to enclose the joint; but it is now the
general opinion that the cartilage which encrusts the articu-
lating extremities of the bones, though bathed in synovial
fluid, is not itself covered by a membrane.

The fibrous portion of the synovial membranes is more
dense and resisting and less elastic than the serous mem-
branes. It is composed of white inelastic fibrous tissue,
with a few elastic fibres and blood-vessels. The latter are
generally not so numerous as in the serous membranes.
The internal surface is lined with small cells of flattened,
pavement-epithelium, with rather large, rounded nuclei.
These cells exist in from one to two or four layers.1

In most of the joints, especially those of large size, as
the knee and hip, the synovial membrane is thrown into
folds which contain a considerable amount of true adipose
tissue. In nearly all the joints, the membrane presents
fringed, vascular processes, called sometimes synovial fringes.
These are composed of looped vessels of considerable size ;
and when injected they bear a certain resemblance to the
choroid plexus. The edges of these fringes present numer-
ous leaf-like, -membranous appendages, of a great variety of
curious forms. They are generally situated near the attach-
ment of the membrane to the cartilage. There is no reason
for supposing that either the adipose folds or the vascular
fringes have any special office in the production of the
eynovial secretion, different from that of other portions of
the membrane, though such a theory has been advanced.

1 KOLLIKER, Handbuch der Gewebelehre des Menschen, Leipzig. 1867, S. 201.

42 SECRETION.

The arrangement of the synovial bursse is very simple.
Wherever a tendon plays over a bony surface, we find a
delicate membrane in the form of an irregularly shaped,
closed sac, one layer of which is attached to the tendon, and
the other to the bone. These sacs are lined with an epi-
thelium like that found in the synovial cavities, and they
secrete a true synovial fluid. Numerous bursse are also
found beneath the skin, especially in parts where the integu-
ment moves over bony prominences, as the olecranon, the
patella, and the tuberosities of the ischium. These sacs,
sometimes called bursse mucosse, are much more common in
man than in the inferior animals, and have essentially the
same function as the deep-seated bursse. The form of both
the superficial and deep-seated bursse is very irregular, and
their interior is frequently traversed by small bands of
fibrous tissue. The synovial sheaths, or vaginal processes,
line the canals in which the long tendons play, particularly
the tendons of the flexors and extensors of the fingers and
toes. They have essentially the same structure as the
bursse, and present two layers, one of which lines the canal,
while the other is reflected over the tendon. The vascular
folds, described in connection with the articular synovial
membranes, are found in many of the bursae and synovial
sheaths.

Pericardial, Peritoneal, and Pleural Secretions. — In
the normal condition of the true serous membranes, the
amount of secretion is very small ; so small, indeed, that it
never has been obtained in quantity sufficient for ultimate
analysis. It is not true that these membranes produce
merely a vaporous exhalation. Their secretion is always
liquid, and, small as it is in quantity, it can be found in the
pericardial sac, and sometimes in the lower part of the ab-
dominal cavity. As the only apparent function of these
fluids is to moisten the membranes, so that the opposing
surfaces can move over each other without undue fric-

SEROUS SECRETIONS. 4:3

tion, only enough fluid is secreted to keep these surfaces in
a proper condition. The error frequently committed by
authors, in describing the serous exhalations as vaporous,
is due to the fact that a vapor is generally given off when
the serous cavities are exposed, either in a living animal or
in one recently killed. This vaporous exhalation takes place
after exposure of the parts ; but if the cavities be observed
without exposing the serous surfaces to the air, a certain
quantity of liquid can be detected. Colin always found
liquid in the peritoneal, pericardial, and pleural cavities of
animals recently killed or opened during life. In these
cavities the opposite surfaces of the serous membrane were
either in contact, or the space between them was filled with
liquid. In one of the small ruminants, he removed the
muscles and the elastic tunic from the lower part of the
abdomen, exposing the transparent peritoneum, and through
this membrane could see liquid collected in the dependent
parts.1

As far as has been ascertained, the secretions of the dif-
ferent serous membranes bear a close resemblance to each
other. They are either colorless, or of a slight amber tinge,
alkaline in reaction, and have a specific gravity of from
1012 to 1020. Their composition resembles that of the
serum of the blood, except that the proportion of water is
very much greater. They contain albumen, chlorides, car-
bonate and phosphate of soda, and a little glucose. These
facts are the result of observations upon the serous fluids of
some of the inferior animals ; 3 and it is exceedingly difficult
to obtain the normal fluids from the human subject. The
elaborate analyses which are sometimes given of the fluids
from the different serous cavities in the human subject are
the results of examinations of large morbid accumulations.8

1 COLIN, Traite de physiologic comparee dts animaux domestiqucs, Paris, 1856,
tome ii., p. 438.
3 COLIN, loc. cit.
* ROBIN, Lemons sur les humeurs, Paris, 1867, p. 262, et seq. This author

44 SECRETION.

The normal quantity of pericardial fluid in the human
subject is generally estimated at from one to two flui-
drachms. Colin found that the pericardial sac of the horse
contained from two and a half to three and a half fluid-
ounces, the cavity being exposed immediately after the death
of the animal from haemorrhage.

The quantity of fluid found in the peritoneal cavity in
horses killed in this way was from ten to thirty-four fluid-
ounces.

The quantity of fluid in the pleural cavity in the same
animal was from three and a half to seven fluidounces.1

These estimates are simply approximative ; but they give
an idea of the normal quantity of liquid which may reason-
ably be supposed to exist in the serous cavities of the
human subject. Judging from the weight of a man of
ordinary size as compared with that of a horse, it may be
stated, in general terms, that the pericardial sac contains
from two and a half to three and a half fluidrachms ; the
peritoneal cavity from one to four fluidounces ; and the
pleural sac from three and a half to seven fluidrachms.

The fluid in the cavity of the tunica vaginalis is small in
quantity, and resembles in every respect the peritoneal secre-
tion. The cephalo-rachidian, or subarachnoid fluid will
be described in connection with the anatomy of the cerebro-
spinal nervous system.

Synovial Fluid. — Although there is a certain similarity
between the serous and the synovial membranes, their secre-
tions differ very considerably in their physical and chemical
characters. Like the serosities, the synovial fluid has simply
a mechanical function ; but it is more viscid, and contains a
larger proportion of organic matter than the serous fluids.
The quantity of fluid in the joints is sufficient to lubricate

has collected the latest analyses of the pleural fluid, the pericardial fluid, the
fluid of ascites, and the fluid of hydrocele.
1 COLIN, loc. cit.

SYNOVIAL FLUID. 45

freely the articulating surfaces. In a horse of medium size
and in good condition, examined immediately after death,
Colin found 1*6 fluidrachms in the shoulder-joint; 1*9
drachms in the elbow-joint ; 1'6 drachms in the coxo-fernoral
articulation ; 2*2 in the femoro-tibial ; and 1*9 in the tibio-
tarsal.1

When perfectly normal, the synovial fluid is either color-
less or of a pale yellowish tinge. It is so viscid that it is
with difficulty poured from one vessel to another. This
peculiar character is due to the presence of an organic sub-
stance called synovine. When this organic matter has been
extracted and mixed with water, it gives to the fluid the
peculiar viscidity of the synovial secretion. The reaction
of the fluid is faintly alkaline, on account of the presence of
a small proportion of carbonate of soda. The fluid, espe-
cially when the joints have been much used, usually con-
tains in suspension pale epithelial cells and a few leucocytes.
The following is the composition of the synovial fluid of the
human subject : a

Composition of the Synovial Fluid.

Water 928'00

Synovine (called albumen) 64'00

Principles of organic origin (belonging to the second class of

Robin) not estimated.

Fatty matter 0'60

Chloride of sodium

6'00
Carbonate of soda

Phosphate of lime 1'50

Ammonio-magnesian phosphate traces.

The observations of Frerichs indicate considerable vari-
ations in the composition and general characters of the
synovial fluid, dependent upon use of the joints. In a stall-
fed ox the proportion of water to solid matter was 969*90
to 30'10; and in animals that took considerable exercise,

1 COLIN, op. cit.t tome ii., p. 440.

2 ROBIN, JLefons sur les humeurs, Paris, 1867, p. 276.

4:6 SECRETION.

the proportions were 948*54: of water to 51*4:6 of solid matter.
In the latter the fluid was more viscid, and contained a
larger proportion of synovine with a smaller proportion of
salts. It was also more deeply colored, and contained a
larger number of leucocytes.1

Like the serous fluids, the synovial secretion is produced
by the general surface of the membrane and not by any
special organs. The folds and fringes which have been
described were supposed at one time to be most active in
secreting the organic matter, but there is no evidence that
they have any such office.

The aqueous humor of the eye and the fluid found in the
labyrinth of the internal ear resemble the serous secretions
in many regards ; but these fluids, with the vitreous humor,
will be considered in connection with the physiological anat-
omy of the eye and the ear.

Mucus.

Mucous Membranes. — The mucous membranes in dif-
ferent situations present important peculiarities in structure,
many of which have already been considered. We have
described, in detail, in the preceding volumes, the mucous
membrane of the air-passages and of the alimentary canal, in
connection with the subjects of respiration and digestion ;
and the membranes in other parts will necessarily be de-
scribed in treating of the physiology of the organs in which
they are found. It will be sufficient at present to take a
general view of the structure of these membranes and the
mechanism of the production of the various fluids known
under the name of mucus.

A distinct anatomical division of the mucous membranes
may be made into two classes, as follows : First, those pro-
vided with pavement-epithelium ; and second, those provided

1 FRERICHS, in WAGNER, Handworterbuch der Physiologic, Braunschweig, 1846,
Band iii., S. 467.

MUCUS. 47

with columnar, or conoidal epithelium. All of the mucous
membranes line cavities or tubes communicating with the
exterior by the different openings in the body.

The following are the principal situations in which the
first variety of mucous membranes, covered with pavement-
epithelium, are found : The mouth, the lower part of the
pharynx, the oesophagus, the conjunctiva, the female ure-
thra, and the vagina. In these situations the membrane is
composed of a chorion made up of inelastic and elastic fibrous
tissue, a few fibro-plastic elements, with capillaries, lym-
phatics, and nerves. The elastic fibres are small and quite
abundant. The membrane itself is loosely united to the
subjacent parts by areolar tissue. The chorion is provided
with vascular papilla, more or less marked ; but in all situ-
ations, except in the pharynx, the epithelial covering fills up
the spaces between these papillse, so that the membrane pre-
sents a smooth surface. Between the chorion and the
epithelium, is an amorphous basement-membrane. The mu-
cous glands open upon the surface of the membrane by their
ducts, but the glandular structure is situated in the submu-
cous areolar tissue. These glands have many of them been
described in connection with the mucous membrane of the
mouth, pharynx, and oesophagus.1 They are generally sim-
ple racemose glands, presenting a collection of follicles ar-
ranged around the extremity of a single excretory duct, lined
or filled with rounded, nucleated epithelium.

The pavement-epithelium covering these membranes ex-
ists generally in several layers, and presents great variety,
both in form and size. The most superficial layers are
of large size, flattened, and irregularly polygonal. The
deeper layers are smaller and more rounded. The size of
these cells is from g-^j- to -g-j-^ of an inch. The cells are
pale, slightly granular, and possess a small, ovoid nucleus,
with one or two nucleoli.

The second variety of mucous membranes, covered with

2 See vol. ii., Digestion, p. 166.

48 SECRETION.

columnar epithelium, is found lining the alimentary canal
below the cardiac orifice of the stomach, the biliary pas-
sages, the excretory ducts of all the glands, the nasal pas-
sages, the upper part of the pharynx, the uterus and Fallo-
pian tubes, the bronchi, the Eustachian tubes, and the male
urethra. In certain situations this variety of epithelium is
provided on its free surface with little hair-like processes
called cilia. During life the cilia are in constant motion,
producing a current always in the direction of the mucous
orifices. Ciliated epithelium is found throughout the nasal
passages, commencing about three-quarters of an inch within
the nose ; the upper part of the pharynx ; the posterior
surface of the soft palate ; the Eustachian tube ; the tym-
panic cavity ; the larynx, trachea, and bronchial tubes, un-
til they become less than -fa of an inch in diameter ; the
neck and body of the uterus ; the Fallopian tubes ; the in-
ternal surface of the eyelids, and the ventricles of the brain.

This variety of mucous membrane is formed of a chorion,
a basement-membrane, and epithelium. The chorion is com-
posed of inelastic and elastic fibres, with fibro-plastic ele-
ments, a few unstriped muscular fibres, amorphous matter,
vessels, nerves, and lymphatics. It is less dense and less
elastic than the chorion of the first variety, and is generally
more closely united to the subjacent tissue. The surface of
these membranes is generally smooth, the only exception be-
ing the mucous membrane of the pyloric portion of the
stomach and the small intestines.

These membranes are all provided with follicular glands,
extending through their entire thickness and terminating in
rounded extremities, sometimes single and sometimes double,
which rest upon the submucous structure. Many of them
are provided also with simple racemose glands, the ducts
passing through the membrane, the glandular structure being
situated in the submucous areolar tissue.1

1 See vol. i., Respiration, p. 361, for a description of the glandular organs

MTCUS. 49

The columnar epithelium covering these membranes rests
upon an amorphous structure, called basement-membrane.
It generally presents but few layers, and sometimes, as in
the intestinal canal, there is only a single layer. The cells
are prismoidal, with a large free extremity, and a pointed
end which is attached. The lower strata of cells are shorter
and more rounded than those in the superficial layer. The
cells are pale, very closely adherent to each other by 'their
sides, and provided with a moderate-sized, oval nucleus with
one or two nucleoli. The length of the cells is from -g^-g- to
-g-J-g- of an inch, and their diameter from ao100 to 2£do of an
inch. When villosities exist on the surface of the mem-
branes, the cells follow the elevations and do not fill up the
spaces between them, as in most of the membranes covered
with pavement-epithelium.

The mucous membrane of the urinary bladder, the
ureters, and the pelvis of the kidneys, cannot be classed in
either of the above divisions. They are covered with mixed
epithelium, presenting all varieties of form between the
pavement and the columnar, some of the cells being caudate
and quite irregular.

Mechanism of the Secretion of Mucus. — Nearly every
one of the great variety of fluids known under the name of
mucus is composed of the products of several different glan-
dular structures. According to Robin, mucus proper is pro-
duced by the epithelial cells of that portion of the membrane
situated on the surface, between the opening of the so-called
mucous follicles or glands ; * while the secretion of these
special glandular organs always possesses peculiar properties.
It is undoubtedly true that certain membranes which do not
possess glands, as the mucous lining of the ureters and a
great portion of the urinary bladder, are capable of secreting

of the air-passages ; and vol. ii., Digestion, pp. 212, 313, and 389,. for a descrip.
tion of the glands of the stomach and intestines.

1 ROBIX, Lefon* stir les humeurs, Paris, 1867, p. 438.
4

50 SECRETION.

mucus. The mucous membrane of the stomach produces an
alkaline, viscid secretion, during the intervals of digestion,
when the gastric tubules do not act ; and the gastric tubules,
during digestion, secrete a fluid of an entirely different char-
acter. The fluid produced by the follicles of the small in-
testine likewise has peculiar digestive properties. These
circumstances, and the fact that the entire extent of the mu-
cous membranes is covered with more or less secretion, show
that the general epithelial covering of these membranes is
capable of secreting a fluid which forms one of the constitu-
ents of what is ordinarily recognized as mucus. It is im-
possible, however, to separate the secretion of the superficial
layer of cells from the other fluids that are found on the
mucous membranes ; and it will be more convenient to re-
gard as mucus, the secretion which is found upon mucous
membranes, except when, as in the case of the gastric or the
intestinal juice, we can recognize a special fluid by certain
distinctive physiological properties.

In the membranes covered with cylinder-epithelium, which
are usually provided with numerous simple follicles, the se-
cretion is produced mainly by these follicles, but in part by
the epithelium covering the general surface. The mem-
branes covered with pavement-epithelium usually contain
but few follicles, and are provided with simple racemose
glands situated in the submucous structure, which are to be
regarded rather as appendages to the membrane. The secre-
tion is here produced by the epithelium on the free surface,
and is always mixed with fluids resulting from the action of
the mucous glands.

There is nothing to be said with regard to the mechanism
of the secretion of mucus beyond what has already been
stated in connection with the general mechanism of secretion.
All the mucous membranes are quite vascular, and the cells
covering the membrane and lining the follicles and glands at-
tached to it have the property of taking from the blood the
materials necessary for the formation of the secretion

circus. 51

These principles pass out of the cells upon the surface of the.
membrane in connection with water and inorganic salts in
variable proportion. Many of the cells themselves are des-
quamated, and are found in the secretion, together with a
few leucocytes, which are produced upon mucous surfaces
with great facility.

Composition and Varieties of Mucus. — In comparing
the secretions of the different mucous membranes, each one
will be found to possess certain distinctive peculiarities, more
or less marked ; but there are certain general characters
which belong to all varieties of mucus. The fluid is usually
a mixture of the secretion from the simple membrane and
the product of its follicles or glandular appendages, and al-
ways contains a certain amount of desquamated epithelium ;
and it is frequently possible, from the microscopical charac-
ters of the epithelium, to indicate the part by which any given
specimen of mucus was secreted. This desquamation of
epithelium must not be regarded as a necessary condition of
the secretion of mucus, any more than the desquamation of
the epidermic scales is to be regarded as a condition neces-
sary to the secretion of perspiration or sebaceous matter. It
is a property of the epidermis and the epithelial covering of
mucous membranes to be regenerated by the formation of
new cells from below, the effete structures being thrown off,
and the admixture of these with mucus is simply accidental.
The leucocytes, formerly called mucus-corpuscles, are the
result of irritation of the mucous membrane, and are not
constant constituents of normal mucus.

All the varieties of mucus are more or less viscid ; but
this character is very variable in the secretions from differ-
ent membranes, in some of them the secretion being quite
fluid, and in others almost semisolid.

The different kinds of mucus vary considerably in general
appearance. Some of them are perfectly clear and colorless ;
but the secretion is generally grayish and semitransparent.

52 SECRETION.

Examined by the microscope, in addition to the mixture of
epithelium and occasional leucocytes, which give to the fluid
its semiopaque character, the mass of the secretion presents, a
very finely striated appearance, as though it were composed
of thin layers of a nearly transparent substance, with many
folds. These delicate striae do not usually interlace with
each other, and are rendered more distinct by the action of
acetic acid. This appearance, with the peculiar effect of
the acid, is characteristic of mucus. Some varieties of mu-
cus present very fine, pale granulations and a few small glob-
ules of oil.

On the addition of water, mucus is somewhat swollen,
but is not dissolved. An exception to this is the secretion
of the conjunctival mucous membrane, which is coagulated
on the addition of water.

As a rule, the reaction of mucus is alkaline ; the only
exception to this being the vaginal mucus, which is very
fluid and distinctly acid.

It is exceedingly difficult to get an exact idea of the prox-
imate composition of normal mucus, from the fact that the
quantity secreted by the membranes in their natural condi-
tion is very small, being just sufficient to lubricate their
surface. All varieties, however, contain a peculiar organic
principle, called mucosine, which gives the fluid its peculiar
viscidity They likewise present a considerable variety of
inorganic salts ; as the chlorides of sodium and potassium,
alkaline lactates, carbonate of soda, phosphate of lime, a
small proportion of the sulphates, and, in some varieties,
traces of iron and silica.1

Of all these constituents, mucosine is the most important,
as it gives to the secretion its characteristic properties. Like
all other organic nitrogenized principles, mucosine is coagula-
ble by various reagents. It is imperfectly coagulated by heat ;
and after desiccation can be made to assume its peculiar con-

1 SIMON, Animal Chemistry with reference to the PJiysiology and Pathology of
Man, Philadelphia, 1846, p. 351.

MUCUS. 53

sistence by the addition of a small quantity of water. It is
coagulated by acetic acid and by a small quantity of the
strong mineral acids, being redissolved in an excess of the
latter. It is also coagulated by strong alcohol, forming a
fibrinous clot soluble in hot and cold water. Mucosine may
be readily isolated by adding water to a specimen of nor-
mal mucus, filtering, and precipitating with an excess of
alcohol. If this precipitate, after having been dried, be ex-
posed to water, it assumes the viscid consistence peculiar
to mucosine. This property serves to distinguish it from
albumen and other organic nitrogenized principles.

Nasal Mucus. — The nasal mucus, being subject to so
many changes from irritation of the Schneiderian membrane,
presents considerable variation in its appearance and compo-
sition. Under perfectly normal conditions, it is very viscid,
clear or slightly opaque and grayish, and strongly alkaline.
It always contains more or less columnar epithelium. In its
behavior to various reagents, it presents the characteristics
which we have ascribed to the secretions of the mucous
membranes generally. The following is the composition of
the normal secretion :

Composition of Nasal Mucus?

Water 933'00 to 947'00

Mucosine (with a trace of albumen ? ) 53'30 " 54'80

Lactate of soda (?) 1-00 " 5'00

Organic crystalline principles 2*00 " T05

Fatty matters and cholesterine not estimated 5 '01

Chlorides of sodium and potassium 5 '60 to 5*09

Calcareous and alkaline phosphates 3'50 " 2'00

Sulphate and carbonate of soda 0:90 not estimated.

Bronchial and Pulmonary Mucus. — This is the secre-
tion of the general mucous surface of the larynx and bron-
chial tubes, mixed with the products of the glands situated
in the substance of these membranes and in the submucous

1 ROBIN, Le?ons sur les humeurs, Paris, 1867, p. 450.

54 SECRETION.

tissue. In addition to this secretion, there is an exhala-
tion of watery vapor containing traces of organic matter,
coming from the air-cells and the bronchial tubes less than
-gij of an inch in diameter, which are not provided with mu-
cous glands. This variety of mucus is alkaline and is quite
similar to nasal mucus in its appearance and general char-
acters. The following is an analysis, by Nasse, of the secre-
tion expectorated in the morning by a healthy man :

Composition of Bronchial and Pulmonary Mucus.1

Water 955-520

Hucosine, with a little albumen 23*754

Watery extract 8-006

Alcoholic extract 1*810

Fat 2-887

Chloride of sodium 5'825

Sulphate of soda 0'400

Carbonate of soda 0'198

Phosphate of soda 0*080

Phosphate of lime, with traces of iron 0'974

Carbonate of lime 0*291

Silica and sulphate of lime 0'255

1,000-000

Mucus secreted l>y the Mucous Membrane of the Ali-
mentary Canal. — Throughout the alimentary canal, from
the mouth to the anus, the lining membrane secretes a cer-
tain quantity of mucus, which does not differ very much
from the mucus found in other situations. This secretion
appears to take place independently of the act of digestion,
and the mucus in most parts of the tract is not known to
possess any peculiar digestive properties. By ligating all of
the salivary ducts, the buccal mucus has been procured. This
secretion is produced by the cells covering the general surface
of the membrane, and is mixed with the secretion of the iso-
lated follicular and racemose glands of the mouth. An ana-

1 NASSE, Ueber die Bestandtheile des normalen Schleims der Luftwege. — Jour-
nal fur praktische Chemie, Leipzig, 1843, Bd. xxix., S. 65.

MUCUS. 55

logous secretion is produced by the mucous membrane of
the pharynx and oesophagus.1 During the intervals of di-
gestion, a viscid, alkaline secretion covers the mucous mem-
brane of the stomach. The digestive secretions of the small
intestine are so viscid that it has been found impossible to
separate them from the true mucous secretion ; but un-
doubtedly a secretion of ordinary mucus is constantly taking
place from the lining membrane of both the small and the
large intestine. This secretion probably has a purely me-
chanical function, serving to lubricate the membranes and
facilitate the movements of the opposing surfaces against
each other.

The mucous membrane of the gall-bladder produces quite
an abundant secretion ; but this is always mixed with the
bile, and will be considered in connection with the composi-
tion of this fluid, though it is not known to possess any pe-
culiar properties.

Mucus of the Urinary Passages. — A small quantity of
mucus is secreted by the urinary passages. This is present
in the normal urine, in the form of a very slight, cloudy de-
posit, which forms after the urine has been allowed to stand
for a few hours. A certain amount of secretion takes place
from the mucous membrane of the bladder, which, as we
have seen, does not possess glands except near the neck.
This secretion takes place in very small quantity, and may
be recognized in the urine by the ordinary microscopical
characters of mucus.

Jfu-cus of the Generative Passages. — The vagina secretes
a small quantity of mucus, which differs from the secretions
of the other mucous membranes in being distinctly acid and
almost entirely wanting in viscidity. The mucus of the
neck of the uterus is clear, viscid, and distinctly alkaline.
This is ordinarily produced in small quantity, but is very

1 See vol. ii., Digestion, p. 166.

56 SECRETION.

abundant during pregnancy. It is the result of the action
chiefly of the large, rounded glands found in this situation.
The mucus of the body of the uterus and of the Fallopian
tubes is alkaline, of a grayish color, and slightly viscid.
The secretions of these parts are greatly modified during
menstruation. These considerations, however, belong prop-
erly to the subject of generation, and will be taken up more
fully in another volume.

Conjunctival Mucus. — A small quantity of a viscid se-
cretion constantly covers the conjunct! val mucous membrane,
and is a mixture of the secretion of the membrane itself
with the fluid produced by the little mucous glands found
near the internal angle of the eye. A peculiarity of this
variety of mucus, mentioned by Robin, is that it becomes
white, like coagulated albumen, by the action of pure water.1

A peculiarity of the mucus from the conjunctiva, the
urethra of the male, and the vagina, is that they readily be-
come virulent when secreted in abnormal quantity. They
then contain a large number of leucocytes, and have a more
or less puriform character ; but the virulent principle is con-
tained in the clear liquid.

General Function of Mucus. — The smooth, viscid, and
adhesive character of mucus, forming, as this fluid does, a
coating for the mucous membranes, serves to protect these
parts, enables their surfaces to move freely one upon the
other, and modifies to a certain extent the process of absorp-
tion. This function is entirely independent of the function
of some of the mucous glands, as the follicles of Lieberkiihn,
which produce secretions only at particular times.

Aside from the mechanical functions of mucus, it has
been shown that this fluid, in connection with the epithelial
covering of the mucous membranes, is capable of preventing
the absorption of certain principles. It is well known, for

1 ROBIN, Lemons sur les humcurs, Paris, 1867, p. 447.

SEBACEOUS FLUIDS. 57

example, that venoms may be applied with impunity to
certain mucous surfaces, while they produce poisonous effects
if introduced into the circulation. These agents are not
neutralized by the secretions of the parts, for they will
produce their characteristic effects upon the system when
removed from the mucous surfaces and introduced into the
circulation ; and it is reasonable to suppose that the mucous
membranes are capable of resisting their absorption. ' This
fact is proven by the following interesting experiment de-
tailed by Robin :

Let an endosmometer be constructed, using a fresh
mucous membrane, on the surface of which the epithelium
and layer of mucus remain intact, and in the interior of
the apparatus, place a saccharine solution, and let the mem-
brane be exposed to a solution containing some venomous
fluid. The liquid will mount in the interior of the ap-
paratus, but the poison will not penetrate the membrane.
If the mucus and epithelium be now removed with the
finger-nail from, even a small portion of the membrane, the
poison will immediately pass through that part of the mem-
brane, and an animal may be killed with the fluid which
now penetrates into the interior of the endosmometer.1

These facts show that mucus is an important secretion.
It not only has a useful mechanical function, but it is in all
probability closely connected with some of the phenomena
of elective absorption which are so often observed, particu-
larly in the alimentary canal.

Sebaceous Fluids.

The general cutaneous surface is constantly lubricated
by a small quantity of a peculiar oily secretion, called
sebum, or sebaceous matter. This secretion is somewhat
modified in certain situations, and an analogous fluid is pro-
duced by glands of a peculiar structure opening into the

' ROBIN, Lemons sur ks humeurs, Paris, 1867, p. 439.

58 SECRETION.

external meatus of the ear. Another fluid, very much like
the ordinary sebaceous matter, is smeared upon the edges of
the eyelids. These secretions, called respectively cerumen
and Meibomian fluid, resemble the secretion of the ordinary
sebaceous glands sufficiently to be classed with it.

Physiological Anatomy of the Sebaceous, Ceruminous,
and Meibomian Glands. — The true sebaceous glands are
found in all parts of the body that are provided with hair ;
and as nearly every part of the general surface presents
either the long, the short, or the downy hairs, these glands
are very generally distributed. They exist, indeed, in
greater or less numbers in all parts of the skin, except the
palms of the hands and the soles of the feet. In the labia
minora in the female, and in portions of the prepuce and
glans penis of the male, parts not provided with hair, small
racemose sebaceous glands are found, which produce secre-
tions differing somewhat from that formed by the ordinary
glands. The glands in the areola of the nipple in the female
are very large, and are connected with small, downy hairs.
Kolliker has observed these glands, not connected with hairs,
upon the nipple of the male.1

Nearly all of the sebaceous glands are either simple
racemose glands, that is, presenting a number of follicles
connected with a single excretory duct, or compound race-
mose glands, presenting several ducts, with their follicles,
opening by a common tube. Although there is this differ-
ence in the size and arrangement of the glands of the gen-
eral surface, they secrete essentially the same fluid, and their
anatomical differences consist simply in a multiplication of
follicles.

The differences in the size of the sebaceous glands bear a
certain relation to the size of the hairs with which they are
connected ; and, as a rule, the largest glands are connected
with the small, downy hairs. These distinctions in size are

1 KOLLIKER, Handbuch der Gewebelehre des Menschen, Leipzig, 1867, S. 571.

SEBACEOUS FLUIDS. 59

so marked, that the glands may be divided into two classes ;
viz., those connected with the long hairs of the head, face,
chest, axilla, and genital organs, and the coarse, short hairs,
and those connected with the fine, downy hairs. A few
small simple follicles are found in the parts not provided
with hairs.1

The glands connected with the larger hair-follicles are
of the simple racemose variety, and are from -^ to ^ of an
inch in diameter. From two to five of these glands are gen-
erally found arranged around the follicle. They discharge
their secretion at about the junction of the lower third with
the upper two-thirds of the hair-follicle.2 The follicles of the
long hairs of the scalp are generally provided each with a
pair of sebaceous glands, measuring from y^-g- to ^ of an
inch in diameter. Encircling the hairs of the beard, the
chest, axilla, and genital organs, are large glands, some of
them JL of an inch in diameter, arranged in groups of from
four to eight.

The glands connected with the follicles of the small,
downy hairs, are so large, compared with the hair-follicles,
that the latter seem rather as appendages to the glandular
structure. These glands are of the compound racemose
variety, and present sometimes as many as fifteen culs-de-
sac. The largest are found on the nose, the ear, the carun-
cula lachrymalis, the penis, and the areola of the nipple,
where they measure from -^ to -^ of an inch. The glands
connected with the downy hairs of other parts are usually
smaller. The glands of Tyson, situated upon the corona of
the glans penis and behind, upon the cervix, are sebaceous
glands of the compound racemose variety.*

The minute structure of the sebaceous glands is very

1 KOLLIKER, Handbuch der Gewebelehre des Mensclien, Leipzig, 1867, S. 146.

2 SAJPEY, Traite (Tanatomie descriptive, Paris, 1852, tome ii., p. 478.

3 A very full and satisfactory account of the distribution and general anat-
omy of the sebaceous glands is to be found in KOLLIKER, Manual of Human
Microscopic Anatomy, London, 1860, p. 135, d seq., and in the later German
edition, Leipzig, 1867, S. 146, et seq.

SECRETION.

simple. The follicles which compose the simple glands, and
the follicular terminations of the simple and compound race-
mose glands, are formed of a delicate, structureless or slightly
granular membrane, with an external layer of inelastic and
small elastic fibres, and are lined by cells. Next the mem-
brane the cells are polyhedric, pale, and granular, most of
FIG. i. them presenting a nucleus and nu-

cleolus; but the follicle itself con-
tains fatty granules and the other
constituents of the sebaceous mat-
ter, with cells filled with fatty
particles. These cells abound in
the sebaceous matter as it is dis-
charged from the duct. The great
quantity of fatty granules and
globules found in the ducts and
follicles of ' the sebaceous glands
renders them dark and opaque when
examined with the microscope by
transmitted light, and their ap-
pearance is quite distinctive. The
larger glands are surrounded with
capillary blood-vessels.

The ceruminous glands of the
ear produce a secretion resembling
the sebaceous matter in many re-
gards, but in their anatomy they
are almost identical with the su-
doriparous glands. They belong
to the variety of glands called
tubular, and consist of a nearly straight tube which pene-
trates the skin, and a rounded or ovoid coil situated in the
subcutaneous structure. These glands are found only in the
cartilaginous portion of the external meatus, where they
exist in great numbers. They are rather more numerous
in the inner than in the outer half of the meatus.

<gp v-^.,

A very large sebaceous gland from

147-)

SEBACEOUS FLUIDS.

The ducts are short and nearly straight, simply penetrating
the different layers of the skin, and are from -^ -g- to -g-^ of an
inch in diameter. Their openings are rounded and about -^-^
of an inch in diameter. They sometimes terminate in the
upper part of one of the hair follicles. They present an ex-
ternal coat of white fibrous tissue, and are lined with several
layers of small, pale, nucleated epithelial cells.

Fio. 2.

Vertical section of the skin of the external auditory meatus. 1, 1, Epidermis ; 2, 2, Der-
ma ; 3. 3. Series of hair- follicles lodged in the substance of the skin ; 4, 4, Series of
sebaceous glands attached to these follicles ; 5. 5. Subcutaneous areolar layer ; 6, 6, Ce-
ruminous slands ; 7.7, Cernminous glands with the ducts divided; 8, 8, Adipose
vesicles. (SAPPET, Traite (Tanatcmie^ Paris, 1852, tome ii., p. 523.)

The glandular coil is an ovoid or rounded, brownish
mass, of from y^ to -g^ or ^ of an inch in diameter. It
is simply a convoluted tube, continuous with the excretory
duct and terminating in a somewhat dilated, rounded ex-
tremity. It presents occasionally, small, lateral protrusion?.
The diameter of the tube is from -g^- to -3^-5- of an inch. It
possesses a fibrous coat with a longitudinal layer of invol-

62 SECRETION.

untary muscular fibres, and externally a few elastic fibres.
It is lined bj a single layer of irregularly polygonal cells,
from -g-gVo- to 12100 of an inch in diameter. These cells con-
tain numerous brownish or yellowish pigmentary granules.
The tube forming the gland contains a clear fluid mixed
with a granular substance containing cells.1

In addition to the ceruminous glands of the ear, numer-
ous sebaceous follicles are found connected with the hair-
follicles here, as in other parts provided with hair. The
arrangement of the ordinary sebaceous glands and the ceru-
minous glands, which are situated in different planes in the
subcutaneous structure, is shown in Fig. 2.

The Meibomian glands of the eyelids have essentially
the same structure as the ordinary sebaceous glands. Their
ducts, however, are longer, and the terminal follicles are ar-
ranged in a peculiar manner by the sides of the tubes, along
their entire length.

These glands are situated partly in the substance of the
tarsal cartilages, between their posterior surfaces and the
conjunctival mucous membrane. They are placed at right
angles to the free border of the eyelids, opening upon the
inner edge, and occupying the entire width of the cartilages.
From twenty-five to thirty glands are found in the upper,
and from twenty to twenty-five in the lower lid.

Each gland consists of a nearly straight excretory duct,
from -5-^-3- to ^-^ of an inch in diameter, communicating
laterally with numerous compound racemose acini, or col-
lections of follicles, measuring from Tjir to y^- of an inch.
From fifteen to twenty of these collections of follicles are
found on either side of the duct in glands of medium length.2
Most of the excretory ducts are nearly straight, but some
are turned upon themselves near their upper extremity.
The general arrangement of these glands is shown in Fig. 3.

1 The measurements of these tubes and cells are taken from Kolliker (op.
cit., 1860, p. 133).

2 SAPPEY, Traite <? anatomic descriptive, Paris, 1852, tome ii., p. 598.

MEEBOMIAX GLANDS.

FIG. 3.

In general structure there is little, if any, difference
between the terminal follicles of the Meibomian glands and
the follicles of the ordina-
ry sebaceous glands. They
are lined with cells meas-
uring from -^ to 1^
of an inch in diameter.
These cells contain nume-
rous fatty globules, but
they do not coalesce into
large drops, such as are
often seen in the ordinary
sebaceous cells.1 The fol-
licles and ducts are filled
with the whitish, oleagi-
nous matter
stitutes the
secretion, or
palpebrale.

In addition to the
Meibomian secretion, the
edges of the palpebral
orifice receive a small
amount of secretion from
ordinary sebaceous glands
of the compound race-
mose variety (ciliary
glands), which are ap-
pended in pairs to each of the follicles of the eyelashes,
and the sebaceous glands attached to the small hairs of the
caruncula lachrymalis.

Ordinary /Sebaceous Matter. — Although it may be in-
ferred, from the great number of sebaceous glands opening

which con-
Meibomian
the sebum

Meibomian glands of the upper lid, magnified
seven diameters. 1, 1, Free border of the lid ;

2. 2. Anterior lip penetrated by the eyelashes -

3. 3, Posterior lip, with the openings of the Mei-
bomian glands ; 4, A gland passing obliquely
at the summit; 5, Another gland oent upon
itself; 6. 6, Two glands in the form of racemose
glands at their origin : 7, A very small gland ;
8, A medium-sized gland. (SAPPEY. Traite
ffanatomie, Paris, 1852, tome ii., p. 597.)

1 KOLLIKER, Handbuch der Gewebdehre des Mensehen, Leipzig, 1867, S. 678.

64 SECRETION.

upon the cutaneous surface, that the amount of sebaceous
matter must be considerable, it has been impossible to collect
the normal fluid in quantity sufficient for ultimate analysis.
In certain parts, as the skin of the nose, where the glands
are particularly abundant, a certain amount of oily secre-
tion is sometimes observed, giving to the surface a greasy,
glistening aspect. This may be absorbed by paper, giving
it the well-known appearance produced by oily matters,
and may be collected in small quantity upon a glass slide
and examined microscopically. It then presents a number
of strongly refracting fatty globules, with a few epithelial
cells. The cells, however, are not numerous in the fluid as
it is discharged upon the general surface ; but if the con-
tents of the ducts and follicles be examined, cells will here
be found in great abundance. Most of the cells, indeed,
remain in the glands, and the oily matter only is discharged.
The object of this secretion is to lubricate the general cuta-
neous surface, and to give to the hairs that softness which
is characteristic of them when in a perfectly healthy con-
dition.

It is only when the action of the sebaceous glands has
become more or less modified, that the secretion can be
obtained in sufficient quantity for chemical analysis ; but we
cannot be certain that the fluid taken under these conditions
is perfectly normal. The analysis by Esenbeck,1 which is
often quoted in works on physiology, was the result of an
examination of the contents of a largely distended hair-
follicle ; and as the secretion was confined for a long time, it
is evident that it must have undergone material alteration.
We cannot, indeed, refer to any ultimate analysis of the
normal sebaceous secretion ; but of all the examinations
that fyave been made of the secretion when it has been

1 ESENBECK, Chemische Untersuchung des Inhalls einer vergrosserten Talgdrusse
der Haul (glandula sebacea) oder einer sagennanten Fettbalg-Gcschwulst (Athe-
roma). — KASTNER'S Archiv far die gesammete Naturlehre, Niirnberg, 1827, B. xii.,
S. 460, et seg.)

ORDINARY SEBACEOUS MATTER. 65

considerably increased in quantity, those of Lutz give the
best idea of what may be supposed to be nearly its ordinary
composition. This observer analyzed the secretion in a case
of general hypertrophy of the sebaceous system. The fluid
which he extracted from the dilated glands was milky- white,
and of about the consistence, when cold, of wax. The mean
of eight analyses of this fluid was as follows : 1

Composition of Sebaceous Matter.

"Water 357

Oleine 270

Margarine 135

Butyric acid and butyrate of soda 3

Caseine 129

Albumen 2

Gelatine 87

Phosphate of soda and traces of phosphate of lime 7

Chloride of sodium 5

Sulphate of soda 5

1,000

This analysis gives the proportions of animal and solid
matters, desiccated in a current of dry air. Eobin, who has
reviewed at considerable length the analytical process em-
ployed by Lutz, regards the matter supposed to be either
caseine or some analogous albuminoid substance, as the or-
ganic matter of the epithelial cells that exist in such great
numbers in distended sebaceous glands. He regards the
weight of the substances designated under the names of al-
bumen, caseine, and gelatine, with a certain quantity of the
water driven off by desiccation, as representing the proportion
of epithelium.8 This view is very reasonable, as the mi-
croscope always shows in these collections great numbers

1 LUTZ, De Fhypertrophie generate du, systems sebace — These, No. 65, Paris,
1860, p. 18. The proportions of oleine and margarine are given on p. 20.

2 ROBTX. Lerons sur les humeurs, Paris, 1867, p. 599.

66 SECRETION.

of epithelial cells. Cholesterine, which is present so fre-
quently in the contents of sebaceous cysts, does not exist
in the normal secretion, nor was it found in the analyses
by Lutz.

During the latter periods of pregnancy and during lacta-
tion, the sebaceous glands of the areola of the nipple become
considerably distended with a grayish-white, opaque secre-
tion, containing numerous oily globules and granules. Fre-
quently the fluid contains also a large number of epithelial
cells. During the periods above indicated, the secretion
here is always much more abundant than in the ordinary
sebaceous glands.

Smegma of the Prepuce and of the Ldbia Minora. — In
the folds of the prepuce of the male and the inner surface
and folds of the labia minora in the female, a small quan-
tity of a whitish, grumous matter, of a cheesy consistence,
is sometimes found, particularly when proper attention is
not paid to cleanliness. The matter which thus collects
in the folds of the prepuce has really little analogy with
the ordinary sebaceous secretion. Examination with the
microscope shows that it is composed almost entirely of
irregular scales of pavement-epithelium, which do not pre-
sent the fatty granules and globules usually observed in
the cells derived from the sebaceous glands. Robin re-
gards the production of this substance as entirely indepen-
dent of the secretion of sebaceous matter, as it is formed
chiefly in parts of the prepuce in which the sebaceous
glands are wanting.1

The smegma of the labia minora is of the same char-
acter as the smegma preputiale ; but it contains drops of
oil, and the other products of the sebaceous glands found
in these parts.

Vernix Caseosa. — The surface of the foetus at birth and

1 ROBIN, Lefonssur les humeurs, Paris, 186Y, p. 587.

VER1OX CASEOSA. % 67

near the end of gestation is generally covered with a whitish
coating, or srnegma, called the vernix caseosa. This is most
abundant in the folds of the skin ; but it generally covers the
entire surface with a coating of greater or less thickness and
of about the consistence of lard. There are great differences
in foetuses at term, as regards the quantity of the vernix ca-
seosa. In some the coating is so slight that it would not be
observed unless on close inspection.

There are few analyses giving an accurate view of the
ultimate composition of this substance ; l and we can form
the best idea of its constitution and mode of formation from
microscopical examination. If a small quantity be scraped
from the surface and be spread out upon a glass slide with
a little glycerine and water, it will be found, on microscopi-
cal examination, to consist of an immense number of epithe-
lial cells, with a very few small fatty granules. In the table
given below it will be seen that these cells, after desiccation,
constituted about ten per cent, of the whole mass. The fatty
granulations are very few, and do not seem to be necessary
constituents of the vernix, as they are of the sebaceous mat-
ter. In fact, the vernix caseosa must be regarded as the
residue of the secretion of the sebaceous glands, rather than
an accumulation of true sebaceous matter.

1 The following table gives an approximative idea of the nature and quan-
tity of the various substances that have been found in the vernix caseosa.
This table was arranged by Robin from analyses by different observers :

Composition of the Vernix Caseosa.

Water 769'80 to 778'70

Nitrogenized matter, mucous or caseous 4-50

Desiccated epithelium 101 '30

Cholesterine, . }

Oleine and margarine, >• IOS'25

Oleates and margarates of potassa and of soda, )

Chloride of sodium, *|

Hydrochlorate of ammonia, t ..„_

Phosphate of soda and of lime, [ '

Ammonio-magnesian phosphate, J

— ROBIN, Lemons sur Us humeurs, Paris, 1867 p. 590.

00 . SECRETION.

The microscopical examination of the vernix caseosa is
interesting from an anatomical point of view, and possesses
considerable importance in certain medico-legal questions.
The cells are polyhedric in form, somewhat flattened from
mutual compression, and have a diameter of from 12100 to
-5^5- of an inch. Their angles are irregular and rounded,
not possessing that sharpness of definition which charac-
terizes the epidermic cells of the foetus. They are colorless,
transparent, very often folded upon themselves, and have no
nuclei. The cells themselves are very slightly granular, but
a few dark fatty granules sometimes adhere to their exterior.
These cells have no analogy with the ordinary epidermic
cells, but resemble rather the cells found in sebaceous collec-
tions. They are regarded, therefore, by Robin, as derived
entirely from the sebaceous glands.1 The secretion of these
glands is discharged upon the surface, and disappears in
great part, leaving a residue of altered epithelial cells.
It is on account of the absence, to a great degree, of oily
matter, that the vernix caseosa is not softened by gentle
heat.

The function of the vernix caseosa is undoubtedly pro-
tective. If we attempt to make a microscopical preparation
of the cells with water, it becomes evident that the coating
is penetrated by the liquid with very great difficulty, even
when mixed with it as thoroughly as possible. Indeed,
we never observe at birth the peculiar effects of prolonged
contact of the cutaneous surface with water. The protect-
ing coating of vernix caseosa allows the skin to perform its
functions in utero, and at birth, when this coating is removed,
the surface is found in a condition perfectly adapted to ex-
tra uterine existence. It is not probable that the vernix

1 ROBIN ET TARDIEU, Memoire sur Vexamin microscopique des laches formees
par le meconium et Fenduitfcetal, pour servir d Thistoire medico-legale de V infan-
ticide ; extraitdes Annales d> hygiene publique et de medecine legale, Paris, 1857, 2e
serie, tome vii.

CERUMEN. 69

caseosa is necessary to facilitate the passage of the child into
the world, for the parts of the mother are always sufficiently
lubricated with mucous secretion.

Cerumen. — A peculiar substance of a waxy consistence
is secreted by the glands that have been described, in the
external meatus, under the name of ceruminous glands,
mixed with the secretion of sebaceous glands connected with
the short hairs in this situation. It is difficult to ascertain
what share these two sets of glands have in the formation of
the cerumen. Robin is of the opinion that the waxy portion
of the secretion is produced entirely by the sebaceous glands,
and that the convoluted glands, commonly known as the
ceruminous glands, produce a secretion like the perspiration.
He calls the latter, indeed, the sudoriparous glands of the
meatus.1 This view is, to a certain extent, reasonable ; for
the sebaceous matter is not removed from the meatus by fric-
tion, as in other, situations, and would have a natural tenden-
cy to accumulate. But the contents of the ducts of the ceru-
minous glands differ materially from the fluid found in the
ducts of the ordinary sudoriparous glands, containing gran-
ules and fatty globules, such as exist in the cerumen. Al-
though the glands of the ear are analogous in their structure,
and, to a certain extent, in their secretion, to the perspira-
tory glands, the fluid which they produce is peculiar. "We
shall see, also, that the perspiratory glands of the axilla and of
some other parts produce secretions differing somewhat from
ordinary perspiration. As far as can be ascertained, the
cerumen is produced by both sets of glands. The sebaceous
glands attached to the hair-follicles probably secrete most
of the oleaginous and waxy matter, while the so-called
ceruminous glands produce a secretion of much greater
fluidity, but containing a certain amount of granular and
fatty matter.

1 ROBIN, Lefons sur les humeurs, Paris, 1867, p. 591.

70 SECRETION.

The consistence and general appearance of cerumen are
quite variable within the limits of health. When first
secreted, it is of a yellowish color, about the consist-
ence of honey, becoming darker and much more viscid
upon exposure to the air. It has a very decided and bit-
ter taste. It readily forms a sort of emulsive mixture with
water.

Examined microscopically, the cerumen is found to con-
tain semisolid, dark granulations of an irregularly polyhe-
dric shape, epithelium from the sebaceous glands, and epi-
dermic scales, both isolated and in layers. Sometimes also
a few crystals of cholesterine are found.

Chemical examination shows that the cerumen is com-
posed of oily matters fusible at a low temperature, a peculiar
organic matter resembling mucosine, with salts of soda, and
a certain quantity of phosphate of lime. The yellow coloring
matter is soluble in alcohol ; and the residue after evapora-
tion of the alcohol is very soluble in water, and may be pre-
cipitated from its watery solution by the neutral acetate of
lead or the chloride of tin. This extract has an exceedingly
bitter taste.

The cerumen lubricates the external meatus, accumu-
lating in the canal around the hairs. Its peculiar bitter
taste is supposed to be efficient in preventing the entrance
of insects.

Meibomian Secretion. — Yery little is known concerning
any special properties of the Meibomian fluid, except that
it mixes with water in the form of an emulsion more readily
than the other sebaceous secretions.1 It is produced in
small quantity, mixed with a certain amount of mucus and
the secretion from the ordinary sebaceous glands attached to
the eyelashes (ciliary glands), and the glands of the carun-
cula lachrymalis, and smears the edges of the palpebral

1 ROBIN, op. cit., p. 592.

MEIBOMTAN FLUID. 71

orifice. TJris oily coating on the edges of the lids, unless
the tears be produced in excessive quantity, prevents their
overflow upon the cheeks, and directs the excess of fluid into
the nasal duct.

CHAPTER III.

MAMMAET SECRETION.

Physiological anatomy of the mammary glands — Condition of the mammary
glands during the intervals of lactation — Structure of the mammary glands
during lactation — Mechanism of the secretion of milk — Conditions which
modify the lacteal secretion — Influence of diet — Influence of liquid ingesta —
Influence of alcoholic beverages — Influence of mental emotions — Quantity
of milk — Properties and composition of milk — Specific gravity of milk —
Coagulation of milk — Microscopical characters of milk — Composition of
milk — Xitrogenized constituents of milk — Non-nitrogenized constituents
of milk — Inorganic constituents of milk — Variations in the composition
of milk — Colostrum — Composition of colostrum — Lacteal secretion in the
newly-born — Composition of the milk of the infant.

THE mammary glands are among the most remarkable
organs in the economy; not only from the peculiar char-
acter of their secretion, which is unlike the product of any
other of the glands, but from the great changes which they
undergo at different periods, both in size and structure.
Rudimentary in early life, and in the male at all periods of
life, these organs are fully developed in the adult female,
only in the latter months of pregnancy and during lactation.
It is true, that in the female, after puberty, the mammary
glands undergo a marked and rapid increase in size ; but
even then they are not fully developed, and if examined
with the microscope, will be found to lack the essential ana-
tomical characters of secreting organs. The physiological
anatomy of the mammary glands consequently possesses

MAMMARY GLAKDS. 73

peculiar interest, aside from the great importance of their
secretion.

It will be found convenient to consider these organs in
three stages of development ; viz., in their rudimentary con-
dition, as they exist in the male and in the female before
puberty ; in the partially-developed state, as they are found
in the unimpregnated female after puberty and during the
intervals of lactation ; and finally, in the fully-developed
condition, when milk is secreted.

Physiological Anatomy of the Mammary Glands.

The form, size, and situation of the mammae in the adult
female are too well known to demand more than a passing
mention. These organs are almost invariably double, and
are situated on the anterior portion of the thorax over the
great pectoral muscles. In women who have never borne
children, they are generally firm, nearly hemispherical, with
the nipple at the most prominent point. In women who
have borne children, the glands, during the intervals of
lactation, are usually larger, are held more loosely to the
subjacent parts, and are apt to become flabby and pendu-
lous. The areola of the nipple is also darker.

Certain rare examples are on record of anomalies in the
number and location of the mammary glands. In some in-
stances three, four, and five distinct glands have existed
instead of two ; * and some examples are related of extra-
ordinary development of the mammary glands in the male,
to such an extent as to afford sufficient nourishment for an
infant.8 A remarkable case of malposition of a mammary
gland is reported by Dr. Eobert, of Marseilles, in Magendie's

1 Reference to a number of these cases is made by Dr. Solly, in the Cyclo-
pcedia of Anatomy and Physiology, London, 1839-1847, vol. iii., p. 251.

8 Quite a number of cases of this kind are on record, many of them well
authenticated. Dr. Dunglison gives a full account of several instances of lac-
tation in the male, attested by competent medical observers. (DUNGLISON,
Human Physiology, Philadelphia, 1856, vol. ii., p. 520.)

74: SECRETION.

Journal of Physiology. In this case there was a well-formed
mammary gland on the external surface of the left thigh,
about four inches below the great trochanter. The mam-
mary glands upon the chest performed their function with
regularity, and were normal in all respects ; but the gland
upon the thigh secreted during lactation such a quantity of
milk, that the woman had nourished all her children, seven
in number, indifferently from the three glands. She had
nursed one of her children in this way for thirty- three
months. It is a remarkable fact, that the mother of this
woman had three mammary glands, one on the left side of
the chest and two on the right. This case is perfectly
authentic, and was reported on by MM. Chaussier and Ma-
gendie, a committee from the French Academy of Sci-
ences.1

In many works on physiology, instances of unusual lac-
tation are quoted ; but although the time and duration of the
process are modified, the character of the secretion is not
altered. A case is reported as occurring in this country,
in which lactation continued in a woman sixty-five years
of age.2

At birth, in both sexes, the mammary glands are nearly
as fully developed as at any time before puberty. They
make their appearance about the fourth month, in the form
of little elevations of the structure of the true skin, which
soon begin to send out processes destined to be developed
into the lobes of the glands. At birth the glands measure
hardly more than one-third of an inch in diameter. At this
time there are from twelve to fifteen lobes in each gland,
and every lobe is penetrated by a duct, with but few

1 CHAUSSIER ET MAGENDIE, Rapport fait d V Academic des Sciences sur une
observation de M. le Dr. Robert, de Marseille, relative d une femme qui a allaite
plusieurs enfans avec une mamelk situee d la cuisse gauche. — Journal de physiologic,
Paris, 1827, tome vii., p. 175.

2 DCNGLISON, Human Physiology, Philadelphia, 1856, vol. ii., p. 518. The
reader is referred to the work of Dr. Dunglison for an account of a number of
very curious instances of unusual lactation.

MAMMARY GLANDS. 75

branches, composed of fibrous tissue and lined with colum-
nar epithelium. The ends of these ducts are frequently
somewhat dilated; but what have been called the gland-
vesicles do not make their appearance before puberty. In
the male the glands are from one half an inch to two inches
broad, and from ^ to J of an inch in thickness. In their
structure, however, they present little if any difference from
the rudimentary glands of the infant.

As the period of puberty approaches in the female, the
rudimentary ducts of the different lobes become more and
more ramified. Instead of each duct having but two or
three branches, the different lobes, as the gland enlarges,
are penetrated by innumerable ramifications, which have
gradually been developed as processes from the main duct.
It is important to remember, however, that these branches
are never so numerous nor so long during the intervals of
lactation as they are when the organ is in full activity.
The ordinary condition of the gland, as compared with its
structure during activity, is that of atrophy.

Condition of the Mammary Glands during the Intervals
of Lactation. — At this time the gland is not a secreting
organ. It presents the ducts, ramifying, to a certain extent,
in the substance of the lobes into which the structure is di-
vided, but their branches are short and possess but few of
the glandular acini that are observed in every part of the
organ during lactation. This difference in the structure
of the gland is most remarkable; and as it passes from
a secreting to a non-secreting condition at the end of lacta-
tion, the ducts retract in all their branches, and most of the
secreting culs-de-sac disappear. At this time the glandular
tissue is of a bluish-white color, and loses the granular ap-
pearance which it presents during activity. The ducts are
then lined with a small, nucleated, pavement-epithelium,
which is not found during the secretion of milk. These
changes, pointed out by Robin, whose observations have

76 SECRETION.

been verified and extended by Sappey,1 are confined almost
exclusively to the secreting structure of the gland. The
interstitial tissue remains about the same, the blood-vessels,
only, being increased in number during lactation. As we are
treating of the mammary glands as secreting organs, a full
description of its structure is deferred until we come to con-
sider it in a state of functional activity.

Structure of the Mammary Glands during Lactation. —
Between the fourth and the fifth month of utero-gestation,
the mammary glands begin to increase in size ; and at term,
they are very much larger than during the unimpregnated
state. At this time the breasts become quite hard ; and the
surface near the areola is somewhat uneven, from the great
development of the ducts. The nipple itself is increased in
size, the papillae upon its surface and upon the areola are
more largely developed, and the areola becomes larger,
darker, and thicker. The glandular structure of the breasts
during the latter half of pregnancy becomes so far developed,
that if the child be born at the seventh month, the lacteal
secretion may generally be established at the usual period
after parturition. Even when parturition takes pi ace at term,
a few days elapse before secretion is fully established, and
the first product of the gland, called colostrum, is very dif-
ferent from the fully-formed milk.

The only parts of the covering of the breasts that
present any peculiarities are the areola and the nipple. The
surface of the nipple is covered with papillae, which are very
largely developed near its summit. It is covered by epithe-
lium in several layers, the lower strata being filled with
pigmentary granules. The true skin covering the nipples is
composed of inelastic and elastic fibres, containing a large
number of sebaceous glands, but no hair-follicles nor sudori-
parous glands. According to Sappey, these glands, which
are from eighty to one hundred and fifty in number, are
always of the racemose variety, and never exist in the form

1 SAPPEY, Traite $ anatomic descriptive, Paris, 1857, tome iii., p. 697.

MAMMARY GLANDS. 77

of simple follicles, as they are described by most anatomists.1
The nipple contains the lactiferous ducts, fibres of inelastic
and elastic tissue, with an immense number of non-striated
muscular fibres. The muscular fibres have no definite direc-
tion, but are so numerous, that when they are contracted,
the nipple becomes very firm and hard. The nipple, though
it may thus become hard upon the application of cold or
other stimulus, presents none of the anatomical characteris-
tics of the true erectile organs, as is erroneously supposed by
some authors ; and its hardening is simply due to contrac-
tion of its muscular fibres.8

The areola does not lie, like the general integument
covering the gland, upon a bed of adipose tissue, but is
closely adherent to the subjacent glandular structures. The '
skin here is much thinner and more delicate than in other
parts, and the pigmentary granules are very abundant in
some of the lower" strata of epidermic cells, particularly dur-
ing pregnancy. The true skin of the areola is composed of
inelastic and elastic fibres, and lies upon a distinct layer of
non-striated muscular fibres. The arrangement of the mus-
cular fibres (sometimes called the sub-areolar muscle) is quite
regular, forming concentric rings around the nipple. These
fibres are supposed to be useful in compressing the ducts
during the discharge of milk. The areolar presents nu-
merous papillae, considerably smaller than those upon the
nipple ; hair-follicles, containing small, rudimentary hairs ;
sudoriparous glands ; and sebaceous glands connected with
the hair-follicles. The sebaceous glands in this situation
are very large, and their situation is indicated by little
prominences at the surface of the areola, which are especi-
ally marked during pregnancy.

The gland itself is of the compound racemose variety.
It is covered in front by a subcutaneous layer of fat, and
posteriorly is enveloped in a fibrous membrane loosely at-

1 SAPPEY, Traite cT anatomic descriptive, Paris, 1857, tome iii., p. 594.

2 For the anatomy of the erectile tissues, see vol. i., Circulation, p. 336.

78 SECRETION.

tached to the pectoralis major. A considerable amount
of adipose tissue is also found in the substance of the gland,
between the lobes.

Separated from the adipose and fibrous tissue, the organ,
is found divided into lobes, from fifteen to twenty-four in
number. These, in their turn, are subdivided into lobules
made up of a greater or less number of acini or culs-de-sac.
The secreting structure is of a reddish-yellow color, and is
distinctly granular, presenting a decided contrast to the pale
and uniformly fibrous appearance of the gland during the
intervals of lactation. If the ducts be injected from the
nipple and be followed into the substance of the gland, each
one will be found distributing its branches to a distinct
lobe ; so that the organ is really made up of a number of
glands, in their structure identical with each other. It will
be most convenient, in studying the intimate structure of
the gland, to begin at the nipple and follow out one of the
ducts to the termination of its branches in the secreting
culs-de-sac,

The canals which discharge the milk at the nipple are
called lactiferous, or galactophorous ducts. They vary in
number from ten to fourteen. The openings of the ducts at
the nipple are very small, measuring only from -fa to ^ of
an inch. As each duct passes down, it enlarges in the nipple
to -fa or -^ of an inch in diameter, and beneath the areola
presents an elongated dilatation, from -J- to J of an inch in
diameter, called the sinus of the duct.1 During lactation a
considerable quantity of milk collects in these sinuses, which
serve as reservoirs. Beyond the sinuses the calibre of the
ducts is from -fa to -J- of an inch. They penetrate the differ-
ent lobes, branching and subdividing, to terminate finally in
the collections of culs-de-sac which form the acini. Most
modern observers are agreed that there is no anastomosis be-
tween the different lactiferous ducts, and that each one is
distributed independently to one or more lobes.

1 KOLLIKER, Handbuch der Gewebelehre des Afenschen, Leipzig, 1867, S. 571.

GLANDS. 79

The intimate structure of the lactiferous ducts is inter-
esting and important. They are possessed of three distinct
coats. The external coat is composed of anastomosing fibres
of elastic tissue, with some fibres of inelastic tissue. The
middle coat is composed of non-striated muscular fibres, ar-
ranged longitudinally and existing throughout the duct,
from its opening at the nipple to the secreting culs-de-
sac. The internal coat is an amorphous membrane, lined
with roundish or elongated cells during the intervals of
lactation and even during pregnancy, but deprived of epi-
thelium during the period when the lacteal secretion is most
active.1

The acini of the gland, which are very numerous, are
\isible to the naked eye, in the form of small, rounded gran-
ules, of a reddish-yellow color. Between these acini there
exist a certain quantity of the ordinary white fibrous tissue
and quite a number of adipose vesicles. The presence of adi-
pose tissiie in considerable quantity in the substance of the
glandular structure is peculiar to the mammary glands.
Each acinus is made up of from twenty to forty secreting
vesicles, or culs-de-sac. These vesicles are irregular in form,
often varicose, and sometimes enlarged and imperfectly bifur-
cated at their terminal extremities. During lactation their
diameter is from -%%-$ to yj-g- of an inch. During pregnancy,
and when the gland has just arrived at its full development,
the secreting vesicles are formed of a structureless membrane,
lined 'with small, nucleated cells of pavement-epithelium.
The nuclei are relatively large, ovoid, and embedded in a
small amount of amorphous matter, so that they almost touch
each other. Sometimes the epithelium is segmented, and
sometimes it exists in the form of a continuous nucleated
sheet. When the secretion of milk becomes active, the epi-
thelium entirely disappears, and reappears as the secretion
diminishes. This observation is due to Robin,8 and has an

1 SAPPEY, Traite cT anatomic descriptive, Paris, 1857, tome Hi., p. 697.

8 LITTRE ET ROBIX, Dictionnaire de medecine, Paris, 1865, Article, MameUe.

SECRETION.

FIG. 4.

important bearing upon the mechanism of the secretion of

milk.

During the intervals of lactation, as the lactiferous ducts

become retracted, the glandular culs-de-sac disappear ; and

in pregnancy, as the gland takes on its full development, the

ducts branch and extend
themselves, and the vesi-
cles are gradually devel-
oped around their ter-
minal extremities. These
changes in the develop-
ment of the mammae at
different periods are most
remarkable, and are not
observed in any other part
of the glandular system.1

Mechanism of the Se-
cretion of Milk. — With the
exception of water and in-
organic principles, all the

Ducts and acini of the mammary piand. (LiT- important and character-

TRfi ET ROBIN. Dictionnaire de medecine, i^l-ir* nrmefi-H-ionfe r»f -flm

Paris, 1865, Article, Mamdle.) m, nipple; lstic Constituents Ol

«, larger ducts ; r, small duct ; «, acini. milk &TQ formed ill the

substance of the mam-
mary glands. The secreting structures have the property
of separating from the blood a great variety of inorganic
principles ; and we shall see, when we come to study the
composition of the milk more minutely, that it furnishes

1 Sir Astley Cooper, in his admirable monograph upon the anatomy and
diseases of the breast, published in 1840, was the first to give any clear idea
of the minute structure of the mammary glands. His observations, however,
have been much extended by later anatomists. The paper on the breast has
been republished in this country. COOPER, The Anatomy and Diseases of the
Breast, with numerous plates. To which are added his various Surgical Papers,
now first published in a collected form, Philadelphia, 1845.

MILK. 81

all the inorganic matter necessary for the nutrition of the
infant, containing, even, a small quantity of iron. Pre-
cisely how the secreting vesicles separate the proper quan-
tity of these principles from, the circulating fluid, we are
unable, in the present state of our knowledge, to determine.
It is unsatisfactory enough to say that the membranes of
the vesicles have an elective action, but this expresses the
extent of our information on the subject.

The lactose, or sugar of milk, the caseine, and the fatty
particles, are all produced, de novo, in the gland. The pecu-
liar kind of sugar here found does not exist anywhere else in
the organism. Even when the secretion of milk is most
active, different varieties of sugar, such as glucose or cane-
sugar, injected into the blood-vessels of a living animal, are
never eliminated by the mammary glands, as they are by the
kidneys ; and their presence in the blood does not influence
the quantity of lactose found in the milk. All that can be
said with regard to the formation of sugar of milk is, that it
is produced in the mammary glands. The mechanism of its
formation is not understood.

Caseine is produced in the mammary glands, probably
by a catalytic transformation of the albuminoid constituents
of the blood. This principle does not exist in the blood,
though its presence here has been indicated by some observ-
ers. The substance in the blood that has been mistaken
for caseine is undoubtedly albumen, which will not respond
to some of the tests on account of the alkalinity of the fluid
in which it is contained. It is well known that the caseine
of milk is precipitated by an excess of sulphate of magnesia ;
but the so-called caseine of the blood is not affected by this
salt, and passes through it like albumen.1

The fatty particles of the milk are likewise produced in
the substance of the gland, and the peculiar kind of fat
which exists in this secretion is not found in the blood.
The mechanism of the production of fat in the mammary

1 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 283.
6

82 SECRETION.

glands is obscure. The particles are not produced in cells
and set free by their rupture, by a process analogous to that
which takes place in the formation of the fatty particles
found in the sebaceous matter, for during the time when
the secretion of milk is most active, the epithelium of the
secreting culs-de-sac has entirely disappeared. The butter
is produced by the action of the amorphous walls of the
vesicles, in the same way, probably, that fat is produced
by the vesicles of the ordinary adipose tissue. At least, this
is all that is known regarding the mechanism of its pro-
duction.

As regards the mechanism of the formation of the
peculiar and characteristic constituents of the milk, the
mammary glands are to be classed among the organs of
secretion, and not those of elimination or excretion; for
none of these elements preexist in the blood, but all appear
first in the substance of the glands.

During the period of secretion, the glands receive a much
larger supply of blood than at other times. Pregnancy
favors the development of the secreting portions of the
glands, but does not induce secretion. On the other hand,
when pregnancy occurs during lactation, it diminishes, mod-
ifies, and may arrest the secretion of milk. The secre-
tion is destined, however, for the nourishment of the child,
and not for use in the economy of the mother — an important
point of distinction from all other secretions — and its produc-
tion presents one or two interesting peculiarities.

In the first place, the secreting action of the mammary
glands is nearly continuous. When the secretion of milk
has become fully established, while there may be certain
periods when it is formed in greater quantity than at others,
there is no absolute interim ttency in its production.

Again, in all the other glandular organs, the epithelial
cells found in their secreting portion seem to be the active
agents in the production of the secretions ; but in the mam-
mary glands, as we have already noted, the epithelium

MILK. 83

entirely disappears from the secreting culs-de-sac during the
period of greatest functional activity of the gland, and
nothing is left to perform the work of secretion but the
amorphous membrane of the vesicles.

Conditions which modify the Lacteal Secretion. — Yery
little is known concerning the physiological conditions -which
modify the secretion of milk. When lactation is fully
established, the quantity and quality of the milk secreted
become adapted to the requirements of the child at differ-
ent periods of its existence. In studying the composition
of the milk, therefore, it will be found to vary considerably
in the different stages of lactation. It is evident that, as
the development of the child advances, a constant increase
of nourishment is demanded ; and, as a rule, the mother is
capable of supplying all the nutritive requirements of the
infant for from eight to twenty months.

During the time when such an amount of nutritive mat-
ter is furnished to the child, the quantity of food taken
by the mother is sensibly increased ; but observations have
shown that the secretion of milk is not much influenced by
the nature of the food. It is necessary that the mother
should be supplied with good, nutritious articles ; but as
far as solid food is concerned, there seems to be no great
difference between a coarse and a delicate alimentation ;
and the milk of females in the lower walks of life, when the
general condition is normal, is fully as good as in women
who are enabled to live luxuriously. It is, indeed, a fact gen-
erally recognized by physiologists, that the secretion of milk is
little influenced by any special diet, provided the alimenta-
tion be sufficient and of the quality ordinarily required by
the system, and that it contain none of the few articles of
food which are known to have a special influence upon lac-
tation. So long as the mother is healthy and well nourished,
the milk will take care of itself; and the appetite is the
surest guide to the proper variety, quality, and quantity of

84: SECRETION.

food. It is very common, however, for females to become
quite fat during lactation ; which shows that the fatty ele-
ments of the food do not pass exclusively into the milk, but
that there is a tendency, at the same time, to a deposition of
adipose tissue in the ordinary situations in which it is found.
It is a matter of common experience, that certain articles,
such as acids and fermentible substances, often disturb the
digestive organs of the child without producing any change
in the milk, that can be recognized by chemical analysis.
The individual differences in women, in this regard, are
very great.

There are certain medicinal substances which are some-
times found to exert a powerful influence in diminishing
or even arresting the secretion of milk, but a full consider-
ation of these belongs to therapeutics. The same remark
applies to the influence of electricity applied directly to the
mammary glands.

The statements with regard to solid food do not apply
to liquids. During lactation there is always an increased
demand for water and liquids generally; and if these be
not supplied in sufficient quantity, the secretion of milk
is diminished, and its quality is almost always impaired. It
is a curious fact, which has been fully established by obser-
vations upon the human subject and the inferior animals,
that while the quantity of milk is increased by taking a
large amount of simple water, the solid constituents are
also increased, and the milk retains all of its qualities as a
nutritive fluid. The late observations on this subject, by
Dancel, illustrate very fully the unusual demand for liquids
during lactation, and their influence upon the mammary
secretion.1

Alcohol, especially when largely diluted, as in malt-
liquors and other mild beverages, is well known to exert an
influence upon the secretion of milk. Drinks of this kind

1 CANCEL, De I1 influence de Veau dans la production du lait. — Comptes rendus,
Paris, 1865, tome Ixi., p. 243.

MILK. 85

almost always temporarily increase the activity of the secre-
tion, and sometimes produce a certain amount of effect upon
the child ; but direct and accurate observations on the actual
passage of alcohol into the milk are wanting. During lac-
tation the moderate use of drinks containing a small propor-
tion of alcohol is frequently beneficial, particularly in assist-
ing the mother to sustain the unusual drain upon the system.
There are, however, few instances of normal lactation in
which their use is absolutely necessary.

It has been conclusively shown that many medicinal
articles administered to the mother pass unchanged into the
mammary secretion, and therapeutists have sometimes at-
tempted to produce the peculiar effects of certain remedies
in this way in the child. This, however, can hardly be
called a physiological action ; but it is interesting to note
that some articles may be eliminated in the milk, while
others pass into other secretions. This elective power we
have already seen is possessed by many of the glands.
Among the articles that pass readily into the milk may be
mentioned, some of the salts of soda, chloride of sodium, the
sesquioxide of iron, and the preparations of iodine. Dr.
Eees detected iodine in the milk in a patient who had taken
but forty-five grains of the iodide of potassium in five-grain
doses three times daily.1 It is generally believed, from the
effects upon the child of remedial agents administered to the
mother, that very many articles of this class pass into the
milk, but in such small quantity that they cannot be de-
tected by the ordinary chemical tests.

It is well known that the secretion of milk may be pro-
foundly affected by violent mental emotions. This is the
case with many other secretions, as the saliva, and the gastric
juice. It is hardly necessary, however, to cite the numerous
instances of modification or arrest of the secretion from this
cause, which are quoted in many works. Yernois and Bec-

1 Cyclopaedia, of Anatomy and Physiology, London, 1839-1847, vol. iii.,
p. 362.

86 SECRETION.

querel mention a very striking case, in which a hospital
wet-nurse, who had lost her only child from pneumonia,
b.ecame violently affected with grief, and presented, as a con-
sequence, an immediate diminution in the quantity of her
milk, with a great reduction in the proportion of salts, sugar,
and butter. In this case the proportion of caseine was in-
creased.1 Sir Astley Cooper mentions two cases in which
the secretion of milk was instantaneously and permanently
arrested from terror.3 These cases are types of numerous
others, which have been reported by writers, of the effects
of mental emotions upon secretion.

In the present state of oar knowledge, we can only com-
prehend the influence of mental emotions upon secretion, by
assuming that they operate through the nervous system ; and
in many of the glands, the influence of the nerves has been
clearly demonstrated by actual experiment. Direct observa-
tions, however, upon the influence of the nerves upon the
mammary glands are few and unsatisfactory. The opera-
tion of dividing the nerves distributed to these glands,
which has occasionally been practised upon animals in lac-
tation, has not been observed to produce any sensible dimi-
nution in the quantity of the secretion.3 It is difficult,
however, to operate upon all the nerves distributed to these
organs.

Quantity of Milk. — It is very difficult to form a reliable
estimate of the average quantity of milk secreted by the hu-
man female in the twenty-four hours. The amount undoubt-
edly varies very much in different persons ; some women
being able to nourish two children, while others, though ap-
parently in perfect health, furnish hardly enough food for one.

1 VERNOIS ET BECQUEREL, Du lait cJiez la femme dans Tctat de sante et dans
fetal de maladie, Paris, 1853, p. 73.

2 COOPER, The Anatomy and Diseases of the Breast, Philadelphia, 1845,
p. 101.

3 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 291.

MILK. 87

Cooper, as the result of direct observation, states that the
quantity that can be drawn from a full breast is usually about
two fluidounces.1 This may be assumed to be about the
quantity contained in the lactiferous ducts when they are mod-
erately distended. Lehmann, taking for the basis of his cal-
culations the observations of Lamperierre,2 who found, as
the result of sixty-seven experiments, that from fifty to sixty
grammes of milk were secreted in two hours, estimates that
the average quantity discharged in twenty-four hours is
1,320 grammes, or about 44*5 fluidounces.3 Robin estimates
that the daily quantity is from thirty-four to one hundred
fluidounces ; 4 but he does not give the data from which
this estimate is formed. Taking into consideration the evi-
dent variations in the quantity of milk secreted by different
women, it may be assumed that the daily production is from
two to six pints.

Certain conditions of the female are capable of ma-
terially influencing the quantity of milk secreted. It is
evident that the secretion is usually somewhat increased
within the first few months of lactation, when the progressive
development of the child demands an increase in the quan-
tity of nourishment. If the menstrual function become re-
established during lactation, the milk is usually diminished
in quantity during the periods, but sometimes it is not af-
fected, either in its quantity or composition. Should the
female become pregnant, there is generally a great diminu-
tion in the quantity of milk, and that which is secreted is
ordinarily regarded as possessing little nutritive power. In
obedience to a popular prejudice, apparently well-founded,
the child is usually taken from the breast as soon as preg-
nancy is recognized. All of these conditions have been

1 COOPER, TJie Anatomy and Diseases of the Breast^ Philadelphia, 1845, p. 93.

2 LAMPERIERRE, Des moyens d reconnaitre la quantite et la qualite de la secre-
tion lactee chez la fenime. — Comptes rendus, Paris, 1850, tome xxx., p. 174.

3 LEHMAXX, Physiological Chemistry, Philadelphia, 1855, vol. ii., p. 63.

4 ROBIN, Lecons sur les humeurs, Paris, 1867, p. 402.

88 SECRETION.

closely studied by Yernois and Becquerel, with reference to
their influence upon the composition of the milk ; and their
observations will be fully considered in treating of the chem-
istry of the mammary secretion. Authors have not noted
any marked and constant variations in the quantity of milk
in females of different ages.

Properties and Composition of the Milk.

The general appearance and characters of ordinary cow's
milk are sufficiently familiar and may serve as a standard
for comparison with the milk of the human female.1 Human
milk is not so white nor so opaque as cow's milk, having
ordinarily a slightly bluish tinge. The milk of different
healthy women presents some variation in this regard. After
the secretion has become fully established, the fluid possesses
no viscidity, and is nearly opaque. It is almost inodorous,
of a peculiar soft and sweetish taste, and when perfectly
fresh, has a decidedly alkaline reaction. The taste of hu-
man milk is sweeter than that of cow's milk. A short
time after its discharge from the gland, the reaction of
milk becomes faintly acid ; but this change takes place
more slowly in human milk than in the milk of most of
the inferior animals.

The average specific gravity of human milk, according to
Yernois and Becquerel, is 1032 ; though this is subject to
considerable variation, the minimum of eighty-nine obser-
vations being 1025, and the maximum, 1046.2 The observa-
tions of most physiological chemists have shown that this
average is nearly correct.

Milk is not coagulated by heat, even after prolonged
boiling ; but a thin pellicle then forms on the surface, which
is probably due to the combined action of heat and the at-

1 The properties and composition of cow's milk have already been consid-
ered in another volume. See vol. ii., Alimentation, p. 77, et seq.

2 VERXOIS ET BECQUEREL, Du lait chez lafemme, Paris, 1853, p. 14.

MILK. 89

mosphere upon the caseine. Although a small quantity of
albumen exists in the milk, this does not coagulate on the
surface by the action of heat, for the scum does not form
when the fluid is heated in an atmosphere of carbonic acid,
or of hydrogen, or in a yacuum.1

AVhen the milk is coagulated by any substance acting
upon the caseine, or when it coagulates spontaneously, it
separates into a curd, composed of caseine with most of
the fatty particles, and a nearly clear, greenish-yellow serum,
called whey. This separation occurs spontaneously, at a
yariable time after the discharge of the milk, taking place
much more rapidly in warm than in cold weather. It is a
curious fact that fresh milk is frequently coagulated during
a thunder-storm, a phenomenon which has neyer been sat-
isfactorily explained.

On being allowed to stand for a short time, the milk
separates, without coagulating, into two tolerably distinct
portions, A large proportion of the globules rise to the top,
forming a yellowish- white, and very opaque fluid, called
cream, leaying the lower portion poorer in globules and
of a decidedly bluish tint. In healthy milk the stratum
of cream forms from one-fifth to one-third of the entire
mass of the milk. In the human subject the skim-milk is
not white and opaque, but is nearly as transparent as the
whey. This is a yery good method of testing the richness
of milk; and little graduated glasses, called lactometers,
haye been, constructed for measuring the thickness of the
layer of cream. The specific grayity of the cream from
milk of the ayerage specific gravity of 1032 is about 1024.
The specific gravity of the skim-milk is about 1034.

Microscopical Characters of the Milk. — If a drop of milk
be examined with a magnifying power of from three hun-
dred to six hundred diameters, the cause of its opacity will
be apparent. It contains an immense number of minute

1 ROBIN, Lemons surles humeurs, Paris, 186?, p. 388.

90 SECEETION.

globules, of great refractive power, held in suspension in a
clear fluid. These are known under the name of milk-
globules, and are composed of margarine, oleine, and a fatty
matter, peculiar to milk, called butyrine. In human milk
the particles are perfectly spherical ; but in cow's milk they
are often polyhedric from mutual compression. This differ-
ence is due to the softer consistence of the butter in human
milk, the globules containing a much larger proportion of
oleine ; and if cow's milk be warmed, the particles also as-
sume a spherical form.

The human milk-globules measure from as^o0 to I21go
of an inch in diameter. They are usually distinct from each
other, but may occasionally become collected into groups
without indicating any thing abnormal. In a perfectly nor-
mal condition of the glands, when the lacteal secretion has
become fully established, the milk contains nothing but a
clear fluid with these globules in suspension. The propor-
tion of fatty matter in the milk is from twenty-five to
forty-eight parts per thousand, and this gives an idea of the
proportion of globules which are seen on microscopical ex-
amination.

There has been a great deal of discussiqn with regard to
the anatomical constitution of the milk-globules. In many
late works it is stated that they are true anatomical ele-
ments, composed of fatty matters surrounded by an albumin-
oid membrane; but other writers assume that the fat is
merely in the form of an emulsion, and is simply divided
into globules and held in suspension, like the fatty particles
of the chyle. ~No one, however, has assumed to have seen
the investing membrane of the milk-globules, and its exist-
ence is only inferred from the behavior of these little par-
ticles in the presence of certain reagents.

It is unnecessary to review in detail the numerous opin-
ions that have been advanced on this subject. As far as
can be ascertained by simple examination, even with the
highest magnifying powers., the globules appear perfectly

MILK. 91

homogeneous ; and the burden of proof rests with those who
profess to be able to demonstrate the existence of .an invest-
ing membrane. Robin, one of the highest authorities on
these subjects, argues against the existence of a membrane,
and opposes the observations of those who assume to have
demonstrated it by explanations of the phenomena produced
by reagents, which do not involve, as a necessity, the pres-
ence of such a structure. The arguments in favor of its ex-
istence are not very satisfactory ; and the experiments upon
which they are based relate chiefly to the action of ether upon
the globules before and after the action of other reagents.

If a quantity of milk be shaken up with an equal volume
of ether, the mixture remains opaque ; but if a little potash
be added, the fatty matters are dissolved, and the mixture
then becomes more or less clear. These facts are all that
can be observed without following out the changes with the
microscope. Robin has shown that the fatty particles are
acted upon when the milk is thoroughly agitated with ether
alone ; and that the opacity is then due to the fact that the
ether, with the fat in solution, is itself in the form of an
emulsion. If the opaque mixture of milk and- ether be ex-
amined with the microscope, globules are seen, larger than,
the ordinary milk-globules, much paler, and possessing much
less refractive power. These he supposes to be composed
of fat and ether. If potash be added, either before or after
the addition of ether, the constitution of the whole mass of
liquid is changed, and it becomes somewhat transparent,
though by no means perfectly clear.1 It is assumed that, in
the first instance, the ether does not attack the globules, be-
cause it has no effect upon the membrane which is supposed
to exist, and that the potash acts upon the membrane, allow-
ing the ether then to take up the fat ; but if the observations
of Robin be correct, it is evident that this view cannot be
sustained.

If dilute acetic acid be added to a specimen of milk under

1 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 399, et seq.

92 SECRETION.

the microscope, the globules become deformed, and some of
them show a tendency to run together ; an appearance which
is supposed by Henle, who was the first to study closely the
action of acetic acid upon the milk-globules, to indicate the
existence of a membrane.1 This deduction, however, is not
justifiable. Acetic acid readily coagulates the caseine, a
principle which is most efficient in maintaining the fat in its
peculiar condition. The coagulating caseine then presses
upon the globules, and produces, in this way, all the changes
in form that have been observed.

Most of the other arguments in favor of the existence of
a membrane have no support in direct observation, and con-
sequently do not demand special consideration ; while all the
facts which we have been able to find relating to this sub-
ject go to show that the fatty matters in the milk are in the
condition of a simple emulsion. The precise condition,
however, of the fluid immediately surrounding the globules
is not fully understood. Certain of the constituents of fluids
capable of forming emulsive mixtures with liquid fats may
form a coating of excessive tenuity immediately around
the globules, but they never constitute distinct membranes
^capable of resisting the action of solvents upon the fats ; and,
in the case of the milk, they do not prevent the mechanical
union of the globules into masses, as occurs in the process
of churning.

Milk-globules less than -g-^Vo °f an mcn ^n diameter pre-
sent under the microscope that peculiar oscillating motion
known as the Brownian movement. This is arrested on the
addition of acetic acid, by coagulation of the caseine.

From these facts, it is evident that the milk-globules are
composed simply of fat in the condition of a fine emulsion.
They are not true anatomical elements, originating by a
process of genesis in a blastema, undergoing physiological
decay, and capable of self-regeneration from materials fur-
nished by the menstruum in which they are suspended, like

1 HENLE, Traite d> anatomic generate, Paris, 1843, tome ii., p. 521.

MILK. 93

the blood-corpuscles or leucocytes. They are simply ele-
ments of secretion.

Composition of the Milk. — "We do not propose, in treat-
ing of the composition of the milk, to consider the various
methods of analysis which have been employed by different
chemists. The only constituent that has ever presented
much difficulty in the estimation of its quantity is caseine ;
but the various processes now employed in its extraction
lead to nearly the same results. The following table, com-
piled by Robin from the analyses of various chemists, gives
the constituents of human milk.1

Composition of Human Milk.

Water 902-717 to 863*149

Caseine (desiccated) 29*000 " 39*000

Lacto-proteine 1*000 " 2*770

Albumen traces " 0*880

; Margarine 17*000 " 25*840

Oleine 7*500 " 11*400
Butyrine, Caprine, Caproi'ne, Ca-

priline 0-500 " 0*760

ae, or lactose) 37*000 " 49'000

Lactate of soda (?) 0*420 " 0*450

Chloride of sodium 0*240 " 0*340

Chloride of potassium 1-440 " 1*830

Carbonate of soda 0*053 " 0'056

Carbonate of lime 0'069 " 0*070

Phosphate of lime of the bones 2'310 " 3'440

Phosphate of magnesia 0*420 " 0*640

Phosphate of soda 0*225 " 0*230

Phosphate of iron (?) 0*032 " 0*070

Sulphate of soda 0*074 " 0*075

Sulphate of potassa traces.

1,000*000 1,000*000
f Oxygen 1*29 \

Gases in solution -] Nitrogen 12*17 !• 30 parts per 1,000 in volume.2

( Carbonic acid 16*54 )

1 ROBIN, Le$ons sur les humeurs, Paris, 1867, p. 395. In copying this table,
the arrangement has been somewhat modified, and an evident arithmetical error
has been corrected.

3 HOPPE, Untersuchungen iiber die Bestandtheile der Milch und ihre nachsten

Butter, 25 to 38 «j ]

94: SECRETION.

The proportion of water in milk is subject to a certain
amount of variation, but this is not so considerable as might
be expected from the great variations in the entire quantity
of the secretion. In treating of the quantity of milk in the
twenty-four hours, we have seen that the influence of drinks,
even when nothing but pure water has been taken, is very
marked ; and although the activity of the secretion is much
increased by fluid ingesta, the quality of the milk is not
usually aifected, and the proportion of water to the solid
matters remains about the same.

Nitrogenized Constituents of Milk. — Very little remains
to be said concerning the nitrogenized constituents of human
milk after what has been stated with regard to the compo-
sition of cow's milk, in another volume.1 The different
principles of this class undoubtedly have the same nutritive
function, and appear to be identical in all varieties of milk,
the only difference being in their relative proportion. It is
a matter of common experience, indeed, that the milk of
many of the lower animals will take the place of human
milk, when prepared so as to make the proportions of its
different constituents approximate the composition of the
natural food of the child. A comparison of the composi-
tion of human milk and cow's milk shows that the former
is poorer in nitrogenized matters, and richer in butter and
sugar ; and consequently, the upper strata of cow's milk,
appropriately sweetened and diluted with water, very nearly
represent the ordinary breast-milk.

Caseine is by far the most important of the nitrogenized
principles of milk, and supplies nearly all of this kind of

Zerstzungen. — VIRCHOW'S Archiv, Berlin, 1859, Bd. xvii., S. 439. The observa-
tions of Hoppe were made upon goat's milk, and in the apparatus used, the milk
was drawn directly into the receiver and carefully protected from contact with
the air. Hoppe criticises the observations of Lehmann and Vogel as probably
incorrect, the fluid not being sufficiently protected from the atmosphere, which
gives, according to Hoppe, an excess in the proportion of oxygen.
1 Sec vol. ii., Alimentation, p. 77, et seq.

MILK. 95

nutritive matter demanded by the child. Lacto-proteine,1 a
principle described by Millon and Commaille, is not so well
defined, and albumen exists in the milk in very small quan-
tity. That albumen always exists in milk can readily be
shown by the following process described by Bernard :
If milk, treated with an excess of sulphate of magnesia so as
to form a thin paste, be thrown upon a filter, the caseine
and fatty matters will be retained, and the clear liquid
that passes through shows a marked opacity upon the ap-
plication of heat or the addition of nitric acid.2

The coagulation of milk depends upon the reduction of
the caseine from a liquid to a semisolid condition. ^Vhen
milk is allowed to coagulate spontaneously, or sour, the
change is effected by the action of the lactic acid which re-
sults from a transformation of a portion of the sugar of milk.
Caseine, in fact, is coagulated by any of the acids, even the
feeble acids of organic origin. It differs from albumen in
this regard, and in the fact that it is not coagulated by heat.
It has been suggested that in fresh milk the caseine exists
in combination with carbonate of soda, and that coagulation
always takes place from the action of acids upon this salt,
by which the caseine is set free. It is true that coagulated
caseine may be readily dissolved in a solution of carbonate
of soda, but it has been shown by the experiments of Selmi,
that coagulation may be induced by the agency of certain
neutral principles, while the milk retains its alkaline reac-
tion. If fresh milk be slightly raised in temperature, and
be treated with an infusion of the gastric mucous membrane
of the calf, coagulation will take place in from five to ten
minutes, the clear liquid still retaining its alkaline reaction.8
This observation has been repeatedly confirmed. Simon

1 MILLOX ET COMMAILLE, Nouvdle substance albumio'ide contenue dans le lait. —
Cornptes rcndus, Paris, 1864, tome lix., p. 301.

2 BERNARD, Liquides de rorganisme, Paris, 1859, tome ii., p. 224.

3 SELMI, RecJierches sur faction de la prtsure dans la coagulation du lait, —
Journal de pharmacie et de chimie, Paris, 1846, 3me serie, tome ix., p. 265.

96 SECRETION.

has also found that the mucous membrane of .the stomach
of an infant a few days old, that had recently died, coagu-
lated woman's milk more readily than the mucous membrane
of the stomach of the calf.1

Non-Nitrogenized Constituents of Milk. — Non-nitro-
genized matters exist in abundance in the milk. The
liquid caseine and the water hold the fats, as we have
seen, in the condition of a fine and permanent emulsion.
This fat has been separated from the milk and analyzed by
chemists, and is known under the name of butter. In
human milk, the butter is much softer than in the milk of
many of the inferior animals, particularly the cow ; but it is
composed of essentially the same constituents, though in
different proportions. In different animals there are de-
veloped, even after the discharge of the milk, certain odor-
ous principles, more or less characteristic of the animal
from which the butter is taken.

The greatest part of the butter consists of margarine.
It contains, in addition, oleine, with a small quantity of
peculiar fats, not very well determined, called butyrine,
caprine, caproine, and capriline. The margarine and
oleine are principles found in the fat throughout the body ;
but the last-named substances are peculiar to the milk.
These are especially liable to acidification, and the acids
resulting from their decomposition give the peculiar odor
and flavor to rancid butter.3 Bromeis estimated the differ-
ent constituents of the butter from cow's milk, and found it
to contain sixty-eight parts of margarine, thirty parts of
oleine, and two parts of butyrine, capronine, and caprine.3

1 SIMON, Animal Chemistry with Reference to the Physiology and Pathology of
Han, Philadelphia, 1846, p. 333.

2 Butyrine was discovered, and the changes which it is liable to undergo
were first described by Chevreul. (Faite pour servir d Vhistoire du beurre de
vache. Extraits d'un memoire lu d VAcademie des Sciences, le 14 juin, 1819.
— Annales de chimie et de physique, Paris, 1823, tome xxii., p. 373.)

8 BROMEIS, Ueber die in der Butter enthaltenen Fette und fetten Sauren. — An~

HULK. 97

Sugar of milk, sometimes called lactine, or lactose, is the
most abundant of the solid constituents of the mammary
secretion. It is this principle that gives to the milk its
peculiar sweetish taste, though this variety of sugar is much
less sweet than cane-sugar. The chief peculiarities of milk-
sugar are, that it readily undergoes change into lactic acid
in the presence of nitrogenized ferments, and takes on .alco-
holic fermentation slowly and with difficulty. At one time,
indeed, it was supposed that milk-sugar could not be decom-
posed into alcohol and carbonic acid; but it is now well
established that this change can be induced, the only pecu-
liarity being that it takes place very slowly. In some parts
of the world, intoxicating drinks are made by the alcoholic
fermentation of milk. Milk-sugar is composed of CiaHwOia
and responds to the ordinary tests for the animal varieties
of sugar.

A consideration of the nutritive action of the fatty and
saccharine constituents of milk belongs properly to the sub-
jects of alimentation and nutrition. It may be stated here,
however, that these principles seem to be as necessary to the
nutrition of the child as the nitrogenized principles ; though
the precise manner in which they affect the development
and regeneration of the tissues has not been ascertained.

Inorganic Constituents of Milk. — It is probable that
many inorganic principles exist in the milk which are not
given in the table ; and the separation of these principles
from their combinations with organic matters is one of the
most difficult problems in physiological chemistry. This
must be the case, for during the first months of extra-uterine

nalen der Chemie und Pharmatie, Heidelberg, 1842, B. xlii., S. 70. The above
is an approximative estimate of the proportions of the various fatty constituents
of butter, deduced from the quantities of fatty acids 'obtained. Bromeis, like
many chemists of that day, supposed that the neutral fats were composed of
the fatty acids combined with glycerine, or the oxide of glycile. It is now gen-
erally admitted that the fatty acids and glycerine are formed by actual decom-
position, and do not exist in combination in the neutral fats.
V

98 SECEETION.

existence, the child derives all the inorganic, as well as the
organic matters necessary to nutrition and development,
from the breast of the mother. The reaction of the milk
depends upon the presence of the alkaline carbonates, and
these principles are important in preserving the fluidity of
the caseine. It is not determined precisely in what form
iron exists in the milk, but its presence here is undoubted.
A comparison of the composition of the milk with that
of the blood will show that most of the important in-
organic principles found in the latter fluid exist also in
the milk.

Hoppe has indicated the presence of carbonic acid, nitro-
gen, and oxygen, in solution, in milk.1 Of these gases, car-
bonic acid is the most abundant. It is well known that the
presence of gases in solution in liquids renders them more
agreeable to the taste, and carbonic acid increases very ma-
terially their solvent properties. Aside from these considera-
tions, the precise function of the gaseous constituents of the
milk is not apparent.

A study of the composition of the milk fully confirms
the fact, which we have already had occasion to state, that
this is a typical alimentary fluid, and presents in itself the
proper proportion and variety of material for the nourish-
ment of the body during the period when the development
of the system is going on with its maximum of activity.
The form in which its different nutritive constituents exist
is such that they are easily digested and are assimilated
with great rapidity.

Variations in the Composition of the Milk.

The most elaborate researches concerning the variations
in the composition of the milk are those of Yernois and
Becquerel. Their observations relate to the composition
of milk both in health and disease ; but we shall consider

1 Loc. dt.

MILK. 99

only the differences this fluid has been found to present under
varying normal conditions. Yernois and Becquerel have in-
dicated a certain amount of variation at different ages and at
different periods in lactation, but they show, at the same time,
that the fluid is not subject to changes in its composition suf-
ficiently great to influence materially the nutrition of the
child. *

If the composition of the milk be compared at different
periods of lactation, it will be found to undergo great
changes during the first few days. In fact, the first fluid
secreted after parturition is so different from other milk,
that it has been called by another name. It is then known
as colostrum, the peculiar properties of which will be con-
sidered more fully hereafter under a distinct head. As the
secretion of milk becomes established, the fluid, from the
first to the fifteenth day, becomes gradually diminished in
density and in its proportion of water and of sugar, while
there is a progressive increase in the proportion of most of
the other constituents ; viz., butter, caseine, and the inor-
ganic salts.1 The milk, therefore, as far as we can judge
from its composition, as it increases in quantity during the
first few days of lactation, is constantly increasing in its
nutritive properties.

The differences in the composition of the milk, taken
from month to month during the entire period of lactation,
are not so distinctly marked. It is difficult, indeed, to
indicate any constant variations of sufficient importance to
lead to the view that the milk varies much in its nutritive
properties at different times, within the ordinary period of
lactation.

If we except the first few months, the secretion is not
found to present any constant variations in density. Yernois
and Becquerel found a notable increase in the proportion of
solid matters from the first to the third month ; the sugar
was increased from the eighth to the tenth month ; the ca-

1 YERNOIS ET BECQUEREL, Du lait ckez lafemme, Paris, 1853, p. 24.

100 SECRETION.

seine was increased from the first day to the second month,
inclusive, and diminished from the tenth to the twenty-
fourth month ; there was a constant and considerable increase
in the proportion of butter, from the first day to the fifth
month, and a diminution from the fifth to the sixth, and
from the tenth to the eleventh month ; there was a slight,
feeble, but almost constant and progressive increase in the
proportion of salts from the first day to the fifth month, and
a diminution at all other periods.1

The differences noted between the milk of primiparse
and multiparse were very slight and not very important. As
a rule, however, the milk of primiparae approached more
nearly the normal standard.

The menstrual periods, when they occur during lactation,
have been found by most observers to modify considerably
the composition and properties of the milk ; and it is well
known to practical physicians that the secretion is then liable
to produce serious disturbances of the digestive system of
the child, though frequently these effects are not observed.
The changes in the composition of the milk which com-
monly occur during menstruation are, great increase in the
quantity of caseine, increase in the proportion of butter and
the inorganic salts, and a slight diminution in the propor-
tion of sugar. The common impression that the milk is
unfit for the nourishment of the child if pregnancy occur
during lactation is undoubtedly well-founded, though analy-
ses of the milk of pregnant women have never been made
on an extended scale. Yernois and Becquerel made but
one examination of this kind, at the third month of gesta-
tion, and found a great increase in the proportion of butter,
slight increase in sugar and the inorganic salts, and a slight
diminution in the proportion of caseine.2

The question is frequently discussed by physiological
writers, whether the milk of fair women is different from
that of brunettes. There are hardly sufficient data, however,

1 Op. tit., p. 31. 2 Op. tit., p. 38.

MILK. 101

to form a definite opinion upon this subject. The analyses of
L'Heritier,1 and Yernois and Becquerel,8 indicate a greater
proportion of most of the solid matters in the milk of
brunettes, with a very slight difference in the proportion of
butter in favor of blondes. Almost all authorities who have
expressed an opinion upon this question give the preference
to the milk of brunettes. Donne, however, expresses him-
self very decidedly against the popular prejudice in favor of
brunettes as nurses. " As regards the color of the skin and
the hair, the results at which I have arrived in nowise jus-
tify the generally-received popular prejudice in favor of
brunettes ; in more than four hundred nurses, I found no
sensible difference in favor of brunettes over blonde women
or over those with chestnut hair; but of nine red-haired
women, five only presented the proper qualities."' It
would be interesting in this connection to determine wheth-
er there be any marked difference in the milk of the black
and the white race, particularly as it has long been the cus-
tom in some parts of the United States to permit white
children to be nursed by black women. Infants that are
nourished in this way apparently thrive as well as those
nursed by white women; and there is no reason to sup-
pose that there is any difference in the milk of the two
races. Sir Astley Cooper mentions some interesting facts
concerning the black women of the West Indies, communi-
cated to him by his nephew, Dr. Young, which show that

1 L'HERITIER, TraitS de chimie pathologique, Paris, 1842, p. 638; YERXOIS ET
BECQUEREL, op. cit., p. 52.

2 L'Heritier was the first to compare critically the milk of blondes with that
of brunettes. In two women, twenty-two years of age, and subjected to the same
regimen, the milk of the brunette contained much more caserne, butter, sugar,
and salts, than the milk of the blonde ; but these two instances presented the ex-
tremes of difference ; and as the mean of all his observations, it was found that
the difference was comparatively slight. Yernois and Becquerel arrived at es-
sentially the same results, except that the proportion of butter was a little
greater in the milk of fair women.

3 DOXXE, Cours de microscopic, Paris, 1844, p. 409.

102 SECRETION.

there is probably no difference between the milk of the
blacks and of Europeans.1

In normal lactation, there is no marked and constant dif-
ference in the composition of milk that has been secreted in
great abundance, and milk which is produced in compara-
tively small quantity ; nor do we observe that difference be-
tween the milk first drawn from the breast and that taken
when the ducts are nearly empty, which is observed in the
milk of the cow.2

The influence of alimentation and the taking of liquids
upon lactation relate chiefly to the quantity of milk, and have
already been considered.8

In treating of the influences which modify the secretion
of milk, we have already alluded to the effects of violent
mental emotions upon the production and the composition of
this fluid. The very remarkable case of profound alteration
of the milk by violent grief, detailed by Yernois and Bec-
querel, is the only one in which the secretion in this condi-
tion has been carefully analyzed. The changes thus pro-
duced in its composition have already been referred to,4 the
most marked difference being observed in the proportion of
butter, which became reduced from 23*79 to 5*14 parts per
1,000.

Colostrum.

Near the end of utero-gestation, during a period which
varies considerably in different women and has not been ac-
curately determined, a small quantity of a thickish, stringy
fluid may frequently be drawn from the mammary glands.
This bears little resemblance to perfectly-formed milk. It
is small in quantity, and is usually more abundant in multi-
part than in primiparae. This fluid, with that secreted for

1 COOPER, The Anatomy and Diseases of the Breast, Philadelphia, 1845, p.
103, et seq.

2 See vol. ii., Alimentation, p. 79.

3 See page 83. 4 See page 86.

COLOSTRUM. 103

the first few days after delivery, is called colostrum. It is
yellowish, semiopaque, of a distinctly alkaline reaction, and
somewhat mucilaginous in its consistence. Its specific gravi-
ty is considerably above that of the ordinary milk, being from
1040 to 1060. As lactation progresses, the character of the
secretion rapidly changes, until it becomes loaded with true
milk-globules and assumes the characters of ordinary milk.

The opacity of the colostrum is due to the presence 'of a
number of different corpuscular elements. Milk-globules, very
variable in size and number, are to be found in the secretion
from the first. These, however, do not exist in sufficient
quantity to render the fluid very opaque, and they are
frequently aggregated in rounded and irregular masses,
held together, apparently, by some glutinous matter. Pecu-
liar corpuscles, first accurately described by Donne, un-
der the name of " granular bodies," and supposed to be
characteristic of the colostrum, always exist in this fluid.1
These are now known as colostrum-corpuscles. They are
spherical, varying in size from 2^Qd to -g-^j- of an inch, are
sometimes pale, but more frequently quite granular, and
contain very often a large number of fatty particles. They
behave in all respects like leucocytes, and are described by
Eobin as a variety of these bodies.3 Many of them are pre-
cisely like the leucocytes found in the blood, lymph, or pus.
Their appearance was very well described by Donne, who
supposed that they were mucus-corpuscles.3 We now know,
however, that the so-called mucus-corpuscle does not differ
from the pus-corpuscle or the white corpuscle of the blood ;
and leucocytes generally, when confined in liquids that are
not subject to movements, are apt to undergo enlargement,
to become fatty, and, in short, present all the different ap-
pearances observed in the colostrum-corpuscles. In addition

1 DONNE, Cours de microscopic, Paris, 1844, p. 400.

2 ROBIN, Sur quelques points de ranatomie et de la physiologic deft leucocytes.—
Journal de la physiologic, Paris, 1859, tome ii., p. 56.

8 DONNE, loc. dt.

104 SECRETION.

to these corpuscular elements, a small quantity of mucosine
may frequently be observed in the colostrum, on microscopi-
cal examination.

On the addition of ether to a specimen of colostrum
under the microscope, most of the fatty particles, both within
and without the colostrum-corpuscles, are dissolved. Am-
monia added to the fluid renders it stringy, and sometimes the
entire mass assumes a gelatinous consistence.

In its proximate composition, the colostrum presents
many points of difference from true milk. It is sweeter to
the taste, and contains a greater proportion of sugar and of
the inorganic salts. The proportion of fat is at least equal
to the proportion in the milk, and is generally greater. In-
stead of caseine, the pure colostrum contains a large propor-
tion of albumen; and as the character of the secretion
changes in the process of lactation, the albumen becomes
gradually reduced in quantity and caseine takes its place.

Without referring in detail to the numerous analyses of
colostrum in the human subject and in the inferior animals,
by Simon, Lassaigne, and others, the following, deduced
from the analyses of Clemm, may be taken as the ordinary
composition of this fluid in the human female :

Composition of the Colostrum.1

Water 945'24 to 851-97

Albumen 29*81 " 80'73

Butter 7-07" 41'30

Sugarofmilk 17'27 " 43*69

Chloride of sodium 0'51 "j

Chloride of potassium 1'25

Phosphates and sulphates of potassa, of lime, > 4*41 " 5*44

and of magnesia 2-96

Phosphate of iron O'Ol J

Colostrum ordinarily decomposes much more readily than
milk, and takes on putrefactive changes very rapidly. If it be
allowed to stand for from twelve to twenty-four hours, it sep-

1 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 409.

COLOSTRUM. 105

arates into a thick, opaque, yellowish cream and a serous
fluid. In an observation by Sir Astley Cooper, nine meas-
ures of colostrum, taken soon after parturition, after twenty-
four hours of repose, gave six parts of cream to three of
milk.1

The peculiar constitution of the colostrum, particularly
the presence of an excess of sugar and inorganic salts,
renders it somewhat laxative in its effects, and it is supposed
to be useful, during the first few days after delivery, in as-
sisting to relieve the infant of the accumulation of meconium-

As the quantity of colostrum that may be pressed from
the mammary glands during the latter periods of utero-
gestation, particularly the last month, is very variable, it
becomes an interesting and important question to determine
whether this secretion have any relation to* the quantity of
milk that may be expected after delivery. This has been
made the subject of careful study by Donne, who arrived at
the following important conclusions :

In women in whom the secretion of colostrum is almost
absent, the fluid being in exceedingly small quantity, viscid,
and containing hardly any corpuscular elements, there is
hardly any milk produced after delivery.

In women who, before delivery, present a moderate quan-
tity of colostrum, containing very few milk-globules and a
number of colostrum-corpuscles, after delivery the milk will
be scanty or it may be abundant, but it is always of poor
quality.

But when the quantity of colostrum produced is con-
siderable, the secretion being quite fluid and rich in corpus-
cular elements, particularly milk-globules, the milk after
delivery is always abundant and of good quality.3

From these observations it would seem that the produc-
tion of colostrum is an indication of the proper development
of the mammary glands ; and the early production of fatty

1 COOPER, The Anatomy and Diseases of the Breast, Philadelphia, 1845, p. 85.
0 DONNE, op. cit., p. 407, et seq.

106 SECRETION.

granules, which are first formed by the cells lining the se-
creting vesicles, indicates the probable activity in the secre-
tion of milk after lactation has become fully established.

The secretion of the mammary glands preserves the char-
acters of colostrum until toward the end of the milk-fever,
when the colostrum-corpuscles rapidly disappear, and the
milk-globules become more numerous, regular, and uniform
in size. It may be stated in general terms that the secretion
of milk becomes fully established and all the characters of
the colostrum disappear from the eighth to the tenth
day after delivery. A few colostrum-corpuscles and masses
of agglutinated milk-globules may sometimes be discovered
after the tenth day, but they are very rare ; and after the fif-
teenth day the milk does not sensibly change in its micro-
scopical or its chpmical characters.

Lacteal Secretion in the Newly-Born.

It is a curious fact that in infants of both sexes there is
generally a certain amount of secretion from the mammary
glands, commencing at birth, or from two to three days after,
and continuing sometimes for two or three weeks. The
quantity of fluid that may be pressed out at the nipples at
this time is very variable. Sometimes only a few drops
can be obtained, but occasionally the fluid amounts to one
or two drachms. Although it is impossible to indicate the
object of this secretion, which takes place when the glands
are in a rudimentary condition, it has been so often observed
and described by physiologists that there can be no doubt
with regard to the nature of the fluid, and the fact that the
secretion is almost always produced in greater or less quan-
tity.

The latest researches upon this subject are those of Gub-
ler and Quevenne, who have given a tolerably complete
analysis of the fluid. The fact of the almost constant oc-
currence of the secretion was fully established, in 1853, by

MILK OF THE IXFANT. 107

Guillot.1 The following is an analysis by Quevenne of the
secretion obtained by Gubler. The observations of Gubler
were very extended, and were made upon about twelve hun-
dred children. The secretion rarely continued more than
four weeks, but in four instances it persisted for two months."

Composition of the Mttk of the Infant.

Water 894'00

Caseine 26'40

Sugar of milk 62*20

Butter 14*00

Earthy phosphates 1-20

Soluble salts (with a small quantity of insoluble phosphates) . 2*20

1,000-00

This fluid does not differ much in its composition from
ordinary milk. The proportion of butter is much less, but
the amount of sugar is greater, and the quantity of caseine
is nearly the same.

Of the other fluids which are enumerated in the list
of secretions, the saliva, gastric juice, pancreatic juice, and
the intestinal fluids have already been considered in connec-
tion with digestion.3 The physiology of the lachrymal se-
cretion will be taken up in connection with the eye, and the
bile will be treated of fully under the head of excretion.

1 GUILLOT, De la secretion du lait chez leg enfants nouveau-nes, et dts accidents
qui peuvent faccompagner. — Archives generales, Paris, 1853, ome serie, tome iL,
p. 513, et seq.

• GUBLER, Jfemoire sur la secretion et la composition du lait chez les enfants
nouveau-nes des deux sexes. — Comptes rendus et memoires de la Societe de Biologie,
annee, 1855, Paris, 1856, p. 289.

3 See vol. ii., Digestion.

CHAPTER IY.

EXCRETION ACTION OF THE SKIN.

IN entering upon the study of the elimination of effete
matters, it is necessary to appreciate fully the broad distinc-
tions between the secretions proper and the excretions, in
their composition, the mechanism of their production, and
their destination. These considerations are again referred
to,1 for the reason that they have not ordinarily received
that attention in works upon physiology which their impor-
tance demands. The mechanism of excretion is insepara-
bly connected with the function of nutrition, and forms one
of the great starting-points in the study of all the modifica-
tions of nutrition in diseased conditions.

Taking the urine as the type of the excrementitious
fluids, it is found to contain none of those principles included
in the class of non-crystallizable, organic nitrogenized mat-
ters, but is composed entirely of crystallizable matters simply

1 See chapter I. on " Secretion in General."

GENERAL CONSIDERATIONS. 109

held in solution in water. The character of these principles
depends upon the constitution of the blood and the general
condition of nutrition, and not upon any formative action in
the glands. The principles themselves represent the ulti-
mate physiological changes of certain constituent parts of
the living organism, and are in such a condition that they
are of no further use in the economy and are simply dis-
charged from the body. Certain inorganic matters are
found in the excrementitious fluids, are discharged with
the products of excretion, and are thus associated with the
organic principles of the economy in their physiological de-
struction, as well as in their deposition in the tissues. Co-
agulable organic matters, such as albumen or fibrin, never
exist in the excrementitious fluids under normal conditions ;
except as the products of other glands may become acciden-
tally or constantly mixed with the excrementitious fluids
proper. The same remark applies to the non-nitrogenized
matters (sugars and fats), which, whether formed in the
organism or taken as food, are consumed as such in the pro-
cess of nutrition. The production of the excretions is con-
stant, being subject only to certain modifications in activity,
dependent upon varying conditions of the system. All of
the elements of excretion preexist in the blood, either in the
precise condition in which they are discharged, or in some
slightly modified form.

Under the head of excretion, it is proposed to consider
the general properties and composition of the different ex-
crementitious fluids ; but the relations of the excrementitious
matters themselves to the tissues will be more fully treated
of in connection with nutrition.

The urine is a purely excrementitious fluid. The perspi-
ration and the secretion of the axillary glands are excre-
mentitious fluids, but contain a certain amount of the secre-
tion of the sebaceous glands. Certain excrementitious
matters are found in the bile, but at the same time, this
fluid contains principles manufactured in the liver, and has

1 10 EXCRETION.

an important function as a secretion, in connection with the
process of digestion.

Physiological Anatomy of the Skin.

The skin is one of the most complex and important
structures in the body, and possesses a variety of functions.
In the first place it forms a protective covering for the gen-
eral surface. It is quite thick over the parts most subject to
pressure and friction, is elastic over movable parts and those
liable to variations in size, and in many situations is covered
with hair, which affords an additional protection to the sub-
jacent structures. The skin and its appendages are bad
conductors of caloric, are capable of resisting very consider-
able variations in temperature, and thus tend to maintain
the normal standard of the animal heat. As an organ of
tactile sensibility, the skin has an important function, being
abundantly supplied with sensitive nerves, some of which
present an arrangement peculiarly adapted to the nice ap-
preciation of external impressions. The skin assists in pre-
serving the external forms of the muscles ; it relieves the
abrupt projections and depressions of the general surface, and
gives roundness and grace to the contours of the body. In
some parts it is very closely attached to the subjacent struc-
tures, while in others it is less adherent, and is provided with
a layer of adipose tissue.

As an organ of excretion, the skin is very important ; and
although the quantity of excrementitious matter exhaled from
it is not very great, and probably not subject to much varia-
tion, the evaporation of water from the general surface is
always considerable, and is subject to such modifications as
may become necessary from the varied conditions of the ani-
mal temperature. Thus, while the skin protects the body
from external influences, its function is important in regu-
lating the heat produced as one of the numerous phenomena
attendant upon the general process of nutrition.

ANATOMY OF THE SKIN. Ill

As the skin presents such a variety of functions, its
physiological anatomy is most conveniently considered in
connection with different divisions of the subject of physi-
ology. For example, under the head of secretion, we have
already taken up the structure of the different varieties of
sebaceous glands. The anatomy of the skin as an organ of
touch will be most appropriately considered in connection
with the nervous system. In this connection we will describe
the excreting organs found in the skin ; and here it will be
most convenient to study briefly its general structure and the
most important points in the anatomy of the epidermic ap-
pendages. A full and connected description of the skin and
its appendages belongs properly to works upon anatomy.

General Appearance of the Skin. — It is unnecessary to
discuss very minutely the general appearance of the skin.
Its color is sufficiently familiar. The tissue of the true skin
is whitish and semitransparent, so that the color of the sub-
jacent parts gives to it a peculiar tint. The blood contained
in its vessels, as is well known, is capable of modifying
greatly the color of the general surface. The deep layer of
the epidermis always contains more or less pigmentary mat-
ter, which gives the colors characteristic of different races,
and produces the variations in complexion that are observed
in different individuals of the same race. The pigment, in
the white races, is but slightly developed at birth, but in-
creases in quantity with age.

The general surface, with the exception of the palms of
the hands and the soles of the feet, is covered with hairs,
which are very largely developed in certain situations. The
furrows and folds of the skin are produced either by the con-
traction of the subjacent muscles ; by a loss of elasticity in
the skin, as in old age ; by an excessive development of fat
in certain parts ; or by the movements of the joints. Faint,
irregular lines are observed on the surface in most parts j but
upon the palms of the hands and the soles of the feet these

112 EXCRETION.

are well marked and regular, particularly upon the palmar
surfaces of the last phalanges, where they are in the form
of concentric curves, so easily observed with the naked eye
that further description is unnecessary. These lines are
formed by the more or less regular arrangement of the papil-
lae of the true skin.

Extent and Thickness of the Skin. — Sappey has made a
number of very careful observations upon the extent of the
surface of the skin. Without detailing the measurements
of different parts, it may be stated, as the general result of
his observations, that the cutaneous surface in a good-sized
man is equal to about twelve square feet ; and in men of
more than ordinary size it may extend to fourteen, fifteen,
or even eighteen square feet. In men of medium size, in
France, the surface does not exceed ten square feet ; and in
women, it is ordinarily from six to eight.1 When we con-
sider the great extent of the cutaneous surface, it is not sur-
prising that the amount of secretion, under certain conditions,
should be enormous. Indeed, under all circumstances, the
amount of elimination is very considerable, and the skin is
really one of the most important of the glandular structures.

The thickness of the skin varies very much in different
parts. Where it is naturally exposed to constant pressure
and friction, as on the soles of the feet or the palms of the
hands, the epidermis becomes very much thickened, and in
this way the more delicate structure of the true skin is pro-
tected. It is well known that the development of the epi-
dermis, under these conditions, varies in different persons,
with the amount of pressure and friction to which the sur-
face is habitually subjected. The true skin is from -^ to $
of an inch in thickness ; but in certain parts, particularly the
external auditory meatus, the lips, and the glans penis, it
frequently measures not more than y^- of an inch.2

1 SAPPEY, Traite d' anatomic descriptive, Paris, 1852, tome ii., p. 447.

2 POUCHET, Precis d'histologie humaine, Paris, 1864, p. 329.

ANATOMY OF THE SKIN. 113

Layers of the Skin. — The skin is naturally divided into
two principal layers, which may be readily separated from
each other by maceration. These are, the true skin (cutis
vera, derma, or corium), and the epidermis, cuticle, or scarf-
skin. The true skin is attached to the subjacent structures,
more or less closely, by a fibrous structure called the sub-
cutaneous areolar tissue, in the meshes of which we com-
monly find a certain quantity of fatty tissue. This layer
is sometimes described under the name of the panniculus-
adiposus. The thickness of the adipose layer varies very
much in different parts of the general surface and in differ-
ent persons. There is no fat beneath the skin of the eyelids,
the upper and outer part of the ear, the penis, and the scro-
tum. Beneath the skin of the cranium, the nose, the neck,
and the dorsum of the hand and foot, the knee and the elbow,
the fatty layer is about -£% of an inch in thickness. In other
parts it usually measures from ^ to ^ of an inch.1 In very
fat persons it may measure one inch or more. Upon the
head and the neck, in the human subject, are muscles at-
tached more or less closely to the skin. These are capable
of moving the skin to a slight extent. Muscles of this kind
are largely developed and quite extensively distributed in
some of the lower animals.

There is no sharply-defined line of demarcation between
the cutis and the subcutaneous areolar tissue ; and the under
surface of the skin is always irregular, from the presence of
numerous fibres which are necessarily divided in detaching
it from the subjacent structures. The fibres which enter into
the composition of the skin near its under surface become
looser in their arrangement, the change taking place rather
abruptly, until they present large alveolae, which generally
contain a certain amount of adipose tissue.

The layer called the true skin is subdivided into a deep,
reticulated, or fibrous layer, and a superficial portion, called

1 KRAUSE, in WAGNER'S Handucdrterbuch der Physiologic, Braunschweig, 1844,
Bd. ii., S. 116.

.114 EXCRETION.

the papillary layer. The epidermis is also divided into two
layers ; an external layer, called the horny layer ; and an in-
ternal layer, called the Malpighian, or the mucous layer,
which is in contact with the papillary layer of the corium.

The Cerium, or True Skin. — The reticulated and the
papillary layer of the true skin are quite distinct. The
lower stratum, the reticulated, is much thicker than the
papillary layer, is dense, resisting, quite elastic, and slightly
contractile. It is composed of numerous bundles of white
fibrous tissue interlacing with each other in every direction,
generally at acute angles. Distributed throughout this layer
are found numerous anastomosing elastic fibres of the small
variety, and with them a number of non-striated muscular
fibres. This portion of the skin contains, in addition, a con-
siderable quantity of amorphous matter which serves to hold
the fibres together. The muscular fibres are particularly
abundant about the hair-follicles and the sebaceous glands
connected with them, and their arrangement is such, that
when they are excited to contraction by cold or by electrici-
ty, the follicles are drawn up, projecting upon the general
surface, and producing the appearance known as " goose-
flesh." Contraction of these fibres is particularly marked
about the nipple, producing the so-called erection of this
organ, and about the scrotum and penis, wrinkling the
skin of these parts. The peculiar arrangement of the little
muscles around the hair-follicles, forming little bands at-
tached to the surface of the true skin and the base of the
follicles, was first described by Kolliker,1 and explains fully
the manner in which the " goose-flesh " is produced. Con-
traction of the skin, in obedience to the stimulus of electrici-
ty, has been demonstrated by Froriep, Brown-Sequard, and
Kolliker, both in the living subject and in executed criminals
immediately after death.3

1 KOLLIKER, Handbuch der Gewebelelire des Memclien, Leipzig, 1867, S. 98.
8 KOLLIKER, Manual of Human Microscopic Anatomy, London, 1860, p. 86.

-ANATOMY OF THE SKIN. 115

The papillary layer of the skin passes insensibly into
the subjacent structure and presents no well-marked line
of division. It is composed chiefly of the same kind of
amorphous matter that exists in the reticulated layer.
The papillae themselves appear to be simply elevations
of this amorphous matter, though they may contain a few
fibres. In this layer we find a number of fibro-plastic
nuclei with a few little corpuscular bodies called by Kobin,
cytoblastions.1

As regards their form, the papillae may be divided into
two varieties ; the simple and the compound. The simple
papillae are conical, rounded, or club-shaped elevations of the
amorphous matter, and are irregularly distributed on the
general surface. The smallest are from -^ to ^^j- of an
inch in length, and are found chiefly upon the face. The
largest are on the palms of the hands, the soles of the feet,
and the nipple. These measure from -^j- to -^-5- of an inch.
Large papillae, regularly arranged in a longitudinal direction,
are found beneath the nails. The regular, curved lines
observed upon the palms of the hands and the soles of the
feet, particularly the palmar surfaces of the last phalanges,
are formed by double rows of compound papillae, which pre-
sent two, three, or four points attached to a single base. In
the centre of each of these double rows of papillae is an ex-
cessively fine and shallow groove, in which are found the ori-
fices of the sudoriferous ducts.

The papillae are abundantly supplied with blood-vessels,
terminating in looped capillary plexuses, and nerves. The
termination of the nerves is peculiar, and will be fully de-
scribed in connection with the organs of touch. The ar-
rangement of the lymphatics, which are very numerous in
the skin, has already been indicated in the general descrip-
tion of the lymphatic system.3

1 LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1865, Article, Cyto-
blastion.

8 See vol. ii., Absorption, p. 430.

116 EXCRETION.

The Epidermis and its Appendages. — The epidermis,
or external layer of the skin, is a membrane composed ex-
clusively of cells, containing neither blood-vessels, nerves,
nor lymphatics. Its external surface is marked by exceed-
ingly shallow grooves, which correspond to the deep furrows
between the papillae of the derma. Its internal surface is
applied directly to the papillary layer of the true skin, and
follows closely all its inequalities. This portion of the skin
is subdivided into two tolerably distinct layers. The in-
ternal layer is called the rete mucosum, or the Malpighian
layer, and the external is called the horny layer. . These
two layers present certain important distinctive characters.

The Malpighian layer is composed of a single stratum
of prismoidal, nucleated cells, containing a greater or less
amount of pigmentary matter, applied directly to all the
inequalities of the derma, and a number of layers of rounded
cells containing no pigment. The tipper layers of cells,
with the scales of the horny layer, are semitransparent and
nearly colorless ; and it is the pigmentary layer chiefly which
gives to the skin its characteristic color and the peculiarities
in the complexion of different races and of different individu-
als. In the negro, this layer is nearly black ; and when the epi-
dermis is removed, the true skin does not present any marked
difference from the skin of the white race. All the epider-
mic cells are somewhat colored in the dark races, but the
upper layers contain no pigmentary granules. The cells
of the pigmentary layer are *from 4 Q\ 6 to 3^0 of an
inch in length, and from go1o0 to 4^d of an inch in their
short diameter. The rounded cells in the upper layers are
from 40100 to -g-oVu" of an inch in diameter. The absolute
thickness of the rete mucosum is from 171OC) to -£$ of an inch.

The horny layer is composed of numerous strata of hard,
flattened cells, irregularly polygonal in shape, generally with-
out nuclei, and measuring from -g-gVs- to ^^ of an inch in
diameter. The deeper cells are thicker and more rounded
than those of the superficial layers.

NAILS AXD HAIR. 117

The epidermis serves as a protection to the more delicate
structure of the true skin, and its thickness is proportionate
to the exposure of the different parts. It is consequently
much thicker upon the soles of the feet and the palms of the
hands than in other portions of the general surface, and its
thickness is very much increased in those who are habitually
engaged in severe manual labor. Upon the face, the eyelids,
and in the external auditory passages, the epidermis is' most
delicate, measuring from -^J-g- to -^-J-^ of an inch in thickness.
Upon the palm it is from -^ to -^ of an inch thick, and upon
the sole of the foot it measures from -^ to -J of an inch.1
These variations depend entirely upon the development of the
horny layer. The thickness of the rete mucosum, although
it presents considerable variation in different parts, is rather
more uniform.

There is constantly more or less desquamation of the epi-
dermis, particularly the horny layer, and the cells are regen-
erated by a blastema exuded from the subjacent vascular
parts. It is probable that there is a constant formation of
cells in the deeper strata of the horny layer, which become
flattened as they near the surface ; but there is no direct
evidence that the cells of the rete mucosum undergo trans-
formation into the hard, flattened scales of the horny layer.

Physiological Anatomy and Uses of ike Nails and
Sairs. — It is unnecessary, in this connection, to discuss very
minutely the anatomy of the nails and hairs. They are or-
dinarily regarded as appendages of the epidermis, produced
by certain peculiar organs belonging to the true skin ; and
an elaborate study of these parts belongs strictly to descrip-
tive and general anatomy. To complete, however, the
physiological history of the skin, it will be necessary to

1 KOLLIKER, Manual of Human Microscopical Anatomy, American Edition,
Philadelphia, 1854, p. 146. Kolliker gives (he. cit.) accurate measurements of
the epidermis in many different portions of the skin, to -which the reader is re-
ferred for further information on this point.

118 EXCRETION.

consider briefly the general arrangement of the cuticular
appendages.

The nails are situated on the dorsal surfaces of the distal
phalanges of the fingers and toes. They serve to protect
these parts, and in the fingers, are also quite important in
prehension. The general appearance of the nails is so famil-
iar that it requires no special description. In their study,
anatomists have distinguished a root, a body, and a free
border.

The root is thin and soft, terminating in rather a jagged
edge, which is turned slightly upward and is received into a
fold of the skin extending around the nail to its free edge.
The length of the root of course varies with the size of the
nail, but it is generally from one fourth to one third of the
length of the body.

The body of the nail extends from the fold of skin which
covers the root to the free border. This portion of the nail,
with the root, is closely adherent by its under surface to the
true skin. It is marked by fine but distinct longitudinal
striae and very faint transverse lines. It is usually reddish
in color, from the great vascularity of the subjacent structure.
At the posterior part is a whitish portion of a semilunar
shape, called the lunula, which has this appearance simply
from the fact that the corium in this part is less vascular, and
the papillae are not so regular as in the rest of the body.
That portion of the skin situated beneath the root and the
body of the nail is called the matrix. It presents highly
vascular papillae, arranged in regular, longitudinal rows, and
receives into its grooves corresponding ridges on the under
surface of the nail.

The free border of the nail begins at the point where the
nail becomes detached from the skin. This is generally cut
or worn away, and is constantly growing ; but if left to itself,
it attains in time a definite length, which may be stated, in
general terms, to be from an inch and a half to two inches.

Examining the nail in a longitudinal section, the horny

NAILS AST) HAIR. 119

layer, which is usually regarded as the true nail, is found to
increase progressively in thickness from the root to near the
free border. If the nail be examined in a transverse section,
it will also be found much thicker in the central portion
than near the edge, and that part which is received into
the lateral portions of the fold becomes excessively thin like
the rest of the root. The thickness of the true nail at the
root is from -^-^ to -j-J-g- of an inch ; and, in the thickest por-
tion of the body, it usually measures from ^ to -^ of an
inch. The nail becomes somewhat thinner at and near the
free border.

Sections of the nails show that they are composed of two
layers, which correspond to the Malpighian and the horny
layer of the epidermis, though they are much more distinct.
The Malpighian layer is applied directly to the ridges of the
bed of the nail, and presents upon its upper surface ridges
much less strongly marked than in the underlying true skin.
This layer is rather thinner than the horny layer, is whitish
in color, and is composed of numerous strata of elongated,
prismoidal, nucleated cells, arranged perpendicularly to the
matrix. These cells are from 3^0 to 17100 of an inch in
length.

The horny layer, which constitutes the true nail, is ap-
plied by its under surface directly to the ridges of the Mal-
pighian layer. It is dense and brittle, and composed of nu-
merous strata of flattened cells, which cannot be isolated
without the use of reagents. If the different strata of this
portion of the nail be studied after boiling in a dilute solu-
tion of soda or potash, it becomes evident that here, as in the
horny layer of the epidermis, the lower cells are somewhat
rouncjed, while those nearer the surface are flattened. These
cells are nearly all nucleated, and measure from 10100 to -y^-g-
of an inch in diameter. The thickness of this layer varies
in different portions of the nail, while the Malpighian layer
is nearly uniform. This layer is constantly growing, and con-
stitutes the entire substance of the free borders of the nails.

120 EXCRETION.

The connections of the nails with the true skin resemble
those of the epidermis ; but the relations of these structures
to the epidermis itself are somewhat peculiar. Up to the
fourth month of foetal life, the epidermis covering the dorsal
surfaces of the last phalanges of the fingers and toes does
not present any marked peculiarities ; but at about the
fourth month, the peculiar hard cells of the horny layer of
the nails make their appearance between the Malpighian
and the horny layer of the epidermis, and at the same time
the Malpighian layer beneath this plate, which is destined
to become the Malpighian layer of the nails, is somewhat
thickened, and the cells assume more of an elongated form.
The horny layer of the nails constantly thickens from this
time ; but until the end of the fifth month, it is covered by
the horny layer of the epidermis. After the fifth month,
the epidermis breaks away and disappears from the sur-
face ; and at the seventh month, the nails begin to increase
in length. Thus, at one time, the nails are actually included
between the two layers of the epidermis ; but after they
have become developed, they are simply covered at their
roots by a narrow border of the horny layer, the epidermis
commencing again under the nail where the free border
leaves the bed. The nails are therefore to be regarded as
modifications of the horny layer of the epidermis, possessing
certain anatomical and chemical peculiarities. The Malpig-
Tbian layer of the nails is continuous with the same layer
of the epidermis, but the horny layers are, as we have seen,
distinct.

One of the most striking peculiarities of the nails is in
their mode of growth. The Malpighian layer is stationary,
but the horny layer is constantly growing, if the nails be
cut, from the root and bed. It is evident that the nails
grow from the bed, as their thickness progressively increases
in the body from the root to near the free border ; but their
longitudinal growth is by far the more rapid. Indeed, the
nails are constantly pushing forward, increasing in thickness

NAILS AXD HATK. 121

as they advance. Xear the end of the body, as the horny
layer becomes thinner, the growth from below is diminished.

Hairs, varying greatly in size and development, cover
nearly every portion of the surface of the body. The only
parts in which they are not found are the palms of the
hands and soles of the feet, the palmar surface of the fingers
and toes, the dorsal surface of the last phalanges of the fin-
gers and toes, the lips, the upper eyelids, the lining of the
prepuce, and the glans penis. Some of the hairs are long,
others are short and stiff, and others are fine and downy.
These differences have led to a division of the hairs into
three varieties.

The first variety includes the long, soft hairs, which are
found on the head, on the face in the adult male, around the
genital organs and under the arms in both the male and the
female, and sometimes upon the breast and over the general
surface of the body and extremities, particularly in the male.

The second variety, the short, stiff hairs, is found at the
entrance of the nostrils, upon the edges of the eyelids, and
upon the eyebrows.

The third variety, the short, soft, downy hairs, are found
on the general surface not occupied by the long hairs, and
the caruncula lachrymalis. In early life, and ordinarily in
the female at all ages, the trunk and extremities are covered
with downy hairs ; but in the adult male, these frequently
become developed into long, soft hairs.

The hairs are usually set obliquely in the skin, and take
a definite direction as they lie upon the surface. Upon the
head and face, and, indeed, the entire surface of the body,
the general course of the hairs may be followed out, and
they present currents or sweeps that have nearly always
the same direction. These " currents " have been carefully
studied by Wilson, and are fully described in his work upon
the healthy skin.1

1 WILSON, Healthy Skin, Philadelphia, 1854, p. 101, d seq.

122 EXCRETION.

The diameter and length of the hairs are exceedingly vari-
able in different persons, especially in the long, soft hairs of
the head and beard. It may be stated in general terms that
the long hairs attain the length of from twenty inches to
three feet in women, and considerably less in men. There
are instances, however, in women, in which the hair of the
head measures considerably more than three feet, but these
are quite unusual. Like the nails, the hair, when left ,to
itself, attains in three or four years a definite length, but
when it is habitually cut it grows constantly. The short,
stiff hairs are from one quarter to one half an inch in length.
The soft, downy hairs measure ordinarily from one twelfth
to one half an inch. Hairs that have never been cut ter-
minate in pointed extremities; and sometimes in hairs that
have been cut, the ends become somewhat pointed, though
they are never so sharp as in the new hairs.

Of the long hairs, the finest are upon the head, where
they average about ^J-g- of an inch in diameter, the extremes
ordinarily being from -3-^5- to -g-J-g- of an inch for the finest,
and from ^J-g- to yj^ of an inch for the coarsest. The hair
is ordinarily coarser in women than in men. Dark hair is
ordinarily coarser than light hair ; and upon the same head
the extremes of variation are sometimes observed.1 The
hairs of the beard and the long hairs of the body are coarser
than the hairs of the head. Wilson estimates that the aver-
age number of hairs upon a square inch of the scalp is about
1,000, and the number upon the entire head about 120,000.

The short, stiff hairs are from -^-^ to yfg- of an inch in
diameter, and the fine, downy hairs from 2o^00 to 1/00 of
an inch. The variations in the color of the hairs in differ-
ent races and in different individuals of the same race are
sufficiently familiar.

When the hairs are in a perfectly normal condition, they
are very elastic, and may be stretched to from one fifth to
one third more than their original length. Their strength

1 WILSON, op. cit., p. 84, et seq.

NAILS AND HAIR. 123

varies with their thickness, but an ordinary hair from the
head will bear a weight of six or seven ounces. A well-
known property of the hair is that of becoming strongly
electric by friction ; and this is particularly well marked
when the weather is cold and dry. The electricity thus
excited is negative. Sections of the shaft of the hairs show
that they are oval, but their shape is very variable, straight
hairs being nearly round, while curled hairs are quite flat.
Another peculiarity of the hairs is that they are strongly hy-
grometric. They readily absorb moisture and become sen-
sibly elongated, a property which has been made use of by
physicists in the construction of delicate hygrometers.

Hoots of the Hairs and Hair -follicles. — The roots of the
hairs are embedded in follicular openings in the skin, which
differ in the different varieties only in the depth to which
they penetrate the cutaneous structure. In the downy hairs,
the roots pass only into the superficial layers of the true
skin ; but in the thicker hairs, the roots pass through the
skin and penetrate the subcutaneous cellulo-adipose tissue.

The root of the hair is softer, rounder, and a little larger
than the'shaft. It becomes enlarged into a rounded bulb at
the bottom of the follicle, and rests upon a f ungiform papilla,
constricted at its base, to which it is closely attached. In
describing the connection between the hairs and the skin,
anatomists mention three membranes forming the walls
of the hair-follicles, and two membranes that envelop the
roots of the hair in the form of a sheath. The study of these
parts is much simplified by keeping constantly in view the
correspondence between the different layers of the follicles
and the layers of the true skin, and the relations of the root-
sheaths with the epidermis.

The follicles are tubular inversions of the structures that
compose the coriurn, and their walls present three distinct
membranes. Their length is from -^ to J of an inch. The
membrane that forms their external coat is composed of

124: EXCRETION.

inelastic fibres arranged for the most part longitudinally,
provided with blood-vessels and a few nerves, containing
some fibro-plastic elements, but deprived entirely of elastic
tissue. This is the thickest of the three membranes and is
closely connected with the corium. Next to this is a fibrous
membrane composed of fusiform, nucleated fibres arranged
transversely. These resemble the organic muscular fibres,
but are believed by Kolliker to be fibres of connective tis-
sue.1 The internal membrane is structureless, and corre-
sponds to the amorphous layer of the true skin. The papilla
at the bottom of the hair-sac varies in size with the size of
the hairs, and is connected with the fibrous layers of the
walls of the follicle. It is composed of amorphous matter
with a few granules and nuclei, and probably contains blood-
vessels and nerves, though these are not very distinct.

Although these different membranes are sufficiently recog-
nizable, it is evident that the hair-sac is nothing more than
an inversion of the corium, with some slight modifications in
the character and arrangement of its anatomical elements.
The fibrous membranes correspond to the deeper layers of
the true skin, wranting the elastic elements, and presenting a
peculiar arrangement of its inelastic fibres, the external
fibres being longitudinal and the internal fibres transverse.
The structureless membrane corresponds to the upper layers
of the true skin, which are composed chiefly of amorphous
matter. The hair-papilla corresponds to the papillae on the
general surface of the corium.

The investment of the root of the hair presents two dis-
tinct layers. The external root-sheath is three or four times
as thick as the inner membrane, and corresponds exactly with
the Malpighian layer of the epidermis. This sheath is con-
tinuous with the bulb of the hair. The internal root-sheath
is a transparent membrane, composed of flattened cells,
mostly without nuclei. This extends from the bottom of the
hair-follicle, and covers the lower two-thirds of the root.

1 KOLLIKER, Handbuch der Gewe belehre des Menscken, Leipzig, 1867, S. 132.

XAIL3 AXD HAIR.

125

FIG. 5.

Summary. — The essential points in the anatomy of the
hair-follicles and the connections of the hairs with the skin
may be summed up in a few words :

The hair-follicle consists of an
inversion of the true skin, with
some modifications in the arrange-
ment of its anatomical elements,
and presents at the bottom an
ovate papilla, upon which the bulb
of the hair rests and to which it
is closely attached. The root of
the hair is invested with two mem-
branes; the outer sheath corre-
sponding to the Malpighian layer
'of the epidermis, and the inner
sheath corresponding to the horny
layer. These membranes, with the
membranes that form the wall of
the follicle, extend to the junction
of the lower two-thirds with the
upper third of the follicle, or the
openings of the sebaceous glands,
with which all the hairs are pro-
vided. If continued upon the skin,
of course the layers would be re-
versed, the inner root-sheath be-

o-ni
epi-

rrvmincr flip nntpr lavpr nf flip *vm Hair and hair-follicle of medium PIZP.

ing IJ - lajei me epi- nia?nified flfty diameters-a, shaft

flpvinii; flip nnfpr rr»nt dlipntTi T^oir>ry of thehair; 6, root; c. bulb, rf. epi-

"Sj" >Ot-sneatn Deing dermis of the hair; V. internal root-

pnntinnrmj; \vitli tViP "\ralr»irrliiQn sheath;/, external sheath; </,

^lt me Jlialplgnian amorphous membrane of the folli-

layer. The hair itself is an ap- fon^^ai^fes^^pma-f

pendage of the epidermis, and is "etory ducts of 'th'e sebace'cu^

glands ; /, derma at the point of
opening of the follicle ; m, mucous
layer of the epidermis ; n, horny
layer of the epidermis ; o. termi-

continuous with the inner root-
sheath, Which Corresponds to the nation of the internal sheath of the
-Hi- i • -i • i T, root of the hair. (KQLLIKER. Ele-
JMalplghian layer. it rests Upon ments <?hi*tologie humaine, Paris,

and is produced by the papilla,

as the nail rests upon the papillae of its matrix. The root of

126 EXCRETION.

the hair and the structure of its sheaths and the hair-follicle
are shown in Fig. 5.

Structure of the Hairs. — The different varieties of hairs
present certain peculiarities in their anatomy, but all of
them are composed of a fibrous structure forming the greater
part of their substance, covered by a thin layer of imbricated
cells. In the short, stiff hairs, and in the long, white hairs,
there is a distinct medullary substance ; but this is wanting
in the downy hairs, and is indistinct in many of the long,
dark hairs.

The fibrous substance is composed of hard, elongated,
longitudinal fibres, which cannot be isolated without the aid
of reagents. They may be separated, however, by treating
with warm sulphuric acid? when they present themselves in
the form 'of dark, irregular, spindle-shaped plates, from -^
to -g^o- of an, inch long, and from -gT1TFF to g-^ of an inch
wide. These contain pigmentary matter of various shades,
occasional cavities filled with air, and a few nuclei. The
pigment may be of any color, from a light yellow to an in-
tense black, and it is this substance that gives to the hair
the great variety in color which is observed in different per-
sons. In the lower part of the root the fibres are much
shorter, and at the bulb become transformed, as it were, into
the soft, rounded cells found in this situation covering the
papilla.

The epidermis of the hair is excessively thin, and is com-
posed of flattened, quadrangular plates, overlying each other
from below upward. These scales, or plates, are without
nuclei, and exist in a single layer over the shaft of the hair
and the upper part of its root ; but in the lower part of the
root the cells are thicker, softer, are frequently nucleated,
and exist in two layers.

The medulla is found in the short, stiff hairs, and it is
often beautifully distinct in the long, white hairs of the head.
According to Sappey, it is found more or less distinctly

SUDDEN BLANCHING OF THE HAIR. 127

marked in all the long hairs, as is seen on transverse section.1
It forms from one-sixth to one-third of the diameter of the
hair. The medulla can be traced, under favorable circum-
stances, from just above the bulb to near the pointed extrem-
ity of the hairs. It is composed of small, rounded cells, from
20*0o to YsVir of an inch in diameter, nucleated, and fre-
quently containing dark granules of pigmentary matter.
Mixed with these cells are numerous air-globules ; and fre-
quently the cells are interrupted for a short distance and
the space is occupied with air. The dark granules of the
medullary cells are supposed by Kolliker to be merely globules
of air.3 The medulla likewise contains a glutinous fluid
between the cells and surrounding the air-globules.

Growth of the Hairs. — Although not provided with
blood and deprived of sensibility, the hairs are connected
with vascular parts and are regularly nourished by imbi-
bition from the papillae. Each hair is first developed in a
closed sac, and at about the sixth month its pointed ex-
tremity perforates the epidermis. These first-formed hairs
are afterward shed, like the milk teeth, being pushed out, as
it were, by new hairs from below, which arise from a second
and more deeply-seated papilla. This shedding of the hairs,
which was first described by Kolliker,8 usually takes place
from two to six months after birth.

The difference in the color of the hair depends upon
differences in the quantity and the tint of the pigmentary
matter; and in old age, the hair becomes white or gray
from a blanching of the cortex and medulla.

Sudden Blanching of the Hair. — It is an interesting
question, in connection with the nutrition of the hair, to
examine the instances so often quoted of sudden blanching
of the hair from violent emotions or other causes. Some

1 SAPPEY, Traite d1 anatomie descriptive, Paris, 1852, tome ii., p. 600.

2 KOLLIKER, Sandbitch der Gewebekhre des Menschen, Leipzig, 1867, S. 130.

3 Op. tit., S. 137.

128 EXCRETION.

physiologists are of the opinion that the hair may become
almost white in the course of a few hours, and this, indeed,
is a popular impression ; but others assume that such sudden
changes never take place, although it is certain that the hair
frequently turns gray in a few weeks. In examining the
literature of this subject, it is difficult to find in the older
works well-authenticated cases of these sudden changes, and
most of those that have been quoted are taken upon the
loose authority of persons evidently not in the habit of mak-
ing scientific observations. Such instances, unsupported by
analogous cases of a reliable character, must necessarily be
rejected, as not fulfilling the rigid requirements demanded
in scientific inquiries, in which all possible sources of error
should be carefully excluded. It is not necessary, therefore,
to quote the instances of sudden blanching of the hair re-
corded by the ancient writers, nor those well-known cases
of later date, so often detailed in scientific works, such as
that of Marie Antoinette or Sir Thomas More ; and it
seems proper to exclude, also, cases in which the blanching
of the hair has been observed only by friends or relatives ;
for in most of them the statements with regard to time are
conflicting and unsatisfactory.

Regarding the subject, however, from a purely scientific
point of view, there are a few instances of late date, in which
sudden blanching of the hair has been observed, and the
causes of this remarkable phenomenon fully investigated by
competent observers ; and it is almost unnecessary to say
that a single well-authenticated case of this kind demonstrates
the possibility of its occurrence, and is interesting in connec-
tion with the reported instances which have not been sub-
jected to proper investigation. One of these cases is report-
ed in Virchow^s Archiv, for April, 1866, by Dr. Landois, as
occurring under the observation of himself and Dr. Lohmer.1
In this case the blanching of the hair occurred in a hospital

1 LANDOIS, Das plotzlicfie Engrauen der Haupihaare. — VIRCHOW'S Archiv,
Berlin, 1866, Bd. xxxv., S. 375.

SUDDEN BLANCHING OF THE HAEK. 129

in a single night, while the patient was under the daily ob-
servation of the visiting physician. As this is one of the
few well-authenticated instances of sudden blanching of the
hair, we will give, in a few words, its essential particulars :

The patient, a compositor, thirty-four years of age, with
light hair and blue eyes, was admitted into the hospital,
July 9, 1865, suffering apparently from an acute attack of
delirium tremens. A marked peculiarity in the disease was
excessive terror when any person approached the patient.
He slept for twelve hours on the night of the eleventh of
July, after taking thirty drops of laudanum. Up to this
time nothing unusual had been observed with regard to the
hair. On the morning of July 12th, it was evident to the
medical attendants and all who saw the patient that the
hair of the head and beard had become gray. This fact was
also remarked by the friends who visited the patient, and he
himself called for a mirror, and remarked the change with
intense astonishment. The patient continued in the hospital
until September 7th, when he was discharged, the hair re-
maining gray.

An interesting point connected with this case is the fact
that the hairs were submitted to careful microscopical exami-
nation. The white hairs were found to contain a great num-
ber of air-globules in the medulla and in the cortical sub-
stance, but the pigment was everywhere preserved. The
presence of air gave the hairs a dark appearance by trans-
mitted light and a white appearance by reflected light. Dr.
Landois quotes, in this connection, instances of blanch-
ing of the hair, in which each hair presented alternate rings
of a white and brown color. Another very curious case of
this kind was lately reported to the Hoyal Society by Mr.
Erasmus "Wilson.1 In this case, the white portions present-
ed, on a microscopical examination, great bubbles of air;

1 WILSON*, On a remarkable Alteration of Appearance and Structure of the Hit-
man Hair. — Proceedings of the Royal Society, London, 1867, vol. xv., Xo. 91, p.
406, et seq.

130 EXCRETION.

but there was no diminution in the quantity of pigmentary
matter. The possibility of sudden blanching of the hair is
further illustrated by a curious observation lately made by
Dr. Brown-Sequard. This physiologist observed in his own
person four white hairs upon the cheeks upon one side, and
seven upon the other, mixed with the dark hairs of the beard.
These he pulled out, and two days after, he found two hairs
upon one side, and three upon the other, that were white
throughout their entire length. This observation he veri-
fied several times, and from this he concludes that there is
no doubt of the " possibility of a very rapid transformation
(probably in less than one night) of black hairs into white."

The microscopical examinations by Dr. Landois and others
leave no doubt as to the cause of the white color of the hair
in cases of sudden blanching ; and the instances we have
just quoted show that the fact of the occurrence of this phe-
nomenon can no longer be called in question. All are
agreed that there is no diminution in the pigment, but that
the greater part of the medulla becomes filled with air, small
globules being also found in the cortical substance. The
hair in these cases presents a marked contrast with hair
that has become gray gradually from old age, when there is
always a loss of pigment in the cortex and medulla. How
the air finds its way into the hair in sudden blanching it
is difficult to imagine ; and the views that have been ex-
pressed on this subject by different authors are entirely theo-
retical.

The fact that the hair may become white or gray in the
course of a few hours renders it probable that many of the
cases reported upon unscientific authority actually occurred ;
and these have all been supposed to be connected with in-
tense grief or terror. The terror was very marked in the
case reported by Dr. Landois. In the great majority of

1 BROWN-SEQUARD, Experiences demontrant que les poik peuvent passer rapide-
ment de noir au blanc, cJiez Vliomme. — Archives de physiologic, Paris, 1869, tome
ii., p. 442.

PERSPIRATION. 131

recorded observations, the sudden blanching of the hair has
been apparently connected with intense mental emotion ;
but this is all that can be said on the subject of causation,
and the mechanism of the change is not understood.

Uses of the Hairs. — The hairs serve an important pur-
pose in the protection of the general surface and in guarding
certain of the orifices of the body. The hair upon the head
and the face protects from cold and shields the head from the
rays of the sun during exposure in hot climates. Although
the amount of hair upon the general surface is small, as it is a
very bad conductor of caloric, it serves in a degree to maintain
the heat of the body. It also moderates the friction upon the
surface. The eyebrows prevent the perspiration from run-
ning from the forehead upon the lids ; the eyelashes protect
the surface of the conjunctiva from dust and other foreign
matters ; the mustache protects the lungs from dust, a func-
tion very important to those exposed to dust in long journeys
or in their daily work ; the short, stiff hairs at the openings
of the ears and nose protect these orifices. It is difficult
to assign any special office to the hairs in some other situ-
ations, but their general uses are sufficiently evident.

Perspiration.

In the fullest acceptation of the term, perspiration em-
braces the entire function of the skin as an excreting organ,
and includes the exhalation of carbonic acid as well as of
watery vapor and organic matter. The office of the skin as
an eliminator is undoubtedly very important ; but the quan-
tity of excrementitious matters with the properties of which
we are well acquainted, such as carbonic acid and urea, thrown
off from the general surface, is small as compared to the
amount exhaled by the lungs and kidneys. If the surface
of the body be covered with an impermeable coating, death
always takes place ; but the phenomena which precede the
fatal result are difficult to explain. The experiments on this

132 EXCKETTON.

subject by Fourcault,1 Bouley and Bernard,2 and others, are
very interesting. In these observations, cutaneous exhalation
was entirely suppressed in horses, rabbits, and other animals,
by covering the surface with an impermeable coating of
varnish or pitch ; and the animals died at periods varying
from a few hours to ten days, the gravity of the symptoms
depending upon the thoroughness with which the coating
had been applied. The experiments of Bernard, particularly,
were most curious and interesting. He confirmed the ob-
servations of Fourcault and Bouley on the effects of covering
the entire surface, in horses, with an impermeable coating,
but he found that when a space of even a few inches was
left uncovered, the animals survived ; and in animals that
were suffering from the effects of a complete coating, if a
small portion were removed, the symptoms were ameliorated
and recovery took place.3 These experiments led Bernard
to the conclusion that death does not take place, after com-
plete suppression of the functions of the skin, from retention
of carbonic acid alone.

One of the well-known objects of cutaneous exhalation
is to keep down the animal temperature by evaporation,
when there is a tendency to too great development of heat
by exercise or from other causes ; and it might be supposed
that the suppression of this function would be one of the
chief causes of the fatal result. It is curious, however, that
in the early experiments of Fourcault,4 and in the later obser-
vations of Bernard, the animals suffered a great diminution
in temperature. Bernard found that death occurred when
the temperature was between 68° and 72° Fahr., always

1 FOURCAULT, Experiences demontrant P 'influence de la suppression mtchanigue
de la transpiration cutanee sur I alteration du sang. — Comptes rendus, Paris,
1838, tome vi., p. 369, and Ibid., 1843, tome xvi., p. 139.

2 BERNARD, Lecons sur Us propriety etc., des li guides de ^organisme^ Paris,
1859, tome ii., p. 177.

3 Op. cit, p. 178.

4 FOURCAULT, loc. cit.

PERSPIRATION. 133

taking place more rapidly when the surrounding temper-
ature was lowered.1

In some later observations upon this subject by Yalentin
and Laschkewitsch, facts, still more curious, have been de-
veloped. Laschkewitsch a found that the peculiar effects of
an impermeable coating to the surface were much less
marked in large than in small animals. Horses treated in
this way lived for several days, but rabbits died in a few
hours. In rabbits, death frequently occurred after coating
only one quarter of the surface. Yalentin and Laschke-
witsch confirmed the observations on the lowering of the
animal temperature; but they found that when the heat
was kept at the normal standard by artificial means, no mor-
bid symptoms were manifested. Neither of these observers
could detect any accumulation of excrementitious or other
morbid principles in the blood ; and the results of their ex-
periments were opposed to the view that death takes place,
under these conditions, from asphyxia. The cause of death
has never, indeed, been satisfactorily explained, partly for
the reason that we are unacquainted with the nature and
properties of all the excrementitious matters exhaled from
the skin ; and it is not easy to understand why coating the
surface should be followed by such a rapid diminution in
the temperature of the body. The experimental facts,
however, would indicate that the skin possesses important
functions with which we are entirely unacquainted. Phy-
siological chemists have detected urea and some other effete
matters in the perspiration, but it is probable that some vol-
atile principles are eliminated by the general surface, which
have thus far escaped observation. The importance of free
action of the skin in the human subject was strikingly illus-
trated in the case of a child who was covered with gold-leaf in

1 BERNARD, op. cit., p. 177.

2 LASCHKEWITSCH, Ueber die Ursacken der Temperatur-Erniedrigung bei Un-
terdriikung der Hautperspiration. — Archiv fur Anatomic, Physiologic, und wis-
senschaftliche Median, Leipzig, 1868, Xo. i., S. 61, et seq.

134: EXCRETION.

order to represent an angel in the ceremonies attending the
coronation of Pope Leo X. This child died a few hours after
the coating had been applied.1

Sudoriparous Glands. — The most numerous and the
most important glands of the skin are those which secrete
the perspiration. The other glands, which have been already
considered, have rather a mechanical function, serving to
keep the skin and its appendages in a proper condition for
the protection of the subjacent parts ; but it is the perspira
tory apparatus alone which is concerned in the great func-
tion of elimination.

With few exceptions, every portion of the skin is pro-
vided with sudoriparous glands. They are not found, how-
ever, in the skin covering the concave surface of the concha
of the ear, the glans penis, the inner lamella of the prepuce,
and, unless the ceruminous glands be regarded as sudo-
riparous organs, the external auditory meatus. Kolliker
states that some other portions of the skin are deprived
of sweat-glands, but he does not indicate their situation.2

On examining the surface of the skin with a low magni-
fying power, especially on the palms of the hands and the
soles of the feet, the orifices of the sudoriferous ducts may
be seen in the middle of the papillary ridges, forming a reg-
ular line in the shallow groove between the two rows of
papillae. The tubes always open upon the surface obliquely.
If a thin section of the skin be carefully made and examined
microscopically, the ducts are seen passing through the dif-
ferent layers and terminating in rounded, convoluted coils
in the subcutaneous structure. These little rounded, or
ovoid bodies, which constitute the sudoriparous, or sweat-
producing apparatus, may be seen attached to the under
surface of the skin, when it is removed from the subjacent
parts by maceration. The perspiratory apparatus consists,

1 LA.SCHKEWITSCH, loc. cit.

2 KOLLIKER, Handbuch der Gewebelehre des Menschen, Leipzig, 1867, S. 139.

PERSPIRATION. 135

indeed, of a simple tube, presenting a coiled mass beneath
the skin, the sudoriparous portion, and a tube of greater
or less length, in proportion to the thickness of the cuta-
neous layers, which is the excretory duct, or the sudoriferous
portion.

The glandular coils vary in size from y^ to -£~ of an inch ;
the smallest coils being found beneath the skin of the penis,
the scrotum, the eyelids, the nose, and the convex surface of
the concha of the ear, and the largest on the areola of the
nipple and the perineum. Yery large glands are found
mixed with smaller ones in the axilla, but these produce a
peculiar secretion which will be specially considered. The
coiled portion of the tube is about -g-fg- of an inch in diame-
ter, and forms from six to twelve convolutions. It consists
of a sharply defined, strong, external membrane, from -^^
to g-J^. of an inch in thickness, very transparent, uniformly
granular, and sometimes indistinctly striated. This is of uni-
form diameter throughout the coil, and terminates in a very
slightly dilated, rounded, blind extremity. It is filled with
epithelium in the form of finely granular matter, usually not
segmented into cells, and provided with small oval nuclei.
The glandular mass is surrounded with a plexus of capillary
blood-vessels, which send a few small branches between the
convolutions of the coil. Sometimes the coil is enclosed in
a delicate fibrous envelope.

The excretory duct is simply a continuation of the glan-
dular coil. Its course through the layers of the true skin is
nearly straight. It then passes into the epidermis between
the papillae of the corium, and presents, in this layer, a num-
ber of spiral turns. The spirals vary in number according
to the thickness of the epidermis. Sappey has found from
six to ten in the palms of the hands, and from twelve to fif-
teen in the soles of the feet. As it emerges from the glandu-
lar coil, the excretory duct is somewhat narrower than the
tube in the secreting portion ; but as it passes through the
epidermis, it again becomes larger. It possesses the same

136

EXCRETION.

FIG. 6.

external membrane as the glandular coil, and is lined gener-
ally by two layers of cells of pavement-epithelium.1

In a section of the skin and
the subcutaneous tissue, involv-
ing several of the sudoriparous
glands with their ducts, it is
seen that the glandular coils are
generally situated at different
planes beneath the skin, as is
indicated in Fig. 6.

Robin has described a vari-
ety of sudoriparous glands in
the axilla, which do not differ so
much from the glands in other
parts in their anatomy, as in
the character of their secretion.2
The coil in these glands is much
larger than in other parts, meas-
uring from -§V to -j3^ of an inch ;
the walls of the tube are thick-
er, and present an investment of
fibrous tissue with an internal
layer of longitudinal, unstriped

Sudoriparous glands, magnified twenty ^ _ ^

diameters. 1,1, Epidermis; 2, 2, MU- muscular fibres , and finally.

cous layer ; 3, 3, Papillae ; 4, 4. Der- J '

ma; 5, 5, Subcutaneous areolar tissue; the tubes of the COll it Self are
6, 6, 6, 6, Sudoriparous glands ; 7. 7,

lined with cells of pavement-

vided. (SAPPEY, Tratte d' 'anatomie. cmitTiplinm Tlipv Jirp VPT*V mi-
Paris, 1852, tome ii., p. 466.) 1TU

merous in the axilla, forming a

continuous layer beneath the skin. Mixed with these glands
are a few of the ordinary variety.

Estimates have been made by different writers of the
absolute number of sudoriparous glands in the body, and

1 SAPPEY, Traite d'anatomie descriptive, Paris, 1852, tome ii., p. 468.

2 ROBIN, Note sur une espece particuliere de glandes de la peau de Vhomme. —
Annales dcs sciences naturelles, Zoologie, 3me serie, Paris, 1845, p. 380.

3 KOLLIKER, Handbuch der Gewebelehre des Menschen, Leipzig, 1867, S. 140.

PERSPERATIOX. 137

the probable extent of the exhalant surface of the skin.
One of the most careful, and probably the most reliable
of these estimates, is that made by Krause ; but like all
estimates of this kind, the results are to be taken as merely
approximative. Krause found great differences in the num-
ber of perspiratory openings in different portions of the skin,
and estimated the number in a square inch in certain ,parts,
as follows : On the forehead, he found 1,258 glands to a
square inch ; on the cheeks, 548 ; on the anterior and lateral
portions of the neck, 1,303 ; on the breast and abdomen,
1,136 ; on the back of the neck, the back, and the nates, 417;
the forearm, inner surface, 1,123, and the outer surface, 1,093 ;
on the hand, palmar surface, 2,736, and dorsal surface, 1,490 ;
on the upper part of the thigh, inner surface, 576, outer sur-
face, 554 ; on the lower part of the thigh, inner surface, 576 ;
on the foot, plantar surface, 2,685, and the dorsal surface,
924.1 From these figures it is estimated that the entire
number of perspiratory glands is 2,381,248 ; and assuming
that each coil when unravelled measures about ^ of an inch,
the entire length of the secreting tubes is about 2J miles.
It must be remembered, however, that the length of the
secreting coil only is given, and that the excretory ducts are
not included.8

Mechanism of the Secretion of Sweat. — The action of the
skin as a glandular organ is continuous and not intermit-
tent ; but under ordinary conditions, the sweat is exhaled
from the general surface in the form of vapor. With regard

1 KRAUSE, Article, Haut. — WAGNER'S Handworterbuch der Physiologic,
Braunschweig, 1844, Bd. ii., S. 131.

2 If the above calculation be approximative^ correct, the estimate given
by Wilson, which is frequently quoted in works on physiology, must be very
much exaggerated. Wilson assumes that the average number of pores to the
square inch of surface is 2,800 ; and including the length of excretory duct,
he estimates that each tube measures about a quarter of an inch. Assuming
that the number of square inches of surface is 2,500 (a little more than the esti-
mate of Haller, which is fifteen square feet) it is estimated that the total length

138 EXCKETION.

to the mechanism of its separation from the blood, nothing
is to be said in addition to the general remarks upon the
subject of secretion ; and it is probable that the epithelium
of the secreting coils is the active agent in the selection of
the peculiar matters which enter into its composition. There
are no examples of the separation by glandular organs of
vapor from the blood, and the perspiration is secreted as a
liquid, and only becomes vaporous as it is discharged upon
the surface.

The influence of the nervous system upon this secretion
is remarkable. It is well known, for example, that an abun-
dant production of perspiration is frequently the result of
mental emotions. Bernard has shown, in a series of inter-
esting experiments, that the nervous influence may be prop-
agated through the sympathetic system. In one of these
observations, he divided the sympathetic in the neck of a
horse, producing, as a consequence, an elevation in tempera-
ture and increase in the arterial pressure in the part supplied
with branches of the nerve. He found, also, that the skin of
the part became covered with a copious perspiration. Upon
galvanizing the divided extremity of the nerve, the secretion
of sweat was arrested.1 "When the skin is in a normal con-
dition, after exercise or whenever there is a tendency to ele-
vation of the animal temperature, there is a determination
of blood to the surface, accompanied with an increase in the
secretion of sweat. This is the case when the body is ex-
posed to a high temperature ; and it is by an increase in the
transpiration from the surface that the animal heat is main-
tained at the normal standard.

Quantity of Cutaneous Exhalation. — The amount of
cutaneous exhalation is subject to great variations, depend-

of perspiratory tubing is nearly twenty-eight miles. In a note, however, it is
stated that the sebiparous system is included in this calculation (ERASMUS WIL-
SON, Healthy Skin, Philadelphia, 1854, p. 63).

1 BERNARD, Liguides de Forganisme, Paris, 1859, tome ii., p. 183.

PERSPIRATION. 139

ing upon conditions of temperature and moisture, exercise,
the quantity and character of the ingesta, etc. Most of these
variations relate to the function of the skin in regulating the
temperature of the body ; and it is probable that the elimi-
nation of excrementitious matters by the skin is not subject,
under normal conditions, to the same modifications, although
positive experiments upon this point are wanting. It is not
designed, in this connection, to discuss all the experiments
that have been made upon the quantity and the modifica-
tions of the cutaneous exhalations, and we will only con-
sider what appear to be the most reliable of the numerous
recorded observations upon this subject. The classical ex-
periments of Sanctorius were among the first attempts to
determine by the balance the relations of the ingesta to the
exhalations ; 1 but these were necessarily imperfect, on ac-
count of the difficulty in constructing proper instruments for
the investigations, and the cutaneous and pulmonary exhala-
tions were estimated together. When there is such a wide
range of variation in different individuals and in the same per-
son under different conditions of season, climate, etc., it is
only possible to give approximate estimates of the quantity
of sweat secreted and exhaled in the twenty-four hours ;
and more recent observations have shown that the calcula-
tions of Seguin and Lavoisier,9 made in 1Y90, are as nearly
correct as possible. These observers estimated the daily
quantity of cutaneous transpiration at about two pounds
(one pound and fourteen ounces). The estimates of Krause s
and of Valentin 4 are a little less, but the difference is not
considerable.

1 SANCTORIUS, Medicina Statica : by JOHN QUINCY, M. D., London, 1723,
p. 43, et seq.

2 SEGUIN ET LAVOISIER, Premier memoiresur la transpiration desanimaux. —
Histoire de V Academic des Sciences, annee, 1790, Paris, 1797, p. 609.

3 KRAUSE, Article, Haul. — WAGNER'S Handworterbuch der Physiologic,
Braunschweig, 1844, Bd. ii., S. 139, et scq.

4 VALENTIN, Lehrbuch der Physiologie des Menschen, Braunschweig, 1844,
Bd. i., S. n

140 EXCRETION.

Under violent and prolonged exercise, the loss of weight
by exhalation from the skin and lungs may become very con-
siderable. It is stated by Mr. Maclaren, the author of an ex-
cellent work on training, that in one hour's energetic fencing,
the loss by perspiration and respiration, taking the average
of six consecutive days, was about three pounds, or accurate-
ly, forty ounces, with a varying range of eight ounces.1

When the body is exposed to a very high temperature,
the amount of exhalation from the surface is immensely in-
creased ; and it is by this rapid evaporation that persons
have been able to endure for several minutes a temperature
considerably exceeding that of boiling water. Dr. South wood
Smith made some very interesting observations on this point
upon workmen employed about the furnaces of gas-works
and exposed to intense heat ; and he found that in an hour,
the loss of weight amounted to from two to four pounds, this
being chiefly by exhalation of watery vapor from the skin.8
In these instances the loss of water by transpiration is sup-
plied constantly by the ingestion of large quantities of liquid.

Properties and Composition of the Sweat. — A very com-
plete and satisfactory analysis of the sweat was made by
Favre, in 1853. After taking every precaution to obtain the
secretion in a perfectly pure state, he collected a very large
quantity, nearly thirty pints (fourteen litres), the result of
six transpirations from one person, which he assumed to
represent about the average in composition.3 The liquid was

1 HACLAREN, Training, in Theory and Practice, London, 1866, p. 89.

2 SOUTH-WOOD SMITH, Tlie Philosophy of Health, London, 1865, p. 284, et seq.
Dr. Smith found great differences in the loss on different days in the same per-
sons, and a great variation in the different persons employed in his experiments.
In his third series of experiments, made upon ten workmen, the minimum of
loss in one hour was two pounds. The maximum was in two persons " who
worked in a very hot place for one hour and ten minutes." One of these lost
four pounds and fourteen ounces, and the other, five pounds and two ounces.

* FAVRE, Recherches sur la composition chimique de la sueur chez Vhomme. —
Archives generales de medecine, Paris, 1853, 5me serie, tome ii., p. 1, et seq.

The analysis of the sweat by Favre is the one most frequently referred to by

PERSPIRATION. 141

perfectly limpid, colorless, and of a feeble but characteristic
odor. Almost all observers have found the reaction of the
sweat to be acid ; but it readily becomes alkaline on being
subjected to evaporation, showing that it contains some of
the volatile acids. In the experiments of Favre it was
found that the fluid collected during the first half hour of
the observation was acid, during the second half hour it was
neutral or feebly alkaline, and during the third half hour,
constantly alkaline. The specific gravity of the sweat is
from 1003 to 1004. 1 The following is the composition of
the fluid collected by Favre :

Composition of the Sweat.

Water 995-573

Urea 0'043

Fatty matters 0*014

Alkaline lactates 0*317

Alkaline sudorates 1-562

Chloride of sodium, ^ 2-230

Chloride of potassium, 0'244

Alkaline sulphates, I soluble in water O012

Alkaline phosphates, a trace.

Alkaline albuminates, J 0-005

Alkaline earthy phosphates (soluble in acidulated water) ... a trace .
Epidermic debris (insoluble) a trace.

1,000-000

"We have already alluded to the functions of the skin as
a respiratory organ and its office in regulating the tempera-
ture of the body by evaporation of what is known as the in-
sensible perspiration ; but the composition of the sweat in-
dicates clearly that the skin is an important organ of excre-
tion. Urea is now known to be a constant constituent of

physiological writers. The subject of the experiment, the surface being first
thoroughly cleansed, was enclosed in a metallic case, exposed to an elevated
temperature, and the transpiration collected as it flowed, and almost imme-
diately analyzed. Each experiment was continued for from an hour to an hour
and a half.

1 ROBIN, Lemons sur les humcurs, Paris, 1867, p. 621.

142 EXCRETION.

the sweat/ and the compounds of sudoric acid are probably
excrementitious in their character, although they have not
yet been detected in the blood or in any of the tissues. The
quantity of urea, under ordinary conditions, is not large ; but
it is well known that its proportion in the sweat is very
much increased when there is deficient elimination by the
kidneys. The sudoric acid, obtained by decomposition of
the sudorates of soda and of potassa, is a nitrogenized sub-
stance, with a formula, according to Favre,a who first de-
scribed it, of C10H8O13 !N". The nature of the volatile acid
has not yet been determined. The fatty matters are proba-
bly produced by the sebaceous glands, and the ordinary
nitrogenized matters are derived from the epidermic scales.
With regard to the inorganic constituents, there is no great
interest attached to any but the chloride of sodium, which
exists in a proportion many times greater than that of all
the other inorganic matters combined.

Peculiarities of the Sweat in Certain Parts. — In the
axilla, the inguino-scrotal region in the male, and the ingui-
no-vulvar region in the female, and between the toes, the
sweat always has a peculiar odor, more or less marked,
which, in some persons, is excessively disagreeable. Donne

1 Fourcroy, according to Berzelius, first indicated the presence of urea in the
sweat of the horse ; and afterward Landerer, Schottin (in cases of renal disease),
Favre, Funcke, and others detected it in the sweat of the human subject.
Funcke obtained it in a much larger proportion than is given by Favre. The
presence of uric acid has never been determined.

FOURCROY, quoted by BERZELIUS, Traite de chimie, Paris, 1833, tome vii.

Berzelius does not give any distinct reference to this observation, and it is not
to be found in the earlier works of Fourcroy.

LANDERER, Decouverte de Puree dans la transpiration. — Journal de chimie

medicate, Paris, 1848, serie iii., tome iv., p. 475.

SCHOTTIN, Ueber die chemischen Bestandtheile des Schweisses. — Archiv fur

physiologische Heilkunde, Stuttgart, 1852, Bd. xi., S. 87.

FUNCKE, Bietrdge zur Kenntniss der Schweisssecretion. — MOLESCHOTT'S Un-

tersucJiengen, Frankfurt a. M., 1858, Bd. iv., S. 56. In one observation Funcke
found 0-112, and in another, 0-199 per cent, of urea in the sweat.

2 FAVRE, loc. cit.

PERSPIRATION. 143

has shown that whenever the secretion has an odor of this
kind its reaction is distinctly alkaline ; and he is disposed to
regard its peculiar characters as due to a mixture of the secre-
tion of the other follicles found in these situations.1 Some-
times the sweat about the nose has an alkaline reaction. In
the axillary region, the secretion is rather less fluid than on
the general surface and frequently has a yellowish color, so
marked, sometimes, as to stain the clothing. The odor is
probably due to the presence of volatile, odorous compounds
of the fatty acids, like the caproates, the valerates, or the
butyrates ; but the presence of these principles has never
been accurately determined.

1 DONNE, Court de microscopie, Paris, 1844, p. 207.

CHAPTEE Y.

PHYSIOLOGICAL ANATOMY OF THE KIDNEYS.

Situation, form, and size of the kidneys — Coats of the kidneys — Division of the
substance of the kidneys — Pelvis, calices, and infundibula — Pyramids —
Cortex — Columns of Bertin — Pyramidal substance — Pyramids of Ferrein —
Tubes of Bellini — Cortical substance — Malpighian bodies — Convoluted
tubes — Narrow tubes of Henle — Intermediate tubes — Distribution of blood-
vessels in the kidney — Vessels of the Malpighian bodies — Plexus around
the convoluted tubes — Veins of the kidney — Stars of Verheyen — Lym-
phatics and nerves of the kidney — Summary of the physiological anatomy
of the kidney.

THE urine is generally regarded by physiologists as the
type of the excrementitious fluids, it having no function to
perform in the economy, but being simply retained in the
bladder to be voided at convenient intervals. All the re-
marks, indeed, that have been made concerning excretion
in general may be applied without reserve to the action of
the kidneys; and there are few subjects in physiology of
greater interest than the process of urinary excretion, with
its relations to nutrition and disassimilation. In entering
upon the study of the functions of the kidneys, it will be
found useful to consider certain points in their anatomy.

The kidneys are symmetrical organs, situated beneath the
peritoneum in the lumbar region, invested by a proper fibrous
coat, and always surrounded by more or less adipose tissue.
They usually extend from the eleventh or twelfth rib down-
ward to near the crest of the ilium ; and the right is always
a little lower than the left. In shape, the kidney is very

ANATOMY OF THE KIDNEYS. 145

aptly compared to a bean ; and the concavity, the deep, cen-
tral portion of which is called the hilum, looks inward
toward the spinal column. The weight of each kidney is
from four to six ounces, usually about half an ounce less in
the female than in the male. The left kidney is nearly
always a little heavier than the right.

Outside of the proper coat of the kidney is a certain
amount of fatty tissue enclosed in a loose fibrous structure.
This is sometimes called the adipose capsule ; but the proper
coat consists of a close net- work of the ordinary white fibrous
tissue, interlaced with numerous small fibres of the elastic
variety. This coat is thin, smooth, and readily removed
from the surface of the organ. At the hilum it is continued
inward to line the pelvis of the kidney, covering the calices
and blood-vessels. This coat, however, is not continued into
the substance of the kidney.

On making a longitudinal section of the kidney, it pre-
sents a cavity at the hilum, bounded internally by the dilated
origin of the ureter. This is called the pelvis. It is lined
by a smooth membrane, which is simply a continuation of
the proper coat of the kidney, and which forms little cylin-
ders, called calices, into which the apices of the pyramids are
received. Some of the calices receive the apex of a single
pyramid, while others are larger, and receive two or three.
The calices unite into three short, funnel-shaped tubes, called
infundibula, corresponding respectively to the superior, mid-
dle, and inferior portions of the kidney. These finally open
into the common cavity, or pelvis. The substance of the
kidney is composed of two distinctly-marked portions called
the cortical, and the medullary, or pyramidal.

The cortical substance is reddish and granular, rather
softer than the pyramidal substance, and is about one-sixth
of an inch in thickness. This occupies the exterior of the
kidney, and sends little prolongations (columns of Bertin l)

1 BERTIK, Memoire pour servir d Fhistoire des reins. — Memoires de F Academic
Royale des Sciences, annee, 1744, Paris, 1748, p. 77.
10

146 EXCRETION.

between the pyramids. The surface of the kidney is marked
by little polygonal divisions, giving it a tabulated appear-
ance. This, however, is simply due to the arrangement
of the superficial blood-vessels. The medullary substance
is arranged in the form of pyramids, sometimes called the
pyramids of Malpighi, from twelve to fifteen or eighteen in
number, their bases presenting toward the cortical substance,
and their apices being received into the calices at the pelvis.
Ferrein subdivided the pyramids of Malpighi into smaller
pyramids (the pyramids of Ferrein), each formed by about
one hundred tubes radiating from the openings at the sum-
mit of the pyramids toward their bases.1 The tubes com-
posing these pyramids were supposed to pass into the corti-
cal substance, forming corresponding pyramids of convoluted
tubes, thus dividing this portion of the kidney into lobules,
more or less distinct. The medullary substance is firm, of a
darker red color than the cortical substance, and is marked
by tolerably distinct striae, which take a nearly straight
course from the bases to the apices of the pyramids. As
these striae indicate the direction of the little tubes that
constitute the greatest part of the medullary substance, this
is sometimes called the tubular portion of the kidney.

There are few subjects connected with the physiological
anatomy of the organism that present greater interest than
the minute anatomy of the kidney ; and this is one of the
organs which has been most closely and persistently studied
by anatomists. Without referring in detail to the investi-
gations of Malpighi,8 whose name is attached to the corpus-
cles of the cortical substance, Bellini,3 who first studied the
straight tubes, Ferrein,4 who described the tubes of the corti-

1 FERREIN, Sur la structure des visceres nommes glanduleux, et particulierement
sur celle des reins et du foie. — Memoires de I ] Academic Royale des Sciences, annee,
1749, Paris, 1753, p. 499, et seq.

2 MALPIGHIUS, Opera Omnia, Lond., 1686, tomus secundus, DeRenibus.

3 BELLINI, Exercitationcs Anatomicce dace de Structura et Usu Renum ut et de
Gustus Oryano, Lugd. Batav., 1711.

4 Op. cit.

ANATOMf OF THE KIDNEYS.

cal substance, and other of the earlier anatomists, we
proceed to study the structure of the kidney as it appears at
the present day from the researches of later anatomists, who
have brought to bear upon their investigations more perfect
methods of injection and the improved microscopes now in
use. Among the authors whose researches have developed
the views now held by the best anatomists, may be men-
tioned Henle,1 Bowman,3 Goodsir,3 Muller,4 Gerlach,* Kolli-
ker,6 Toynbee,7 Huschke,8 Isaacs,9 with some quite recent
German and French observers, who have lately advanced
new and interesting views that have an important bearing
upon the mechanism of the secretion of urine.

The arrangement of the secreting portion of the kidneys
classes them among the tubular glands, presenting a system
of tubes, or canals, some of which are supposed simply to
carry off the urine, while others separate the excrementitious
constituents of this fluid from the blood. It is difficult to
determine precisely where the secreting tubes merge into
the excretory ducts, but it is the common idea that the cor-
tical substance is the active portion, while the tubes of the
pyramidal portion simply conduct away the excretion.10

1 HENLE, Traite cTanatomie generate, Paris, 1843, tome ii., p. 503, et seq.,
and Zur Anatomic der Niere, Gottingen, 1862.

2 BOWMAN, On the Structure and Use of the Malpighian Bodies of the Kidney.
— Philosophical Transactions, London, 1842, p. 57, et seq.

3 GdODSiR, London and Edinburgh Monthly Journal of Medical Science, Lon-
don and Edinburgh, 1842, p. 474.

4 MUELLER, Manuel de physiologic, Paris, 1851, tome i., p. 369, et seq.

5 GERLACH, Beitrdge zur Structurkhre der Niere. — MULLER'S Archiv, 1845,
S. 378, in CANST ATI'S Jahresbericht, Erlangen, 1846, S. 36.

6 KOLLIKER, Ueher Flimmerbewegung in denPrimordialnieren, Idem, S. 36.

7 TOYXBEE, On tlie Minute Structure of the Human Kidney. — Medico- Chirur-
gical Transactions, London, 1846, vol. xxix., p. 303, et seq.

8 HUSCHKE, Encyclopedic anatomique, Splanchnologie, Paris, 1845, tome v.,
p. 285, et seq.

9 ISAACS, ResearcJies into Uie Structure and Physiology of the Kidney, and
On the Function of the Malpighian Bodies of the Kidney. — Transactions of the
New York Academy of Medicine, Xew York, 1857, vol. i., p. 377, et seq.

10 TODD AND BOWMAN, Physiological Anatomy and Physiology of Man, Phila-

148 EXCRETION.

Pyramidal Substance. — Each papilla, as it projects into
the pelvis of the kidney, presents from two hundred to
five hundred little openings, from -g-J-g- to y^- of an inch in
diameter.1 The tubes leading from the pelvis immediately
divide at very acute angles, generally dichotomatously, until
a bundle of tubes arises, as it were, from each opening.
These bundles constitute the pyramids of Ferrein. In their
course, the tubes are slightly wavy and nearly parallel with
each other. These are called the straight tubes of the kid-
ney, or the tubes of Bellini. They extend from the apices
of the pyramids to their bases, and pass then into the corti-
cal substance. The pyramids contain, in addition to the
straight tubes, a delicate fibrous matrix and numerous blood-
vessels; which latter, for the most part, pass beyond the
pyramids, to be finally distributed in the cortical substance.
Recent researches have shown that some of the convoluted
tubes dip down into the pyramids, returning to the cortical
substance in the form of loops. This arrangement will be
fully described in connection with the cortical portion.

The tubes of the pyramidal substance are composed of a
strong, structureless basement-membrane, lined with granu-
lar, nucleated cells. According to the researches of Bow-
man, the tubes measure from -g-J-g- to -%fa of an inch in diame-
ter at the apices, and near the bases of the pyramids their
diameter is about -g-J-g- of an inch.3 The membrane of the
tubes is dense and resisting, and portions of it with the epi-
thelial lining removed can generally be seen in microscopical
examinations, when the pyramidal substance has been sim-
ply lacerated with needles. This membrane is from 3ooo0
to 20000 of an inch in thickness.8

The cells lining the straight tubes exist in a single layer

delphia, 1857, p. 789. This is the idea advanced in nearly all works on physi-
ology, when any opinion is expressed with regard to the relative activity of the
cortical and the pyramidal portions of the kidney.

1 KOLLIKER, Manual of Human Microscopic Anatomy, London, 1860, p. 404.

8 TODD AND BOWMAN, op. cit., p. 793.

3 KOLLIKER, op. tit., p. 406.

AXATOMY OF THE KCDXEYS. 149

applied to the basement-membrane. They are thick, irregu-
larly polygonal in shape, and contain numerous albuminoid
granules. They present one, and occasionally, though rarely,
two granular nuclei with one or two nucleoli. They are very
liable to alteration, and are only seen in the normal condi-
tion in a perfectly fresh, healthy kidney. Their diameter is
about 15100 of an inch. The calibre of the tubes is reduced
by the thickness of their lining epithelium to -g-J-g- or -g-J-g- of an
inch.

Cortical Substance. — In the cortical portion of the kid-
ney are found numerous tubes, differing somewhat from the
tubes of the pyramidal portion in size and in the character
of their epithelial lining, but presenting the most marked
difference in their direction. These tubes are somewhat
larger than the tubes of pyramidal substance, and are very
much convoluted, interlacing with each other inextricably
in every direction. Scattered pretty uniformly through this
portion of the kidney, are rounded or ovoid bodies, about
four times the diameter of the convoluted tubes, known as
the Malpighian bodies. At one time there was considera-
ble difference of opinion with regard to the relation of these
bodies to the tubes ; but the researches of Bowman, Isaacs,
and later anatomists, have established, without doubt, the
fact that they are simply flask-like terminal dilatations of
the tubes themselves.

As the result of the researches of Bowman, Goodsir, and
Isaacs, the cortical portion of the kidney is now regarded as
composed of a delicate fibrous matrix,1 which forms a sort
of skeleton for the support of the secreting portion with its
blood-vessels. The tubes of this portion are convoluted and
somewhat larger than the straight tubes, but are continuous
with them, terminating finally in the Malpighian bodies.

1 The fibrous matrix of the kidney was first described in detail by Goodsir,
in 1842 (loc. cit.\ but its existence was afterward denied by such eminent anat-
omists as Henle, Frerichs, and others. This structure was very accurately de-
scribed by Isaacs (op. cit.\ and has since been admitted by most observers.

150 EXCRETION.

The researches of late anatomists, however, particularly in
Germany, have shown that this simple view of the course
and termination of the tubes of the cortical substance must
be somewhat modified ; though as far as the anatomy of the
organ has any bearing upon our ideas concerning the mech-
anism of the secretion of urine, the views of physiologists
need undergo no material change. However interesting the
subject might be, it would be out of place to follow out
critically and in detail all the recent investigations into the
anatomy of these parts, and we will simply describe the
structure, direction, and relations of the tubes of the cortical
substance, as they appear from the most reliable modern in-
vestigations.

The tubes of the cortical substance present considerable
variations in size, and instead of a single system continuous
with the straight tubes and terminating in the Malpighian
bodies, we can distinguish three well-defined varieties :

1. The ordinary convoluted tubes, directly connected
with the Malpighian bodies. 2. Small tubes, continuous
with the convoluted tubes, dipping down into the pyramids
and returning to the cortical portion in the form of loops. 3.
Large, communicating tubes, forming a plexus connecting
the different varieties of tubes with each other and finally
with the straight tubes of the pyramidal portion.

The relation of these tubes can be better understood by
reference to Fig. 7, taken from a recent work by Dr. Ch. F.
Gross.1 This represents diagrammatically the course of a
uriniferous canal in the human subject. 1, Surface of a renal
papilla ; 2, Surface of the kidney ; 3, Boundary of the pyra-
midal substance; a, a, Malpighian corpuscles; &, Z>, Convo-
luted tubes ; <?, <?, Straight portion of the tubes ; d, d, Narrow
tubes of Henle ; £, 0, Loops ; /, /, Large tubes of Henle ;
<7, <?, Communicating tubes, uniting with several others to
form A, a tube of Bellini.

In tracing out the course and the relations of the tubes,

1 GROSS, Essai sur la structure microscopique du rein, Strasbourg, 1868.

ANATOMY OF THE KIDNEYS.
FIG. 7.

151

152 EXCRETION.

which recent observations have shown to be somewhat in-
tricate, it will be found most convenient to commence with
a description of the Malpighian bodies, and follow the course
of the tubes from these bodies to their connections with the
straight tubes of the pyramidal substance.

Malpighian Bodies. — These are ovoid or rounded termi-
nal dilatations of the convoluted tubes, of somewhat variable
size, measuring from -g-^- to yj-g- of an inch in diameter. They
are composed of a membrane continuous with that which
forms the convoluted tubes, of the same homogeneous char-
acter, but somewhat thicker, measuring about 2o^0o of an
inch, while the membrane of the tubes is only about 4o^00
of an inch in thickness. This sac — sometimes called the
capsule of Miiller — encloses a mass of convoluted blood-
vessels, and is lined with a layer of nucleated epithelial
cells. The question of the existence of epithelium within
the Malpighian body and the anatomical characters of the
cells have been the subject of considerable discussion. Bow-
man, in his original essay on the kidney, makes the state-
ment repeatedly that the vessels are bare within the capsule ;
and this has led some authors to suppose that he did not
recognize the presence here of any epithelium whatsoever.
This view favors the idea that the Malpighian bodies sepa-
rate only water from the blood, and that the cells lining the
convoluted tubes secrete the solid principles of the urine.
Bowman has never denied the existence of epithelium within
the capsule, but he regards it as of a different character from
that lining the tubes. His statement with regard to it is as
follows : " The epithelium is continued in many cases over
the whole inner surface of the capsule ; in other instances I
have found it impossible to detect the slightest appearance
of it over more than a third of the capsule." There can
be no doubt with regard to the constant presence of epithe-
lial cells within the capsule of the Malpighian bodies, particu-
larly since the researches of Gerlach, by whom they were

1 BOWMAN, op. cit., p. 60.

AN ATOMY, OF THE KIDNEYS. 153

accurately described and figured, in IS^S,1 and the later con-
firmatory observations of Kolliker,* Isaacs,8 and numerous
other anatomists. It only remains to describe the charac-
ters of the cells as compared with those lining the convo-
luted tubes, and to ascertain whether they line the capsule
alone, or are also attached to the vascular tuft.

Bowman believed that the cells, when they existed,
simply lined the capsule, and that the blood-vessels were en-
tirely bare ; while Gerlach described cells attached to the
blood-vessels, and Isaacs regarded these cells as entirely dif-
ferent from those attached to the membrane. From the
great number of observations made by Isaacs upon the kid-
neys of different animals, there can be hardly any doubt
concerning the correctness of the latter view ; for not only
did he describe minutely the difference between the cells of
the capsule and those attached to the tuft, but he found that
the walls of the cells of the capsule were dissolved by dilute
nitric acid, " while comparatively little effect was produced
upon those of the tuft, thus showing a difference in their
constitution and organization." * We must, therefore, rec-
ognize in the Malpighian body two varieties of cells, differ-
ing in size, form, and situation ; one variety lining the cap-
sule, and the other covering the vascular tufts.

Nearly all observers who have studied the anatomy of
the kidney practically agree that the cells attached to the
capsule are smaller and more transparent than those lining
the convoluted tubes. They are ovoid, nucleated, and finely
granular. The cells covering the vessels, however, are larger
and more opaque, and resemble the epithelium lining the
tubes. They measure from I410o to 10100 of an inch in diam-
eter, by about ^5\Q of an inch in thickness.

Tubes of the Cortical Substance. — Following out the
tubes in the cortical substance from the Malpighian bodies,
we find first a short, constricted portion, which has sometimes

1 GERLACH, op. c'd. 8 Loc. cit. 3 Loc. cit. 4 ISAACS, op. cit., p. 405.

154 EXCRETION.

been called the neck of the capsule. The tube soon dilates
to the diameter of about -^J-g- of an inch, when its course be-
comes exceedingly intricate and convoluted. These are
what have been known as the convoluted tubes of the
kidney. The membrane of these tubes is transparent and
homogeneous, but quite firm and resisting. It measures
about 40000 of an inch in thickness. It is lined throughout
with a single layer of rounded or irregularly polygonal epi-
thelial cells, from -j-fVtr to 10100 of an inch in diameter, some-
what larger, consequently, than the cells lining the straight
tubes. These cells are nucleated and usually quite granular.
It has been found that in many of the lower orders of ani-
mals, the cells lining the neck of the capsule are provided
with vibratile cilia. Bowman has described ciliated epi-
thelium in the kidneys of reptiles,1 and Johnson speaks of
the cilia as found in other classes.2 Isaacs has observed
feeble movements in cells from the kidneys of some of the
mammalia,3 and it is possible that they may exist in man,
though their presence has never been actually demonstrated.

The course of the tubes, after they have lost the charac-
ters which were formerly supposed to be peculiar to the tubes
of the cortical substance, and their anastomoses, have attracted
much attention within the last few years. It has been shown
by Henle, and the most important points in his observations
have been confirmed by numerous anatomists, that the con-
voluted tubes, instead of connecting directly with the tubes
of the pyramidal substance, are continuous with a system of
smaller tubes, which pass into the pyramids in the form of
loops.4

Narrow Tubes of Henle. — According to the most re-
cent observations, the convoluted tubes above described,

1 Op. cit., p. 73.

3 JOHNSON, Cydopcedia of Anatomy and Physiology, London, 1847-1849,
vol. iv., part i., p. 246, Article, Ren.

3 Op. cit., p. 383.

4 Henle first described looped tubes of very small diameter projecting into
the pyramidal substance, but did not fully recognize the connections of these

ANATOMY OF THE KIDNEYS. 155

after a long and tortuous ramification in the cortical sub-
stance, invariably become continuous, near the pyramids,
with tubes of much smaller diameter, which form loops, ex-
tending to a greater or less depth into the pyramids. The
loops formed by these canals (the narrow tubes of Henle) are
nearly parallel with the tubes of Bellini, and are much more
numerous near the bases of the pyramids than toward the
apices.1 The diameter of these tubes is very variable, and
they present enlargements at irregular intervals in their
course. The narrow portions are about 2^QO of an inch in
diameter, and the wide portions, about twice this size. Ac-
cording to Gross, this narrow portion is never absent, and is
lined by small, clear cells with very prominent nuclei.8 The
wider portions are lined by larger granular cells. JSTear the
bases of the pyramids, the wide portion sometimes forms the
loop ; but near the apices, the loop is always narrow. The
difference in the size of the epithelium is such, that while
the diameter of the tube is variable, its calibre remains nearly
uniform. The membrane of these tubes is quite thick,
thicker, even, than the membrane of the tubes of Bellini.

Intermediate Tubes. — After the narrow tubes of Henle
have returned to the cortical substance, the^ communicate
with a system of flattened, ribbon-shaped canals, measuring
from 12100 to 10100 of an inch in diameter, with excessively
thin, fragile walls, lined by clear pavement-epithelium.
These tubes take an irregular and somewhat angular course
between the true convoluted tubes, and finally empty into
the branches of the straight tubes of Bellini, thus estab-

tubes with the large convoluted tubes of the cortical substance and the tubes
of Bellini, as has been done by later investigators. An excellent review of the
views of Henle on this subject is given by Gross (loc. cit., p. 6, et seq.}. The
connection of these tubes with the ordinary convoluted tubes, and through them
with the Malpighian bodies, has been fully established by the very elaborate
researches of Schweigger-Seidel. (Die Nieren des Henschen, Halle, 1865, Taf. iv.)

1 Most of the facts with regard to these looped canals we have recently
been enabled to verify in a very elegant section of the kidney of the human
subject, prepared by Dr. R. T. Edes, of Boston Highlands, Mass.

8 GROSS, op. cit., p. 26.

156 EXCKETTON.

lishing a communication between the tubes coming from
the Malpighian bodies and the tubes of the pyramidal sub-
stance. They are called the intermediate tubes, or the
canals of communication. Some observers have described
them as forming an anastomosing plexus, but this disposi-
tion is not definitely established.

The tubes into which the intermediate canals open join
with others, generally two by two, and pass in a nearly
straight direction into the pyramids, where they continue to
unite with each other in their course, becoming, consequently,
less and less numerous, until they open at the apices of the
pyramids into the infundibula and the pelvis of the kidney.

Distribution of Blood-vessels in the Kidney. — The blood-
vessels of the kidney present certain interesting peculiarities
in their distribution, which have been very successfully stud-
ied by Bowman, Isaacs, and many other anatomists, by means
of minute injections of the renal arteries and veins. With the
improved methods of injection now employed, their arrange-
ment can be readily followed.

The renal artery, which is quite voluminous in propor-
tion to the size%f the kidney, enters at the hilum, and divides
into four branches. By numerous smaller branches it then
penetrates between the pyramids, and ramifies in the col-
umns of cortical substance which occupy the spaces between
the pyramids (columns of Bertin). The main vessels, which
are generally two in number, occupy the centre of the col-
umns of Bertin, sending off in their course, at short intervals,
regular branches on either side toward the pyramids. When
these branches reach the boundary of the cortical substance,
they turn upward and follow the periphery of the pyramid
to its base. Here the vessels form an arched, anastomosing
plexus, which is situated exactly at the boundary which sep-
arates the rounded base of the pyramid from the cortical
substance. This plexus presents a convexity looking toward
the cortical substance, and a concavity toward the pyra-

ANATOMY OF THE KIDNEYS. 157

mid. It is so arranged that the interstices are just large
enough to admit the collections of tubes that form the so-
called pyramids of Ferrein.

From this arcade of vessels, branches are given off in two
opposite directions. From its concavity, numerous small
branches, measuring at first from y^-g- to -^j- of an inch in
diameter, pass downward toward the papillae, giving off
small ramifications at very acute angles, and becoming re-
duced in size to about -^-^ of an inch. These vessels —
called sometimes the arteriolae rectae — surround the straight
tubes and pass into capillaries in the substance of the pyra-
mids and at their apices.

From the convex surface of the arterial arcade, numerous
branches are given off at nearly right angles. These pass
into the cortical substance, breaking up into a large number
of little arterial twigs, from y-L- to -g-^- of an inch in diame-
ter, which penetrate the MalpigoiaH bodies at a point oppo-
site to the origin of the convoluted tubes. Once within the
capsule, the arteriole breaks up into from five to eight
branches, which then divide dichotomatously into vessels
measuring from d^QQ to 1g100 of an inch in diameter, ar-
ranged in the form of coils and loops, constituting a dense,
rounded mass (the Malpighian coil), filling up the capsule.
These vessels break up into capillaries without anastomoses.
Their coats are amorphous and provided with numerous
nuclei rather shorter than those found in the general capil-
lary system.

The blood is collected from the vessels of the Malpighian
bodies by veins, sometimes one, and frequently three or four,
which pass out of the capsule and form a second capillary
plexus surrounding the convoluted tubes. "When there is but
one vein, it emerges near the point of penetration of the
arteriole. The walls of the vein are much more fragile than
those of the arteriole, and consequently, in ordinary micro-
scopical preparations of the cortical substance, the arteriole
is left attached, while the veins are torn off.

158

EXCKETION.

The efferent vessels, immediately after their emergence
from the capsule, break up into a very fine and delicate
plexus of capillaries, closely surrounding the convoluted
tubes. These form a true plexus, the branches anastomosing
freely in every direction ; and the distribution of vessels in

this part resembles
essentially the vascu-
lar arrangement in
the glands generally.
Bowman has called
the branches which
connect together the
vessels of the Mal-
pighian tuft and the
capillary plexus sur-
rounding the tubes,
the portal system of
the kidney.1 These
intermediate vessels
form a coarse plexus
around the prolonga-
tions of the pyramids
of Ferrein into the
cortical substance.
The renal or emul-

Malptehian bodies, injected, and convoluted tubes from gent Vein takes its Ol'i-
the kidney of the sheep. (Is AACS, Structure and Phys- . . , « ,1

iology of the Kidney.— Transactions of the New York gin, in part ironi the
Academy of Medicine, 1857, vol. i., p. 391.) .,, n

capillary plexus sur-
rounding the convoluted tubes, and in part from the vessels
distributed in the pyramidal substance. A few branches
come from vessels in the envelopes of the kidney, but these
are comparatively unimportant. The plexus surrounding
the convoluted tubes empties into venous radicles, which
pass to the surface of the kidney, and these present a num-
ber of little radiating groups, each converging toward a cen-

1 BOWMAN, op. cit., p. 63.

ANATOMY OF THE KIDNEYS. 159

tral vessel. This arrangement gives to the vessels of the
fibrous envelope of the kidney a peculiar stellate appear-
ance. These are sometimes called the stars of Yerheyen.
The large trunks which form the centres of these stars then
pass through the cortical substance to the rounded bases of
the pyramids, where they form a vaulted venous plexus cor-
responding to the arterial plexus already described. The
vessels distributed upon the straight tubes of the pyramidal
substance form a loose plexus around these tubes, except at
the papillae, where the net-work is much closer. They then
pass into the plexus at the bases of the pyramids to join with
the veins from the cortical substance. " From this plexus a
number of larger trunks arise and pass toward the hilum
in the centre of the inter-pyramidal substance, enveloped
in the same sheath with the arteries. Passing thus to the
pelvis of the kidney, the veins converge into from three
to four great branches, which unite to form the renal, or
emulgent vein. A preparation of all the vessels of the kid-
neys shows that the veins are much more voluminous than
the arteries.1

The lymphatics of the kidney are few, and, according to
Sappey, only exist in the substance of the organ, converging
toward the hilum. This author does not admit the exist-
ence of superficial lymphatics.

The nerves are quite numerous, and are derived from the
solar plexus, their filaments following the artery in its dis-
tribution in the interior of the organ and ramifying upon
the walls of the vessels.

1 In a recent pamphlet on a circulation peculiar to the kidney of mammals,
a French author assumes to have demonstrated an arrangement of blood-
vessels in the cortical substance very different from that which we have de-
scribed. The glandular character of the Malpighian bodies and their connec-
tion with the convoluted tubes are denied. There is apparently so little basis
for these peculiar views, that it does not seem necessary to discuss them in
detail, and we will simply refer the reader to the original monograph. (SUCQUET,
Ifune circulation du sang specials au rein des animaux vertebres mammif&res, et
de la secretion des urines qiCelle y produit, Paris, 1867.)

160 EXCRETION.

Summary of the Physiological Anatomy of the ^Kidney.
— The division of the kidneys into the cortical and pyrami-
dal substance is quite apparent to the naked eye. The pyra-
mids are distinctly striated, and present, in this regard, and
in their darker color, a marked difference from the cortical
substance. At the apex of each pyramid there are from two
hundred to five hundred little orifices, from -^-^ to yj-g- of
an inch in diameter, which connect with the straight tubes.
From these openings the tubes branch at a very acute angle,
each one leading to a bundle or system of straight canals,
forming the collections called the pyramids of Ferrein. The
branches of these tubes (the tubes of Bellini) are about -$fa
of an inch in diameter, and are composed of a structureless
membrane lined by nucleated epithelial cells.

When these tubes arrive at the bases of the pyramids and
pass into the cortical substance, they increase slightly in size,
and are lined with granular and rounded cells of epithelium.
They then become excessively convoluted, connect with
certain other tubes in their course, and after forming loop-
like processes extending into the pyramids, finally terminate
in rounded or ovoid dilatations (the Malpighian bodies).
These dilated extremities measure from -^^ to y-J-g- of an inch
in diameter.

The Malpighian bodies are composed of a fibrous capsule
(the capsule of Muller), and each one contains a mass of con-
voluted blood-vessels surrounded by nucleated epithelial cells.

The loop-like processes dip down into the pyramids and
return to the cortical substance, present a filamentous, con-
stricted portion, and are here called the narrow tubes of
Henle. The communicating tubes, which connect these
canals with the straight tubes of the pyramidal substance,
are sometimes called "intermediate tubes." They are flat-
tened or ribbon-shaped, with very delicate walls, and are
lined by transparent pavement-epithelium.

Throughout the kidney there is a delicate stroma of
fibrous tissue, in the meshes of which are lodged the blood-

ANATOMY OF THE KIDXEYS. 161

vessels, the straight tubes of the pyramidal substance, and
the tubes and Malpighian bodies of the cortical substance.

The renal artery penetrates the kidney at the hilum,
sends branches between the pyramids, which are distributed
in the form of an arched arterial plexus over the upper por-
tion and the bases of the pyramids, following exactly the
boundary between the pyramidal and the cortical substance.
From these vessels, branches are given off both on the con-
vexity and the concavity of the arches. JSTumerous small
branches (arteriolse rectse) pass downward along the straight
tubes toward the papillae, becoming capillary as they sur-
round the tubes. Other branches take an opposite direc-
tion and pass into the cortical substance, breaking up into
little twigs, each one of which penetrates a capsule of Muller
and divides in its interior into a mass of looped, convoluted
vessels which constitute the Malpighian coil. The blood
is carried away from the Malpighian bodies by one, two, or
three vessels, which are then immediately distributed in a
close plexus around the tubes of the cortical substance.
From this plexus, the radicles of the renal vein pass to the
surface of the kidney, where they present a stellate arrange-
ment, converging toward several large central vessels (the
stars of Yerheyen). These central vessels penetrate the cor-
tical substance and form an arched venous plexus over the
rounded bases of the pyramids. This plexus also receives by
its concave surface venous branches from the pyramidal
substance. The blood is then emptied into larger veins,
passing between the pyramids in the same sheath with the
arteries, to form the renal or emulgent vein.

CHAPTER VI.

MECHANISM OF THE FORMATION AND DISCHARGE OF TJEINE.

Formation of the excrementitious constituents of the urine in the tissues,
absorption of these principles by the blood, and separation of them from
the blood by the kidneys — Effects of removal of both kidneys from a liv-
ing animal — Effects of tying the ureters in a living animal — Extirpation of
one kidney — Influence of blood-pressure, the nervous system, etc., upon
the secretion of urine — Effects of the destruction of all the nerves going
to the kidneys — Alternation in the action of the kidneys upon the two
sides — Changes in the composition of the blood in passing through the
kidneys — Physiological anatomy of the urinary passages — Mechanism of
the discharge of urine.

THE striking peculiarities which the kidney presents in
its structure, as compared with the true glands, and the fact
of the voluntary discharge of its secretion at certain inter-
vals, would naturally lead to a closer study of the mechanism
of the production and discharge of the urine, than we have
given under the general head of mechanism of the formation
of the excretions. The composition of the urine, also, will
be found to be exceedingly complex, and its various ingre-
dients bear the closest relation to the processes of nutrition
and disassimilation ; all of which considerations render it of
the greatest importance to ascertain the precise mode of its
formation, and to study all the conditions by which this pro-
cess may be modified. In the present state of our knowl-
edge, we must certainly regard the excrementitious con-
stituents of the urine as formed essentially in the system at
large, and merely separated from the blood by the kidneys ;
and a consideration of these effete principles belongs to the

FOKMATION OF THE TJEENE. 163

subject of nutrition. It remains for us, then, in this connec-
tion, to treat, in general terms, of the way in which these
substances find their way into the urine.

The most important constituent of the urine is urea ; a
cry stalliz able nitrogenized substance, which is discharged by
the skin as well as by the kidneys. This has long been
recognized as an excrementitious principle ; but the first
observations that gave any definite idea of the mechanism
of its production were made by Prevost and Dumas,1 in
1821. At the time these experiments were made, chemists
were not able to detect urea in the normal blood ; but Pre-
vost and Dumas extirpated the kidneys from living animals
(dogs and cats), and found an abundance of urea in the
blood, after certain symptoms of blood-poisoning had been
manifested. The first experiments were performed by
removing one kidney by an incision in the lumbar region,
and at the end of three or four days, after the animal had
recovered from the first operation, removing the other.
After the second operation the animals lived for from five
to nine days. For the first two or three days there were no
symptoms of blood-poisoning. Watery discharges from the
stomach and intestinal canal occurred after a few days, and
finally stupor and other marked evidences of nervous dis-
turbance supervened, when the presence of urea in the blood
could be easily determined. These observations were con-
firmed and extended by Segalas and Yauquelin, in 1822, who
presented to the French Academy of Medicine a specimen
of nitrate of urea extracted from the blood of a dog, taken
sixty hours after extirpation of the kidneys, giving its pro-
portion to the weight of blood employed.3 A few years
later, the observations of Prevost and Dumas were con-

1 The observations of Prevost and Dumas, Segalas, Marchand, and others,
have already been referred to (see p. 25).

- SEGALAS, Sur des nouvelles experiences relatives aux proprietes medicamenteuses
de Puree, et sur le gendre de mort qui produit la noix vomique. — Journal de physio*
logie, Paris, 1822, tome ii., p. 356.

EXCRETION.

firmed in the human subject. In this case urea was found
to have accumulated in the blood as the consequence of an
injury received in the lumbar region.1

Since that time, as the processes for the determination
of urea in the animal fluids have been improved, this sub-
stance has been detected in minute quantity in the normal
blood by Marchand,a Picard,3 Poisseuille and Gobley,4 and
many others. Picard, indeed, carefully estimated and com-
pared the proportions of urea in the renal artery and the
renal vein, and found that the quantity in the blood was
diminished about one-half in its passage through the kid-
neys.6 According to Robin, who apparently accepts the
results obtained by Picard, the blood in the renal vein con-
tains much less urea, urates, creatine, creatinine, chloride
of sodium, etc., than the blood of the renal artery.6 Still
later urea has been found by Wurtz to exist in the lymph
and chyle in larger quantity even than in the blood.7

These facts, which have been almost universally regarded
as established, have led physiologists to adopt the view that
the peculiar excrementitious principles found in the urine
are not produced by the kidneys, but are formed in the sys-
tem by the general process of disassimilation, are taken up
from the tissues by the blood, either directly or through the

1 SHEARMAN, Case of Mechanical Injury to the Kidneys, followed by Coma ;
Suppression of the Secretion of Urea by the Kidneys, and Absorption of the Urea
into the Blood- — Recovery. — The Monthly Journal of Medical Science, Edinburgh
and London, 1848, vol. viii. (New Series, vol. ii.), p. 666.

2 MA.RCHAND, Sur la presence de Turee dans le sang. — Annales des sciences natu-
relles, Paris, 1838, 2me serie, tome x., p. 46.

3 PICARD, De la presence de Vuree dans le sang, These, Strasbourg, 1856.

4 POISSEUILLE ET GOBLEY, Recherches sur Vuree. — Comptes rendus, Paris, 1859,
tome xlix., p. 164, et seq. Poisseuille and Gobley found, as a rule, more urea
in the arterial than in the venous system. The blood from the carotid con-
tained 0*225 parts per 1000 ; that from the portal vein, 0'171 ; from the splenic
vein, 0*225, from the renal veins, 0'164 ; and from the femoral vein, 0'136.

5 Op. cit., p. 38.

6 ROBIN, Zecons sur les humeurs, Paris, 1867, p. 117.

7 See vol. ii., Lymph and Chyle, pp. 520, 528.

FOLIATION OF THE URINE. 165

lymph, and are merely separated from the blood in the kid-
neys ; and it has consequently been pretty generally assumed
that nearly, if not all, the constituents of the urine preexist
in the circulating fluid. There is, indeed, no well-defined
principle in the urine that has not been actually demon-
strated in the blood. As an additional argument in favor
of this view of the mechanism of the urinary excretion, it has
been ascertained that when the kidneys are interrupted in
their function, there is a tendency to the elimination of the
excrementitious principles of the urine by the lungs, skin,
and alimentary canal ; and that these matters only accumu-
late in the blood after this vicarious effort has failed to effect
their complete discharge.

These ideas have seemed to be so completely justified by
facts, that they have been applied to the mechanism of ex-
cretion by other organs, such as the skin and the liver ; but
within a few years, the older observations with regard to
nephrotomized animals have been discredited; and it has
been asserted, as the result of experiment, that urea and the
urates do not accumulate in the blood after removal of the
kidneys, .but that this result only follows when both ureters
have been tied. The experiments on which this idea is based
have been applied mainly to the pathology of uraemic intoxi-
cation, but it is evident that they bear directly upon the
mechanism of excretion. It is not assumed, however, that
excrementitious principles are not formed by the disassimi-
lation of the tissues ; but it is asserted that urea and the
urates are produced in the kidneys by a transformation of
the excrementitious matters, creatine, creatinine, etc., which
exist in the blood. It is foreign to our purpose to discuss in
exten-so the pathological conditions produced by the retention
of the urinary principles in the blood ; and we shall consider
this question only so far as it bears upon the physiology of
excretion.

The original experiments of Prevost and Dumas are very
strong arguments in favor of the view that has been so long

166 EXCRETION.

almost unquestioned ; viz., that urea is simply separated
from the blood by the kidneys ; but the more recent obser-
vations of Bernard and Barreswill, Hammond, and others,
while they confirm the first experiments on this subject,
have added very considerably to our knowledge of the
mechanism of ursemic poisoning after extirpation of the
kidneys. The kidneys, it has been found, can readily be
removed from living animals, dogs, cats, rabbits, etc., with-
out any great disturbance immediately following the opera-
tion. Bernard and Barreswill found that animals from
which both kidneys had been removed did not usually pre-
sent any distinctive symptoms for a day or two after, except
that they vomited and passed an unusual quantity of liquid
from the intestinal canal. During this period, the blood
never contained an abnormal quantity of urea ; but the
contents of the stomach and intestine were found to be
highly animoniacal. During this time, also, the secretions
from the stomach and intestines, particularly the stomach,
became continuous, as well as increased in quantity. Ani-
mals operated upon in this way usually live for four or five
days, and then die in coma following upon convulsions.
Toward the end of life, the secretion of gastric and intestinal
fluids becomes arrested, probably from the irritating effects
of ammoniacal decomposition of their contents, and then, and
then only, urea is found to accumulate enormously in the
blood.1

It is thought by Bernard that the hypersecretion by the
gastric and intestinal mucous membrane, in nephrotomized
animals, is an effort on the part of the system to eliminate
the urea, which is decomposed by contact with these mem-
branes into carbonate of ammonia. This view is sustained
by the fact that when urea is introduced into the alimentary
canal in living animals, it disappears almost immediately

1 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 36, el seq. These
experiments were first published by Bernard and Barreswill in the Archives ge-
nerates de medecine, Paris, 1847, tome xiii., p. 449.

FORMATION -OF THE URIXE. 167

and is replaced by the ammoniacal salts.1 Consequently,
after removal of the kidneys, we should not expect to find
an increased quantity of urea in the blood, until its elimina-
tion by the mucous membrane of the alimentary canal has
ceased ; but the fact that it then accumulates in large quan-
tity cannot be doubted.

The results of the experiments of Dr. Hammond entirely
correspond with those obtained by Bernard and Barreswill.
He has also confirmed the fact, observed by Segalas and
Yauquelin, that urea is an active diuretic when injected in
small quantity into the veins of a healthy animal ; 3 and that
in this case it does not produce any poisonous effects, but is
immediately eliminated. But when urea is injected into
the vascular system of a nephrotomized animal, it produces
death in a very short time, with the characteristic symptoms
of uraemic poisoning.3 We have frequently removed both
kidneys from dogs, and when the operation is carefully per-
formed, the animals live for from three to five days. In some
instances they have been known to live for twelve days or
even longer,4 but death always takes place finally with
symptoms of blood-poisoning.

The experiments which are supposed to show that urea
and the urates are actually formed in the kidneys — to which
we have already alluded — were made with the view of com-
paring the effects of removal of both kidneys with those
produced by tying the ureters. According to the observa-
tions of Oppler, the blood contains much more urea after
the ureters are tied than after removal of the kidneys.6 Perls
states, as the result of experiments on rabbits, that no accu-
mulation of urea in the muscular substance can be proved

1 BERNARD, op. cit., p. 51.

2 SEGALAS, loc. cit.

3 HAMMOND, Physiological Memoirs — Urcemic Intoxication, Philadelphia,
1863, p. 347.

4 HAMMOND, op. cit., p. 303.

5 OPPLER, Beitrdge zur Lehre von der Uramie. — VIRCHOW'S Archiv, Berlin,
1861, Bd. xxi., S. 260, et aeq.

168 EXCRETION.

after removal of the kidneys ; but that this occurs only after
tying the ureters, and the quantity seems to be greatest in
the first twenty-four or forty-eight hours after the operation.1
Essentially the same results were obtained by Zalesky,2 who
asserts that the proportion of urea in the blood after removal
of the kidneys in dogs is about the same as in the normal
condition. These experiments, which are directly opposed
in their results to the well-considered observations of Pre-
vost and Dumas, Bernard and Barreswill, Hammond, and
many others, cannot be accepted unless it be certain that all
the necessary physiological conditions have been fulfilled.
In the first place, it was positively demonstrated, as early as
184:7, that urea does not accumulate in the blood immediately
after removal of the kidneys, but only toward the end of
life, and then it is found in enormous quantity.3 In the sec-
ond place, it is well known that the operation of tying the
ureters is followed by an immense pressure of urine in the
kidneys, which not only disturbs the eliminative action of
these organs, but affects most seriously the general functions.

1 PERLS, in CANSTATT'S JahresbericM, Wurzburg, 1865, S. 194. The experi-
ments of Perls are not sufficiently extended to be very satisfactory. Rejecting
one experiment in which the animal was killed twenty-four hours after removal
of the kidneys — when no accumulation of urea could be expected — there are
three examinations of the muscular substance after death from removal of the
kidneys, and four after death from tying the ureters. In an examination after
removal of the kidneys, 2'32 parts per 1,000 of nitrate of urea were found ; in
the second, there were no crystals in the extract ; and in the third there were
slight traces of urea. These animals died three or four days after the opera-
tion. Five examinations were made of the muscular substance in animals
that died after tying the ureters. In three of these examinations, urea was
found in considerable quantity ; and in the remaining two, urea was present in
very small quantity in one instance, and in the other, it is not stated that any
urea was found. No examinations were made of the blood. These experi-
ments on the accumulation of urea in nephrotomized animals are hardly suffi-
cient to overthrow the researches of Prevost and Dumas, and others by whom
their observations have been confirmed.

2 ZALESKY, Untersuchungen uber den urcemischen Process und die Function der
Nieren, Tubingen, 1865.

8 BERNARD AND BARRESWILL, loc. cit.

FORMATION OF THE UKINE. 169

Since the influence of the nervous system upon the secre-
tions has been so closely studied, it is evident that the pain
and disturbance consequent upon the accumulation of urine
above the ligated ureters must have an important reflex ac-
tion upon the secretions ; and this would probably interfere
with the vicarious elimination of urea and other excremen-
titious principles by the stomach and intestines. It is well
known to practical physicians that an arrest of these secre-
tions, in cases of organic disease of the kidneys, is liable to
be followed immediately by evidences of uraemia, and that
grave ursemic symptoms are frequently removed by the ad-
ministration of remedies that act promptly and powerfully
upon the intestinal canal. As additional evidence of the
great disturbance of the system, aside from the mere accu-
mulation of excrementitious principles in the blood, which
must result from tying the ureters, we have the intense dis-
tress and general prostration, always so prominent in cases
of nephritic colic, where there is only temporary obstruction
of one ureter. The pathological condition of the kidneys
which follows the operation of tying the ureters was observed
by Bicherand, many years ago,1 and the observations of
Oppler, Perls, and Zalesky, on this subject are not entirely
novel.8

From a careful review of the important facts bearing
upon this question, there does not seem to be any valid
ground for a change in our ideas concerning the mode of
elimination of urea and the other important excrementi-
tious constituents of the urine. There is every reason to

1 RICHERAND ET BfiRARD, Nouveaux elemens de physiologic, Paris, 1833, tome
it, p. 142.

Richerand noted great disturbance in animals, thirty-six hours after tying
both ureters. In a cat on which this operation had been performed, death took
place on the third day. " The kidneys were swollen, softened, and, as it were,
macerated ; all the organs, all the humors, and the blood itself, participated hi
this urinous diathesis." (Loc. cit., p. 143.)

8 MILNE-EDWARDS, Lemons sur la physiologic, Paris, 1862, tome vii., pp. 457,
459.

170 EXCRETION.

suppose that these principles are produced in the various
tissues and organs of the body during the process of disassim-
ilation,'are taken up by the blood, and are simply separated
from the blood by the kidneys. There may be unimportant
modifications of some of these principles in the kidneys
or in the urine, such as the conversion of a certain amount
of creatine into creatinine, but the great mass of excremen-
titious matter is separated from the blood by the kidneys
unchanged.

Extirpation of one kidney from a living animal is not
necessarily fatal. "We have frequently performed this opera-
tion as a class-demonstration, and kept the animal for weeks
and months, without observing any indications of disturbance
in the eliminative functions. If the operation be carefully
performed, the wound will generally heal without any diffi-
culty, and in most instances the remaining kidney seems
sufficient for the elimination of urine for an indefinite period.
In all of our experiments, save one, the animals, killed long
after the wound had healed, never presented any marked
symptoms of the retention of excrementitious matters in
the blood. It is a noticeable fact, however, that in many
instances they showed a marked change in disposition, and
the appetite became voracious and unnatural. These ani-
mals would sometimes eat faeces, the flesh of dogs, etc.,
and, in short, presented certain of the phenomena so fre-
quently observed after extirpation of the spleen.

In no instance have we been able to observe enlargement
of the remaining kidney, even many months after the extirpa-
tion of one of these organs. In one experiment, of which a
record of the facts was made at the time, a dog, from which
one kidney had been removed, was kept for one year and
nine months and then killed while in perfect health. The
remaining kidney presented no abnormal characters, and was
of the same size as the other, which had been preserved in
alcohol. There appears to be a general but rather indefinite

EXTIRPATION OF ONE KIDNEY. 171

idea that, when one kidney is removed, in order that the
other shall accomplish the function of both, it must undergo
hypertrophy. This is stated as a fact by Paget,1 though we
have failed to find any very positive observations bearing
upon the question.3 It does not seem probable that the
secreting structure of an organ like the kidney, after it has
once attained its full development, can undergo physiologi-
cal hypertrophy, or be the seat of the development of new
secreting substance. Whenever the kidney is found hyper-
trophied in the human subject, it is due to the deposition in
its substance of non-secreting tissue, which generally inter-
feres very seriously with its function. It is more reasonable
to suppose that Nature has provided in the kidneys, as in
the lungs and other organs, more working substance than is
absolutely required for the elimination of the excrementitious
constituents of the urine ; and that even when one kidney
is removed, the other is competent to eliminate the amount
of excrementitious matter that is produced under ordinary
conditions of the system.

The exceptional experiment in which the animal died
after extirpation of one kidney is quite interesting : Octo-
ber 6, 1864, we removed one kidney from a small cur-dog,
about nine months old, by an incision in the lumbar region.
The animal did not appear to suffer from the operation, and
the wound healed kindly. The only marked effects were
great irritability of disposition and an exaggerated and per-
verted appetite. He would attack the other dogs in the
laboratory without provocation, and would eat with avidity
faeces, putrid dog's flesh, and articles which the other ani-
mals would not touch, and which he did not eat before the
operation. On the morning of ]STovember 18th, forty-three

1 PAGET, Lectures on Surgical Pathology, Philadelphia, 1854, p. 33.

2 In some of the experiments of Zalesky, it is stated, in general terms, that
about a month after the extirpation of one kidney, the other is enlarged. It is
not apparent, however, that the size and weight of the two kidneys were actu-
ally compared. (Op. cit., p. 22.)

172 EXCRETION.

days after the operation, the dog appeared to be uneasy,
cried frequently, and at 12 o'clock went into convulsions,
which continued until 3J- p. M., when he died.

In one other instance, in which a dog was kept for more
than a year after extirpation, of one kidney, it was occasion-
ally observed that the animal was rather quiet and indisposed
to move for a day or two, but this always passed off, and
when he was killed he was as well as before the operation.

Influence of the Nervous System, Blood-pressure !, etc.,
upon the Secretion of Urine. — There are numerous instances
in which very marked and sudden modifications in the action
of the kidneys take place under the influence of fear, anxiety,
hysteria, etc., when the impression must have been transmit-
ted through the nervous system. Although little is known
of the final distribution of the nerves in the kidney, it
has been ascertained that here, as elsewhere, filaments from
the sympathetic system ramify upon the walls of the blood-
vessels, and thus are capable of modifying the quantity and
the 'pressure of blood in these organs.

It may be stated as a general proposition, that an increase
in the pressure of blood in the kidneys increases the flow of
urine ; and that when the blood- pressure is lowered, the flow
of urine is correspondingly diminished. This fact will in a
measure account for the increase in the flow of urine during
digestion ; but it cannot serve to explain all of the modifica-
tions that may take place in the action of the kidneys. The
fact above stated, although it has been long recognized by
physiologists, has lately been very fully illustrated by the
experiments of Bernard. This observer measured the pres-
sure of blood in the carotid artery of a dog, and carefully
noted the quantity of urine discharged in the course of a
minute from one of the ureters. Afterward, by tying the
two crural, the two brachial, and the two carotid arteries, he
increased the blood-pressure about one-half, and the quantity
of urine discharged in a minute was immediately increased

MODIFICATIONS OF THE SECRETION OF UKEN'E. 173

by a little more than fifty per cent. In another animal, he
diminished the pressure by taking blood from the jugular
vein, and the quantity of urine was immediately reduced
about one-half.1 His later observations on this subject
showed that the increase in the quantity of urine produced
by exaggerated pressure of blood in the kidneys was capable
of being modified through the nervous system. In these ex-
periments, the nerves going to one kidney were divided,
which produced an increase in the arterial pressure and a
consequent exaggeration in the quantity of urine from the
ureter on that side. The pressure was then further increased
by stopping the nostrils of the animal. The quantity of
urine was increased by this on the side on which the nerves
had been divided, but the pain and distress from want of air
arrested the secretion upon the sound side.2

The precise influence which special nerves exert upon the
secretion of urine has not yet been positively ascertained.
Some important facts, however, bearing upon this subject
have been developed of late years. In his interesting and
novel experiments upon artificial diabetes in animals, Ber-
nard found that when irritation was applied to the floor of
the fourth ventricle, in the median line, exactly in the mid-
dle of the space comprised between the origin of the pneu-
mogastrics and the auditory nerves, the urine was increased
in quantity and became strongly saccharine. When the irri-
tation was applied a little above this point, the urine was sim-
ply increased in quantity, but contained no sugar ; and when
the puncture was made a little below, sugar appeared in the
urine, without any increase in the quantity of the secretion.3
It has also been observed that section of the spinal cord in
the upper part of the dorsal region arrests, for a time, the
secretion of urine.4

1 BERNARD, Liquidts de Forganisme, Paris, 1859, tome ii., p. 155.
- Unpublished lectures delivered at the College of France in the Summer
of 1861.

3 BERNARD, Lemons de physiologic experimentale, Paris, 1855, p. 339.

4 BERNARD, Unpublished lectures, 1861.

174 EXCRETION.

Bernard, in following out his ideas with regard to the
mechanism of secretion, supposes that there are certain
nerves derived from the sympathetic system, the galvaniza-
tion of which will arrest the flow of urine ; and others, be-
longing to the cerebro-spinal system, called by him the
motor nerves of the gland, which, when galvanized, should
increase the flow of urine ; but the kidney, unlike the true
glandular organs, will continue to secrete for a time when
removed from all nervous influence. He has divided the
sympathetic nerves that penetrate with the blood-vessels
at the hilum, and galvanized them, producing an arrest of
secretion during the entire period of the galvanization.1
With regard to the determination of the motor nerve of the
kidney, the experiments are not so satisfactory ; and while
there may be nerves capable of exciting the secretion of
urine, analogous to the motor nerves of the salivary glands,
this has never been actually demonstrated.

The final effect of division of all the nerves going to the
kidney is very curious. The immediate effect of destruction
of these nerves is to increase largely the amount of blood
sent to the kidney, the organ then pulsating like an aneuris-
mal tumor. In experiments on this subject by Miiller and
Peipers, the flow of urine was sometimes arrested by divi-
sion of these nerves, but occasionally it continued. In these
observations, the nerves were destroyed by applying a liga-
ture tightly to the vessels as they enter at the hilum, includ-
ing every thing but the ureter. The ligature was then
loosened, so as to admit the blood, but the nerves were
bruised and destroyed.3 We have just referred to the
observations of Bernard, in which the flow of urine was
temporarily increased by this operation. The secretion
of urine continues, however, for only a few hours. It then
ceases, and the nutrition of the kidney becomes profound-
ly affected, its tissue breaking down into a putrid, seini-

1 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 163.

2 MUELLER, Manuel de physiologic, Paris, 1851, tome i., p. 391.

MODIFICATIONS OF THE SECRETION OF URINE.

fluid mass, which probably enters the blood and is the cause
of death.

The other physiological conditions that affect the urinary
excretion influence the composition of the urine and the
quantity of excrementitious matters separated by the kid-
neys. These will be more appropriately considered under
the head of nutrition and disassimilation. It is sufficient to
remark, in this connection, that during digestion, when the
composition of the blood is modified by the absorption of
nutritive matters, the quantity of urine is usually increased.
This is particularly marked when a large amount of liquid
is taken. There are certain modifications due to the con-
dition of the blood in disease, but these do not belong to
the subject of physiology. The same may be said of the
elimination of foreign matters introduced into the circula-
tion, and the excretion of sugar by the kidneys when this
substance is produced in the system in excess.

The prompt separation of certain matters from the blood
by the kidneys has been illustrated by experiments upon ani-
mals, and by observations on the human subject in cases of
extroversion of the bladder, in which the urine could be im-
mediately collected as it flowed from the ureters. In a case
of this kind observed by Erichsen, the ferrocyanide of potas-
sium taken into the stomach after a fast of eleven hours
appeared in the urine in one minute. In this case, numer-
ous experiments were made with other articles, which it is
unnecessary to follow out in detail.1

As the excrementitious principles eliminated by the kid-
neys are being constantly produced in the tissues by the
process of disassimilation, the formation of urine is constant ;
presenting, in this regard, a marked contrast with the inter-
mittent flow of most of the secretions proper, as distinguished

1 ERICHSEN, Observations and Experiments on the Rapidity of the Passage of
some Foreign Substances through the Kidnies, and on some Points connected with
the Excretion of the Urine. — London Medical Gazette, London, June 27, 1845,
New Series, vol. ii., p. 363.

176 EXCEETION.

from the excretions. It was noted by Erichsen,1 in his case
of extroversion of the bladder, and it has been further shown
by experiments upon dogs, that there is an alternation of
action upon the two sides. Bernard exposed the ureters in
a living animal and fixed a small silver tube in each, so that
the secretion of both kidneys could be readily observed ; and
he noted that a large quantity of fluid was discharged from
one side for from fifteen to thirty minutes, while the flow
from the other side was slight and in some instances was
entirely arrested. The flow then commenced with activity
upon the other side, while the discharge from the opposite
ureter was diminished or arrested.2 We are already familiar
with this mode of action in the parotid glands.3

Changes in the Composition of the Blood in passing
through the Kidneys. — Some of the changes in the blood in
its passage through the kidneys have already been noted.
The most important of these consist in a diminution in the
proportion of urea, the urates, and other of the excrementi-
tious principles found in the urine. This would be expected,
inasmuch as these principles are constantly present in the
urine, and have been shown to be derived exclusively from
the blood. It has been ascertained, also, that the blood of
the renal veins contains less water than the blood of any
other part of the venous system.4 The constant separation
of water from the blood by the kidneys, for the purpose of
carrying off the soluble excrementitious principles, is an ex-
planation of this fact. It was also observed by Simon, a
number of years ago, that the blood of the renal veins does

1 ERICHSEN, loc. tit, p. 361. In this case, the openings of both ureters
were exposed to view, and Erichsen states that " the two ureters do not open
at the same time, but with an irregularly alternating action."

2 BERNARD, Unpublished lectures delivered at the College of France in the
Summer of 1861. During the progress of this course of lectures, we had an
opportunity of observing the alternate action of the two kidneys,

3 See vol. ii., Digestion, p. 160.

4 ROBIN, Lefons sur les humeurs, Paris, 1867, p. 80.

CHANGES IN THE BLOOD IN THE KIDNEYS. 177

not coagulate readily, and that it is impossible to obtain
fibrin from it in the ordinary way by stirring with rods.1 It
is difficult in the present state of our knowledge to give any
satisfactory physiological explanation of this disappearance
of fibrin in the kidneys. Absence of fibrin has also been
noted by Lehmann in the blood of the hepatic veins.*

Reference has already been made to the researches of
Bernard, showing that the blood coming from many of the
glands during their functional activity is but little darker
than arterial blood.3 The action of the kidneys is constant,
and the quantity of blood which they receive is enormous.
Unless the function of these organs be disturbed, the blood
p'assing through them cannot be deoxygenated, and is con-
sequently red, containing a large quantity of oxygen and
a very small proportion of carbonic acid. This fact we have
often noted, and it has been observed by all who have exam-
ined the renal veins in living animals. In comparative
analyses for gases of the blood of the renal artery and vein,
Bernard found, in one examination, no carbonic acid in
either specimen ; the proportion of oxygen being twelve
parts per hundred in volume for the artery, and ten parts
for the vein. These observations were made at a tempera-
ture of from 50° to 53° Fahr. Making the analyses at about
the temperature of the body, 104° to 113°, the quantity of
carbonic acid was three parts for the artery and 3*13 parts for
the vein ; and the proportion of oxygen was 19*46 parts for
the artery and 17*26 parts for the vein. TVhen the secretion
of urine was arrested by irritation of the kidney, the blood
became black in the vein, and the quantity of oxygen dimin-
ished, with a corresponding increase in the proportion of
carbonic acid.4

These observations show that during secretion most of

1 SIMON, Animal Chemistry, Philadelphia, 1846, p. 178.

2 LEHMAXN, Physiological Chemistry, Philadelphia, 1855, Tol. i., p. 319.

3 See page 21.

4 BERNARD, Liquids de Vorganisme, Paris, 1859, tome ii., p. 160.

178 EXCEETION.

the blood sent to the kidneys is for the purpose of furnishing
water and the excrementitious principles of the urine, and
but little is used for ordinary nutrition. Secretion appears
to have no marked influence upon the consumption of oxygen
and the production of carbonic acid.

Physiological Anatomy of the Urinary Passages. — The
chief physiological interest attached to the anatomy of the
urinary passages is connected with the discharge of the urine
from the kidneys into the bladder, and the process of mictu-
rition ; and it will be necessary, consequently, to give but a
brief account of the structure of these parts.

The excretory ducts of the kidneys, the ureters, commence
each by a funnel-shaped sac, the pelvis, which is applied to
the kidney at the hilum. This sac presents little tubular
processes, called calices, into which the apices of the pyra-
mids are received. The ureters themselves are membranous
tubes of about the diameter of a goose-quill, becoming much
reduced in calibre as they penetrate the coats of the bladder.
They are from sixteen to eighteen inches in length, passing
from the kidneys to the bladder behind the peritoneum.
They have three distinct coats ; an external coat, composed
of fibrous tissue, the ordinary white fibres mixed with elas-
tic fibres of the small variety ; a middle coat, composed of
different layers of non-striated muscular fibres ; and a mucous
coat.

The external coat requires no special description. It is
continued into the calices and is continuous with the fibrous
coat of the kidney at the apices of the pyramids.

The fibres of the muscular coat present two principal
layers ; an external longitudinal layer, and an internal
transverse, or circular layer, to which is added near the
bladder a layer of longitudinal fibres, internal to the circu-
lar fibres.

The mucous lining is thin, smooth, and without any fol-
licular glands. It is thrown into slight longitudinal folds,

ANATOMY OF THE URINARY PASSAGES. 179

when the tube is flaccid, which are easily effaced by disten-
tion. The epithelium exists in several layers, and is remark-
able for the irregular shape of the cells. They present,
usually, numerous dark granulations, and one or two clear
nuclei, with distinct nucleoli. Some of the cells are flat-
tened, some are rounded, and some are caudate, with one or
two prolongations.

Passing to the base of the bladder, the ureters become
constricted, penetrate the coats of this organ obliquely,
their course in its walls being a little less than one inch
in length. This valvular opening allows the free passage
of the urine from the ureters, but compression or distention
of the bladder closes the orifices and renders a return of the
fluid impossible.

The bladder, which serves as a reservoir for the urine,
varies in its relations to the pelvic and abdominal organs
as it is empty or more or less distended. When perfectly
empty, it lies deeply in the pelvic cavity, and is then a
small sac, of an irregularly triangular form. As it be-
comes filled, it assumes a globular or ovoid form, rises up
in the pelvic cavity, and, when excessively distended, may
project into the abdomen. When the urine is voided at the
normal intervals, the bladder, when filled, contains about a
pint of liquid ; but under pathological conditions, it may
become distended so as to contain ten or twelve pints, and in
some instances of obstruction, it has been found to contain
even more. The bladder is usually more capacious in the
female than in the male. It is held in place by certain
ligaments and folds of the peritoneum, which it is unneces-
sary to describe in this connection, but which are so arranged
as to allow of the various changes in volume and position
which the organ is liable to assume under different degrees
of distention.

The anatomy of the coats of the bladder possesses a cer-
tain amount of physiological interest. These are three in
number. The external coat is simply a reflection of the

180 EXCEETION.

peritoneum, covering the posterior portion completely, from
the openings of the ureters to the summit, about one-third
of the lateral portion, and a small part of the anterior portion.

The middle, or muscular coat, consists of fibres of the
non-striated or involuntary variety, arranged in three toler-
ably distinct layers.

The external muscular layer is composed of longitudinal
fibres, which arise from parts adjacent to the neck, and pass
anteriorly, posteriorly, and laterally over the organ, so that
when they are contracted they diminish its capacity chiefly
by shortening its vertical diameter. The anterior fibres of
this layer arise from the body of the pubis and the symphy-
sis by tendinous bands, known to most anatomists as the
anterior ligaments. These tendinous fibres spread out on
the prostate and are attached to its anterior surface. As
the fibres on the anterior surface pass over the summit of
the bladder, they interlace, and some of them are continuous
with the fibres coming from the posterior surface. The
posterior fibres arise from the base of the prostate, and, after
forming a distinct band an inch or an inch and a quarter in
breadth, spread out on the posterior surface of the bladder.
The lateral fibres arise from the sides of the prostate and
spread out upon the lateral surfaces of the bladder. In the
female, the posterior fibres arise ^from the dense fibrous
membrane between the neck of the bladder and the vagina,
and the lateral fibres from the perineal aponeurosis, the
anterior fibres arising from the pubis as in the male. The
fibres of the external layer are of a pinkish hue, being much
more highly colored than the other layers.

The middle muscular layer is formed of circular fibres,
arranged, on the anterior surface of the bladder, in distinct
bands at right angles to the superficial fibres. They are
thinner and less strongly marked on the posterior and lateral
surfaces.

The internal muscular layer is composed of excessively
pale fibres arranged in longitudinal fasciculi, the anterior

ANATOMY OF THE URINARY PASSAGES. 181

and lateral bundles anastomosing with each other as they-
descend toward the neck of the bladder, by oblique bands
of communication, and the posterior bundles interlacing in
every direction, forming an irregular plexus. Here they
are not to be distinguished from the fibres of the middle
layer. This arrangement has given to these fibres the name
of the plexiform layer, and it gives to the interior of the
bladder its reticulated appearance. This layer is continuous
with the muscular fibres of the urachus, the ureters, and the
urethra.

The sphincter vesicas is composed of a band of smooth
fibres, about half an inch in breadth and one eighth of an
inch in thickness, embracing the neck of the bladder and
the posterior half of the prostatic portion of the urethra.
The tonic contraction of these fibres prevents the flow of
urine, and during the ejaculation of the seminal fluid, it
ofiers an obstruction to its discharge into the bladder.

It is seen, from this arrangement of the muscular fibres
of the bladder, that they are capable by their contraction of
expelling the greatest part of the urine when the sphincter
is relaxed.

The mucous membrane of the bladder is smooth, rather
pale, thick, and loosely adherent to the submucous tissue,
except over the corpus trigonum. The epithelium exists in
several layers, and presents the same diversity in form that
is observed in the pelvis of the kidney and the ureters ; viz.,
the deeper cells are elongated and resemble the columnar
epithelium, while the cells on the surface are flattened. In
the neck and fundus of the bladder are a few mucous
glands ; some in the form of simple follicles, and others
collected so as to form glands of the simple racemose variety.

The corpus trigonum is a triangular body, lying just
beneath the mucous membrane at the base of the bladder,
and extending from the urethra in front to the openings of
the ureters. It is composed of white fibrous tissue, with a
few elastic and muscular fibres. At the opening of the

182 EXCRETION.

urethra, it presents a small projecting fold of mucous
membrane, which is sometimes called the uvula vesicse.
Over the whole of the surface of the trigone, the mucous
membrane is very closely adherent, and is never thrown
into folds, even when the bladder is entirely empty.

The blood-vessels going to the bladder are ultimately
distributed to its mucous membrane. They are not very
numerous, except at the fundus, where the mucous mem-
brane is tolerably vascular. Lymphatics have been described
as existing in the walls of the bladder, but Sappey, whose
researches in the lymphatic system have been very extended
and successful, has failed to demonstrate them in this situa-
tion.1 The nerves of the bladder are derived from the hypo-
gastric plexus.

The urethra is provided with muscular fibres and is lined
by a mucous membrane, the anatomy of which wTill be more
fully considered in connection with the function of genera-
tion. In the female the epithelium of the urethra is like
that of the bladder. In the male the epithelial cells are
small, pale, and of the columnar variety.

Mechanism of the Discharge of Urine. — In some of the
lower orders of animals, in which the urine is of a semisolid
consistence, the movement of vibratile cilia in the uriniferous
tubes probably aids in the discharge of the urine ; but in the
human subject, the existence, even, of cilia is doubtful, and
the urine is discharged into the pelvis of the kidneys and
the ureters by pressure due to the act of separation of the
fluid from the blood. Once discharged into the ureters, the
course of the urine is determined in part by the vis a tergo,
and in part, probably, by the action of the muscular coats
of these canals. Miiller has found that the ureters can be
made to undergo a powerful local contraction upon the ap-
plication of an intense galvanic current ; a and Bernard has

1 SAPPEY, Traite cTanatomie descriptive, Paris, 1857, tome iii., p. 516.
9 MUELLER, Manuel de physiologic, Paris, 1851, tome L, p. 396.

DISCHARGE OF THE URINE. 183

shown that this may be produced by galvanization of the
anterior root of the eleventh dorsal nerve.1 Notwithstand-
ing these facts, it is difficult to estimate the amount of influ-
ence ordinarily exerted by peristaltic contractions of the
ureters ; but when there is excessive accumulation of urine
in the bladder, or when there is obstruction from any cause,
such as the presence of a renal calculus, these contractions
are probably quite energetic.

When the urine has accumulated to a certain extent in
the bladder, a peculiar sensation is experienced which leads
to the act for its expulsion. This desire to discharge the
urine is probably due to the impression produced by the
distention of the bladder, and is conveyed to the nervous
centres through the sympathetic system. The intervals at
which it is experienced are exceedingly variable. The urine
is usually voided before retiring to rest and upon rising in
the morning, and generally two or three times, in addition,
during the day. It is dependent, however, very much upon
habit, upon the quantity of liquids ingested, and upon the
degree of activity of the skin ; the latter conditions modify-
ing the quantity of urine.

Evacuation of the bladder is accomplished by the mus-
cular walls of the organ itself, aided by contractions of the
diaphragm and the abdominal muscles and certain muscles
which operate upon the urethra, and is accompanied by
relaxation of the sphincter vesicae. This act is at first
voluntary, but once commenced, it may be continued by
the involuntary contraction of the bladder alone. During
the first part of the process, the distended bladder is com-
pressed by the voluntary contraction of the diaphragm and
the abdominal muscles ; and this, after a time, excites the
action of the bladder itself. A certain period usually elapses
then before the urine begins to flow. When the bladder
contracts, aided by the muscles of tho abdomen and the dia-

1 Unpublished lectures delivered by Bernard at the College of France in the
Summer of 1861.

184: EXCRETION.

phragm, the resistance of the sphincter is overcome, and a
jet of urine flows with considerable force from the urethra.
All voluntary action may then cease for a time, and the
bladder will nearly empty itself; but the force of the jet
may at any time be considerably increased by voluntary
effort.

It is a question whether the bladder be capable of entirely
emptying itself by the action of its muscular walls. That
almost all the urine may be expelled in this way in the
human subject there can be no doubt ; and it has been shown
by experiments upon some of the inferior animals that the
bladder may be completely evacuated when it has been
removed from the abdominal cavity. This fact was observed
long ago by Magendie in dogs.1 In vivisections we have
frequently observed the bladder so firmly contracted that it
could contain hardly more than a few drops of liquid.

Toward the end of the expulsive act, when the quantity
of liquid remaining in the bladder is slight, the diaphragm
and the abdominal muscles are again called into action, and
there is a convulsive, interrupted discharge of the small
quantity of urine that remains. At this time the impulse
from the bladder, and, indeed, the influence of the abdomi-
nal muscles and diaphragm, are very slight, and the flow of
urine along the urethra is aided by the contractions of its
muscular walls and the action of some of the perineal mus-
cles, the most efficient being the accelerator urinse ; but with
all this muscular action, a few drops of urine generally re-
main in the male urethra after the act of urination is accom-
plished. The process of evacuation of urine in the female is
essentially the same as in the male, with the exception of the
slight modifications due to differences in the direction and
length of the urethra.

The movements of the bladder are regulated by the ner-
vous system. According to the researches of Budge, the
influence of the nervous system operates through the sympa-

1 MAGENDIE, Precis elementaire de physiologic, Paris, 1836, tome ii., p. 485.

DISCHARGE OF THE TJRINE. 185

thetic, and he has described a centre in the spinal cord,
which presides over the contractions of the lower part of the
intestinal canal, the bladder, and the vasa deferentia. This
he calls the genito-spinal centre, and he has located it, in ex-
periments upon rabbits, in the spinal cord opposite to the
fourth lumbar vertebra. From this centre the nervous fila-
ments pass through the sympathetic nerve which communi-
cates with the ganglion corresponding to the fifth lumbar
vertebra.1 These experiments have been somewhat extended
by M. Giannuzzi, who operated upon dogs. The location
of a centre in the spinal cord somewhere in the lumbar re-
gion was confirmed, and it was further ascertained that
certain filaments passed to the bladder from a point corre-
sponding to the third lumbar vertebra, going through the
mesenteric ganglia, to form part of the hypogastric plexus.
Xervous filaments also passed directly to the bladder from a
point in the spinal cord opposite the fifth lumbar vertebra.
When the spinal cord at these points was irritated with the
point of a needle, contraction of the muscular walls of the
bladder was produced ; but this result did not follow when
the irritation was applied to the cord after division of the
nerves above mentioned.2

1 BUDGE, Lehrbuch der speciellen Physiologic des Henschen, Leipzig, 1862,
S. 510.

9 GIAXXUZZI, Recherches physiologiqucs sur Ics nerfs motcurs de la vessie. —
Journal de la physiologic, Paris, 1863, tome vi., p. 29.

CHAPTER YII.

PEOPERTIES AND COMPOSITION OF THE HEINE.

General physical properties of the urine — Quantity, specific gravity, and reaction
— Composition of the urine — Urea — Origin of urea — Compounds of uric
acid — Hippurates and lactates — Creatine and creatinine — Oxalate of lime —
Xanthine — Fatty matters — Inorganic constituents of the urine — Chlorides
— Sulphates — Phosphates — Coloring matter and mucus — Gases of the
urine — Variations in the composition of the urine — Variations with age and
sex — Variations at different seasons and at different periods of the day —
Variations produced by food — Urina potus, urina cibi, and urina sanguinis
— Influence of muscular exercise — Influence of mental exertion.

THE importance of an exact knowledge of the properties
and composition of the urine has long been recognized by
physiologists ; and our literature is full of observations, more
or less valuable, upon this subject, dating from the discovery
of urea by Hillaire Rouelle,1 in the latter part of the last
century, to the present time. It is impossible, however, to
follow out in detail even the most important of the chemical
researches upon the different urinary constituents, without
exceeding the limits of pure human physiology ; and the ob-
servations of the earlier authors, Scheele, Bergmann, Cruick-
shank,3 Fourcroy, Yauquelin, Frout, and many others, have

1 MILNE-EDWARDS, Lemons sur la physiologie, Paris, 1862, tome vii., p. 395.
This author gives a very full account of the earlier chemical researches into the
composition of the urine, which resulted in a description of the properties of
urea. The observations of Rouelle were quite imperfect ; but the more elabo-
rate researches of Scheele, Bergmann, and others, which will be cited further on,
gave a pretty correct idea of the chemical characters of this important excretion.

8 Cruickshank was the first to describe the formation of crystals of the
nitrate of urea. He added to the concentrated urine an equal bulk of nitrous (?)

PROPERTIES OF THE TJRLNE. 187

now little more than an historical interest. But this can
hardly be said of the analysis by Berzelius, made early in the
present century ; for even in recent authoritative works upon
physiology, these are quoted as the most elaborate and relia-
ble of the quantitative examinations of the renal excretion.1
In treating of this subject, we propose to give simply the
chemistry of the urine as it is understood at the present day,
dwelling particularly upon its relations to the physiology of
nutrition and disassiinilation. In doing this it will be neces-
sary to consider carefully the quantity, specific gravity, re-
action, etc., of the urine, with the variations observed under
different physiological conditions.

General Physical Properties of the Urine.- — The color
of the urine is very variable within the limits of health, de-
pending chiefly upon the character of the food, the quantity
of drink, and the activity of the skin. As a rule, the color
is yellowish, or amber, with more or less of a reddish tint.
The fluid is perfectly transparent, free from viscidity, and
exhales, when first passed, a peculiar aromatic odor, which
is by no means disagreeable. Soon after the urine cools, it
loses this peculiar odor, and has the odor known as urinous.
This continues until the liquid begins to undergo decompo-
sition. The color and odor of the urine are usually modified
by the same physiological conditions. "When the fluid con-
tains a relatively large amount of solid matters, the color is
more intense, and the urinous odor more penetrating ; and
when its quantity is increased by an excess of water, with
the low specific gravity, the color is pale, and the odor faint.
The urine passed in the morning is usually more intense in
color than that passed during the day.

acid and an equal weight of water. This produced at first violent effervescence,
and when cold, a large quantity of flat, shining crystals made their appearance.
These crystals were undoubtedly nitrate of urea (CRUICKSHANK, Experiments on
Urine and Sugar, in HOLLO, Cases of the Diabetes Mellitus, London, 1798, p. 441).
1 BERZELIUS, Suite du memoire sur la composition des fluides animaux. — An-
nales de chimie, Paris, 1814, tome Ixxxix., p. 38.

188 EXCRETION.

It is somewhat difficult to measure the exact temperature
of the urine at the moment of its emission. In some recent
observations on this subject, by Dr. Byasson, in which a very
delicate thermometer was used, and extraordinary care was
taken to prevent any change in temperature before the esti-
mate was made, the temperature, under physiological condi-
tions, varied but a small fraction of a degree from 100° Fahr.1
It is important to know the normal temperature of the urine,
as it is liable to vary very considerably in certain diseases.

Quantity, Specific Gravity, and Reaction of the Urine.
— In estimating the total quantity of urine discharged in the
twenty-four hours, it is important to take into consideration
the specific gravity, as an indication of the amount of solid
matter excreted by the kidneys. We have already alluded
to some of the variations in quantity constantly occurring in
health, as depending upon the proportion of water • but the
amount of solid matters excreted is usually more nearly uni-
form. It must also be taken into account that differences
in climate, habits of life, etc., in different countries, have an
important influence upon the daily quantity of urine. Dr.
Parkes has collected the results of twenty-six series of obser-
vations made in America, England, France, and Germany,
and finds the average daily quantity of urine in healthy male
adults, between twenty and forty years of age, to be fifty-
two and a half fluidounces, the average quantity per hour
being two and one-tenth fluidounces. The extremes were
thirty-five and eighty-one ounces.3

In attempting to decide the question whether a certain
quantity of urine passed be abnormal or within the limits of
health, it is important to recognize, if possible, certain limits
of physiological variation. Becquerel states that the varia-
tions in the proportion of water in the urine likely to occur

1 BYASSON, Essai sur la relation qui exisle d V etat physiologiqw entre Vactivite
cerebrate et la composition des urines, Paris, 1868, p. 42, table.

2 PARKES, The Composition of tJie Urine, London, 1860, p. 6.

PROPERTIES OF THE TJKINE. 189

in health are between twenty-ssven and fifty fluidounces ; *
but his average of the total quantity in the twenty-four hours
is only forty-four ounces, which is rather lower than the one
we are disposed to adopt. The circumstances that lead to a
diminution in the proportion of water are usually more effi-
cient in their operation than those which tend to an increase ;
and the range below the healthy standard is rather wider
than it is above. All these estimates, however, are merely
approximative. Assuming that the usual quantity in the
male is about fifty ounces, it may be stated, in general terms,
that the range of normal variation is between thirty and
sixty ; and that when the quantity varies much from these
figures, it is probably due to some pathological condition.

According to the researches of Becquerel, the quantity
of water discharged by the kidneys in the twenty-four hours
is a little greater in the female than in the male ; but in the
female the specific gravity is lower, and the amount of solid
constituents is relatively and absolutely less.2

The specific gravity of the urine should always be
estimated in connection with the absolute quantity in the
twenty-four hours. Those who assume that the daily quan-
tity is about fifty ounces give the ordinary specific gravity
of the mixed urine of the twenty-four hours, at 60° Fahr., as
about 1020. The specific gravity is liable to the same vari-
ations as the proportion of water, and the density is increased
precisely as the amount of water is diminished. The ordi-
nary range of variation in specific gravity is between 1015
and 1025 ; but without positively indicating any pathologi-
cal condition, it may be as low as 1005, or as high as 1030.

The reaction of the urine is acid in the carnivora and
alkaline in the herbivora. In the human subject it is usually
acid at the moment of its discharge from the bladder ; though
at certain periods of the day it may be neutral or feebly

1 BECQUEREL ET RODIER, Traite de chimie pathologique appliquee d la medecint
pratique, Paris, 1854, p. 273.

8 BECQUEREL ET RODIER, op. tit., p. 270, table.

190 EXCRETION.

alkaline, depending upon the character of the food. The
acidity may be measured by carefully neutralizing the urine
with an alkali, in a solution that has previously been grad-
uated with a solution of oxalic acid of known strength ; and
the degree of acidity is usually expressed by calling it equiv-
alent to so many grains of crystallized oxalic acid.

As the result of numerous observations made by Yogel
and under his direction, the total quantity of acid in the
urine of the twenty-four hours in a healthy adult male is
equal to from two to four grammes, or, omitting fractions,
thirty to sixty grains of oxalic acid. The hourly quantity
in these observations was equal, in round numbers, to from
one and a half to three grains of acid. The proportion of
acid was found to be very variable in the same person at
different periods of the day. In one individual, upon whom
the greatest number of observations was made, the average
hourly quantity of acid at night was 2'9 grains ; in the fore-
noon, 2 grains; and in the afternoon, 2*3 grains. "In a
series of experiments made upon four different persons, the
quantity was found to be greatest at night, least in the fore-
noon, and between these extremes in the afternoon." 1 The
observations upon this subject by Prof. Dalton show that
the variations noted by Yogel, in Germany, probably exist
in this country, under the conditions of life met with in our
large cities. Dr. Dalton found, in his own person, that the
maximum of acidity was at night and in the early morning,
the minimum being in the forenoon, and the mean in the
afternoon and evening.2

In estimating the degree of acidity of the urine, it is
necessary to test the fluid as soon as possible after it is dis-
charged from the bladder ; for its acidity rapidly increases
after emission — until ammoniacal decomposition sets in — by
the formation of organic acids, particularly the lactic.

1 NEUBAUER AND VOGEL, A Guide to the Qualitative and Quantitative Analysis
of the Urine, TJie New Sydenham Society, London, 1863, pp. 296, 389.

2 DALTON, A Treatise on Human Physiology, Philadelphia, 1867, p. 335.

PROPERTIES OF THE URINE. 191

There has been considerable discussion and difference of
opinion among physiological chemists with regard to the
cause of the acid reaction of the urine. At the moment of
its discharge from the bladder, it is distinctly, and even
strongly acid ; but it will not decompose the carbonates, like
most acid solutions.1 The weight of chemical authority upon
this point is in favor of the view that there is no free acid in
the urine when it is first passed, although the lactic acid,
the acid lactates, and perhaps some other of the organic
acids may be produced after emission, as the result of decom-
position ; but nearly all authors agree that it contains the
acid phosphate of soda. The phosphates exist in the fluids
of the body in at least three different conditions. The basic
phosphate of soda, for example, possesses three atoms of the
base, and has an alkaline reaction. In contact with carbonic
acid, this salt may lose one atom of the base, forming the car-
bonate of soda and what is called the neutral phosphate, the
latter, however, having a feebly alkaline reaction. In contact
with uric acid, the neutral phosphate may lose still another
atom of base, forming the urate of soda and the acid phos-
phate ; and according to Neubauer and Yogel,a Robin,8 and
others, it is in this form that it exists in the urine, and the
presence of this salt is the cause of its acidity. The acid
phosphate of soda may or may not be associated, in the hu-
man subject, with the acid phosphate of lime, which ordi-
narily gives the intensely acid reaction to the urine of the
carnivora.

Composition of the Urine.

Regarding the excrementitious constituents of the urine
as a measure, to a certain extent, of the general process of
disassimilation, it is probably more important to recognize
the absolute quantity of these principles discharged in a

1 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 642.

2 Loc, cit.

3 Op. cit,, pp. 65, 293.

192 EXCRETION.

definite time than to learn simply their proportions in the
urine ; and in making out a table of the composition of the
urine, we will give, as far as possible, the absolute quantity
of its different constituents excreted in twenty-four hours.
This latter point, however, will be more elaborately consid-
ered in connection with the .characters of the individual
excrementitious principles and their variations under physio-
logical conditions. In compiling this table, we have taken
advantage of the elaborate bibliographical and experimental
researches of Prof. Robin, contained in his recent work upon
the humors,1 but have made some changes and corrections
in his list of urinary constituents :

1 ROBIN, Le$ ons sur les humeurs, Paris, 1867. In the table given by Robin
(p. 654), there is evidently a very serious error in one of the figures giving the
proportion of water. In quotations from this table in a very recent French
work on the chemistry of the urine, this error is corrected (BERGERET, De V urine,
Paris, 1868, pp. 13, 24).

Although this table represents, very nearly, the latest and most reliable
observations upon the relative and absolute quantities of the urinary constitu-
ents, there are a few minor points that demand some explanation. For exam-
ple, Robin estimates the proportion of hippurates at a little less than the pro-
portion of urates, while many writers of high authority speak of the hippurates
as excreted in rather larger quantity (PARKES, TJie Composition of the Urine,
London, 1860, p. 13, and NEUBAUER AND VOGEL, A Guide to tlie Qualitative
and Quantitative Analysis of the Urine, London, 1863, p. 33) ; but the investi-
gations with regard to the daily excretion of hippuric acid have not been so
definite and satisfactory as those on which the estimates of the excretion of
uric acid are based. Robin gives, also, the proportion of creatine as 1*4 to 2 '6
parts per 1,000, and of creatinine, 0'2 to 0'4 per 1,000 ; and most authors give
in the urine a larger proportion of creatinine. This difference, however, is
not important, for, as far as the process of excretion is concerned, these two
substances may be regarded as a single principle ; creatine being readily con-
verted into creatinine in the urine by simple decomposition. In our endeavor to
make this table as complete as possible, we have reduced the figures given by
many authors to represent the amounts of uric acid, phosphoric acid, sulphuric
acid, chlorine, etc., to the quantity of the salts as they actually exist. This is
particularly important in a work on physiology, for chlorine and the various
acids just enumerated are not proximate constituents of the urine, except when
combined with bases. It is simply a matter of convenience to estimate them
separately, and the proportions of salts are readily calculated from the combin-
ing equivalents of the different elements.

COMPOSITION OF THE URINE. 193

Composition of the Human Urine.

"Water (in 24 hours, 27 to 50 fluidounces — Becquerel) ...... 967'47 to 940-36

Urea (in 24 hours, 355 to 463 grains— Robin) ............. 15'00 " 23'00

Urate of soda, neutral and acid ......

Crate of ammonia, neutral and acid (in
small quantity) ...................

Urate of potassa (traces) ............

Urate of lime (traces) .

(In 24 hrs., 6 to

9 grs. of uric acid

^-Becquerel-or9

to 14 grs. of urates,

estimated as neut.

Urate of magnesia (traces) J urate of soda.)

Hippurate of soda. . . . j (In 24 hrs., about 7'5 grs. of hip-

Hippurate of potassa . > puric acid — Thudichum — equiv. to 1*00 " 1*40

Hippurate of lime. . . . ) about 8'7 grs. of hippurate of soda.)

Lactate of soda \

Lactate of potassa ...!• (Daily quantity not estimated). . 1-50 " 2'60

Lactate of lime )

Creatine ) (In 24 hours, about 11 -5 grains

Creatinine f of both— Thudichum) 1-60 " 3'00

Oxalate of lime (daily quantity not estimated) traces " I'lO

Xanthine not estimated.

Margarine, oleine, and other fatty matters O'lO to 0'20

Chloride of sodium (hi 24 hours, about 154 grains — Robin) 3'00 " 8'00

Chloride of potassium traces.

Hydrochlorate of ammonia 1'50 to 2'20

Sulphate of soda. . . 1 ^ 24hr3'' 23 to 38 «"• of sulPhu-
Sulphate of potassa ric acid-Thudichum. About equal
Sul hate of lim f parts of sulPnate of soda and sulphate 3'00 " 7*00

of potassa — Robin — equiv. to from
' J 22-5 to 37-5 grs. of each.)
Phosphate of soda, neutral l (Daily quantity not esti-

Phosphate of soda, acid. . j" mated) 2'50 " 4'30

Phosphate of magnesia (in 24 hrs., 7'7 to 11 '8 grs. — Neubauer) 0'50 " 1-00
Phosphate of lime, acid. . ) (In 24 hrs., 4'7 to 5'7 grs. —

Phosphate of lime, basic. . ) Neubauer) 0'20 " 1'30

Ammonio-magnesian phosphate (daily quantity not estim.). . 1'50 " 2'40
(Daily excretion of phosphoric acid, about 56 grs. — Thudichum.)

Silicic acid 0'03 " 0'04

Urrosacine ^ 0.10 « Q.$Q

Mucus from the bladder \ *

1,000-00 1,000-00

Gases of the Urine. (Parts per 1,000 in volume.)
Oxygen, in solution ................................... 0'82

Nitrogen, in solution. (Mean of fifteen observations — Morin) 9'59

Carbonic acid, in solution ............................. 19'62

Proportion of solid constituents, from 32'63 to 59'89 parts per 1,000.
13

194 EXCRETION.

Urea, C3H4N3O2.

As regards quantity, and probably as a measure of the
activity of the general process of disassimilation, urea is the
most important of the urinary constituents ; and this sub-
stance, with the changes which it undergoes in the urine
and the mode of its production in the system, has been most
carefully studied by physiologists. Regarding the daily ex-
cretion of urea as a measure of nutritive force and physio-
logical waste, its consideration would come properly under
the head of nutrition, in connection with all other substances
known to be the results of disassimilation ; but it is more
convenientN to treat of its general physiological properties,
and some of its variations in common with other excremen-
titious principles separated by the kidneys, in connection
with the composition of the urine.

The formula for urea, showing the presence of a large
proportion of nitrogen, would lead us to suppose that it is
one of the products of the waste of the nitrogen ized princi-
ples of the body. It is found, under normal conditions, in
the urine, the lymph and chyle, the blood, the sweat, and
the vitreous humor.1 Its presence has lately been demon-
strated also in the substance of the healthy liver in both
carnivorous and herbivorous animals;2 and it has further
been shown by Zalesky that it exists in minute quantity in
the muscular juice.8 Under pathological conditions, as has
been already intimated, urea finds its way into various

1 MILLON, Presence de Puree dans Phumeur vitree de Fail. — Annuaire de chimie,
Paris, 1848, p. 431. The discovery of urea in the vitreous humor was con-
firmed by Marchand and by Wohler (Ibid., 1849, p. 540).

8 The presence of urea in the substance of the liver in diseased conditions
has frequently been observed, and lately its existence has been conclusively
demonstrated in the healthy liver by Meissner. (Eeitrdge zur Kenntniss des
Stoffwechsels im thierischen Organismus. — Centralblatt fur die mediciniscJien Wis-
scnschaften, 1868, No. 18, S. 275.)

3 ZALESKY, Untersuchungen iiber den Uraemischen Process, Tubingen, 1865,
Tabelle iii.

UREA. 195

other fluids, such as the secretion from the stomach, the
serous fluids, etc.

In connection with the chemical properties of urea, it is
interesting to note that it is one of the few organic proxi-
mate principles that can be produced synthetically in the
laboratory of the chemist.1 As early as 1828, Wohler ob-
tained urea by adding sulphate of ammonia to a solution of
cyan ate of potassa.3 The products of this combination are
sulphate of potassa, with cyanic acid and ammonia in a form
to constitute urea. The cyanate of ammonia is isomeric with
urea, and the change is effected by a simple rearrangement
of its elements, the formula being NH^OjC^O (cyanate of
ammonia), equivalent to C3H4]N'aO3 (urea). It has long been
known that urea, in contact with certain animal substances,
is readily convertible into carbonate of ammonia. This trans-
formation is theoretically accomplished by adding to urea four
atoms of water. C3H4N 3O, (urea) + 4 HO = 2 (KH4O,CO2).
It has recently been stated by Kolbe, that when carbonate of
ammonia is heated in sealed tubes to the temperature at which
urea commences to decompose, it is converted into urea.3 The
decomposition of urea resulting in the carbonate of ammonia
may be easily effected by various chemical means. As this
occurs in the spontaneous decomposition of urea in the urine
and elsewhere, it has been supposed that the symptoms of
blood-poisoning following retention of the urinary constit-
uents, in cases of disease of the kidneys, are due to the
decomposition of the urea into carbonate of ammonia, and
not to the presence of the urea itself in the blood. Many
interesting experiments and observations have been made
upon this subject, but it is now pretty generally admitted

1 It is interesting, also, in this connection to refer to the synthesis of another
of the organic proximate principles ; viz., neurine, which has lately been accom-
plished by Wurtz (Comptes rendus, Paris, 1868, tome Ixv., p. 1015).

2 WOHLER, Sur la formation artificielle de Vuree. — Annales de chlmie et de
physique, Paris, 1828, tome xxxvii., p. 330.

3 Journal of Anatomy and Physiology, Cambridge and London, 1868, vol. ii.,
p. 430.

196 EXCRETION.

that the weight of evidence is against the carbonate-of-
ammonia theory of uraemia.

Except as regards the probable changes that take place
in the process of transformation of certain constituents of the
tissues into urea, the chemical history of this substance does
not present much physiological interest. Urea may be read-
ily extracted from the urine, by processes fully described in
all the modern works upon physiological chemistry ; and its
proportion may now be easily estimated by the new meth-
ods of volumetric analysis. It is not so easy, however, to
separate it from the blood or the substance of any of the
tissues, on account of the difficulty in getting rid of the other
organic matters and the great facility with which it under-
goes decomposition.

When perfectly pure, urea crystallizes in the form of long,
four-sided, colorless, and transparent prisms, which are with-
out odor, neutral, and in taste something like saltpetre.
These crystals are very soluble in water and in alcohol, but
are entirely insoluble in ether. In its behavior to reagents,
urea acts as a base, combining readily with certain acids,
particularly the nitric and oxalic. It also forms combina-
tions with certain salts, such as the oxide of mercury, chlo-
ride of sodium, etc. It exists in the economy in a state of
watery solution, with perhaps a small portion of it modified
by the presence of chloride of sodium.

Origin of Urea. — There are two probable sources of
urea in the economy, assuming that it always preexists in
the blood and is not formed in the kidneys. One of these
is in the disassimilation of the nitrogenized constituents of
the tissues, and the other in a transformation in the blood
of an excess of the nitrogenized elements of food. Urea, as
we have already seen, exists in considerable quantity in the
lymph and chyle, and is found, also, in small proportion, in
the blood. It has lately been detected in still smaller quan-
tity in the muscular tissue ; 1 but chemists have thus far been

1 ZALESKY, loc. dt. Meissner found urea in the muscles, liver, and brain,

UREA. 197

unable to extract it from any other of the solid tissues, under
normal conditions, except the substance of the liver. The
fact that it exists in considerable quantity in the liver has
led to the supposition that this is the organ chiefly concerned
in its production.1 "With the small amount of positive
information that we have upon this point, the view that
the liver produces urea, while the kidneys are the organs
chiefly concerned in its elimination, must be regarded as
purely hypothetical. But if it be true that urea is the re-
sult of the physiological wear of the nitrogenized elements
of the body, the liver would probably produce its share, in
the ordinary process of disassimilation. The fact that urea
has not yet been detected in normal muscular tissue is by no
means a conclusive argument against its formation in this
situation. We have lately shown that, although the liver is
constantly producing sugar, none can be detected in its
substance, for the reason that it is washed out as fast as it
is formed, by the current of blood.2 In the case of the
muscles, it is by no means improbable that the lymph, and
perhaps the blood, washes out the urea constantly, and keeps

in rabbits and dogs, after extirpation of the kidneys (Bericht uber Versuche
der Uramie betreffend. — Zeitschrift fur rationelk Medicin, Leipzig u. Heidelberg,
1866, Dritte Reihe, Bd. xxvi., S. 232).

1 MEISSXER, Beitrdge zur Kenntniss des Stoffwecfisels im thierischen Organis-
mus. — CentralUatt fur die medidnischen Wissenschaften, 1868, Xo. 18, S. 275.
Meissner refers to Heynsius and Stokvis as having previously indicated, though
in an imperfect manner, the presence of urea in the liver. Parkes states that
•when portions of the substance of the liver have been destroyed by disease, the
urea is sometimes deficient in the urine, and that it has appeared to him that
" the want of urea was hi proportion to the amount of hepatic tissue destroyed "
(The Composition of the Urine, London, 1860, p. 284).

2 FLINT, Jr., Experiments undertaken for the purpose of reconciling some of the
Discordant Observations upon the Glycogenic Function of the Liver. — New York
Medical Journal, Jan., 1869, vol. viii., p. 373, et seq. The experiments detailed
hi this article we have since repeated in public demonstrations, and confirmed
most fully. In our later observations, we showed absence of sugar in the blood
from the portal vein and the substance of the liver, and the presence of a large
quantity of sugar in the blood from the hepatic veins. The dog upon which
these observations were made was in full digestion.

198 EXCEETION.

these parts free from its presence during normal conditions.
In some late experiments by Meissner, in which the observa-
tions of Prevost and Dumas on the accumulation of urea in
the blood of nephrotomized animals were confirmed, urea
was found in dogs and rabbits, after removal of the kidneys,
not only in the liver, but in the muscles and brain.1

Although our experimental knowledge does not warrant
the unreserved conclusion that urea is produced primarily
in the nitrogenized parts of the organism, particularly the
muscular tissue, this view is exceedingly probable ; and we
must wait for further information on this subject, until phys-
iological chemists are able to follow out more closely the
exact atomic changes that intervene between the functional
operation of organized parts and the change of their sub-
stance into excrementitious matters.

When we come to consider the influence of food upon
the composition of the urine, it will be seen that an excess
of nitrogenized matter taken into the alimentary canal causes
a proportionate increase in the quantity of urea discharged.
This fact has led to the supposition that a part of the urea
contained in the urine is the result of a direct transformation
in the blood of the nitrogenized alimentary principles. This
view must be regarded as purely hypothetical. "We do not
even know the nature of the process by which the nitroge-
nized elements of the tissues are transformed into excremen-
titious matter, and we are still more ignorant of the essential
characters of nutrition proper. When more nitrogenized
food is taken than is absolutely necessary, it is evident that
the excess must be discharged from the system. This is
never discharged in the same form in which it enters, like
an excess of chloride of sodium or other inorganic matter,
but it is well known that a series of complicated changes,
called catalytic, are necessary, even before organic matters
can be taken into the blood by absorption. There is 110 evi-

1 MEISSNER, Bericht uber Versuche der Urdmie betreffend. — Zeitschrift fur
rationelle Medicin, Leipzig u. Heidelberg, 1866, Dritte Reihe, Bd. xxvi., S. 232.

UKEA. 199

dence of the direct transformation of these principles into
urea before they have become part of the organized struc-
tures, except in a comparison of the proportions of nitrogen
ingested and discharged ; and this proves nothing with re-
gard to the nature of the intermediate processes. At the
present time, the most rational supposition is, that the nitro-
genized elements of food nourish the corresponding constitu-
ents of the body, which are constantly undergoing conversion
into excrementitious matters. Observations which have ap-
peared to demonstrate the formation of urea directly from
albuminoid substances have not been confirmed.1

There are certain arguments, based upon comparisons
of the atomic constitution of urea with the elements of uric
acid, creatine, and creatinine, in favor of the view that urea
is the product of a higher degree of oxidation of the other ex-
crementitious matters above-mentioned. It has been found,
also, that urea may be formed artificially from uric acid,
creatine, creatinine, xanthine, hypoxanthine, and some other
bodies of similar nature.8 That certain bodies are mutually
convertible by the addition or subtraction of a few elements
of water, there can be no doubt. Examples of these simple
transformations are, the change of starch (C12H10O10), dex-
trine, etc., into glucose (C13H14O14) ; the change of creatine
(C8H9X3O4) into creatinine (C8H7^"3O3), etc. ; but the atomic
changes necessary for the conversion into urea of the princi-
ples from which this substance has been assumed to be pro-
duced are much more complicated. There is no positive
proof that the proportion of these various principles in the
muscles, blood, and urine, bears an inverse ratio to the pro-
portion of urea. Again, the argument that the excrements
of reptiles contain an excess of uric acid because the activity
of oxidation is less than in the mammalia is met by the fact
that in birds, where the amount of oxygen consumed is

1 MILNE-EDWARDS, Lemons sur la physiologic, Paris, 1862, tome vii., pp.
400, 401.

8 XEUBAUER AND VOGEL, op. tit., p. 9

200 EXCRETION.

greater, the proportion of urates is enormous ; and urea is
not generally found in this class, but is contained only in
the excrements of the rapacious birds, and here only in small
quantity.1

There are no sufficient reasons for regarding urea as the
final result of oxidation of certain of the tissues of the body,
uric acid, creatine, etc., being substances in an intermediate
stage of transformation ; and we are forced to admit that
this principle is formed during the general process of disas-
similation, probably from the nitrogenized elements of the
body, by a destructive action, with the exact nature of
which we are as yet imperfectly acquainted.

The daily amount of urea excreted is subject to very
great variations. It is given in the table as ranging between
355 and 463 grains. This is much less than the estimates
frequently given; but when the quantity has been very
large, it has generally depended upon an unusual amount
of exercise, of nitrogenized food, or the weight of the body
has been above the average. Parkes gives the results of
twenty-five different series of observations on this point.
The lowest estimate is 286'1 grains, and the highest 688'4
grains.2

Compounds of Uric Add.

Uric acid (C6ILN~2O3 + HO) seldom, if ever, exists in a free
state in the normal urine. It is exceedingly insoluble, requir-
ing from fourteen to fifteen thousand times its volume of cold
water, and from eighteen to nineteen hundred parts of boil-
ing water for its solution.3 It was at one time supposed to
exist in the urine in sufficient quantity to give it its acid re-
action ; but it has since been ascertained that its solution does
not redden litmus. Its presence in the urine uncombined
must be regarded as a pathological condition ; still, it is often

1 MILNE-EDWARDS, Lemons sur la physiologic, Paris, 1862, tome vii., p. 445.

2 PARKES, 27ic Composition of the Urine, London, 1860, p. 7.

3 NEUBAUER AND VOGEL, op. cit., p. 27.

COMPOHtO)S OF URIC ACID. 201

found in urinary deposits, where it is interesting to study the
peculiar and varied forms of its crystals. Frequently, in ta-
bles of the composition of the urine, the proportion of uric
acid is given, but this is simply a matter of convenience, and
has precisely the same signification as the estimates of the
proportions of sulphuric or phosphoric acid. None of these
acids constitute, of themselves, proximate principles of the
urine, but are always combined with bases.

In normal urine, uric acid is combined with soda, ammo-
nia, potassa, lime, and magnesia. Of these combinations,
the urate of soda and the urate of ammonia are by far the
most important and constitute the great proportion of the
urates, the urates of potassa, lime, and magnesia existing
only in minute traces. The urate of soda is very much more
abundant than the urate of ammonia.1 The union of uric
acid with the bases is very feeble. If from any cause the
urine become excessively acid after its emission, a deposit
of uric acid is liable to occur. The addition of a very small
quantity of almost any acid is sufficient to decompose the
urates, when the uric acid appears after a few hours in a
crystalline form.

Uric acid, probably in combination with bases, was found
in the substance of the liver in large quantity by Cloetta ; a
and his observations have been confirmed by recent German
authorities.8 It is more than probable that the urates also
exist in the blood and pass ready-formed into the urine;
but their proportion in the blood is so slight under normal
conditions, that their presence in this fluid has not been defi-

1 The urates of soda exist in two forms ; the neutral urate, in which there
is one equivalent of the acid, and the acid urate, with two equivalents of acid.
There are likewise neutral and acid urates of ammonia. The neutral salts exist
hi by far the larger quantity.

2 CLOETTA, De la presence de Vinosite, de facide urique, etc., dans diverse* par-
ties du corps animal. — Journal de la physiologic, Paris, 1858, tome i., p. 802.
Cloetta also noted the presence of uric acid in the substance of the spleen.

3 MEISSKER, op. tit. — Centralblatt fur die meditinischen Wissenschaften, 1868,
No. 15, S. 226, et seq.

202 EXCRETION.

nitely determined, except in birds, where Meissner has lately
found it in considerable quantity.1 The fact that the urates
exist in the liver, and in no other part — except, perhaps, the
spleen — has led Meissner to the opinion that this organ is the
principal seat of the formation of uric acid. However this
may be — and the facts do not seem sufficiently definite to
lead to such an exclusive opinion — it is certainly not formed
in the kidneys, but is simply separated by these organs from
the blood. Meissner did not succeed in finding uric acid in
the muscular tissue, though the specimens were taken from
the same animals in which he had found large quantities in
the liver.

We have already discussed the theory of the change of
uric acid into urea. In the present state of our knowledge,
we must regard the urates, particularly the urate of soda, as
among the products of disassimilation of the nitrogenized
constituents of the body ; and we should admit that as yet
we are unable to designate the precise seat of their forma-
tion, or to follow out all the processes involved in their pro-
duction.

The daily excretion of uric acid, given in the table, is
from six to nine grains ; which is equal to from nine to four-
teen grains of urates estimated as neutral urate of soda.
Like urea, the proportion of the urates in the urine is sub-
ject to certain physiological variations, which will be con-
sidered further on.

IRppurates and Lactates.

The compounds of hippuric acid (C18H9NO6), which are
so abundant in the urine of the herbivora, are now known to
be constant constituents of the human urine. Robin states
that hippuric acid is always to be found in the urine of
children, but that it is sometimes absent temporarily in
the adult.9 The presence of this acid in the normal human

1 Loc. dt. 2 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 678.

HIPPUKATES AND LACTATES. 203

urine seems to have been first established by Liebig ; l and
his researches have since been confirmed by numerous other
observers. Lehmann, particularly, has been able to find
this acid in his own urine, not only when on a purely vege-
table diet, but during the use of a mixed diet. He is of the
opinion that this principle frequently escapes observation
when the urine has been evaporated too rapidly.3

The hippurates have been detected in the blood of the
ox by Yerdeil and Dolfuss,3 and have since been found in
the blood of the human subject ; 4 and there can be scarcely
any doubt that they pass, ready-formed, from the blood into
the urine. With regard to the exact mode of origin of the
hippurates, we have even less information than upon the
origin of the other urinary constituents already considered.
Experiments have shown that the proportion of hippuric
acid in the urine is greatest after taking vegetable food;
but it is found after a purely animal diet, and probably also
exists during fasting. "We must be content at present simply
to class the hippurates among the products of disassimila-
tion, without attempting to specify their exact mode of origin.5
The daily excretion of hippuric acid amounts to about Y'5
grains ; 6 equivalent to about 8*7 grains of hippurate of soda.

Hippuric acid itself, unlike uric acid, is quite soluble in
water and in a mixture of hydrochloric acid. It requires
six hundred parts of cold water for its solution, and a much
less proportion of warm water. Under pathological con-
ditions, it is sometimes found free in solution in the urine.

1 LIEBIG, Sur facide contenu dans Furine des quadrupedes herbivores. — Annales
de chimie et de physique, Paris, 1830, tome xliii., p. 188, et seq.

2 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol i., p. 179.

3 ROBIN ET VERDEIL, Chimie anatomique, Paris, 1853, tome ii., p. 446.

4 MILNE-EDWARDS, Lemons sur la physiologic, Paris, 1857, tome i., p. 201.

5 The reader is referred to works treating specially of the urine, for specu-
lations concerning the origin and pathological relations of hippuric acid. An
analysis of numerous observations on this subject has been made by Parkes.
(Composition of the Urine, London, 1860, pp. 13, 29.)

6 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p.
416.

204 EXCRETION.

The lactates of soda, potassa, and lime exist in very con-
siderable proportion in the normal urine. They are un-
doubtedly derived immediately from the blood, passing,
ready-formed, into the urine, where they exist in simple wa-
tery solution. According to Robin, the lactates are formed
in the muscles, in the substance of which they can be read-
ily detected.1 We have no positive information with regard
to the precise mode of formation of these salts. It is prob-
able, however, that the lactic acid is the result of transfor-
mation of glucose. As a curious chemical fact, it is inter-
esting to note that the lactic acid contained in the lactates
extracted from the muscular substance is not absolutely
identical w^ith the acid resulting from the transformation of
the sugars. The former have been called paralactates, and
they contain one equivalent of water less than the ordinary
lactates. According to Robin, the compounds of lactic acid
in the urine are in the form of paralactates.3

Although the inosates (compounds of inosine, C12H12O12)
have never been detected in the urine, Robin is of the opinion
that traces of these salts are separated from the blood by
the ,kidneys, from the fact that they exist normally in the
blood and in the muscular tissue.3

We have little or no information with regard to the re-
lations of the inosates to excretion.

Creatine, C8H9O4NS + 2HO, and Oreatmme, C8H7O2¥3.

Creatine and creatinine are undoubtedly identical in
their relations to the general process of disassimilation, for
one is easily converted into the other, out of the body, by
very simple chemical means ; and there is every reason to
suppose that, in the organism, they are the products of
physiological waste of the same tissue or tissues. These
principles have been found in the urine, blood, muscular

1 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 681.

2 Loc. cit. 3 Loc. cit.

CREATINE A3TD CBEATININE. 205

tissue, and brain.1 Scherer has demonstrated the presence
of creatine in the amniotic fluid.8 By certain chemical
manipulations, both creatine and creatinine may be changed
into urea ; and the fact that these substances are now known
to be constant constituents of the urine leaves no doubt
that they are to be classed among the excrementitious prin-
ciples. Chevreul, who first discovered creatine in the ex-
tract of muscular tissue, regarded it as one of the nutri-
tive principles of meat ; * but the subsequent researches of
Heintz,4 Liebig,5 and others, who found it in the urine, re-
vealed its true character. Verdeil and Marcet e have since
found both creatine and creatinine in the blood ; and these
principles are now generally regarded as excrementitious
matters, taken from the tissues by the blood, to be eliminated
by the kidneys.

Creatine has a bitter taste, is quite soluble in cold water
(one part in seventy-five), and is much more soluble in hot
water, from which it separates in a crystalline form on cool-
ing. It is but slightly soluble in alcohol, and is insoluble in
ether. A watery solution of creatine is neutral. It does
not readily form combinations as a base ; but it has lately
been made to form crystalline compounds with some of the
strong mineral acids, the nitric, hydrochloric and sulphu-
ric.7 According to Neubauer and Yogel, when boiled for
a long time with baryta, it is changed into urea and sar-

1 You, Ueber das Verhdten des Kreatins, Kreatinins und Harnstoffs im Thier-
korper.— Zeitechrift fur Biologie, Miinchen, 1868, Bd.iv., S. 78.

2 SCHERER, Analyse d'un liquide amniotique. — Annuaire de chimie, Paris, 1850,
p. 576.

3 CHEVREUL, Uhtersuchungen uber die chemische Zusammensdzung der Fleisch-
briihe. — Journal fur praktische Chemie, Leipzig, 1835, Bd. vi., S. 120, et seq.

4 HEINTZ, Ueber eine nene Sdure im menschlichen Ham. — Annalen der Physik
und Chemie, Leipzig, 1844, Bd. Ixii., S. 602.

5 LIEBIG, Recherches de chimie medicate. — Comptes rendus, Paris, 1847, tome
xxiv., p. 69, et seq.

6 ROBIN ET YERDEIL, Tratte de chimie anatomique, Paris, 1853, tome ii., pp.
480, 489.

7 XEUBAUER AND VOGEL, op tit., p. 17.

206 EXCRETION.

cosine ; but the recent researches of Yoit have pretty con-
clusively shown that this change does not take place in the
living organism, and that probably none of the urea of the
urine is produced in this way.1 "When boiled with the strong
acids, creatine(C8H9O4N3 + 2HO) loses four atoms of water,
and is changed into creatinine (C8H7O2N3). This change
takes place very readily in decomposing urine ; which con-
tains neither urea nor creatine, but a large quantity of crea-
tinine, when far advanced in putrefaction.

Creatinine is more soluble than creatine, and its watery
solution has a strong alkaline reaction. It is dissolved by
eleven parts of cold water, and is even more soluble in
boiling water. It is slightly soluble in ether, and is dis-
solved by one hundred parts of alcohol. This substance is
regarded as one of the most powerful of the organic bases,
readily forming crystalline combinations with a number of
acids. According to Thudichum, who has very closely stud-
ied the physiological relations of these substances, creatine
is the original excrement itious principle produced in the
muscular substance, and creatinine is formed in the blood
by a transformation of a portion of the creatine, somewhere
between the muscles and the kidneys ; " for, in the muscle,
creatine has by far the preponderance over creatinine ; in
the urine, creatinine over creatine." '

In the present state of our knowledge, there is very little
to be said with regard to the physiological relations of crea-
tine and creatinine, except that they are probably to be
classed among the excrementitious principles resulting from
the disassimilation of the muscular tissue. As they exist
in considerable quantity in the muscular substance, it be-
comes a question whether, in the urine of carnivorous ani-
mals, they are not derived from the food ; but they could
have no such origin in the herbivora, nor in the urine of

1 VOIT, Ueber das Verlialten des Kreatins, Kreatinins und Harnstoffs im Thier-
korper. — Loc. cit., p. 116.

2 THUDICHUM, Pathology of the Urine, London, 1858, p. 120.

CKEATINE AUD CREATINIXE. 207

starving animals. Thudichum mentions the fact that they
are particularly abundant in the muscles of wild animals,
and that the proportion diminishes in the same animals dur-
ing captivity. He cites the instance of a fox that had been
fed on meat for two hundred days at the Anatomical Insti-
tution in Giessen, in which the proportion of creatine was
not one-tenth part that contained in the flesh of foxes caught
by hunting.1 It has likewise been found that the propor-
tion of creatine is very small in fat meat.

It has been assumed by many authors that inasmuch as
the muscular tissue of the heart is in almost constant action,
it should contain more creatine than any other portion of
the muscular system;2 but the late observations on this
point by Hofrnann, Halenke, and Yoit, show that the re-
verse of this is the case. These physiologists compared the
proportion of creatine in the heart and in the muscles of
the extremities, in oxen and in the human subject, and al-
ways found the quantity much less in the heart ; 3 still the
proportion of creatine has been found to be greater in tetan-
ized muscles than in the muscular tissue after repose.

From the meagreness of our facts with regard to the phys-
iological relations of creatine and creatinine, it is evident
that there is much to be learned before we can understand
the process of its formation in the healthy organism and the
probable results of its retention or deficient elimination in
disease. At present we can only say that these principles
are probably produced in greatest part in the muscular tis-
sue. The fact that creatine has lately been demonstrated in
the brain would lead to the supposition that it is also one of
the products of disassimilation of the nervous substance.

The average daily excretion of creatine and creatinine is
estimated by Thudichum at about 11-5 grains. Of this he

1 Op. tit., p. 120.

2 THUDICHUM, loc. cit.

ROBIX ET YERDEIL, Traite de chimie anatomique, Paris, 1853, tome ii.,

p. 481.

3 YOIT, loc. tit., p. 84.

208 EXCRETION.

estimates that 4*5 grains consist of creatine, and 7 grains, of
creatinine.1

Oxalate of Lime, CaO,C3O3 + 2HO.

This salt is not constantly present in the normal human
urine, though it may exist in considerable quantity without
denoting any pathological condition. It is exceedingly inso-
luble, and the appearance of its crystals in urinary deposits is
very characteristic. According to Robin, a trace may be re-A
tained in solution by the chlorides and the alkaline phosphates
in the urine.3 This salt may find its way out of the system
by the kidneys, after it has been taken with vegetable food
or with certain medicinal substances. The ordinary rhubarb,
or pie-plant, contains a large quantity of oxalate of lime,
which, when this article is taken, will pass into the urine.
It is probable, however, that a certain quantity of the oxa-
late may be formed in the organism. Pathologists now
recognize a condition called oxaluria, characterized by the
appearance of oxalate-of-lime crystals in the urinary sedi-
ments ; and sometimes the quantity in the urine is so large,
and its presence is so constant, that it forms vesical calculi
of considerable size.

Inasmuch as pathological facts have shown pretty con-
clusively that oxalic acid may appear in the system without
being introduced with the food, some physiologists have en-
deavored to show how it may originate from a change in cer-
tain other of the proximate principles from which it can be
produced artificially out of the body. One of the substances
from which oxalic acid can be thus formed is uric acid. It
remains, however, to show that this may take place in the
living organism. Woehler and Frerichs injected into the
jugular vein of a dog a solution containing about twenty-
three grains of urate of ammonia. In the urine, taken a

1 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p.
416.

2 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 674.

XANTHIXE. 209

short time after, there was no deposit of uric acid, but there
appeared numerous crystals of oxalate of lime. The same
result followed in the human subject, on the administration
of sixty-seven grains of urate of ammonia by the mouth.1
These questions have more of a pathological than a physio-
logical interest ; for the quantity of oxalate of lime in the
normal urine is insignificant, and this salt does not repre-
sent any of the well-known processes of disassimilation;

Xanthine (C10H6!N"4O4). — Traces of this substance have
been found in the normal human urine, but its proportion
has not been estimated, and we are as yet but imperfectly
acquainted with its physiological relations. Under pathologi-
cal conditions, it occasionally exists in sufficient quantity to
form urinary calculi. It has been found in the liver, spleen,
thymus, pancreas, muscles, and brain. It is insoluble in wa-
ter, but is soluble in both acid and alkaline fluids. Hypo-
xanthine (C10H4N"4O2) has never been found in normal urine,
though it exists in the muscles, liver, spleen, and thymus.
Leucine (C12H,aN"aO4) exists in the pancreas, salivary glands,
thyroid, thymus, suprarenal capsules, lymphatic glands,
liver, lungs, kidney, and gray substance of the brain. It has
never been detected in the normal urine. The same remarks
apply to tyrosine (C18HnNO6), though it is not go extensively
distributed in the economy, taurine (C4H7]N~O6S3), and cys-
tine (C6H6N4O4S2). The last two, however, contain sulphur,
and may have peculiar physiological and pathological rela-
tions that we do not at present understand.

These various substances are mentioned, though some of
them have not been demonstrated in the normal urine, for
the reason that there is evidently much to be learned with
regard to the various products of disassimilation as they are
represented by the composition of the urine. While some

1 WOEHLER TTND FRERiCHS, Ueber die Verdnderungen, welche namentUch or-
ganische Stoffe lei ihren Uebergange in den Horn erleiden. — Journal fur
tische Chimie, Leipzig, 1848, Bd. xliv.,S. 65.
14

210 EXCRETION.

of these may not be actual proximate principles, but sub-
stances produced by the processes employed for their extrac-
tion, some, which have thus far been discovered only under
pathological conditions, may yet be found in health, and
they represent, perhaps, important physiological acts.1

Fatty Matter. — A certain quantity of fat and fatty acids
are said to exist in the normal urine.2 Their proportion,
however, is small, and the mere fact of their presence, only,
is of physiological interest.

Inorganic Constituents of the Urine.

It is by the kidneys that the greatest quantity and variety
of inorganic principles are discharged from the organism;
and it is probable that even now we are not acquainted with
the exact proportion and condition of all the principles of
this class contained in the urine. In all the processes of nu-
trition, it is found that the inorganic constituents of the blood
and tissues accompany the organic matters in their various
transformations, though they are themselves unchanged. In
fact, the condition of union of the inorganic with the or-
ganic principles is so intimate, that they cannot be com-
pletely separated without incineration. In view of these
facts, it is evident that a certain part, at least, of the inor-
ganic salts of the urine is derived from the tissues, of which,
in combination with organic matters, they have formed a
constituent part. As the kidneys frequently eliminate from
the blood foreign matters taken into the system, and are
capable sometimes of throwing off an excess of the normal
constituents which may be introduced into the circulation,
it can be readily understood how a large proportion of some

1 For further information concerning these principles, the reader is referred
to works treating of the pathology as well as the physiology of the urine. A
succinct statement of our positive knowledge regarding the doubtful principles
is given by Robin (Leyons sur les humeurs, Paris, 1867, p. 688, et seq.).

2 ROBIN, op. cit.t p. 690.

INORGANIC CONSTITUENTS OF THE TJKINE. 211

of the inorganic matters of the urine is derived from the
food.

From the fact that the inorganic matters discharged in
the urine are generally the same as those introduced with
the food, and that they vary in proportion with the consti-
tution of the food, it is difficult to ascertain how far their
presence and quantity in the urine represent the processes
of disassimilation. One thing, however, is certain : that the
organic constituents of the food, the blood, the tissues, and
the urine, are never without inorganic matter in considera-
ble variety ; and it is more than probable that the presence
of these salts in a tolerably definite proportion influences the
processes of absorption and secretion and has an important
bearing upon nutrition ; but we are as yet so imperfectly
acquainted with the processes of nutrition of the tissues, that
we cannot follow out all the relations of the inorganic mat-
ters, first to nutrition, and afterward to disassimilation.

Chlorides. — Almost all of the chlorine in the urine is in
the form of chloride of sodium ; the amount of chloride of
potassium being insignificant and not of any special physio-
logical importance. It is unnecessary, in this connection, to
describe the well-known properties of common salt ; and the
means for determining its presence and proportion in the
urine are fully treated of in works upon physiological chem-
istry. All that we have to consider is its importance and sig-
nificance as a urinary constituent.

By reference to the table of the composition of the urine,
it is seen that the proportion of chloride of sodium is subject
to very great variations, the range being from three to eight
parts per thousand. This at once suggests the idea that the
quantity excreted is dependent to a considerable extent upon
the amount taken in with the food ; and, indeed, it has been
shown by numerous observations that this is the fact.1 The

1 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p. 162.
— XEUBAUER AND YOGEL, A Guide to the Qualitative and Quantitative Analysis of

212 EXCRETION.

proportion of chloride of sodium in the blood seems to be
tolerably constant ; and any excess that may be introduced
is thrown off chiefly by the kidneys. It has been shown con-
clusively that deprivation of common salt in the food after
a time is followed by serious disturbances in the general pro-
cess of nutrition ; and it is an acknowledged fact that this
proximate principle is a constituent of every tissue of the
body, except the enamel of the teeth. As the chlorides are
deposited with the organic matter in all the acts of nutrition,
they are found to be eliminated constantly with the products
of disassimilation of the nitrogenized parts, and their absence
from the food does not completely arrest their discharge in the
urine. According to Robin, by suppressing salt in the food,
its daily excretion may be reduced to from thirty to forty-five
grains, the normal quantity being from one hundred and
fifty to one hundred and sixty grains. This quantity is less
than the amount contained in the ingesta, and under these
circumstances there is a gradual diminution in the nutritive
activity. " This fact demonstrates the necessity of adding
chloride of sodium to the food." J It is an interesting patho-
logical fact, that in all acute febrile disorders, the proportion
of chlorine in the urine rapidly diminishes, and is frequently
reduced to one hundredth of the normal amount.3 The
quantity rapidly increases to the normal standard during
convalescence. Most of the chlorides of the urine are in
simple watery solution; but a certain proportion of the
chloride of sodium exists in combination with urea.

The daily elimination of chloride of sodium is about one
hundred and fifty-four grains (Robin). The great variations
in its proportion in the urine under different conditions of
alimentation, etc., will explain the differences in the esti-
mates given by various authorities.

the Urine, New Sydenham Society, London, 1863, p. 396. — ROBIN, Lemons sur Ifs
humeurs, Paris, 1867, p. 662.

1 ROBIN, op. cit., p. 663.

2 NEUBAUER AND VOGEL, op. cit., p. 397.

INORGANIC CONSTITUENTS OF THE TJKINE. 213

Sulphates. — There is very little to be said regarding the
sulphates, beyond the general statements concerning the in-
organic principles of the urine. The proportion of these
salts is here very much greater than in the blood, in which
there exists only about 0*28 of a part per thousand. Inas-
much as the proportion in the urine is from three to seven
parts per thousand, it seems probable that the kidneys elimi-
nate these principles as fast as they find their way into the
circulating fluid either from the food or from the tissues.1
Like other principles derived in great part from the food,
the normal variations in the proportion of sulphates in the
urine are very great. It is unnecessary to consider in detail
the variations in the amount of sulphates discharged in the
urine, depending upon the ingestion of different salts or upon
diet, for all the recorded observations have been followed
by the same results, and show that the ingestion of sulphates
in quantity is followed by a corresponding increase in the
proportion eliminated. Numerous experiments on this point
have been made by Yogel and others.1

Thudichum estimates the daily excretion of sulphuric
acid at. from twenty-three to thirty-eight grains.3 Assum-
ing, with Eobin, that the sulphates consist of about equal
parts of sulphate of potassa and sulphate of soda, with traces
of sulphate of lime,4 the quantity of salts would be from 22*5
to 37*5 grains of sulphate of potassa and an equal quantity
of sulphate of soda.

Phosphates. — The urine contains phosphates in a variety
of forms ; but inasmuch as it is not known that any one of
the different combinations possesses peculiar relations to the
process of disassirnilation, as distinguished from the other
phosphates, the phosphatic salts may be considered together.

1 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 663.

2 XEUBAUER AXD VOGEL, op. cit, p. 404.

3 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p. 416.

4 ROBIN, loc. cit.

214 EXCKETTON.

The remarks which we have just made with regard to the
chlorides and the sulphates are applicable, to a certain ex-
tent, to the phosphates. These salts exist constantly in the
urine, and are derived in part from the food, and in part
from the tissues. Like other inorganic matters, they are
united with the nitrogenized elements of the organism, and
when these are changed into excrementitious principles, and
are separated from the blood by the kidneys, they pass with
them and are discharged from the organism.

It becomes a question of importance, now, to consider
how far the phosphates are derived from the tissues, and
what proportion comes directly from the food. This point
is peculiarly interesting, from the fact that phosphorus has
been shown to exist in the nerve-tissue, and it has been in-
ferred that the excretion of phosphates represents, to some
extent, the physiological wear of the nervous system.

All observers agree that the quantity of phosphates in
the urine is in direct relation to the proportion in the food,
and that an excess of phosphates taken into the stomach is
immediately thrown off by the kidneys.1 It is a familiar
fact, indeed, that the phosphates are deficient and the car-
bonates predominate in the urine of the herbivora, while the
reverse obtains in the carnivora ; and that variations, in this
respect, in the urine may be produced by feeding animals
with different kinds of food. Yerdeil made some very inter-
esting comparative analyses of the blood for the alkaline
phosphates in the herbivora, the carnivora, and in man*. He
found the proportion very small in the ox, as compared with
the dog, and intermediate in the human subject. The pro-
portion of phosphates in the blood of the dog was greatly
diminished by feeding with potato.2 Deprivation of food di-
minishes the quantity of phosphates in the urine, but a certain

1 NEUBAUER AND VOGEL, op. tit., p. 411.

HAMMOND, On the Excretion of Phosphoric Add by the Kidneys. — Physio-
logical Memoirs, Philadelphia, 1863, p. 29, et seq.

2 ROBIN ET VERDEIL, Chimie anatomique, Paris, 1853, tome ii., p. 330.

INORGANIC CONSTITUENTS OF THE URINE. 215

proportion is discharged, derived exclusively from the tissues.
We have already noted the fact that the products of disassim-
ilation of the nitrogenized principles are never discharged
in health without being accompanied with certain inorganic
salts, such as the chlorides, sulphates, and phosphates.

In connection with the fact that phosphorus exists (in
precisely what condition it is not known) in the nervous
matter, it has been stated that mental exertion is always at-
tended with an increase in the elimination of phosphates ;
and this has been advanced to show that these salts are
specially derived from disassimilation of the brain-substance.
Experiments show that it is not alone the phosphates that are
increased in quantity under these conditions, but urea, the
chlorides, sulphates, and inorganic matters generally;1 and
in point of fact, any physiological conditions which increase
the proportion of nitrogenized excrementitious principles in-
crease as well the elimination of inorganic matters. It can-
not be assumed, therefore, that the discharge of phosphates is
specially connected with the activity of the brain. We learn
nothing from pathology upon this point, for although numer-
ous observations have been made upon the excretion of
phosphoric acid in disease — Vogel having made about one
thousand different analyses in various affections* — no defi-
nite results have been obtained.

From these facts it is seen that there is no physiological
reason why we are able to connect the elimination of the
phosphates with the disassimilation of any particular tissue
or organ, especially as these salts in some form are univer-
sally distributed in the organism.

1 HAMMOND, Urological Contributions. — American Journal of the Medical
Sciences, Philadelphia, 1856, Xew Series, vol. xxxi., p. 334.

BYASSOX, Essai sur la relation qui existe d Vetat physiologique entre

Vactivite cerebrale et la composition des urines, Paris, 1868, p. 66. By reference
to the table by Byasson on page 48, it will be seen that the proportion of sul-
phuric acid in the urine is more than doubled by mental exertion, while the
proportion of phosphoric acid is increased less than one-third.

2 NEUBAUER AND VOGEL, op. tit., p. 413, et seq.

21 6 EXCRETION.

Observations have been made upon the hourly variations
in the discharge of phosphoric acid at different periods of the
day ; but these do not appear to bear any absolute relation
to known physiological conditions, not even to the process
of digestion.1

Of the different phosphatic salts of the urine, the most
important are those in, which the acid is combined with soda.
These exist in the form of the neutral and acid phosphates.
The acid salt has one equivalent of the base, and is supposed
to be the cause of the acidity of the urine at the moment of
its emission. The so-called neutral salt is slightly alkaline,
and has two equivalents of base. The proportion of the
phosphates of soda in the urine is larger than that of any of
the other phosphatic salts, but the daily amount excreted has
not been estimated. The phosphate of magnesia is a constant
constituent of the urine, as well as the acid and the basic phos-
phate of lime. The daily excretion of phosphate of magne-
sia amounts to from 7 *T to 11*8 grains, and of the phosphates
of lime, from 4'Y to 5*7 grains.2 According to Robin, there
always exists in the urine a small quantity of the ammonio-
magnesian phosphate, but it never, in health, exists in suffi-
cient quantity to form a crystalline deposit.8 The daily
excretion of the phosphates is, as we have seen, subject to
great variations, but the average quantity of phosphoric acid
excreted daily may be estimated at about fifty grains, or,
more accurately, fifty-six grains.4

The urine contains, in addition to the inorganic prin-
ciples above described, a small quantity of silicic acid ;
but, as far as we know, this has no physiological im-
portance.

1 The reader is referred to the work of Neubauer and Vogel for a fuller
consideration of the physiological and pathological relations of the phos-
phates.

2 NEUBAUER AND VOGEL, op. cit., p. 59.

3 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 6"66.

4 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p.
416.

COLORING MATTER AND MUCUS. 217

Coloring Matter and Mucus.

The peculiar color of the urine is due to the presence of
a nitrogenized principle, known to physiological chemists
under a variety of names. We have mentioned it in the
table as urrosacine. It is also called urochrome, urohsema-
tine, uroxanthine, and purpurine. "We have no accurate
account of its ultimate composition, and all that is known
about its constituents is that it contains carbon, oxygen,
hydrogen, and nitrogen, and probably iron.1 Although its
exact ultimate composition is not absolutely settled, its con-
stituents are supposed to be the same as those of the coloring
matter of the blood, the proportion of oxygen being very
much greater. These facts point to the probability of the
formation of urrosacine from hsematine.

The quantity of coloring matter in the normal urine is
very small. It is subject to considerable variation in disease,
and almost always is fixed by deposits and calculi of uric
acid or the urates, giving them their peculiar color. This
principle first makes its appearance in the urine, and is prob-
ably formed in the kidneys. So little is known of its phys-
iological or pathological relations to the organism, that it
does not seem necessary to follow out all of the chemical de-
tails of its behavior in the presence of different reagents.

The normal urine always contains a small quantity of
mucus, with more or less epithelium from the urinary pas-
sages, and a few leucocytes. These form a faint cloud in
the lower strata of healthy urine, after a few hours' repose.
The properties of the different kinds of mucus have already
been considered.8 An important peculiarity, however, of
the mucus contained in normal urine is that it does not seem
to excite decomposition of the urea, and that the urine may
remain for a long time in the bladder without undergoing
any putrefactive change.

1 ROBIN ET VERDEIL, Chimie anatomique, Paris, 1853, tome iii., p. 398.

2 See page 51.

218 EXCRETION.

Gases of the Urine.

In the process of separation of the urine from the blood
by the kidneys, a certain proportion of the gases in solution
in the circulating fluid is also removed. For a long time,
indeed, it has been known that the normal human urine con-
tained different gases, but lately some very interesting ob-
servations on this subject have been made by M. Morin,1 in
which the proportions of the free gases in solution have been
accurately estimated. By using the method employed by
Magnus in estimating the gases of the blood,2 Morin was
able to extract about two and a half volumes of gas from a
hundred parts of urine. By careful experiments, he ascer-
tained that a certain quantity of gas remained in the urine,
and could not be extracted by his ordinary process. This
amounted to about one-fifth of the whole volume of gas.
Adding this to the quantity of gas extracted, he obtained
the proportions to one litre of urine, in cubic centimetres,
which are given in the table, viz. :

Oxygen 0*824

Nitrogen 9'589

Carbonic acid 19*620

These proportions represent the average of fifteen obser-
vations upon the urine secreted during the night.

The proportion of these gases was found by Morin to be
subject to certain variations. For example, after the inges-
tion of a considerable quantity of water or any other liquid,
the proportion of oxygen was considerably increased (from
0*824, to 1*024:), and the carbonic acid was diminished more

1 MORIN, Recherches sur les gas libres de Vurine. — Journal de pharmacie et de
chimie, Paris, 1864, tome xlv., p. 396, et seq.

2 The method of Magnus as applied to the gases of the urine does not in-
volve the elements of inaccuracy which we have pointed out with reference to
the blood (see vol. i., Respiration, p. 462) ; for in the urine there is no tendency
to the disappearance of oxygen and the formation of carbonic acid, such as is
due in the blood to the action of the corpuscles.

VARIATIONS LST THE TTBIXE. 219

than one-half. The most interesting variations, however,
were in connection with muscular exercise. After walking
a long distance, the exercise being taken both before and
after eating, the quantity of carbonic acid was found to be
double that contained in the urine after repose. The pro-
portion of oxygen was very slightly diminished, and the
nitrogen was somewhat increased. The variations of these
gases, however, were insignificant.

florin explains the great increase in the proportion of
carbonic acid, by the greater respiratory activity during
exercise. It is well known, indeed, that muscular exercise
largely increases the proportion of carbonic acid in the blood
and the quantity eliminated by the lungs ; and as the car-
bonic acid of the urine is undoubtedly derived from the
blood, we should expect that the same conditions would in-
crease its proportion in this secretion.

It is not probable that the kidneys are very important as
eliminators of carbonic acid from the system, but it is cer-
tain that the presence of this gas in the urine assists in the
solution of some of the saline constituents of this fluid, no-
tably the phosphates.

Variations in the Composition of the Urine.

The urine represents in its varied constituents not only
a great part of the physiological disintegration of the organ-
ism, but it contains elements evidently derived from the
food. Its constitution is varying with every different con-
dition of nutrition, with exercise, bodily and mental, with
sleep, age, sex, diet, respiratory activity, the quantity of cu-
taneous exhalation, and, indeed, with every condition that
affects any part of the system. There is no fluid in the body
that contains such a variety of principles, as a constant con-
dition, but in which the proportion of these principles is
so variable. It is for this reason that we have given in
the table of the composition of the urine the ordinary lim-

220 ' EXCRETION.

its of variation of its different constituents; and it has
been found necessary, in treating of the individual excre-
mentitious principles, to refer to some of the variations in
their proportion in the urine. In treating more specially
of the physiological variations of the urine, we shall only
refer in general terms to conditions that produce wide and
important changes in the proportion of its constituents ; and
under the head of nutrition, we will consider how far the
absolute quantities of the urinary principles and other ex-
crementitious substances represent the physiological waste
which is always coincident with the repair of parts. A full
and complete history of all the variations in the urine would
be inconsistent with the scope of this work.1

Variations with Age and Sex. — There are decided dif-
ferences in the composition of the urine at different periods
of life and in the sexes. These must depend in part upon
the different conditions of nutrition and exercise, and in
part upon differences in the food. Although the quantities
of excrementitious matters present great variations, their re-
lations to the organism are not materially modified, except,
perhaps, at an early age ; and the influence of sex and age
is merely felt as they affect the diet and general habits of
life.

It is stated by most authors that the urine of the foetus
is highly albuminous ' and contains no urea; but examina-
tions of the urine in the foetus and newly born have been
so few that we know very little regarding its constitution
and normal variations. The researches of the authorities
on this subject, quoted by Parkes,3 leave the question of the
composition of the urine in the foetus and during the first

1 For more extended details of the variations of the urine in health and dis-
ease, the reader is referred to special treatises. Dr. Parkes considers these
points very fully. (PARKES, The Composition of the Urine in Health and Disease,
and under the Action of Remedies, London, 1859, pp. 39-179.)

5 Op. tit., p. 41, etseq.

VARIATIONS IN THE HEINE. 221

days of extra-uterine life still uncertain. In a specimen of
urine taken from a still-born child delivered with forceps,
examined by Drs. Elliot and Isaacs, the presence of urea
was determined beyond a doubt. This urine was of a pale
straw-color, like clear syrup in consistence, of an acid re-
action, and a specific gravity of 1007*5. It contained neither
sugar nor albumen. Well-marked crystals of the nitrate and
of the oxalate of urea were obtained from this specimen.1
Dr. Beale found urea in a specimen taken at the seventh
month.3

With our present imperfect knowledge of the compo-
sition of the urine at the earliest periods of existence, it is
impossible to deduce any conclusions regarding the pro-
duction of the excrementitious principles at this time ; and
it would be unprofitable to detail the unsatisfactory and
conflicting examinations to be found in works devoted spe-
cially to the urine.

Observations upon children between the ages of three
and seven are more definite. At this period of life, the
amount of urea excreted in proportion to the weight of the
body is about double that in the adult. The amount of chlo-
rine in children is about three times the quantity in the
adult ; and the proportionate amount of other solid matters
is also greater. The amount of water excreted by the kid-
neys in children, in proportion to the weight of the body, is
very much greater than in the adult, being more than double.
From eight years of age to eighteen, the urinary excretion
becomes gradually reduced to the adult standard.3 It has
been noticed by Gallois, that crystals of oxalate of lime are
much more frequent in the urine of children between four
and fourteen years of age than in the adult.4

1 ELLIOT, Urine in Foetal Life. — American Journal of the Medical Sciences,
Philadelphia, 1857, New Series, vol. xxxiii., p. 555.

8 BEALE, Kidney Diseases, Urinary Deposits, and Calculous Disorders, Phila-
delphia, 1869, p. 125.

3 PARKES, op. cit., pp. 44, 45.

* GALLOIS, De F oxalate de chaux, Paris, 1859, p. 14.

222 EXCRETION.

There are not many definite observations on record upon
the composition of the urine in the latter periods of life. It
has been shown, however, that there is a decided diminution,
at this period, in the excretion of urea, and that the absolute
quantity of the urine is somewhat smaller.

The absolute quantity of the urinary excretion in women
is less than in men, and the same is true of the proportionate
amount of these principles to the weight of the body ; still,
the differences in the proportionate excretion are not very
marked, and the amount of all these principles being subject
to modifications from the same causes as in men, the small
deficiency, in the few direct observations upon record, may
be in part, if not entirely, explained by the fact that women
usually perform less mental and physical work than men,
and that their digestive system is generally not so active.

Variations at Different Seasons, and at Different Peri-
ods of the Day. — The changes in the quantity and com-
position of the urine which may be directly referred to
the conditions of digestion, temperature, sleep, exercise,
etc., have long been recognized by physiologists ; but it is
difficult, if not impossible, so to separate these influences,
that the true modifying value of each can be fully appre-
ciated. For example, there is nothing which produces such
marked variations in the composition of the urine as the
digestion of food. So marked, indeed, is its influence, that
some writers of authority incline to the belief that the
greatest part of what have been regarded as the most im-
portant excrementitious matters is derived from the food,
and not from physiological disintegration of the tissues.
Under strictly physiological conditions, the modifying in-
fluence of digestion must always complicate observations
upon the effects of exercise, sleep, season, period of the
day, etc. ; and the urine is continually varying in health,
with the physiological modifications in the other processes
and conditions of life. It will be sufficient for our purpose

VARIATIONS IN THE URESE. 223

to note the most important of these variations and endeavor
to appreciate the conditions which combine to produce them,
assigning to each one its proper value.

At different seasons of the year and in different climates,
the urine presents certain variations in its quantity and com-
position. It seems necessary that a tolerably definite quan-
tity of water should be discharged from the body at all
times ; and when the temperature or hygrometric condition
of the atmosphere is favorable to the action of the skin, as
in a warm, dry climate, the quantity of water in the urine is
diminished, and its proportion of solid matters correspond-
ingly increased. On the other hand, the reverse obtains
when the action of the skin is diminished from any cause.
This fact is a matter of common remark, as well as of scien-
tific observation.

At different periods of the day, the urine presents con-
stant and important variations. It is evident that the spe-
cific gravity must be constantly varying with the proportion
of water and solid constituents. According to Dalton, the
urine first discharged in the morning is dense and highly col-
ored ; that passed during the forenoon is pale and of a low
specific gravity ; and in the afternoon and evening it is again
deeply colored, and its specific gravity is increased.1 The
acidity is also subject to tolerably definite diurnal variations,
which have already been noted.3

Variations produced ~by Food. — An immense number
of observations have been made upon the influence of ordi-
nary food, and upon diet restricted to particular articles.
These facts have necessarily been considered more or less
fully in connection with the origin of the urinary constit-
uents ; but it is important, in studying the influence of mus-
cular exercise, mental effort, etc., to constantly bear in mind
the variations occurring under the influence of the ingesta*

1 D ALTON, A Treatise on Human Physiology, Philadelphia, 1867, p. 335.

2 See page 190.

224: EXCRETION.

"Water and liquids generally always increase the propor-
tion of water in the urine and diminish the specific gravity.
This is so marked after the ingestion of large quantities
of liquids, that the urine passed under these conditions is
sometimes spoken of by physiologists as the urina potus.
This must be borne in mind in clinical examinations of the
urine. It is a curious fact, however, that when an excess of
water has been taken for purposes of experiment, the diet
being carefully regulated, the absolute amount of solid mat-
ters excreted is considerably increased. This is particularly
marked in the urea, but it is noticeable in the sulphates and
phosphates, though not to any great extent in the chlorides.
The results of experiments on this point seem to show that
water taken in excess increases the activity of disassimi-
lation.1

The ordinary meals invariably increase the solid constit-
uents of the urine ; the most constant and uniform increase
being in the proportion of urea. This, however, depends to
a great extent upon the kind of food taken. The increase
is usually noted during the first hour after a meal, and at-
tains its maximum at the third or fourth hour. The inor-
ganic matters are increased, as well as the excrementitious
principles proper. The urine passed after food has been
called urina cibi, under the idea that it is to be distinguished
from the urine supposed to be derived exclusively from disas-
similation of the body, the urina sanguinis.

It is an interesting and important question to determine
the influence of different kinds of food upon the composition
of the urine, particularly the comparative effects of a nitrogen-
ized and a non-nitrogenized diet. Lehmann has made some
very striking observations upon this point, and his results have
been fully confirmed by many other physiologists of author-
ity. Without discussing elaborately all of these observations,
it is sufficient to state that the ingestion of an excess of ni-
trogenized principles always produced a great increase in

1 PARKES, op. cit., p. 67, et seq.

IN THE UKDsE. 225

the proportion of the nitrogenized constituents of the urine,
particularly the urea. On a non-nitrogenized diet, the pro-
portion of urea was found to be diminished more than one-
half. The results of the experiments of Lehmann are so
striking that we quote them in full :

" My experiments show that the amount of urea which
is excreted is extremely dependent on the nature of the
food which has been previously taken. On a purely animal
diet, or on food very rich in nitrogen, there were often two-
fifths more urea excreted than on a mixed diet ; while, on a
mixed diet, there was almost one-third more than on a purely
vegetable diet ; while, finally, on a non-nitrogenous diet, the
amount of urea was less than half the quantity excreted
during an ordinary mixed diet.

" In my experiments on the influence of various kinds of
food on the animal organism, and especially on the urine, I
arrived at the above results, which in mean numbers may be
expressed as follows : On a well-regulated mixed diet I dis-
charged, in twenty-four hours, 32*5 grammes of urea (I give
the mean of fifteen observations) ; on a purely animal diet,
53*2 grammes (the mean of twelve observations) ; on a vege-
table diet, 22*5 grammes (the mean of twelve observations) ;
and on a non-nitrogenous diet, 15 '4 grammes (the mean of
three observations)." 1

With regard to the influence of food upon the inorganic
constituents of the urine, it may be stated in general terms
that the ingest ion of mineral substances increases their pro-
portion in the excretions. "We have already alluded to this
fact in treating of the different inorganic salts.

There are certain articles which, when taken into the
system, the diet being regular, seem to retard the process of

1 LEHMAXX, Physiological Chemistry, Philadelphia, 1855, vol. L, pp. 150, 151.

These results were fully confirmed in the very interesting experiments of
Prof. Hammond upon the nutritive value of albumen, starch, and gum, when
singly and exclusively used as food ( Transactions of the American Medical As-
sociation^ Philadelphia, 1857, vol. x., p. 513, et seq.).
15

226 EXCRETION.

disassimilation ; or, at least, they diminish in a marked man-
ner the amount of matters excreted, particularly the urea.
Alcohol has a very decided influence of this kind. Its ac-
tion may be modified by the presence of salts and other
matters in the different alcoholic beverages, but in all direct
experiments, alcohol, taken either under normal conditions
of diet, when the diet is deficient, or when it is in excess,
diminishes the excretion of urea. The same is true of tea
and coffee.1

Influence of Muscular Exercise. — There can be no doubt
that muscular exercise, under ordinary conditions of diet, in-
creases the proportion of many of the solid constituents of
the urine, particularly the urea. It is impossible to come to
any other conclusion after studying the elaborate researches
of Lehmann,a Hammond,3 and others upon this subject. It
must be remembered, in considering the effects of exercise
upon the elimination of excrementitious matters, that the
modifications in the urine produced by food are very consid-
erable. "We have purposely considered the influence of food
before taking up other modifying conditions, so as to make
apparent an important element of error in some recent ob-
servations, which are at variance with the prevailing ideas
on this subject. When, for example, it has been shown that
restriction to a non-nitrogenous diet will immediately dimin-
ish the daily elimination of urea more than one-half, it is
evident that the diet must always be fully considered in ex-
periments upon the effects of exercise or other modifying
circumstances.

There is another important point, also, which is not al-
ways taken into consideration in comparative observations

1 This subject has already been considered under the head of Alimentation.
See vol. ii., Alimentation, p. 102, et seq.

2 LEHMANN, Physiological Chemistry, Philadelphia, 1855; vol. i., p. 151.

8 HAMMOND, The Relations which exist between Urea and Uric Acid. — American
Journal of the Medical Sciences., Philadelphia, January, 1865, and Physiological
Memoirs, Philadelphia, 1863, p. 13.

VARIATIONS IN THE URINE. 227

upon the absolute quantities of urea eliminated during exer-
cise and repose, and that is the elimination of this principle
by the cutaneous surface. We have already seen that urea
is a constant constituent of the sweat. Speck, who found
that exercise usually increased the elimination of excremen-
titious matters, noted the fact that urea was not increased in
the urine when the sweat was very abundant.1

The very elaborate analysis of the principal observa-
tions on this subject by Parkes shows the discrepancies in
the experiments of different authors, and points out several
of the sources of error.2 The weight of experimental evi-
dence at that time was decidedly in favor of an increase in
the elimination of urea by exercise ; and the observations
opposed to this view involved inaccuracies which would ex-
plain, in part at least, the contradictory results obtained.
Lately, new observations have been made, which are assumed
by some to show an actual diminution by exercise in the
quantity of urea excreted. Fick and Wislicenus,3 Frank-
land,4 and Haughton 5 have attempted to show that this is

1 SPECK, Ueber die Wirkung der bis zur Ermudung gesteigerten korperlichen
Austrengung unter verschiedenen Verhaltnissen auf den Stoffwechsel. — Archiv zur
Forderung der wissenschaftlichenHeilkunde, Gottingen, 1860, Bd. iv., S. 591.

2 PARKES, The Composition of the Urine, London, 1860, p. 85, et scq. Dr.
Parkes has made some interesting observations, since the publication of
his work on the urine, upon the influence of muscular exercise, under a non-
nitrogenous diet, upon the elimination of urea. He found the amount of nitrogen
in the excreta slightly increased over the amount eliminated during a period
of rest, on the same diet The elimination by the skin and intestines was taken
into account in these experiments. PARKES, On tJie Elimination of Nitrogen by
the Kidneys and Intestines, during Rest and Exercise, on a Diet without Nitrogen.
— Proceedings of the Royal Society, London, 1867, vol. xv., Xo. 89, p. 339, et seq.

3 FICK AND WISLICENUS, On the Origin of Muscular Power. — London, Edin-
burgh and Dublin Philosophical Magazine, London, Jan.-June, 1866, vol. xxxi.,
p. 485, et seq.

4 FRANKLAND, On the Origin of Muscular Power, Ibid, July-Dec., 1866, vol.
xxxii., p. 182, et seq.

5 HAUGHTON*, Address on the Relation of Food to Work done by the Body, and
its Bearing upon Medical Practice. — The Lancet, London, Aug. 15, Aug. 22, and
Aug. 29, 1868.

EXCRETION.

the fact, and have come to the conclusion that muscular
force involves chiefly the consumption of non-nitrogenous
principles and the production of carbonic acid. While the
experiments on this subject have been so meagre, it would
be unprofitable to enter into an elaborate discussion of their
merits, particularly as they have not been directed specially
to the influence of exercise upon the composition of the
urine, but to the amount of muscular power developed by
different kinds of food. This subject has not been reduced
to such an absolute certainty that we are able to calculate
mathematically the heat-units, the digestion-coefficients, and
the amount of " work " produced by any given quantity of
food ; and such calculations cannot, as yet, take the place of
actual experimental observations. What we want to know
is the measurable influence of muscular exercise upon the
proportion of certain of the constituents of the urine, under
normal alimentation, every other modifying condition being
taken into account. There can be no doubt that, with ordi-
nary mixed diet, the elimination of urea is increased by exer-
cise. Fick and Wislicenus made their observations, extend-
ing over a period of between one and two days, under a diet
of non-nitrogenized matter ; and Prof. Haughton compared
his observations, made in July, with an average of experi-
ments made at different seasons, taking no account of the
action of the skin. It may be true that, with a purely non-
nitrogenous diet, exercise fails to increase the quantity of
urea eliminated by the kidneys, as appears from the observa-
tions of Fick and Wislicenus ; but further experiments are
necessary to settle even this point ; and recent observations
by Parkes show that this is not always the case.1

With regard to the influence of muscular exercise upon
the other constituents of the urine, experiments are some-
what contradictory. Sometimes the water is lessened, and
sometimes it is increased ; this probably depending upon the
activity of the cutaneous exhalation. Sometimes the uric

1 See page 227, note.

VARIATIONS IN THE TJEINE. 229

acid is increased, and sometimes diminished. The sulphates,
phosphates, and chlorides are generally increased.

The general result of experimental observations on the
effects of exercise upon the urine may be summed up in the
proposition that this condition increases the activity of the
nutritive processes, and produces a corresponding activity in
the function of disassimilation, as indicated by the amount
of excrementitious matters separated by the kidneys.1

Influence of Mental Exertion. — Although the influence
of mental exertion upon the composition of the urine has
not been very much studied, the results of the investigations
which have been made upon this subject are, in many re-
gards, quite satisfactory. It is a matter of common remark
that the secretion of urine is very often modified to a very
great extent through the nervous system. Fear, anger, and
various violent emotions sometimes produce a sudden and co-
pious secretion of urine containing a large amount of water,
and this phenomenon is very often observed in cases of hys-
teria. Yery intense mental exertion will occasionally pro-
duce the same result. We have often observed a frequent
desire to urinate during a few hours of intense and unre-
mitting mental labor; and on one occasion, being struck
with the amount of urine voided, it was found, on exami-
nation, to present scarcely any acidity and a specific gravity
of about 1002. The interesting point in this connection,
however, is to observe the influence of mental labor upon

1 Dr. J. C. Draper made, in 1856, a number of observations upon the effect
of exercise on the excretion of urea, from which he concluded that rest does
not diminish this excretion, and that exercise does not increase, but actually
lessens, the quantity discharged. These conclusions are arrived at by compar-
ing the amount of urea excreted by a patient confined to the bed with a frac-
tured leg, with the average of eighteen observations upon other persons. The
necessary experimental conditions are no better fulfilled in the other observa-
tions than in this, and the conclusions arrived at cannot therefore be accepted,
in opposition to the accurate experiments of other observers (DRAPER, 7s Mus-
cular Motion the Cause of tJie Production of Urea ? — New York Journal of Medi-
cine, 1856, New Series, vol. xvi., p. 155, et seg.).

230 EXCKETION.

the elimination of solid matters, as contrasted with the
amount of excretion during complete repose, the condi-
tions of alimentation in the two instances being identical.

The most extended series of observations upon this sub-
ject, in which all the necessary experimental conditions were
fulfilled, are those of Prof. Hammond. These experiments
commenced with a standard series of observations, under fixed
conditions of diet, exercise, etc., extending over a period of
ten days. With a view, then, of determining the influence
of increased mental exertion, the number of hours in the day
appropriated to study was doubled, the conditions of food
and exercise remaining the same as in the standard series.
The average of a series of observations, extending over ten
days, showed an increase in the quantity of the urine, and
an increase, also, in the quantity of all of its solid constituents,
with the exception of uric acid, the proportion of which was
notably diminished. The amount of variation was as follows :

Average of ten days in the standard series : Quantity of
urine, 37*95 oz. ; urea, 671*32 grains; uric acid, 14*44
grains ; chlorine, 154'29 grains ; phosphoric acid, 43*66
grains ; and sulphuric acid, 38*47 grains.

Average of ten days with increased mental exertion :
Quantity of urine, 43*56 oz. ; urea, 749*33 grains ; uric acid,
10*75 grains ; chlorine, 172*62 grains ; phosphoric acid, 66*15
grains ; sulphuric acid, 49*05 grains.

In another series of experiments, also extending over ten
days, in which there was absence, as far as practicable, of
mental exertion, the quantity of urine was diminished, and
there was a decrease in the proportion of all of its solid con-
stituents.1

These interesting observations have since been confirmed
by a number of different series of experiments ; 3 and in a

1 HAMMOND, Urological Contributions. — American Journal of the Medical Sci-
ences, Philadelphia, 1856, New Series, vol. xxxi., p. 330, etseq., and Physiological
Memoirs, Philadelphia, 1863, p. 17, etseq.

2 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, pp.
163, 164.

VARIATIONS IN THE URINE. 231

very interesting work upon the influence of cerebral activity
upon the composition of the urine, by Byasson, they have
been somewhat extended. Byasson found that by mental
exertion the quantity of urine was increased ; the amount
of urea was also increased; the phosphoric acid was in-
creased about one-third ; the sulphuric acid was more than
doubled ; and the chlorine was nearly doubled.1

These facts have an important bearing upon our knowl-
edge of the effects of mental exertion upon the process of
disassimilation of the nervous tissue. They show that nearly
all of the solid principles contained in the urine are in-
creased in quantity by prolonged intellectual exertion, but
they fail to point to any one excrementitious principle, either
organic or inorganic, which is specially connected with the
physiological wear of the brain. It has been assumed that
elimination of the phosphates, increased out of proportion
to the increase of the other solid matters of the urine, is one
of the constant effects of intellectual effort ; but this view
is not sustained by direct physiological experiments, nor by
facts in pathology. We have already discussed this question
somewhat elaborately, under the head of the phosphates of
the urine.8

1 BYASSOX, Essai sur la relation qui existe d fetal physiologique entre Vactivite
c'er'dbrale et la composition des urines, Paris, 1868, p. 48, Table.
8 See p. 215.

CHAPTEE VIII.

PHYSIOLOGICAL ANATOMY OF THE LFVEK.

Coverings and ligaments of the liver — Capsule of Glisson — Lobules — Branches
.of the portal vein, the hepatic artery and duct — Interlobular vessels — Lob-
ular vessels — Origin and course of the hepatic veins — Interlobular veins —
Structure of a lobule of the liver — Hepatic cells — Arrangement of the
bile-ducts in the lobules — Anatomy of the excretory biliary passages —
Vasa aberrantia — Gall-bladder — Hepatic, cystic, and common ducts —
Nerves and lymphatics of the liver — Mechanism of the secretion and dis-
charge of bile — Secretion of bile from venous or arterial blood — Quantity
of bile— Variations in the flow of the bile — Influence of the nervous sys-
tem on the secretion of bile — Discharge of bile from the gall-bladder.

THE liver, by far the largest gland in the body, is now
known to have several entirely distinct functions ; and one
of the most important of these has already been fully con-
sidered, in connection with digestion.1 It is true that we
know very little with regard to the exact office of the bile in
digestion, but that this function is essential to life, there can
be no doubt. "We have, however, more positive information
with regard to the excrementitious function of the liver and
the changes which the blood undergoes in passing through
its substance; and the study of these functions is closely
connected with the anatomy of the liver and the chemical
constitution of the bile.

Physiological Anatomy of the Liver.

It is unnecessary, in this connection, to dwell upon the
ordinary descriptive anatomy of the liver. It is sufficient

1 See vol. ii., Digestion, p. 360, et seq.

PHYSIOLOGICAL ANATOMY OF THE LIYEE. 233

to state that it is situated just below the diaphragm, in the
right hypochondriac region, and is the largest gland in the
body, weighing, when moderately filled with blood, about
four and a half pounds. Its weight is somewhat variable,
but it is stated by Sappey that in a person of ordinary adi-
pose development, its proportion to the weight of the body
is about one to thirty.1 In early life, the liver is relatively
larger, its proportion to the weight of the body, in' the new-
born child, being as one to eighteen or twenty.2

The liver is covered externally by peritoneum, folds or
duplicatures of this membrane being formed as it passes from
the surface of the liver to the adjacent parts. These consti-
tute four of the so-called ligaments that hold the liver in place.
The proper coat of the liver is a very thin, but dense and resist-
ing fibrous membrane, adherent to the substance of the organ,
but detached without much difficulty, and very closely united
to the peritoneum. This membrane is of variable thickness
at different parts of the liver, being especially thin in the
groove for the vena cava. At the transverse fissure it sur-
rounds the duct, blood-vessels, and nerves, and penetrates
the substance of the organ in the form of a vagina, or sheath,
surrounding the vessels and branching with them. This
membrane, as it ramifies in the substance of the liver, is
called the capsule of Glisson. It will be more fully described
in connection with the arrangement of the hepatic vessels.

The substance of the liver is made up of innumerable
lobules, of an irregularly ovid or rounded form, and about
^5- of an inch in diameter. The space which separates these

1 SAPPEY, Traite cFanatomie descriptive, Paris, 1857, tome ii., p. 261. Sappey
made a number of examinations of the weight of the normal liver, with the ves-
sels moderately distended with water, in order to represent, in a measure, its
physiological condition. He estimated the weight from the average of ten liv-
ers, taken from both sexes and at different ages after adult life, at two kil., or
about four and a half pounds. The weight of the liver with the vessels empty
is about three and one-third pounds.

2 WILSON, Cyclopaedia of Anatomy and Physiology, London, 1839-47, vol. iii.,
p. 178, Article, Liver.

EXCRETION.

lobules is about one-quarter of the diameter of the lobule,
and is occupied with the blood-vessels, nerves, and ramifica-
tions of the hepatic duct, all enclosed in the fibrous sheath.
In a few animals, as, for example, the pig and the polar-bear,
the division of the hepatic substance can be readily made
out with the naked eye ; but in man and in most of the
mammalia, the lobules are not so distinct, though their ar-
rangement is essentially the same. Although the lobules
are intimately connected with each other from the fact that
branches going to a number of different lobules are given off
from the same interlobular vessels, they are sufficiently dis-
tinct to represent, each one, the general anatomy of the
secreting substance of the liver ; but before we study the
minute structure of the lobules, it will be convenient to fol-
low out the course of the vessels and the duct, after they
have penetrated at the transverse fissure. In this descrip-
tion we will follow, in the main, the observations of Iviernan,
who has given, probably, the most accurate account of the
vascular arrangement in the liver.1

At the transverse fissure, the portal vein, collecting the
blood from the abdominal organs, and the hepatic artery, a
branch of the coeliac axis, penetrate the substance of the
liver, with the hepatic duct, nerves, and lymphatics, all en-
veloped in the fibrous vagina, or sheath, known as the cap-
sule of Glisson. The portal vein is by far the larger of the
two blood-vessels, and its calibre may be roughly estimated
at from eight to ten times that of the artery.

The vagina, or capsule of Glisson, is composed of fibrous
tissue, in the form of a dense membrane, closely adherent to
the adjacent structure of the liver, and enveloping the ves-
sels and nerves, to which it is attached by a loose areolar
tissue. The attachment of the blood-vessels to the sheath is
so loose, that the branches of the portal vein are collapsed
when not filled with blood ; presenting a striking contrast

1 KIERXAK, The Anatomy and Physiology of the Liver. — Philosophical Trans-
actions, London, 1833, p. 711, et seq.

PHYSIOLOGICAL ANATOMY OF THE LIVER. 235

to the hepatic veins, which are closely adherent to the sub-
stance of the liver, and remain open when they are cut
across. This sheath is prolonged over the vessels as they
branch and follows them in their subdivisions. It varies
considerably in thickness in different animals. In man and
the mammalia generally, it is rather thin, becoming more
and more delicate as the vessels subdivide, and is entirely
lost before the vessels are distributed in the interlobular
spaces.

The vessels distributed in, and coming from the liver are
the following :

1. The portal vein, the hepatic artery, and the hepatic
duct, passing in at the transverse fissure, to be distributed
in the lobules. The blood-vessels are continuous in the lob-
ules with the radicles of the hepatic veins. The duct is to
be followed to its branches of origin in the lobules.

2. The hepatic veins ; vessels that originate in the lo-
bules, and collect the blood distributed in their substance by
branches of the portal vein and hepatic artery.

Branches of the Portal Yein, the Hepatic Artery and
Duct. — These vessels follow out the branches of the capsule
of Glisson, become smaller and smaller, and finally pass
directly between the lobules. In their course, however,
they send off lateral branches to the sheath ; and those who
follow exactly the description of Kiernan, call this the vagi-
nal plexus. The arrangement of the vessels in the sheath is
not in the form of a true anastomosing plexus, although
branches pass from this so-called vaginal plexus between the
lobules. These vessels, according to Sappey, do not anasto-
mose or communicate with each other in the sheath.1

The portal vein does not present any important pecu-
liarity in its course from the transverse fissure to the inter-
lobular spaces. It subdivides, enclosed in its sheath, until
its small branches go directly between the lobules, and in

1 SAPPEY, Traite cT anatomic descriptive, Paris, 1857, p. 288.

236 EXCRETION.

its course it sends branches to the sheath (vaginal vessels),
which afterward go between the lobules. The distribution
of the hepatic artery, however, is not so simple. This vessel
has three sets of branches. As soon as it enters the sheath
with the other vessels, it sends off minute branches (vasa
vasorum), to the walls of the portal vein, the larger branches
of the artery itself, the walls of the hepatic veins, and a very
rich net-work of branches to the hepatic duct. When the
hepatic artery is completely injected, the walls of the hepatic
duct are seen almost covered with vessels. In its course,
the hepatic artery also sends branches to the capsule of
Glisson (capsular branches), which join with the branches
of the portal vein to form the so-called vaginal plexus.
From these vessels a few arterial branches are given off and
pass between the lobules. The hepatic artery cannot be
followed beyond the interlobular spaces. According to Kol-
liker and others, the terminal branches of the hepatic artery
do not open into the radicles of the hepatic veins, but into
small branches of the portal vein, within the capsule of
Glisson.1

The hepatic duct follows the general course of the portal
vein ; but its structure and relations are so important and
intricate that they will be described separately.

Interlobular Vessels. — Branches of the portal vein, com-
ing from the terminal ramifications as the vessel branches
within the capsule and the branches in the walls of the cap-
sule, are distributed between the lobules, constituting the
greatest part of the so-called interlobular plexus. These are
situated between the lobules and surround them ; each ves-
sel, however, giving off branches to two or three lobules, and
never to one alone. They do not anastomose, and conse-
quently do not constitute a true plexus. The diameter
of these interlobular vessels varies from I414o to ^-^ of an
inch.2 In this distribution, the blood-vessels are followed

1 KOLLIKER, Handbuch der Gewebelehre des Menscken, Leipzig, 1867, S. 443.

2 KOLLIKER, op. cit.t 1867, S. 441.

PHYSIOLOGICAL ANATOMY OF THE LITER. 237

by branches of the duct, much less numerous and smaller,
measuring only ^soo °^ an mcn ? and some, even, have been
measured that are not more than 3^ of an inch in diam-
eter.1

Lobular Vessels. — In the interlobular plexus, the ramifi-
cations of the hepatic artery are lost, and this can no longer
be traced as a distinct vessel. One of the peculiarities of its
arrangement, as we have seen, is that the artery 'does not
empty into the radicles of the efferent vein, but joins the
portal vessels as they are about to be distributed in a true
capillary plexus in the substance of the lobules. In the lob-
ules themselves, consequently, we have only to study the
arrangement of the portal plexus, with the mode of origin of
the hepatic veins and the relations of the hepatic duct.

The arrangement of the lobular plexus of blood-vessels
is very simple. From the interlobular veins, a number of
branches (eight to ten) are given off and penetrate the lobule.
As the interlobular vessels are situated between different
lobules, each one sends branches into two and sometimes
three of these lobules ; so that, as far as vascular supply is
concerned, these divisions of the liver are never absolutely
distinct.

After passing from the interlobular plexus into the
lobules, the vessels immediately break up into a close net-
work of capillaries, from -g-^ to ^Vrr °f an incn *n diame-
ter,3 which occupy the lobules with a true plexus. These
vessels are very numerous; and when they are fully dis-
tended by artificial injection, their diameter is greater than
that of the intervascular spaces. It must be remembered,
however, that in the study of the liver by minute injections,
as in other parts, the vessels probably are distended so that
they occupy more space than they ever do under the physio-
logical conditions of the circulation. The blood, having been

1 BEALE, On some Points in the Anatomy of the, Liver of Man and Vertebrate
Animals, London, 1856, p. 58.

2 KOLLIKER, op. tit., 1867, S. 442.

238

EXCKETKW.

distributed in the lobules by this lobular plexus, is collected
by venous radicles of considerable size into a single central
vessel in the long axis of the lobule, called the intralobular
vein. A single lobule, surrounded with an interlobular
vessel, showing the lobular capillary plexus, and the central
vein (the intralobular vein) cut across, is represented in
Fig. 9.

FIG. 9.

Transverse section of a single hepatic lobule. 1, Intralobular vein, cut across ; 2, 2, 2, 2,
Afferent branches of the intralobular vein : 8, 3, 3, 3, 3, 3, 3, 3, 3, Interlobnlar branches
of the portal vein— with its capillary branches, forming the lobular plexus, extending
to the radicles of the intralobular vein. (SAPPEY. Traite d'anatomie, Paris, 1857,
tome iii., p. 297.)

With regard to the mode of origin of the hepatic duct in
the substance of the lobule, recent researches have shown
that it begins by a very fine anastomosing plexus of vessels,
with amorphous walls, situated between the liver-cells ; but
there are many different opinions on this subject, and we
will defer its full consideration until we take up the anatomy
of the secreting structures in the lobules.

Origin and Course of the Hepatic Veins. — The blood
distributed in the lobular capillary plexus furnishes the ma-
terials for the formation of bile, and undergoes those changes

PHYSIOLOGICAL ANATOMY OF THE LIVER. 239

produced by the action of the liver as a ductless gland ; in
other words, it is in and around this plexus that all the
physiological functions of the liver are performed. It is
then only necessary that the blood should be carried from
the liver to go to the right side of the heart ; and the ar-
rangement of the hepatic veins is accordingly very simple.

Intralobular Veins. — The innumerable capillaries of
the lobules converge into three or four venous radicles (rep-
resented in Fig. 9), which empty into a central vessel, from
ToVo- to TFF °f an mcn m diameter.1 This is the intralob-
ular vein. If a liver be carefully injected from the hepatic
veins, and sections be made in various directions, it will be
seen that the intralobular veins follow the long axis of the
lobules, receiving vessels in their course, until they empty
into a larger vessel, situated at what may be termed the
base of the lobules. These vessels have been called, by
Kiernan, the sublobular veins. They collect the^ blood in
the manner just described from all parts of the liver, unite
with others, becoming larger and larger, until finally they
form the three hepatic veins, which discharge the blood from
the liver into the vena cava ascendens.

The hepatic veins differ somewhat in their structure
from other portions of the venous system. Their walls are
thinner than those of the portal veins ; they are not en-
closed in a sheath, and are very closely adherent to the he-
patic tissue. It is this provision which makes the force of
respiration from the thorax so efficient in the circulation in
the liver.2 Here, indeed, a force added to the action of the
heart is especially necessary ; for the blood is passing in the
liver through a second capillary plexus, having already been
distributed in the capillaries of the alimentary canal and
other abdominal organs, before it is received into the portal
vein. It has also been noted that the hepatic veins possess
a well-marked muscular tunic, very thin in man, but well
developed in the pig, the ox, and the horse, and composed

1 KOLLIKER, op. cit., 1867, S. 442. 2 See vol. i., Circulation, p. 322.

240 EXCRETION.

of unstriped muscular fibres interlacing with each, other in
every direction.1

In addition to the blood-vessels just described, the liver
receives venous blood from vessels which have been called
accessory portal veins, coming from the gastro-hepatic omen-
tum, the surface of the gall-bladder, the diaphragm, and the
anterior abdominal walls. These vessels penetrate at dif-
ferent portions of the surface of the liver, and may serve as
derivatives when the circulation through the portal vein is
obstructed.

Structure of a Lobule of the Liver. — Each hepatic lob-
ule, bounded and more or less distinctly separated from
the others by the interlobular vessels, contains blood-vessels,
radicles of the hepatic ducts, and the so-called hepatic cells.
The arrangement of the blood-vessels has just been de-
scribed; but in all preparations made by artificial injection,
the space occupied by the blood-vessels is exaggerated by
excessive distention, and the difficulties in the study of the
relations of the ducts and the liver-cells are thereby much
increased. Under any conditions, there are few questions,
if any, in minute anatomy, that are so complicated as that
of the origin of the bile-ducts in the lobules. If we were to
attempt a critical analysis of the important investigations
made upon this subject during the last thirty-five years, we
would only illustrate the great diversity of opinion among
eminent authors upon difficult anatomical questions. As
the important problem in the minute anatomy of the lobules
has been the relations of the cells to the radicles of the bile-
ducts, we will first take up the structure of the cells.

Hepatic Cells. — If a scraping from the cut surface of a
fresh liver be examined with a moderately high magnifying
power, the field of view will be found filled with numerous
rounded, ovoid, or irregularly polygonal cells, measuring from
rsW to TTOT °f an mch m diameter. In their natural con-

1 SAPPEY, op. cit., p. 300.

PHYSIOLOGICAL AST ATOMY OF THE LIVER.

dition, they are more frequently ovoid than polygonal, and
when they have the latter form, the corners are always
rounded. These cells present one and sometimes two nu-
clei, sometimes with and sometimes without nucleoli. The
presence of numerous small pigmentary granules gives to
the cells a peculiar and characteristic appearance ; and, in
addition, nearly all of them contain a few granules or small
globules of fat. Sometimes the fatty and pigmentary mat-
ter is so abundant as to obscure the nuclei. The addition
of acetic acid renders the cells pale and the nuclei more dis-
tinct. By appropriate reagents, animal starch (probably
glycogenic matter) has been demonstrated in the substance
of the cells.1

Arrangement of the Bile-ducts in the Lobules. — Before
the publication of the researches of Kiernan, no reasonable
speculations, even, had been made with regard to the ulti-
mate arrangement of the bile-ducts. Kiernan supposed that
the lobules contained a reticulated net-work of ducts com-
municating with the ducts in the interlobular spaces ; but
he only inferred their existence, and his figures, which have
been extensively copied, are merely diagrammatic.2 The
same arrangement essentially was described by Prof. Leidy>
who figures a net-work of canals in the lobules, lined with
the liver-cells ; but the evidence in favor of this view is not
convincing.3 The results of the researches of Beale were at
one time adopted by many anatomists. Beale supposed
that there existed in the lobules delicate tubes, about as
wide as the liver-cells, each tube enclosing a row of these
cells.4 The presence of this delicate membrane, however,

1 SCHIFF, De la nature des granulations qui remplissent les cellules hepatiques :
Amidon animate. — Comptes rendus, Paris, 1859, tome xlviii., p. 880.

2 KIERXAN, op. cit. — Philosophical Transactions, London, 1833, p. 711, ft seq.

3 LEIDY, Researches into the Comparative Structure of the Liver. — American
Journal of the Medical Sciences, Philadelphia, 1848, Xew Series, vol. xv., p. 13,
el seq.

4 BEALE, On some Points in the Anatomy of the Liver of Man and Vertebrate
Animals, London, 1856, p. 73.

24:2 EXCRETION.

was not satisfactorily demonstrated. Kolliker formerly ac-
cepted in part the views advanced by Beale ; but his ideas
upon this subject, in all but the last edition of his work,
have not been very definite.1

Such is the condition of the question of the origin of the
biliary ducts, as it is understood by most English and Amer-
ican authors; and although the above statement does not
represent all the views entertained by different anatomists,
it is sufficient to show the exceedingly indefinite condition
of the whole subject. Kolliker, indeed, in a letter to Dr.
Sharpey, of London (1867), and in the last edition of his
work on histology, abandons his former views, and states
that he has become fully convinced of the accuracy of recent
observations which lead to an entirely new description
of the bile-ducts ; a and Prof. Leidy, in his work on anat-
omy, published in 1861, does not commit himself to any
definite opinion on the subject.3 Late researches have
shown that the following is probably the true relation of
the ultimate ramifications of the bile-ducts in the lobules to
the hepatic cells :

In the substance of the lobules is an exceedingly fine
and regular net- work of vessels, of uniform size, about 10}00
of an inch in diameter,4 which surround the liver-cells, each
cell lying in a space bounded by inosculating branches of
these canals. This plexus is entirely independent of the

1 KOLLIKER, Manual of Human Microscopic Anatomy, London, 1860, p.
346.

2 Journal of Anatomy and Physiology, Cambridge and London, 1868, vol.
ii., p. 163. These views have been adopted by Kolliker in the last edition of
his work on Microscopic Anatomy (Handbuch der Gewcbelehre, Leipzig, 1867, S.
428).

3 LEIDY, An Elementary Treatise on Human Anatomy, Philadelphia, 1861,
p. 327.

4 This is the result of the measurements by Dr. Stiles (Bulletin of tJie New
York Academy of Medicine, 1868, vol. iii., p. 351), of the ducts in the livers of
the bullocks that died of the " Texas disease," which we have verified in the
same specimen. The measurements given by Frey are about the same (Hand-
buch der Histoloaic, Leipzig, 1867, a 558).

PHYSIOLOGICAL ANATOMY OF THE LIVEK.

243

FIG. 10.

blood-vessels, and it seems to enclose in its meshes each indi-
vidual cell, extending from the periphery of the lobule,
where it is in communication with the interlobular bile-
ducts, to the intralobu-
lar vein in the centre.
The vessels probably
have excessively thin,
homogeneous walls —
though the existence of
their membrane has not
been positively demon-
strated— and are with-
out any epithelial lin-
ing, being much small-
er, indeed, than any
epithelial cells with
which we are acquaint-
ed. This arrangement,

/. . -, , Portion of a transverse section of an hepatic lo-

aS lar as IS KnOWll, naS bule of the rabbit, magnified 400 diameters, ft,

capillary blood-vessels; ^, capillary bile-ducts;
/. liver-cells. (KQLLIKER, Handbuch der Gfeuxte-
lehre des Mewchen, Leipzig, 1867, S. 428.)

no analogue in any
other secreting organ.

Although it is within three or four years only that the
reticulated bile-ducts of the lobules have attracted much
attention, they were discovered in the substance of the
lobules, near the periphery, by Gerlach, in 1848.1 It is evi-
dent, from an examination of his figures and description,
that he succeeded in filling with injection that portion of
the lobular network near the borders of the lobules, and
demonstrated the continuity of their vessels with the inter-
lobular ducts ; but he did not recognize the vessels nearer
the centre of the lobule. His views, however, received very
little attention, and are not even mentioned in most of the
authoritative works on general anatomy. Within the last

1 GERLACH, Handbuch der allgemeinen und speddlen Gewebekhre, Mainz, 1848,
S. 280, et seq.

24:4 EXCRETION.

few years, Budge,1 Andrejevic,2 Mac-Gillavry,3 Chrzonszc-
zewsky,4 Wyss,5 Hering,6 Frey,7 Eberth,8 Kolliker,9 and
others have investigated this interesting question, by vari-
ous methods, and have arrived at the most positive and satis-
factory results. It is now demonstrated, beyond a doubt,
that there are either canals or interspaces between the
liver-cells in the lobules, and that these open into the in-
terlobular hepatic ducts. It is still a question of discussion,
whether these passages are simple spaces between the cells,
or are lined by a membrane ; but this point has no great
physiological importance, and we can readily imagine that
it would be exceedingly difficult to demonstrate a membrane
forming the wall of a tube, the whole measuring but 10^00
of an inch. In the investigations which have thus demon-
strated the arrangement of the finest bile-ducts in the
lobules, the livers of rabbits have been found to present the
most favorable conditions. It has been assumed, however,
that in the method of study by artificial injection, the ap-
pearance of canals might be due to the extravasation of the
fluid, which might possibly take on a regular arrangement
between the cells. This is an error of observation that
would not be unlikely to occur ; but not only have these fine

1 BUDGE, Ueber den Verlauf der Gallengdnge. — Archiv fur Anatomic, Physi-
ologic und wissenschaftlichen Medicin, Leipzig, 1859, S. 642, et seq.

2 ANDRE jEVi6, Ueber denfeineren Bau der Leber. — SitzungsbericMe der mathe-
matisch-naturwissenschaftlichen Classe der Kaiserliclien Akademie der Wissen-
schaften, Wein, 1861, Bd. xliii., I. Abtheilung, S. 379, et seq.

3 MAC-GILLAVRY, Zur Anatomie der Leber, Idem, Wein, 1865, Bd. i., II.
Abtheilung, S. 207, et seq.

4 CHRZONSZCZEWSKY, Zur Anatomie und Physiologic der Lebcr. — VIRCHOW'S
Archiv, Berlin, Jan., 1866, Bd. xxxv., S. 153, et seq.

5 WYSS, Beitrag zur Histologie der icterischen Leber. — VIRCHOW'S Archiv, Ber-
lin, April, 1866, Bd. xxxv., S. 553, et seq.

6 BERING, Ueber den Bau der Wirbelthierleber. — Sitzungberichte, etc., Wein,
1866, Bd. liv., I. Abtheilung, S. 335.

7 FREY, Handbuch der Histologie, Leipzig, 1867, S. 557, et seq.

8 EBERTH, Untersuchungen uber die normale und pathologische Leber. — VIR-
cnow's Archiv, Berlin, Mai, 1867, Bd. xxxix., S. 70, et seq.

9 KOLLIKER, Handbuch der Gewebelehre, Leipzig, 1867, S. 428.

EXCRETORY BILIARY PASSAGES. 2:t5

ducts been filled by injection and their connection with the
interlobular ducts apparently established, they have been
observed filled with inspissated bile in icteric livers.1 A
method of study, very ingenious and highly satisfactory in
its results, was adopted by Chrzonszczewsky. He intro-
duced into the blood-vessels or stomach of a living animal a
solution of indigo-carmine, and within one or two hours,
killed the animal, when the whole net-work of ducts in the
lobules was found unbroken and connected with the inter-
lobular vessels. The drawings of these appearances accom-
panying the memoir are exceedingly beautiful.*

A peculiarly favorable opportunity for observing the
bile-ducts in the lobules was presented in the livers of ani-
mals that died of the so-called " Texas cattle-disease." This
was taken advantage of by Dr. R. C. Stiles, who was able
to verify, in the most satisfactory manner, the facts which
have lately been established by the German anatomists.3 In
these livers, the finest bile-ducts were found filled with bright
yellow bile, and their relations to the liver-cells were beauti-
fully distinct. In the examination of these specimens, the
presence of what appeared to be detached fragments of these
little canals is an argument in favor of the view that they
were lined by a membrane of excessive tenuity. These in-
teresting anatomical points were demonstrated by Dr. Stiles
before the Xew York Academy of Medicine, and we have
since been able to verify them in every particular.

Anatomy of the Excretory Biliary Passages. — There
can be scarcely any doubt of the connection between the in-
tercellular biliary plexus in the substance of the lobules and

1 WTSS, loc. cit. 2 Loc. cit.

3 STILES, Bulletin of tJie New York Academy of Medicine, 1868, vol. iii., p.
350 ; Report of the New York State Cattle Commissioners, in connection with the
Special Report of the Metropolitan Board of Health on the Texas Cattle-Disease. —
Transactions of the New York State Agricultural Society, Albany, 1868, vol.
xxvii. — 1867, Part ii., pp. 1137, 1160; and Third Annual Report of the Me-
tropolitan Board of Health of the State of New York, Albany, 1868, p. 303.

246 EXCRETION.

the interlobular ducts. We shall see, further on, that the
ducts, in their course from the lobules to the intestine, are
provided with numerous small racemose glands, which prob-
ably secrete a mucus that is mixed with the bile ; but, in all
probability, the peculiar elements of the bile are formed in
the lobules, and the canals situated between the lobules and
leading from them to the larger ducts are merely excre-
tory.

Between the lobules the ducts are very small, the smallest
measuring about -^-gVo" °f an ^ncn m diameter. They are
composed of a delicate membrane, lined with small, flat-
tened epithelium. According to Robin, the cells lining the
excretory ducts are ciliated ; l but this is not the view gener-
ally adopted. The ducts larger than 12100 of an inch have
a fibrous coat, formed of inelastic, with a few elastic ele-
ments, and in the larger ducts there are, in addition, a few
non-striated muscular fibres. The epithelium lining these
ducts is of the columnar variety, the cells gradually under-
going a transition from the pavement form as the ducts in-
crease in size. In the largest ducts there is a distinct mu-
cous membrane, with mucous glands.

Throughout the whole extent of the biliary passages,
from the interlobular canals to the ductus choledochus, are
little utricular or racemose glands, varying in size in differ-
ent portions of the liver, called, by Robin, the biliary acini.
These are situated, at short intervals, by the sides of the
canals. The glands connected with the smallest ducts are
simple follicles, from -g-J-g- to ^-J-g- of an inch long. The
larger glands are formed of groups of these follicles, and
measure from -g-J-^ to y^- of an inch in diameter. The glands
are only found connected with the ducts ramifying in the
substance of the liver, and do not exist in the hepatic, cystic,
and common ducts. They are composed of a homogeneous
membrane, lined with small, pale cells of pavement-epithe-

1 LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1865, p. 611, Article,
Foie.

EXCKETGBY BILIARY PASSAGES.

247

Hum. If the ducts in the substance of the liver be isolated,
they are found covered with these little groups of follicles,
and have the appearance of an ordinary racemose gland, ex-
cept that the acini are relatively small and scattered. This
appearance is represented in Fig. 11.

FIG. 11.

Anastomoses, and racemose glands attached to the biliary ducts of the pig, magnified
eighteen diameters. 1. 1. Branch of an hepatic duct, with the surface almost entirely
covered with racemose glands opening into its cavity ; 2, Branch in which the glands
are smaller and less numerous ; 3, 3, 3, Branches of the duct with still simpler
glands: 4. 4. 4, 4. Biliary ducts with simple follicles attached; 5, 5, 5, 5, Same, with
6, Anastomoses in arches ; 7, 7, 7, Angular a

fewer follicles ; 6. 6. 6, 6, 6,

8. 8. 8. 8. Anastomoses by transverse branches.

1857, tome iii., p. 279.)

anastomoses :
(SAPPEY, Traiie tfanaLamie, Paris.

The excretory biliary ducts, from the interlobular vessels
to the point of emergence of the hepatic duct, present nu-
merous anastomoses with each other in their course.

Vasa Aberrantia. — In the livers of old person?, and oc-
casionally in the adult, certain vessels are found ramifying
on the surface of the liver, but always opening into the
biliary ducts, which have been called vasa aberrantia. These
are never found in the foetus or in children. They are, un-
doubtedly, appendages of the excretory system of the liver,
and are analogous in their structure to the ducts, but are

248 EXCRETION.

apparently hypertrophied, with thickened, fibrous walls, and
present, in their course, irregular constrictions, not found in
the normal ducts. The racemose glands attached to them
are always very much atrophied. Sappey is of the opinion
that these are ducts leading to lobules on the surface of the
liver which have become atrophied.1

Gall-bladder, Hepatic, Cystic, and Common Ducts. —
The hepatic duct is formed by the union of two ducts, one
from the right and the other from the left lobe of the liver.
It is about an inch and a half in length, and joins at an
acute angle with the cystic duct, to form the ductus commu-
nis choledochus. The common duct is about three inches
in length, of the diameter of a goose-quill, and opens into
the descending portion of the duodenum. It passes obliquely
through the coats of the intestine, and opens into its cavity
in connection with the principal pancreatic duct. The cys-
tic duct is about an inch in length and is the smallest of
the three canals.

The structure of these ducts is essentially the same.
They have a proper coat, formed of white fibrous tissue, a
few elastic fibres, and a few non-striated muscular fibres.
The muscular tissue is not sufficiently distinct to form a
separate coat. The mucous membrane is always found
tinged yellow with the bile, even in living animals. It is
marked by numerous minute excavations, and is covered
with cells of columnar epithelium. This membrane con-
tains numerous mucous glands.

The gall-bladder is an ovoid or pear-shaped sac, about
four inches in length, one inch in breadth at its widest por-
tion, and capable of holding from an ounce to an ounce and
a half of fluid. Its fundus is covered entirely with peri-
toneum, but this membrane passes only over the lower sur-
face of the body.

The proper coat of the gall-bladder is composed of white
fibrous tissue with a few elastic fibres. In some of the lower

1 SAPPEY, op. cit., tome iii., p. 283.

XERVE3 AND LYMPHATICS OF THE LIVER. 249

animals there is a distinct muscular coat, but a few scattered
fibres only are found in the human subject. The mucous
coat is of a yellowish color, and marked with numerous
very small, interlacing folds, which are exceedingly vascular.
Like the membrane of the ducts, the mucous lining of the
gall-bladder is covered with columnar epithelium. In the
gall-bladder are found numerous small racemose glands,
formed of from four to eight follicles lodged in the submu-
cous structure. These are essentially the same as the glands
opening into the ducts in the substance of the liver, and
secrete a mucus, which is mixed with the bile.

Nerves and Lymphatics of the Liver. — The nerves of the
liver are derived from the pneumogastric, the phrenic, and
the solar plexus of the sympathetic. The branches of the
left pneumogastric penetrate with the portal vein, while the
branches from the right pneumogastric, the phrenic, and the
sympathetic surround the hepatic artery and the hepatic duct.
All of these nerves penetrate at the transverse fissure and
follow the blood-vessels in their distribution. They have
not been traced farther than the terminal ramifications of
the capsule of Glisson, and their exact mode of termination
is unknown.

The lymphatics of the liver are very numerous. They
are divided into two layers : the superficial layer, situated
just beneath the serous membrane; and the deep layer,
formed of a plexus surrounding the lobules and situated
outside of the blood-vessels. The superficial lymphatics
from the under surface of the liver, and that portion of
the deep lymphatics which follows the hepatic veins out
of the liver, pass through the diaphragm and are con-
nected with the thoracic glands. Some of the lymphatics
from the superior or convex surface join the deep vessels
that emerge at the transverse fissure, and pass into glands
below the diaphragm, while others pass into the thoracic
cavity.

250 EXCRETION.

Mechanism of the Secretion and Discharge of Bile. —
The liver lias no analogue in the glandular system, either in
its anatomy or its physiology. There is no gland in the
economy which we know to have two distinct functions,
such as the secretion of bile, and the production of certain
elements destined to be taken up by the current of blood
as it passes through. In other words, there is no organ in
the body which has at the same time the functions of an or-
dinary secreting gland and a ductless gland. If we regard
the liver-cells as the anatomical elements which prodiice the
bile, it is evident that their number is very much out of pro-
portion to the amount of bile secreted ; and the liver itself
is an organ of much greater size than it seems to us would
be required for the mere secretion of bile. "We explain this
disproportionate size by the fact that the liver has other
functions as a ductless gland.

There is no gland in which the arrangement of secreting
tubes is the same as in the liver. It is hardly possible that
the intercellular plexus of fine tubes in the lobules should be
any thing but the plexus of origin, or the secreting portion
of the hepatic duct. These are certainly not blood-vessels,
and the only vessels that could have the appearance we have
described, except the bile-ducts, are the lymphatics ; but the
communication between these vessels and the excretory bile-
ducts, and the fact that they have been seen distended with
bile in icteric livers, are pretty conclusive evidence of their
nature. This arrangement, then, must be regarded as pe-
culiar to the liver, as the arrangement of a capillary plexus,
surrounded with cells and enveloped in a dilated extremity
of a secreting tube, is peculiar to the kidney and is found
in no other glandular organ.

Do the liver-cells, situated outside of the plexus of origin
of the biliary duct, secrete the bile, which is taken up by
these delicate vessels and carried to the excretory biliary pas-
sages ? There are very good reasons for answering this ques-
tion in the affirmative ; though, if we do, we must recognize

MECHANISM OF THE SECRETION OF BILE. " 251

the fact that the same cells produce glycogenic matter. As
far as. we are able to understand the mechanism of secretion,
it seems necessary that a formed anatomical element, known
as a secreting cell, should elaborate, from materials furnished
by the blood, the elements of secretion ; and this cannot be
accomplished by a structureless membrane, like that which
forms the walls of the bile-ducts.1 Under this view, assum-
ing that bile, as bile, first makes its appearance in these
little lobular tubes, the liver-cells are the only anatomical
elements capable of producing the secretion. With regard
to the mechanism of this secreting action, we have nothing
to say beyond our general remarks in the first chapter.
With the view we have just expressed, certain elements of
the bile are separated from the blood, and others are manu-
factured out of materials furnished by the blood by the
liver-cells, and are taken up by the delicate plexus of vessels
situated between the cells. The discharge of the fluid is
like the discharge of any other of the secretions, except that
a portion is temporarily retained in a diverticulum from the
main duct, the gall-bladder.

The two distinct functions of the liver now recognized
by many physiologists, namely, the secretion of bile and
the formation of sugar, have led to the question of the ex-
istence in the liver of two anatomically distinct portions
or organs, corresponding to its double physiological func-
tion. This view, indeed, has been advanced by several
eminent anatomists. Robin recognizes two distinct parts
in the liver ; a biliary organ and a glycogenic organ. He
regards the lobules, with their liver-cells and blood-vessels,
as the parts concerned in the glycogenic function of the
liver, and the little glands which open into the biliary ducts
all along their course (see Fig. 11) and are arranged on
the duct "in the form of leaves of fern," as the biliary

1 An exception to this rule is in the secretion of milk during the period of
greatest activity of the mammary glands. (See p. 79.)

252 EXCRETION.

organ.1 The same independence of the glycogenic and bil-
iary portions of the liver has been argued by others. Among
the latest publications on this subject is a review of the
question by Accolas ; 3 but although this was published in
1867, there is no mention of the late researches, to which
we have referred so fully, on the origin of the ducts in the
lobules.

The fact of bile being found in the lobular canals and
the demonstration of the direct communication of these
canals with the excretory biliary ducts are powerful ar-
guments in favor of the view that the bile is formed in the
lobules, and probably by the liver-cells. What, then, is the
function of the little acini connected exclusively with the
biliary ducts ? The similarity of their structure to that of the
ordinary mucous glands, and to the mucous glands of the
gall-bladder especially, would lead to the supposition that
they secrete a mucous fluid. It is well known that the bile
taken from the gall-bladder contains more mucus than that
discharged directly from the liver ; but the bile of the he-
patic duct in most animals is somewhat viscid and contains a
certain amount of mucus. This is the view entertained by
Sappey, who states that the bile is viscid in different animals
in proportion to the development of these little glands ;
and in the rabbit, in which the glands do not exist, the bile
is remarkably fluid.3

Inasmuch as there is no direct evidence that the racemose
glands attached to the excretory biliary passages have any
thing to do with the secretion of the essential constituents
of the bile, and as they are not even to be found in some
animals that produce a considerable quantity of bile, we
must regard the question of the isolation of two organs in

1 LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1865, p. 611, Article,
Foie, and Lemons sur les humeurs, Paris, 1867, p. 551, et seq.

2 ACCOLAS, Essai sur Vorigine des canalicules hepatiques et sur I 'independance
des appareils biliaire et glycogene dufoie, Strasbourg, 1867.

3 SAPPEY, Traite d1 anatomic descriptive, Paris, 1857, tome iii., p. 280.

MECHANISM OF THE SECRETION OF BILE. 253

the liver, one for the secretion of bile and the other for the
production of sugar, as still unsettled. There is no evi-
dence, indeed, that the bile is secreted anywhere but in the
hepatic lobules.

Secretion of Bile from Venous or Arterial Blood. —
Xumerous experiments have been made with the. view of
determining whether the bile be secreted from the blood
brought to the liver by the portal vein, or from the blood of
the hepatic artery. The immense quantity of blood distrib-
uted in the liver by the portal vein led first to the opinion
that the impurities were separated from this blood to form
the bile, and that the hepatic artery had little or nothing to
do with the secretion. This, indeed, was the view adopted
by Glisson,1 one of the earliest writers on the anatomy and
functions of the liver. But since Bernard discovered the
glycogenic function of the liver, this subject has assumed
additional importance ; and it becomes a question whether
the materials for the secretion of bile may not be furnished
by one vessel (the hepatic artery), while the other (the portal
vein) is specially concerned in the formation of glycogenic
matter. This theoretical view, however, is not carried out
by well-established anatomical facts or by physiological ex-
periments. It is not yet possible to separate the liver ana-
tomically into two organs, one for the secretion of bile and
the other for the production of sugar. It seems certain, also,
from numerous experiments,3 that bile may be secreted from
the blood of the portal vein after a ligature has been applied
to the hepatic artery ; and it is equally certain, from the re-
cent experiments of Ore,8 that, if the portal vein be obliter-
ated so gradually that the animal does not die from the op-
eration, bile is secreted from the blood of the hepatic artery.

1 GLISSOXIUS, Anatomia Hepatis, London, 1654, p. 383.

2 LOXGET, Traite de physiologic, Paris, 1869, tome ii., p. 305.

3 ORE, Influence de V obliteration de la veine porte *ur la secretion de la bile. —
Comptesrendus, Paris, 1856, tome xliii., p. 463.

254 EXCRETION.

The experiments of M. Ore are very curious and in-
structive. After having repeatedly made the experiment of
applying a tight ligature to the portal vein, producing thereby
very grave sympt6ms and death so speedily that the effects
upon the secretion of bile could not be satisfactorily ob-
served, he modified his operations so as to effect a gradual
obliteration of the vein. This he accomplished by simply
applying a loose ligature, and tightening it from time to
time until it came away. By this mode of procedure he suc-
ceeded in observing the secretion of bile six days or more
after the application of the ligature ; and, on killing the
animals, he found the portal vein entirely obliterated and
no communicating branches by which the blood could get
from the portal system to the liver. From these observa-
tions it is concluded that the bile is secreted from the blood
of the hepatic artery.

In support of this view, several instances of obliteration
of the portal vein in the human subject are cited in works
upon physiology. In a note to the communication of Ore
in the Comptes rendus, Andral reports the case of a patient
that died of dropsy, and on post-mortem examination the
portal vein was found obliterated. In this instance the gall-
bladder was found full of bile.1 In addition, instances in
which the portal vein emptied into the vena cava have been
reported,2 and in none was there any deficiency in the secre-
tion of bile.

If the experiments upon the effects of tying the hepatic
artery, and the observations of instances of obliteration of
the portal vein and of congenital malformation, in which the
portal vein does not go to the liver, be equally reliable, there

1 Comptes rendus, Paris, 1856, tome xliii., p. 46*7.

2 ABERNETHT, Account of two Instances of Uncommon Formation, in the Viscera
of the Human Body, — Philosophical Transactions, London, 1793, p. 59.

LAWRENCE, Account of a Child born without a Brain, which lived four

Days ; with a sketch of the principal deviations from the ordinary Formation of the
Body ; Remarks on their Production, and a view of some Physiological Inferences to
which they lead. — Medico- Chirurgical Transactions, London, 1814, vol. v., p. 174.

QUANTITY OF BILE. 255

is but one conclusion to be drawn from them ; and that is,
that bile may be secreted from either venous or arterial
blood. This view is not inconsistent with what we know
of the general process of secretion and its applications to
the production of bile. Regarding the bile as in part an
excrementitious fluid, its effete element — cholesterine — is
contained both in the blood of the portal vein and in the he-
patic artery. Its recrementitious principles — glycocholates,
taurocholates, etc. — we suppose are produced de novo in
the liver, out of materials furnished by the blood. The
exact nature of the production of elements of secretion by
glandular cells we do not understand ; but there is no good
reason to suppose that the principles necessary for the for-
mation of bile may not be furnished by the blood of the
portal vein, as well as by the hepatic artery.

The view most nearly in accordance with all the facts
bearing on the question is, that bile is produced in the liver
from the blood distributed in its substance by the portal
vein and the hepatic artery, and not from either of these
vessels exclusively ; and that the bile may continue to be se-
creted, if either one of these vessels be obliterated, provided
the supply of blood be sufficient.

Quantity of JSile.^-The estimates of the daily quantity
of bile in the human subject must be merely approximative ;
and our only ideas on this point are derived from experi-
ments upon the inferior animals. The most complete and
reliable observations on this subject are those of Bidder and
Schmidt, and were made upon animals with a fistula into the
gall-bladder, the ductus conimunis having been tied.1 These
observers found great variations in the daily quantity in dif-
ferent classes of animals, the quantity in the carnivora being
the smallest. Applying their results to the human subject,
assuming that the amount is about equal to the quantity
secreted by the carnivora, the daily secretion in a man

1 BIDDER UND SCHMIDT, Die Verdauungssafte, Leipzig, 1852, S. 209.

256 EXCRETION.

weighing one hundred and forty pounds would be about two
and a half pounds.1

Variations in the Flow of the Bile. — We have already
considered, in another section, the variations in the flow of
bile, and their relation to the process of intestinal digestion.8
It is sufficient in this connection to repeat that the discharge
from a biliary fistula in a dog increases immediately after
eating ; that it is at its maximum from the second to the
eighth hour, during which time it does not vary to any great
extent ; after the eighth hour it begins to diminish, and from
the twelfth hour to the time of feeding, it is at its minimum.
Prof. Dalton made observations on the flow of bile from a
fistula into the duodenum, which would represent the physi-
ological discharge of bile into the intestine more nearly
than observations with a biliary fistula. He found that
by far the largest quantity passes into the intestines im-
mediately after feeding and within the first hour.3 These
results agree in all essential particulars with previous obser-
vations on this subject — which have been very numerous —
and they show that while the bile is discharged much more
abundantly during intestinal digestion than during the in-
tervals of digestion, its production and discharge are con-
stant. This, we shall see in the next chapter, is a strong
argument in favor of the view that the liver has an excre-
mentitious function.

The bile is stored up in the gall-bladder to a consider-
able extent during the intervals of digestion. If an animal
be killed at this time, the gall-bladder is always distended ;

1 This is the estimate adopted by Dalton (Treatise on Human Physiology,
Philadelphia, 1867, p. 172). In our own experiments, made on a dog with a
biliary fistula, the object was not so much to ascertain the entire quantity of
bile in the twenty-four hours as to note the variations in its flow. The estimate
was made in a dog that had become somewhat enfeebled, and is undoubtedly
too low. (See vol. ii., Digestion, p. 375.)

2 See vol. ii., Digestion, p. 375.

3 DALTON, op. cit., p. 176.

DISCHARGE OF THE BILE. 25 T

but it is found empty, or nearly so, in animals killed during
digestion.

The influence of the nervous system upon the secretion
of bile has been very little studied, and the question is one
of great difficulty and obscurity. The liver is supplied very
abundantly with nerves, both from the cerebro-spinal and
the sympathetic system, and some observations have been
made upon the influence of the nerves on its glycogenic
function ; but with regard to the secretion of bile, we can
only apply our general remarks concerning the influence of
the nervous system on secretion.1

The bile is discharged through the hepatic ducts like the
secretion of any other gland. During digestion, the fluid
accumulated in the gall-bladder passes into the ductus com-
munis, in part by contractions of its walls, and in part, prob-
ably, by compression exerted by the distended and congested
digestive organs adjacent to it. It seems that this fluid,
which is necessarily produced by the liver without inter-
mission, separating from the blood certain excrementitious
matters, is retained in the gall-bladder for use during
digestion.

1 See page 28, et seq.

The extent of our knowledge of the influence of the nervous system on the
secretion of bile is well presented in the following paragraph :

" The nervous system has assuredly a very great influence on the resorption
of bile or on an obstacle offered to its discharge ; but we know nothing distinct
relative to this action, although we cannot deny it in the face of instances where
fear has been sufficient to suddenly produce icterus. The cause of this can
only be attributed to the influence of the pneumogastric or the grand sympa-
thetic (BERNARD, Liquides de Vorganlsme, Paris, 1859, tome ii., p. 212).

CHAPTER IX.

EXCRETORY FUNCTION OF THE LIVER.

ALTHOUGH the function of the bile in intestinal digestion
is essential to life, we know very little of its mode of action ;
and we have thought proper to defer until now a full con-
sideration of the properties and composition of this secretion.
For an account of what is known of its digestive function,
the reader is referred to the section of volume second, treat-
ing of digestion. We shall show, in this connection, that the
liver excretes one of the most important of the effete princi-
ples ; but before taking up the relations of the bile as an ex-
cretion, it will be necessary to study its general properties
and composition.

General Properties of the Bile. — The secretion, as it
comes directly from the liver, is somewhat viscid ; but after
it has passed into the gall-bladder, its viscidity is much
greater from further admixture of mucus.

The color of the bile is very variable within the limits

PROPERTIES OF THE BILE. 259

of health. It may be of any shade between a dark, yellow-
ish green and a reddish brown. It is semitransparent, ex-
cept when the color is very dark. In different classes of
animals the variations in color are very great. In the pig
it is bright yellow ; in the dog it is dark brown ; -and in the
ox it is greenish yellow. As a rale, the bile is dark green
in the carnivora and greenish yellow in the herbivora.

The specific gravity of the human bile, according to Prof.
Dalton, is 1018 ; 1 but this is somewhat lower than the aver-
age usually given, which is from 1020 to 1026.3 "When the
bile is perfectly fresh, it is almost inodorous, but it readily
undergoes putrefactive changes. It has an excessively dis-
agreeable and bitter taste. It is not coagulated by heat.
When mixed with water and shaken, it becomes frothy,
probably on account of the tenacious mucus and its sapona-
ceous constituents.

It is generally stated that the bile is invariably alkaline.
This is true of the fluid discharged from the hepatic duct,3
although the alkalinity is not strongly marked; but the
reaction varies after it has passed into the gall-bladder.
Bernard found it sometimes acid and sometimes alkaline
in the gall-bladder, in animals — dogs and rabbits — killed
under various conditions ; * but many of these animals were
suffering from the effects of severe operations. In the
hepatic ducts the reaction is always alkaline ; and there are
no observations on human bile that show that the fluid is
not alkaline in all of the biliary passages.

We have already noted the fact that the epithelium of
the biliary passages is strongly tinged with yellow, even in
living animals. This is due to the remarkable facility with
which the coloring principle of the bile stains the animal
tissues. This is very well illustrated in icterus, when even a

1 DALTON, Treatise on Human Physiology, Philadelphia, 1867, p. 159.

2 LONGET, Traite de physiologic, Paris, 1868, tome i., p. 278.

3 ROBIN, Lemons sur les humeurs, Paris, 1867, p. 538.

4 BERNARD, Liquides de forganisme, Paris. 1859, tome ii., p. 212.

260 EXCRETION.

small quantity of this coloring matter finds its way into the
circulation.

Perfectly normal and fresh bile, examined with the micro-
scope, presents only a certain amount of mucus, the charac-
ters of which we have already described. There are no
formed anatomical elements characteristic of this fluid. The
fatty and coloring matters are in solution, and not in the
form of globules or granules.

Composition of the Bile.

It is a remarkable fact, that although the bile, in a per-
fectly fresh and normal condition, may be obtained from the
inferior animals with the greatest facility, no satisfactory
analyses of its characteristic principles were made before the
examinations of ox-gall by Strecker, in 1848. The bile is,
however, one of the most important, but least understood,
of the animal fluids ; and our scanty information with regard
to its functions has been in a measure due to the want of an
exact knowledge of its physiological chemistry. We shall
study the composition of the bile very closely, and shall show
that it contains two classes of constituents ; one class — ele-
ments of secretion — which is reabsorbed ; and another — an
element of excretion — which is discharged in a modified form
in the faeces. The latter involves a newly-described function
of the liver, but our information is much more positive and
definite concerning it than with regard to the digestive action
of the bile. In treating of the subject of digestion, we have
already indicated some of the difficulties, which have been
but imperfectly overcome, in the study of the action of the
bile as a true secretion, or a recrementitious fluid. The rea-
son why the same obscurity has prevailed, until very recently,
with regard to the function of the bile as an excretion is
that physiologists have regarded what are known as the
biliary salts as the only really important constituents ; and
these salts have eluded chemical investigation after the dis-
charge of the bile into the small intestine. Our recent posi-

COMPOSITION OF THE BILE. 261

tive knowledge of the excrementitious function of the liver
is due to the recognition of cholesterine, an invariable con-
stituent of the bile, as one of the most important of the
elements of excretion.

Composition of Human

Water .......................................... 915'00 to 819'00

Taurocholate, or choleate of soda (NaO,C6aH46XOi4S2) 56-50 " 106-00

Glycocholate, or cholate of soda (XaOjCsa^aNOn) ____ traces.

Cholesterine (C25H230) ............................ 1'60 to 2-66

Biliverdine ...................................... 14'00 " 30*00

{. 8.2Q „ 31.QO
Margarine, oleine, and traces of soaps . )' '

Choline (C10H13X02) .............................. traces.

Chloride of sodium ............................... 2'77 to 3*50

Phosphate of soda ............................... 1-60 " 2'50

Phosphate of potassa ............................. 0'75 " 1'50

Phosphate of lime ............................ ____ 0'50 " 1'35

Phosphate of magnesia. ........................... 0"45 " 0*80

Salts of iron. .................................... 0'15 " 0*30

Salts of manganese ............................... traces " 0"12

Silicic acid ...................................... 0'03 " 0'06

Mucosine ....................................... traces.

Loss.. 3-45 to 1-21

1,000-00 1,000-00

There are no peculiarities in the composition of the
bile, as regards its inorganic constituents, which demand
more than a passing mention. It contains no coagulable
organic principle, except mucosine, and all of its constitu-
ents are simply solids in solution. The quantity of solid
matter is very large, and the proportion of water relatively
small ; but in comparing its proportion of water with that
of other fluids in the body, as the blood-plasma, lymph and
chyle, milk, etc., it must be remembered, as is suggested by

1 This table of the composition of the bile is compiled from Robin (Lemons
sur les humeiirs, Paris, 1867, p. 542). In making up the table, the difference be-
tween the sum of the constituents and 1,000 has been put in as " loss." We
have omitted leucine, tyrosine, and urea, as their existence as proximate prin-
ciples of normal bile is doubtful.

262 EXCRETION.

Robin,1 that all of these contain water entering into the
composition of their coagulable principles ; so that their pro-
portion of water, as it is ordinarily given, is really not greater
than in the bile. Among the inorganic salts, we find chloride
of sodium in considerable quantity, and a large proportion of
phosphates. "We also note the presence of salts of iron, of
manganese, and a small proportion of silicic acid.2

The fatty and saponaceous matters demand hardly any
more extended consideration. A small quantity of margarine
and oleine are held in solution, partly by the small propor-
tion of soaps, but chiefly by the taurocholate of soda. These
principles sometimes exist in larger quantity, and may be
discovered in the form of globules. The proportion of soaps
is very small. Lecithene, a phosphorized fat, is mentioned by
Robin and others, but its constitution is not definitely set-
tled. All that is known of this principle is that it is a
neutral fatty substance extracted from the bile, and is capa-
ble of being decomposed into phosphoric acid and glycerine.
Choline (C10H13NO2) is a peculiar alkaloid found in the bile
in exceedingly minute quantity.

Biliary Salts.

The principles which we have called biliary salts are
compounds of soda with peculiar organic acids, found no-
where but in the liver, and undoubtedly produced in this
organ from materials furnished by the blood. The fact that
the bile possesses peculiar principles has long been recog-
nized. It is unnecessary, however, to follow out in detail
the earlier chemical investigations into their properties ; for
the biliary matter of Berzelius and the picromel and biliary
resin of Thenard are now known to be composed of sev-
eral distinct proximate principles. Our exact knowledge

1 ROBIN, Legons sur les humeurs, Paris, 1867, p. 543.

2 The presence of hydrochlorate of ammonia and the ammonio-magnesian
phosphate has lately been indicated in the bile by M. Bergeret (de Saint-Leger).
— Journal de Vanatomie, Paris, 1869, tome vi., p. 437.

BILIARY SALTS. 263

of these substances dates from the analysis of ox-bile by
Strecker. He obtained two peculiar acids, cholic and choleic
acid, which he found in the bile, in combination with soda.1
In the subsequent researches of Lehmann, these acids are
called, respectively, glycocholic and taurocholic acid, and
the salts, glycocholate and taurocholate of soda.2

In human bile, the proportion of glycocholate of soda is
very small, the biliary matter existing almost entirely in the
form of the taurocholate. The taurocholate may be precipi-
tated from an alcoholic extract of bile by ether, in the form
of dark, resinous drops. These do not crystallize, and the
amount of glycocholate, which is precipitated in the same
way and soon assumes a crystalline form, is very slight.
Prof. Dalton, who has studied the biliary salts very closely,
at first was unable to obtain any crystalline matter from
human bile, but he has lately found it in minute quantity.3

Taurocholate of Soda (NaO,CMH4iNO14S,).— There is
some doubt whether the resinous drops obtained by the ad-
dition of an excess of ether to a strong alcoholic extract of
bile consist of a proximate principle in a perfectly pure
state. These drops are not crystallizable, and this has led
to the opinion, expressed by Robin and Yerdeil, that they
are impure.4 In fact, even now, there is a certain amount
of obscurity with regard to the character of these peculiar
biliary salts. In ox-bile, the non-crystallizable and the
crystallizable salts exist together; but in human bile, the

1 STRECKER, Untersuchung der Ochsgalle. — Annalen der Chemie und Pharmacie,
Heidelberg, 1848, Bd. Ixv., S. 1, et seq. ; Beobacktungen iiber die Gratte ver-
schiedener Thiere, Idem, 1849, Bd. Ixx., S. 149, et seq. An analysis of these ob-
servations is given in the Journal de pharmacie et de chimie, Paris, 1848, tome
xiii., p. 215 ; 1849, tome xv., p. 153 ; and tome xvi., p. 450.

2 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. ii., p. 201,
ct seq.

3 DALTON, Treatise on Human Physiology, Philadelphia, 1867, p. 167.

4 ROBIN ET YERDEIL, Traite de chimie anatomique, Paris, 1853, tome ii.,
p. 473.

264 EXCBETION.

greatest part is in the 'form of what we know as the tauro-
cholate of soda.

These salts may be readily obtained from ox-bile and
separated from each other by the following process : The
bile is first evaporated to dryness and pulverized. The dry
residue is then extracted with absolute alcohol and filtered.
In this part of the process, Dr. Dalton uses five grains of the
dry residue to one fluidrachm of alcohol.1 The filtered fluid
is of a clear, yellowish color, and contains fats and coloring
matter, in addition to the biliary salts. To precipitate the
biliary salts, a small quantity of ether is added, which pro-
duces a dense, white precipitate that redissolves by agitation.
Another small quantity of ether is again added, and the
precipitate thus produced is dissolved by shaking the mix-
ture. This process is repeated carefully, adding the ether
and shaking the mixture after each step, until the precipi-
tate becomes permanent. An excess of ether — from eight
to ten times the bulk of the alcoholic extract used — is then
added, the test-tube or flask is carefully corked, and the
mixture is set aside to crystallize. Gradually the dense,
white precipitate falls to the bottom of the vessel or becomes
attached in the form of resinous drops to the sides of the
glass ; and in from six to twenty-four hours it begins to form
delicate acicular crystals, arranged in rosettes. These are
crystals of the glycocholate of soda; and the non-crystal-
lizable matter remaining is the taurocholate of soda.

To separate these two salts, the ether is rapidly poured
off, and the crystalline and resinous residue is dissolved in
distilled water. On the addition to this solution of a little
acetate of lead, the glycocholate is decomposed and precipi-
tated in the form of glycocholate of lead, leaving the tauro-

1 DALTON, Treatise on Human Physiology, Philadelphia, 1867, p. 162, ct seq.,
and On the Constitution and Physiology of the Bile. — American Journal of the
Medical Sciences, Philadelphia, 1857, New Series, vol. xxxiv., p. 305, et seq. The
details of the processes for the extraction of the biliary salts are taken from
Dalton, who has studied this subject very carefully, and whose method is simple
and entirely satisfactory.

BILIAKY SALTS. 265

cholate in solution. The glycocholate of lead is then sepa-
rated by filtration, and the subacetate of lead is added to the
filtered fluid. This decomposes the taurocholate, and the
taurocholate of lead is precipitated. The subacetate of lead
will decompose both the glycocholate and the taurocholate,
but the glycocholate only is acted upon by the acetate of
lead. The glycocholate and the taurocholate of lead are
then carefully washed and treated separately with the car-
bonate of soda, which gives the original salts in nearly a
pure state.

The taurocholate of soda is a proximate principle of
the bile, and it is not necessary to describe fully in detail
the purely chemical processes by which it is decomposed.
With a little care, the taurocholic acid may be obtained in a
state of tolerable purity, and by prolonged boiling with pot-
ash, may be decomposed into a new acid and taurine. Some
confusion exists in the books about the name of this new
acid. Strecker calls it cholalic acid, and applies the name
of cholic acid to what we have described as glycocholic acid.
As we have adopted the nomenclature of Lehmann, we will
call it cholic acid. Its formula is C48H89O9HO. The for-
mula for taurine is C4H7NO8S2. It must be remembered,
however, that these substances are formed artificially and are
not true proximate principles. They have been described in
explanation of the name taurocholic acid, which has been
applied to it on the assumption that the different biliary
acids are formed of cholic acid united with taurine or other
basic substances.

If human bile be treated in the manner just described,
frequently no crystalline matter is obtained, and when it
exists, it is in very small quantity. The great mass of the
precipitate is composed of the taurocholate of soda. This,
when it has been thoroughly purified, is whitish and gummy,
very soluble in water and alcohol, and insoluble in ether.
It is melted with slight heat, and is inflammable. Its reac-
tion is neutral. It has a peculiar, sweetish-bitter taste. The

266 EXCRETION.

proportion of this principle in the bile is always very large,
though subject to considerable variation. It has very little
in common with the salts of fatty origin, either in its general
properties or composition, inasmuch as it is entirely insolu-
ble in ether, and its acid contains nitrogen. Another pecu-
liarity in its composition, and one which serves to distinguish
it from the glycocholate of soda, is that it contains two
atoms of sulphur. One of its important properties in the
bile is that it aids in the solution of the fats contained in
this fluid, and to a certain extent, probably, in the solution
of cholesterine.

Glycocholate of Soda (NaO,0MH4rN"On).— We have ne-
cessarily described the process for the extraction of the
glycocholate of soda, in connection with the taurocholate.
The glycocholate is crystallizable and is more easily obtained
in a condition of purity. The chief chemical points of dif-
ference between these salts are, that the glycocholate is pre-
cipitated by the acetate of lead as well as the subacetate, the
acetate having no effect upon the taurocholate of soda, and
that the glycocholic acid does not contain sulphur. By
treating glycocholic acid with potash at a high temperature,
it is decomposed into cholic acid and glycine, or glycocoll
(C4H5]^04). It is this which has given it the name of glyco-
cholic acid. In their physiological relations, the two biliary
salts are, as far as we know, identical.

Origin of the Biliary Salts. — There can be no doubt
that these principles are elements of secretion, and are pro-
duced de novo in the substance of the liver. In no instance
have they ever been discovered in the blood in health ; and,
although they present certain points of resemblance with
some of the constituents of the urine, they have never been
found in the excreta. In experiments made by Miiller,1

1 MUELLER, Manual de physiologic, Paris, 1851, tome L, p. 122.

CHQLESTEKESTE. 267

Kunde,1 Lehmann,3 and Moleschott,3 on frogs, in which the
liver was removed and the animal survived several days, and
in the observations of Moleschott, between two and three
weeks, it was found impossible to determine the accumula-
tion of the biliary salts in the blood. There is no reason,
therefore, for supposing that these principles are products of
disassimilation. Once discharged into the intestine, they
undergo certain changes, and can no longer be recognized by
the usual tests ; but experiments have shown that, changed
or unchanged, they are absorbed with the elements of food.4
They are probably the elements concerned in the digestive
function of the bile.

Cholesterine^ C26H22O.

Before the publication, in 1862, of a memoir on a new
excretory function of the liver, the function and relations of
cholesterine were not known, and this substance was hardly
mentioned in most works on physiology. As we believe
that it must now be recognized as one of the most impor-
tant of the products of disassimilation, it becomes interesting
and important to study its properties more closely.

The first description we have of cholesterine is by
Fourcroy, who states that it was discovered by Poulletier
de la Salle, in 1Y82.5 Fourcroy also described adipocire,
which he likened to cholesterine, although he did not con-

1 KUNDE, De Hepatis Extirpatione, Dissertatio Inauguralis, Berolini, 1850.

2 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. L, p. 476.

s MOLESCHOTT, Sur la secretion du sucre et de la bile dans le foie. — Comptes
rendus, Paris, 1855, tome xl., p. 1040.

Moleschott was more successful, in these experiments, than any of those who
had preceded him. He extirpated the liver from a great number of frogs, and
succeeded in keeping them alive for two or three weeks ; but he could never
detect in the blood the bile-pigment or the biliary salts.

4 See vol. ii., Digestion, p. 374, et seq.

5 FOURCROY, Memoire sur la nature des alterations qtfeprouvent quelques hu-
meurs animates, par Veffet des maladies etpar Vaction des remedes. — Memoires de
la Societe Royale de Medecine, 1782-1783, Paris, 1788, p. 489. The substance

268 EXCRETION.

sider the two substances identical.1 In 1814, Chevreul gave
a full description of cholesterine, and extracted it from the
bile of the human subject and some of the inferior ani-
mals.3 It was afterward found by different observers, in
gall-stones, intestinal concretions, cysts, and tumors. In
1830, Denis described a substance in the blood, which he
thought was cholesterine, and its discovery in this fluid is
attributed to him by most authors ; but in 1838, he acknowl-
edged the error of his first observation,8 and admits that
cholesterine, with a new substance analogous to it, called
seroline, was discovered in the blood, in 1833, by Boudet.4

Cholesterine is now recognized as a normal constituent
of various of the tissues and fluids of the body. Most
authors state that it is found in the bile, blood, liver, nervous
tissue, crystalline lens, meconium, and faecal matter. "We
have found it in all these situations, with the exception of
the faeces,6 where it does not exist normally, having been
transformed into stercorine in its passage down the intestinal
canal.8

In the fluids of the body, cholesterine exists in solution ;
but by virtue of what constituents it is held in this condition,

described by Fourcroy was undoubtedly cholesterine; but it remained for
Chevreul to describe its properties accurately and give it the name by which it
is now known. The observations of Chevreul will be referred to further on.

1 FOURCROY, Deuxieme memoir e sur les matieres animates trouvees dans la Ci-
metiere des Innocens d Paris. — Annales de chimie, Paris 1791, tome viii., p.
62, et seq.

2 CHEVREUL, Reclierches chimiques sur plusieurs corps gras, Cinquieme me-
moire. Des corps qu'on a appelle adipocire. — Annales de chimie, Paris, 1815, toine
xcvi., p. 7.

3 DENIS, Essai sur ^application de la chimie d V etude physiologique du sang de
rhomme, Paris, 1838, p. 147.

4 BOUDET, Nouvelles rechercJies sur la composition du serum du sang humain. —
Annales de chimie et de physique, Paris, 1833, tome lii., p. 337.

5 For a table of the quantities of cholesterine in various situations, see an
article by the author, on a New Excretory Function of the Liver. — American Jour-
nal of the Medical Sciences, Philadelphia, 1862, New Series, vol. xliv., p. 313.

6 See vol. ii., Digestion, p. 399, et seq.

CHOLE8TEBINE. 269

is not entirely settled. It is stated that the biliary salts have
the power of holding it in solution in the bile, and that the
small amount of fatty acids contained in the blood hold it in
solution in that fluid ; but direct experiments on this point
are wanting. In the nervous substance and in the crystalline
lens, it is united " molecule d molecule " to the other elements
which go to make up these tissues. After it is discharged
into the intestinal canal, when it is not changed into sterco-
rine, it is to be found in a crystalline form ; as in the meco-
nium, and in the faeces of animals in a state of hibernation.
In pathological fluids and in tumors, it is found in a crystal-
line form, and may be detected by microscopic examination.

Cholesterine is usually described as a non-nitrogenized
principle, having all the properties of the fats, except that
of saponification with the alkalies. Its chemical formula is
given as C26HMO. It is neutral, inodorous, crystallizable,
insoluble in water, soluble in ether, very soluble in hot alco-
hol, though sparingly soluble in cold. It is inflammable,
and burns with a bright flame. It is not attacked by the
alkalies, even after prolonged boiling. When treated with
strong sulphuric acid, it strikes a peculiar red color, which
is mentioned by some as characteristic of cholesterine. We
have found that it possesses this character in common with
the so-called seroline.1

Cholesterine may easily and certainly be recognized by
the form of its crystals, the characters of which can be made
out by means of the microscope. They are rectangular or
rhomboidal, exceedingly thin and transparent, of variable
size, with distinct and generally regular borders, and fre-
quently arranged in layers, with the borders of the lower
strata showing through those which are superimposed. This
arrangement of the crystals takes place when cholesterine
is present in considerable quantity. In pathological speci-

1 This similarity in the reactions of cholesterine and seroline with sulphu-
ric acid is mentioned by Berard (Cours de physiologie, Paris, 1851, tome iii.,
p. 117).

270 EXCRETION.

mens, the crystals are generally few in number and isolated.
The plates of cholesterine are frequently marked by a cleav-
age at one corner, the lines running parallel to the borders ;
and frequently they are broken, and the line of fracture is
generally undulating. Lehmann attaches a great deal of
importance to measurements of the angles of the rhomboid.
According to this author, the obtuse angles are 100° 30', and
the acute 79° 30V "We have examined a great number of
specimens of cholesterine, extracted from the blood, bile,
brain, liver, and occurring in tumors, and have not observed
that the crystals have definite angles. Frequently the
plates are rectangular, and sometimes almost lozenge-shaped.
It is by the transparency of the plates, the parallelism of
their borders, and their tendency to break in parallel lines,
that we recognize cholesterine. Lehmann seems to consider
the tablets of this substance as regular crystals having in-
variable angles. From examination during crystallization,
it seems more probable that they are not crystals, but frag-
ments of micaceous sheets, which, from their extreme tenuity,
are easily broken. In examining a specimen from the me-
conium, which was simply extracted with hot alcohol, it was
easy to observe a transparent film forming on the surface of
the alcohol soon after it cooled, and this, on microscopic
examination, in situ, disturbing the fluid as little as possible,
was found to be marked by long parallel lines. When the
fluid had partially evaporated, the crust became broken and
the fragments took the form of the ordinary crystals of cho-
lesterine, but they were larger and more regular. The tab-
lets were exceedingly thin, and regularly divided into deli-
cate plates, with the characteristic corner-cleavages of the
cholesterine ; and as the focus of the instrument was changed,
new layers were brought into view.

Crystals of cholesterine melt at 293° Fahr., but are formed
again when the temperature falls below that point. Accord-
ing to Lehmann, they may be distilled in vacuo at 680°,

1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. i., p. 244.

CHOLESTERES'E. 271

without decomposition. The determination of the fusing
point is one of the means of distinguishing it from seroline,1
which fuses at 90° 8'.

Without considering in detail the processes which have
been employed by other observers for the extraction of cho-
lesterine from the blood, bile, and various tissues of the body,
we will simply describe the method which has been found
most convenient in the various analyses we have made for
this substance. In analyses of gall-stones, the process is very
simple ; all that is necessary being to pulverize the mass,
extract it with boiling alcohol, and filter the solution while
hot, the cholesterine being deposited on cooling. If the crys-
tals be colored, they may be redissolved, and filtered through
animal charcoal. This is the process employed by Poulletier
de la Salle, Fourcroy, and Chevreul. It is only when this
substance is mixed with fatty matters, that its isolation is a
matter of any difficulty. In extracting cholesterine from
the blood, we have operated on both the serum and clot, and
in this way have been able to demonstrate it in greater quan-
tities in this fluid than have been observed by others, who
have employed only the serum. The following is the pro-
cess for quantitative analysis, which was determined upon
after a number of experiments :

The blood, bile, or brain, as the case may be, is first care-
fully weighed, then evaporated to dryness over a water-bath,
and pulverized in an agate mortar. The powder is then
treated with ether, in the proportion of about a fluidounce
for every hundred grains of the original weight, for from
twelve to twenty-four hours, agitating the mixture occasion-
ally. The ether is then separated by filtration, throwing a
little fresh ether on the filter so as to wash through every
trace of the fat, and the solution set aside to evaporate. If
the fluid, especially the blood, have been carefully dried and
pulverized, when the ether is added, it divides it into a very
fine powder and penetrates every part. After the ether has

1 LEHMANN, loc. cit.

272 EXCRETION.

evaporated, the residue is extracted with boiling alcohol, in
the proportion of about a fluidrachm for every hundred
grains of the original weight of the specimen, filtered while
hot into a watch-glass, and allowed to evaporate spontane-
ously. To keep the fluid hot while filtering, the whole appa-
ratus may be placed in the chamber of a large water-bath,
or, as the filtration is generally rapid, the funnel may be
warmed by plunging it into hot water, or steaming it, taking
care that it be carefully wiped. We now have the choleste-
rine mixed with a certain quantity of saponifiable fat. After
the fluid has evaporated, we can see the cholesterine crystal-
lized in the watch-glass, mingled with masses of fat. This
we remove by saponification with an alkali ; and for 'this
purpose, we add a moderately strong solution of caustic pot-
ash, which we allow to remain in contact with the residue
for from one to two hours. If much fat be present, it is best
to heat the mixture to a temperature a little below the boil-
ing point ; but in analyses of the blood this is not necessary.
The mixture is then to be largely diluted with distilled water,
thrown upon a small filter, and thoroughly washed till the
fluid which passes through is neutral. "We then dry the
filter, and fill it up with ether, which, in passing through,
dissolves out the cholesterine. The ether is then evaporated,
the residue extracted with boiling alcohol, as before, the
alcohol collected on a watch-glass previously weighed, and
allowed to evaporate. The residue consists of pure choleste-
rine, the quantity of which may be estimated by weight.

The accuracy of this process may be tested by means of
the microscope ; for the crystals have so distinctive a form,
that it is easy to determine, by examining the watch-glass,
whether the cholesterine be perfectly pure. In making this
analysis quantitatively, it is necessary to be very careful in
all the manipulations ; and for determining the weight of
such minute quantities, an accurate and delicate balance,
one, at least, that will turn with the thousandth of a gramme,
carefully adjusted, must be employed. With these precau-

BILIVEKDINE. 273

tions, the quantity of cholesterine in any fluid or solid may
be determined with perfect accuracy ; and the estimate may
be made in so small a quantity as from fifteen to twenty
grains of blood. In analyzing the brain and bile, we found
it necessary to pass the first ethereal solution through animal
charcoal, to get rid of the coloring matter. In doing this,
the charcoal must be washed with fresh ether till the solu-
tion which passes through is brought up to the original
quantity. The other manipulations are the same as in ex-
aminations of the blood. In examining the meconium, we
found that the cholesterine which crystallized from the first
alcoholic extract was so pure that it was not necessary to
subject it to the action of an alkali.

The proportion of cholesterine in the bile is not very
large. In the table, it is estimated at^from 1*60 to 2*66
parts per thousand. In a single examination of the hu-
man bile, we found the proportion 0'618 of a part per
thousand.

The origin and destination of this principle involve, as
we believe, an office of the liver which has not hitherto been
recognized by physiologists ; and we will consider these ques-
tions specially, under the head of the excretory function of
the liver.

Biliverdine.

The coloring matter of the bile bears a certain resem-
blance to the coloring matter of the blood, and is supposed
to be formed from it in the liver. It gives to the bile its
peculiar tint, and has, as we have remarked, the property of
coloring the tissues with which it comes in contact. When-
ever the flow of bile is seriously obstructed, the coloring
matter is absorbed by the blood, and can be readily detected
in the serum, in the urine, and in the color of the skin and
conjunctiva. In the bile it is liquid, but it may be coagu-
lated and extracted by various processes. It does not exist
naturally in the form of pigmentary granulations.
18

274 EXCRETION.

This principle is precipitated from the bile by boiling
with milk of lime. The filtered residue is then decomposed
with hydrochloric acid, which unites with the lime and
leaves a fatty residue of an intense green color. The fat is
then removed by repeated washings with ether (a very long
and difficult process). The precipitate is then redissolved
in alcohol with ether added, which gives to the liquid a
bluish-green color, and leaves, after evaporation, a dark-
green powder. This powder contains iron, but its pro-
portion has never been accurately estimated. The mat-
ter thus obtained is insoluble in water and in chloroform,
but is soluble in ether, alcohol, sulphuric and hydrochloric
acid.1

It is unnecessary to follow out in detail all of the chemi-
cal investigations which have been made into the ultimate
composition and the modifications of this and the other col-
oring matters. According to Robin,8 the empirical formula
for biliverdine, deduced from the analyses of Scherer, is
C24H16NO4 . No account is taken in these analyses of the
iron, the existence of which cannot be doubted.

Upon the addition of nitric acid, or better, of nitric mixed
with nitrous acid, biliverdine is acted upon in a peculiar way,
producing a play of colors, which is recognized as one of the
tests for bile.

Tests for Bile.

It is frequently desired, particularly in pathological in-
vestigations, to ascertain, by some easy test, the fact of the
presence or absence of bile in various of the fluids and solids
of the body. It is, indeed, a most interesting physiological
question to determine the course and destination of the
biliary salts after the bile has passed into the intestinal
canal ; and this can be done only by the application of ap-
propriate tests to the contents of the alimentary tract and

1 ROBIN ET VERDEIL, Traite de chimie anatomique, Paris, 1853, tomeiii., p. 389.
'.ROBIN, jtepong.sw les humeurs, Paris, 1867, p. 550.

TESTS FOB BILE. 275

the blood of the portal system. The ingredients of the bile
which it is important to detect are biliverdine, the biliary
salts, and cholesterine. The last-named substance can be
detected best by applying the method which we have just
described for its extraction ; but several tests have been pro-
posed for the detection, on the one hand, of the coloring
matter of the bile, and on the other, of the peculiar, biliary
salts.

Test for Biliverdine. — There is one test so simple and
easy of application, that it alone will suffice for the prompt
detection of biliverdine. This is peculiarly applicable to
the urine, where the presence or absence of bile frequently
becomes an important question.

We are led generally to suspect the presence of bile in
the fluids of the body by the peculiar color. If we spread
out the suspected fluid in a thin stratum upon a white sur-
face, as a porcelain plate, and add a single drop of nitric acid,
or, what is better, nitroso-nitric acid, if the coloring matter
of bile be present, a peculiar play of colors will be observed
at the circumference of the drop of acid as it diffuses itself.
The color will rapidly change from blue to red, orange,
purple, and finally yellow. This is due to the action of the
acid upon the biliverdine ; and this test will not indicate the
presence of either cholesterme or the biliary salts. It is
used, therefore, only when we wish to determine the presence
of the coloring matter of the bile.

Test for the Biliary Salts. — The best, and, indeed, the
only reliable test for the biliary salts, was proposed many
years ago by Pettenkofer,1 and is now generally known as
Pettenkofer's test. This requires some care and practice in
its application, but it is entirely reliable ; and although it
has been objected that there are other substances than the

1 PETTENKOFER, Notiz uber eine neue Reaction auf Galle und Zucker.—An-
nalen der Chemie und Pharmacie, Heidelberg, 1844, Bd. Hi., S. 90.

276 EXCRETION.

biliary salts which produce similar reactions, these are not
met with in the animal fluids, and consequently are not
liable to produce confusion. If a considerable quantity of
bile be present in any fluid, and if there be not a large ad-
mixture of animal matters, the test may be employed with-
out any preparation ; but in delicate examinations, it is
best to evaporate the suspected liquid, extract the residue
with absolute alcohol, precipitate with ether, and dissolve
the ether-precipitate in distilled water. By this means a
clear solution is obtained, which will react distinctly, even
when the biliary salts exist in very small quantity. Petten-
kofer's test is applicable to any of the biliary salts, whatever
6e their form, and the reaction is dependent upon the pres-
ence of cholic acid, which enters into the composition of all
the varieties of the biliary acids.

The following is one of the most common methods of
employing Pettenkofer's test : To the suspected solution we
add a few drops of a strong solution of cane-sugar in water.
Sulphuric acid is then slowly added, to the extent of about
two-thirds of the bulk of the liquid. It is recommended to
add the acid slowly, so that the temperature shall be but
little raised. If a large quantity of the biliary salts be
present, a red color shows itself almost immediately at the
bottom of the test-tube, and soon extends through the en-
tire liquid, rapidly deepening until it becomes of a dark lake
or purple. If the biliary matters exist in very small pro-
portion, it may be several minutes before any red color
makes its appearance, and the change to a purple is corre-
spondingly slow, the whole process occupying from fifteen to
twenty minutes. Many organic matters may be rendered
dark by the action of the acid, and the sugar itself will be
acted upon, even if no bile be present, but the color due to
the sugar alone is yellow. The peculiar play of colors above
described can easily be recognized after a little practice, and
is observed only in the presence of the biliary salts.

The ordinary modifications in the application of this test

EXCRETORY FUNCTION OF THE LIVER. 277

are unimportant. Some recommend to add the sulphuric
acid first, and then to add the solution of sugar ; and some,
after adding to the liquid two-thirds of its volume of sul-
phuric acid, drop into the mixture one or two lumps of cane-
sugar. The reaction with the biliary salts is essentially the
same, whichever of these methods be employed.

Excretory Function of the Liver.

In 1862, in studying the properties and physiological re-
lations of cholesterine, we gave the first definite account of
an excretory function of the liver. The experiments and
observations upon which we based our conclusions were
extended and laborious, and, as far as we know, have not
been repeated in detail by other observers ; but the results
must be taken as positive, if the accuracy of the experiments
be admitted, and they have been adopted, to a greater or less
extent, by scientific authorities. The details of these ex-
periments are too elaborate to be given in full, as contained
in the original memoir.1

The few statements with regard to the function of choles-
terine to be found in works published before 1862 are very
indefinite. In most works on physiology, this substance is
hardly mentioned, it being generally regarded as a curious
principle, interesting only to the physiological chemist. We
have given, in the memoir referred to, extracts from the
works of Carpenter, Lehmann, Mialhe, and Dalton, which
contain all that is said of the probable function of choles-
terine ; and these quotations, which embody about all that
we could find on the subject, show that its office was not in
the least understood. Inasmuch as cholesterine is the only
excrernentitious principle as yet discovered in the bile, bear-
ing the same relation to this fluid that urea does to the urine,

1 FLINT, Jr., Experimental Researclies into a New Excretory Function of the
Liver. — American Journal of the Medical Sciences, Philadelphia, 1862, New Se-
ries, vol. xliv., p. 305, et seq. ; and RechercJies experimentales sur une nouveUe
fonction du foie, Paris, 1868.

278 EXCRETION.

it is evident that the ideas of physiologists, with regard to
any excretory function of the liver, must have been very
indefinite before the relations of cholesterine had been de-
termined.

The first question which arises is whether the liver has
any excretory function. Some authors, notably Blondlot,
have assumed that the bile is purely excrement! tious and
has no function as a secretion. This question we have fully
discussed in another place.1 The confusion that has arisen
with regard to this point has been due to the fact that those
who adopted the view that the bile was simply an excretion
denied to it any digestive properties ; while, on the other
hand, those who believed it to be concerned in digestion
would not admit that it was an excretion. "We have shown
conclusively, in treating of intestinal digestion, that the bile
is so important in this process, as to be essential to life ; but
we have shown, at the same time, that the liver eliminates
from the blood one of the most important of the products of
disassimilation. It will be found important, as bearing upon
the probable function of the bile, to apply to this fluid the
general considerations contained in the first chapter, on the
distinctions between secretions and excretions.

Cells of glandular epithelium are constantly manufac-
turing, out of materials furnished by the blood, the elements
of the true secretions ; but these elements do not preexist
in the blood, they appear de novo in the secreting organ,
and never accumulate in the system when the function of the
secreting organ is disturbed. Again, the true secretions are
not discharged from the body, but have a function to perform
in the economy, and are poured out by the glands intermit-
tently, at the times when this function is called into action.
As far as the biliary salts (the taurocholate and glycocholate
of soda) are concerned, the bile corresponds entirely to the
true secretions. These principles are manufactured by the
liver, they do not preexist in the blood, and they do not ac-

1 See vol. ii., Digestion, p. 362, et seq.

EXCRETORY FUNCTION OF THE LIVER. 279

cumulate in the blood when their formation in the liver is
disturbed. The researches of Bidder and Schmidt and others
have shown that although we cannot detect the biliary salts
in the blood or chyle coming from the intestine, these princi-
ples are not discharged in the faeces.1 All of these facts point
to an important function of the bile as a secretion. It is true
that it is discharged constantly, but during digestion its flow
is very much more abundant than at any other time. It is
pretty well established that during the intervals of the flow
of the secretions, the glands are manufacturing the materials
of secretion, which are washed out, as it were, in the great
afflux of blood which takes place during what has been
called the functional activity of the gland. Now if the liver,
in addition to its function as a secreting organ, be constantly
forming bile for the purpose of eliminating an excremen-
titious matter, it is to be expected that the bile would always
contain a certain proportion of its elements of secretion.

The constant and invariable presence of cholesterine in
the bile assimilates it in every regard to the excretions, of
which the urine may be taken as the type. Cholesterine
always exists in the blood and in certain of the tissues of
the body. It is not produced in the substance of the liver,
but is merely separated from the blood by this organ. It
is constantly passed into the intestine, and is discharged,
although in a modified form, in the faeces. We know of no
function which it has to perform in the economy, any more
than urea, or any other of the excrementitious principles
of the urine ; and we have shown, in the memoir already
referred to, that it accumulates in the blood in certain cases
of organic disease of the liver and gives rise to certain symp-
toms of blood-poisoning.

Origin of Cholesterine. — Cholesterine exists in largest
quantity in the substance of the brain and nerves. It is
also found in the substance of the liver — probably in the

1 See vol. ii., Digestion, p. 374.

280 EXCRETION.

bile contained in this organ — the crystalline lens, and the
spleen ; l but with these exceptions, it is found only in the
nervous system and blood. Two views present themselves
with regard to its origin. It is either deposited in the- ner-
vous matter from the blood, or is formed in the brain and
taken up by the blood. This is a question, however, which
can be settled experimentally, by analyzing the blood for
cholesterine as it goes to to the brain by the carotid, and as
it comes from the brain by the internal jugular. The cho-
lesterine being found also in the nerves, and, of course, a
large quantity of nervous matter existing in the extremities,
it is desirable at, the same time to make an analysis of the
venous blood from the general system.

With a view of determining this question, we made the
following experiments :

Experiment I. — In this experiment, specimens of blood
were taken from the carotid, the internal jugular, the vena
cava, hepatic veins, hepatic artery, and portal vein, in a liv-
ing animal (a dog about six months old). In addition, we
took a specimen of bile from the gall-bladder, and some of
the substance of the brain. These were all carefully ex-
amined for cholesterine, and the following were the main
results : In the brain cholesterine was found in large quan-
tity. There was no cholesterine in the extract of the blood
from the carotid, examined three days after, and but a few
crystals, eleven days after. Cholesterine was almost imme-
diately discovered in the extract of the blood from the in-
ternal jugular, and the crystals were present in large num-
bers on the twelfth day. In this experiment the animal was
etherized when the blood was taken, and the examinations

1 In 1854, Marcet described a substance extracted from the spleen, which
he thought was analogous to cholesterine (An account of the Organic Chemical
Constituents, or Immediate Principles of the Excrements of Man and Animals
in the Healthy State. — Philosophical Transactions, London, 1854, p. 269); and in
1857, he fully recognized its existence in this organ (On the Immediate Prin-
ciples of the Excrements of Man and Animals in the Healthy State. — Philosophical
Transactions, London, 1857, p. 412).

EXCRETORY FUNCTION OF THE LIVER. 281

for cholesterine were not quantitative. In the succeeding
experiments, the proportion of cholesterine in the different
specimens of blood was accurately estimated, and, in most
of them, no anaesthetic was used during the operative pro-
cedure.

Experiment II. — A medium-sized adult dog was put un-
der the influence of ether, and the carotid artery, internal
jugular, and femoral vein exposed. Specimens of blood
were drawn, first from the internal jugular, next from the
carotid, and last from the femoral vein. These specimens
were received into carefully -weighed vessels, and weighed.

They were then analyzed for cholesterine by the process
already described, and the following results obtained :

Quantity of Blood. Cholesterine. Cholesterine per
grains. grains. 1,000 pte.

Carotid 179-462 0'139 0'774

Internal jugular 134'780 O'lOS O'SOl

Femoral vein 133-886 0-108 0'806

Percentage of increase in the blood from the jugular over the arterial

blood 3-488

Percentage of increase in the blood from the femoral vein 4'134

This experiment shows an increase in the quantity of
cholesterine in the blood in its passage through the brain,
and an increase, even a little greater, in the blood passing
through the vessels of the posterior extremity. To facilitate
the operation, however, the animal was brought completely
under the influence of ether, which, from its action on the
brain, would not improbably produce some temporary dis-
turbance in the nutrition of that organ, and consequently
interfere with the experiment. For the purpose of avoiding
this difficulty, we performed the following experiments with-
out administering an anaesthetic :

Experiment III. — A small young dog was secured to the
operating-table, and the internal jugular and carotid ex-
posed on the right side. Blood was taken, first from the
jugular, and afterward from the carotid. The femoral vein

282 EXCBETION.

on the same side was then exposed, and a specimen of blood
was taken from that vessel. The animal was very quiet
under the operation, though no anaesthetic was used, so that
the blood was drawn without any difficulty and without the
slightest admixture.

The three specimens were analyzed for cholesterine, with
the following results :

Quantity of Blood. Cholesterine. Cholesterine per
grains. grains. 1,000 pts.

Carotid 143-625 0-679 0-967

Internal jugular 29'956 0'046 1-545

Femoral vein 45'035 0'046 1-028

Percentage of increase in the blood from the jugular over the arterial

blood 59-772

Percentage of increase in the blood from the femoral vein 6*308

Experiment IY. — A large and powerful dog was secured
to the operating-table, and the carotid and internal jugular
exposed. Specimens of blood were taken from these vessels,
first from the jugular, and were carefully weighed and ana-
lyzed for cholesterine in the usual way. The following re-
sults were obtained :

Blood. Cholesterine. Cholesterine per

grains. grains. 1,000 pts.

Carotid 140*847 0-108 0*768

Internal jugular 97*811 0'092 0'947

Percentage of increase in the blood passing through the brain 23*307

Experiment III. shows a very considerable increase in the
quantity of cholesterine in the blood passing through the
brain, while the increase is comparatively slight in the blood
of the femoral vein. The proportion of cholesterine is also
large in the arterial blood, compared with other observations.

Experiment IY. shows but a slight difference in the
quantity of cholesterine in the arterial blood in the two ani-
mals ; the proportion in the animal that was etherized being
0*774: per 1,000, and in the animal that was not etherized
0-768 per 1,000, the difference being but 0'006 ; but, as was
suspected, the ether seemed to have an influence on the quan-

EXCRETORY FUNCTION OF THE LIVER.

tity of cholesterine absorbed by the blood in its passage
through the brain. In the first instance the increase was
but 3-4:88 per cent., while in the latter it was 23'307 per cent.

The natural conclusions to be drawn from these observa-
tions, with regard to the origin of cholesterine in the econ-
omy, are the following: It has been ascertained that the
brain and nerves contain a large quantity of this substance,
which is found in hardly any other of the tissues of the body ;
and these experiments, especially Experiments III. and IV.,
show that the blood that comes from the brain contains a
much larger quantity of cholesterine than the blood supplied
to this organ.

The conclusion is, then, that cholesterine is produced in
the brain, and is taken up by the blood as it passes through
this organ.

But the brain is not the only part where cholesterine is
produced. It will be seen by Experiment II. that there is
4'134 per cent., and in Experiment III. 6'30S per cent, of
increase in the cholesterine in the passage of the blood
through the inferior extremities, and probably about the
same in other parts of the muscular system. In examining
these tissues chemically, we find that the muscles contain no
cholesterine, but that it is abundant in the nerves ; and as
we have found that the proportion of cholesterine is im-
mensely increased in the passage of the blood through the
great centre of the nervous system, taken, as the specimens
were, from the internal jugular, which collects the blood
mainly from the brain and very little from the muscular sys-
tem, it is rendered very probable that, in the general venous
system, the cholesterine which the blood contains is produced
in the substance of the nerves.

If this be true, and if cholesterine be one of the prod-
ucts of the disassimilation of nervous tissue, its formation
would be proportionate in activity to the nutrition of the
nerves ; and any thing which interfered to any great extent
with their nutrition would diminish the quantity of choleste-

284 EXCRETION.

rine produced. In the production of urea by the general
system, which is an analogous process, muscular activity in-
creases the quantity, and inaction diminishes it, on account
of the effect upon nutrition. In cases of paralysis, we have
a diminution of the nutritive forces in the parts affected,
especially of the nervous system, which, after a time, be-
comes so disorganized that although the cause of the paraly-
sis be removed, the nerves cannot resume their functions. It
is true we have this disorganization taking place to a certain
extent in the muscles, but it is by no means as marked as
it is in the nerves. We should be able, then, to confirm the
observations on animals, by examining the blood in cases of
paralysis, when we should expect to find a very marked dif-
ference in the quantity of cholesterine, between the venous
blood coming from the paralyzed parts, and the blood from
other parts of the body. "With this point in view we made
analyses of the blood from both arms, in three cases of
hemiplegia.

Case I. — Sarah Rumsby, set. 47, was affected with hemi-
plegia of the left side. Two years ago she was taken with
apoplexy, and was insensible for three days. When she re-
covered consciousness, she found herself paralyzed on the left
side. She said she had epilepsy four or five years before the
attack of apoplexy. Now she has entire paralysis of motion
on the affected side, with the exception of some slight power
over the fingers, but sensation is perfect. The speech is not
affected. The general health is good.

Case II. — Anna Wilson, set. 23, Irish, was affected with
hemiplegia of the right side. Four months ago she was taken
with apoplexy, from which she recovered in one day, with loss
of motion and sensation on the right side. She is now im-
proving and can use the right arm slightly. The leg is not
so much improved, because she will make no effort to use it.

Case III. — Honora Sullivan, Irish, set. 40, was affected
with hemiplegia of the right side. About six months ago
she was taken with apoplexy, and recovered consciousness

EXCRETORY FUNCTION OF THE LIVER.

285

the next day, with paralysis. The leg was less affected than
the arm, from the first. The cause was supposed by Dr.
Flint, the attending physician, to be due to an embolus.
Her condition is now about the same, as regards the arm, but
the leg has somewhat improved.

These cases all occurred at the Black well's Island Hos-
pital. The treatment in all consisted of good diet, frictions,
passive motion, and use of the paralyzed members as much
as possible.

A small quantity of blood was drawn from both arms in
these three cases. It was drawn from the paralyzed side, in
each instance, with great difficulty, and but a small quantity
could be obtained.

The specimens were all examined for cholesterine, with
the following results :

Table of Quantity of Cholesterine in Blood of Paralyzed
and Sound Sides, in three cases of Hemiplegia.

Blood.

Choles-
terine.

Cholesterine per 1,003.

grains.

Case I. Paralyzed side.

55-458

The watch-glass contained 0'031
of a grain of a granular sub-
stance, but the most careful
examination failed to show a

Do. Sound side.

128-407

0-062

single crystal of cholesterine.
0-481.

Case II. Paralyzed side.
Do. Sound side.

18-381
66-396

0-062

Same as Case I.
0-808.

Case III. Paralyzed side.
Do. Sound side.

21-842
52-261

0-031

Same as Case I.
0-579.

The result of these examinations is very interesting : not
a single crystal of cholesterine was found in any of the three
specimens of blood from the paralyzed side, while about the
normal quantity was found in the blood from the sound side.
As the nutrition of other tissues is interfered with in paraly-

286 EXCRETION.

sis, it is impossible to say positively, from these observations
alone, that the cjiolesterine is produced in the nervous sys-
tem only. But the nutrition of the nerves is undoubtedly
most affected ; and these observations, taken in connection
with the preceding experiments on animals, point very
strongly to such a conclusion.

Our experiments upon animals were so marked and in-
variable in their results, even when performed under differ-
ent conditions, that they can leave hardly any doubt of the
fact that the blood, in passing through the brain, takes up
cholesterine. It is more difficult to show, by actual demon-
stration, that the general system of nerves also gives up
cholesterine to the blood ; but the fact that the venous blood
coming from the extremities contains more cholesterine than
the arterial blood, taken in connection with the fact that
none of the tissues of the extremities contain cholesterine,
except the nerves, renders it more than probable that the
nerves, as well as the brain, are the seat of the formation of
this principle.

The observations upon the cases of paralysis are interest-
ing, taken in connection with the experiments on animals.
Such observations should, of course, be much more elaborate
and extended to lead, of themselves, to positive results ; but
they go far to confirm our views with regard to the probable
origin of cholesterine in the nervous system.

Elimination of Cholesterine by the Liver. — We at-
tempted to demonstrate experimentally the separation of
cholesterine from the blood by the liver, in the same way
that we demonstrated its passage into the blood circulating
through the brain. In the first series of experiments on
this subject, we endeavored to show, on the same animal,
the origin of cholesterine in certain parts, and the mechanism
of its elimination. In these experiments, which were only
approximative, as we had not then succeeded in extract-
ing the cholesterine perfectly pure, we commenced with the

EXCRETORY FUNCTION OF THE LIVER. 287

arterial blood, examining it as it went into the brain by the
carotid, analyzing the substance of the brain, then analyzing
the blood as it came out of the brain by the internal jugular,
examining the blood as it went into the liver by the hepatic
artery and portal vein, examining the secretion of the liver,
then the blood as it came out of the liver by the hepatic
vein, examining also the blood of the vena cava in the abdo-
men. The analyses of the blood from the carotid, internal
jugular, and vena cava have already been referred to in
treating of the origin of the cholesterine. It will be remem-
bered that there was a large quantity of this substance in
the internal jugular, and but a small quantity in the carotid,
showing that it was formed in the brain. "We now give the
conclusion of these observations, which bears upon the sepa-
ration of the cholesterine from the blood :

Experiment I. — Specimens of blood were taken from the
hepatic artery, portal vein, and hepatic vein, and a small
quantity of bile from the gall-bladder. These specimens
were treated in the manner already indicated ; i. e., evapo-
rated and pulverized, extracted with ether, the ether evapo-
rated, and the residue extracted with boiling alcohol, this
evaporated, a solution of caustic potash added, and the
specimen then subjected to a microscopical examination.

Microscopical examination of the extract from the portal
vein showed quite a number of crystals of cholesterine.
These were observed after the fluid had nearly evaporated.

Microscopical examination of the extract from the he-
patic artery, made after the fluid had nearly evaporated,
showed a considerable amount of cholesterine ; more than
was observed in the preceding specimen. There were also
observed a few crystals of stercorine.

The first examination of the extract from the hepatic
vein, which was made just before the potash was added,
showed a number of fatty masses, with some crystals of ster-
corine. The solution of potash was then added, and two
days after, another careful examination was made, discov-

288 EXCRETION.

ering nothing but fatty globules and granules. The watch-
glass was then set aside and was examined eleven days
after, when the fluid had entirely evaporated. At this
examination, a few crystals of cholesterine were* observed
for the first time. There were also a number of crystals of
margaric and stearic acid.

All the examinations of the extract from the bile showed
cholesterine ; and the precipitate consisted, indeed, of this
substance in a nearly pure state.

Taking these experiments in connection with the first
observations on the carotid and internal jugular, while the
one series demonstrates pretty conclusively that cholesterine
is formed in the brain, the other shows that it disappears, in
a measure, from the blood in its passage through the liver,
and is passed into the bile. In other words, it is formed in
the nervous tissue, and is prevented from accumulating in the
blood by its excretion by the liver. This suggests an inter-
esting series of inquiries ; and this fact, fully substantiated,
would be as important to the pathologist as to the physiolo-
gist. But in order to settle this question, it is necessary to
do something more than make an approximative estimate
of the quantity of cholesterine removed from the blood by
the liver. The quantity thus removed in the passage of
the blood through this organ should be estimated, if pos-
sible, as closely as the quantity which the blood gains in its
passage through the brain. But this estimate is more diffi-
cult. The operation for obtaining the specimens of blood,
in the first place, is much more serious than that for collect-
ing blood from the carotid and internal jugular. It is very
difficult to take the unmixed blood from the hepatic vein ;
and the exposure of the liver, if prolonged, may interfere
with its eliminative function, in the same way that exposure
of the kidneys arrests, in a few moments, the flow from the
ureters. It is probable, however, that the administration
of ether does not interfere with the elimination of choles-
terine by the liver, as it does, apparently, with its formation

EXCRETORY FUNCTION OF THE LIVER. 289

in the brain. Anaesthetics, we know, have a peculiar and
special action on the brain, but do not interfere with the
functions of vegetative life, such as secretion or excretion ;
and, we may suppose, would not interfere with the depurative
function of the liver. It is fortunate that this is the case,
for the operation of taking blood from the abdominal ves-
sels is immensely increased in difficulty by the struggles of
an animal that is not under the influence of an anaesthetic.

With the view of settling the question of the disappear-
ance of a portion of the cholesterine of the blood in its
passage through the liver, by an accurate quantitative analy-
sis, we repeated the operation for drawing blood from the
vessels which go into, and emerge from the liver. In the
first trial the blood was drawn so unsatisfactorily, and the
operation was so prolonged, that it was not thought worth
while to complete the analysis, and the experiment was
abandoned. In the following one we were more successful.

Experiment II. — A good-sized bitch" (pregnant) was
brought completely under the influence of ether, the abdo-
men laid freely open, and blood drawn, first from the hepatic
vein, and next from the portal vein. The taking of the
blood was entirely satisfactory, the operation being done
rapidly, and the blood collected without any admixture. A
specimen of blood was then taken from the carotid, to repre-
sent the blood from the hepatic artery.

The three specimens of blood were then examined in the
usual way for cholesterine, with the following results :

Blood. Cholesterine. Cholesterine per

grains. grains. 1,000 pts.

Arterial blood 159-537 0'200 1-257

Portal vein 168-257 0*170 1-009

Hepatic vein 79*848 0*077 0'964

Percentage of loss in arterial blood in its passage through the liver... . 23'309
Do. do. the blood of the portal vein 4*460

This experiment proves positively, what there was good
ground for supposing from Experiment I., that cholesterine
19

290 EXCRETION.

is separated from the blood by the liver ; and here we may
note, in passing, a striking coincidence between the analysis
in a previous experiment, in which the blood was studied in
its passage through the brain, and the one just mentioned,
where the blood was studied in its passage through the liver.
The gain of the arterial blood in cholesterine in passing
through the brain was 23*307 per cent., and the loss of this
substance in passing through the liver is 23*309 per cent.
There must be, of course, the same quantity separated by
the liver that is produced by the nervous system, it being
formed, indeed, only to be separated by this organ, its for-
mation being continuous, and its removal necessarily the
same, in order to prevent its accumulation in the circulating
fluid. The almost exact coincidence between these two
quantities, in specimens taken from different animals, though
not at all necessary to prove the fact just mentioned, is still
very striking.

It is shown by Experiment II. that the portal blood, as it
goes into the liver, contains but a small percentage of cho-
lesterine over the blood of the hepatic vein, while the per-
centage in the arterial blood is large. The arterial blood is
the mixed blood of the entire system ; and as it probably
passes through no organ before it gets to the liver, that di-
minishes its cholesterine, it contains a quantity of this sub-
stance, which must be removed. The portal blood, coming
from a limited part of the system, contains less cholesterine,
though it gives up a certain quantity. In the circulation of
the liver, the portal system largely predominates, and is
necessary to other important functions of this organ, such
as the production of sugar ; but soon after the portal vein
enters the liver, its blood becomes mixed with that from
the hepatic artery, and from this mixture the cholesterine is
separated. It is only necessary that blood, containing a
certain quantity of cholesterine, should come in contact with
the bile-secreting cells, in order that this substance be sepa-
rated. The fact that it is eliminated by the liver is proven

EXCRETORY FUXCTIOX OF THE LIVEB. 291

with much less difficulty than that it is formed in the nervous
system. In fact, its presence in the bile, and the necessity
of its constant removal from the blood, consequent on its
constant formation and absorption by this fluid, are almost
sufficient in themselves to warrant the conclusion that it is
removed by the liver. This, however, is put beyond a doubt
by the preceding analyses of the blood going to and. coming
from this organ.

In treating of the composition of the feeces, we have con-
sidered so fully the changes which the cholesterine of the bile
undergoes in its passage down the intestinal canal, that it
is not necessary to refer to this portion of the subject again.1
We have made but one examination of the quantity of ster-
corine contained in the daily fecal evacuation, and assuming
that the amount of cholesterine excreted by the liver in
twenty-four hours is equal to the amount of stercorine found
in the evacuations, the quantity is about ten and a half
grains. This corresponds with the estimates of the daily
quantity of cholesterine excreted, calculated from its propor-
tion in the bile and the estimated daily amount of bile pro-
duced by the liver.

To complete the chain of the evidence leading to the
conclusion that cholesterine is an excrementrtious principle,
formed in certain of the tissues and eliminated by the liver,
it is only necessary to show that it is liable to accumulate in
the blood when the eliminating function of the liver is in-
terrupted. It will be remembered that it was only after ex-
tirpation of the kidneys, followed by accumulation of urea
in the blood, that Prevost and Dumas were able to demon-
strate the preexistence of this principle in the circulating
fluid, and indicate the mechanism of its separation from the
blood by the kidneys. This mode of study has been applied
to certain of the elements of the bile, though without suc-
cess; for Muller, Kunde, Lehmann, and Moleschott, who
have extirpated the livers from frogs, looked in the blood

1 See vol. ii., Digestion, p. 399, et seq.

292 EXCRETION.

only for the biliary salts.1 "We have not been able to re-
peat these experiments on frogs, and analyze the blood for
cholesterine, but we have arrived at very positive results
in the study of the blood in diseased conditions of the
liver, that are interesting alike to the physiologist and the
pathologist.

It has long been recognized that cases of ordinary ictei as
are not of a grave character, while there are cases in which
the jaundice, though less marked as regards color, is a very
different condition. Chemists have analyzed the blood, in
the hope of explaining this difference by the presence, in the
grave cases, of the taurocholate and glycocholate of soda;
but their failure to detect these principles leaves the ques-
tion still uncertain. The real distinction, arguing from
purely theoretical considerations, would lie in the propo-
sition that, in cases of simple jaundice, there is merely a
resorption from the biliary passages of the coloring matter
of the bile, and in grave cases — which are almost invaria-
bly fatal — there is retention of cholesterine in the blood.

We have not been able, on account of the insolubility of
cholesterine, to observe the effects of injecting it into the
blood-vessels, but we have had an opportunity of making an
examination of the blood of a patient in the last stages of
cirrhosis of the liver, accompanied with jaundice, and com-
pared it with an examination of the blood of a patient suffer-
ing from simple icterus. Both of these patients had decolo-
ration of the faeces ; but in the first the icterus was a grave
symptom, accompanying the last stages of disorganization
of the liver ; while in the latter it was simply dependent on
duodenitis, and the prognosis was favorable and verified by
the result. As icterus accompanying jaundice is of very in-
frequent occurrence, we were fortunate in having an oppor-
tunity of comparing the two cases.

Without giving in full the details of these cases and the
examinations, which are contained in our original memoir

1 See p. 267.

EXCRETORY FUNCTION OF THE LIVER. 293

on cholesterine,1 it is sufficient here to state the main results
of the examinations of the blood and faeces.

In the case of simple jaundice from duodenitis, in which
there was no great disturbance of the system, a specimen of
blood, taken from the arm, presented undoubted evidences
of the coloring matter of the bile, but the proportion of
cholesterine was not increased, being only 0*508 of a part
per thousand. The faeces contained a large proportion of
saponifiable fat, but no cholesterine or stercorine.

In the case of cirrhosis with jaundice, there were ascites
and great general prostration. This patient died a few days
after the blood and faeces had been examined, and the liver
was found in a condition of cirrhosis, with the liver-cells
shrunken, and the gall-bladder contracted. In this case the
blood contained 1*850 pts. of cholesterine per thousand, more
than double the largest quantity we had ever found in health.
The faeces contained a small quantity of stercorine.

Inasmuch as cases frequently present themselves in which
there are evidences of cirrhosis of the liver, with little, if
any, constitutional disturbance, while others are attended
with grave nervous symptoms, it seemed an interesting ques-
tion to determine whether it be possible for cholesterine to
accumulate in the blood without the ordinary evidence of
jaundice. WQ had an opportunity of examining the blood
in two strongly-contrasted cases of cirrhosis, in neither of
which was there jaundice.

One of these patients had been tapped repeatedly (about
thirty times), but the ascites was the only troublesome symp-
tom, and his general health was pretty good. In this case
the proportion of cholesterine in the blood was only 0*246 of
a part per thousand, considerably below the quantity that we
had found in health.

The other patient had cirrhosis, but was confined to the
bed and was very feeble. The proportion of cholesterine in

1 American Journal of the Medical Sciences, Philadelphia, 1862, New Series,
vol. xliv., p. 349, et seq.

294 EXCRETION.

the blood in this case was 0*922 of a part per thousand, a lit-
tle above the largest proportion we had found in health.

Like the examinations of the blood in the three cases of
paralysis, these pathological observations are not sufficient,
in themselves, to establish the function of cholesterine ; but
taken in connection with our other experiments, they fully
confirm our views with regard to the excretory function of
the liver. It is pretty certain that organic disease of the
liver, accompanied with grave symptoms generally affecting
the nervous system, does not differ in its pathology from
cases of simple jaundice in the fact of retention of the bili-
ary salts in the blood ; but these grave symptoms, it is more
than probable, are due to a deficiency in the elimination of
cholesterine — the true excrementitious principle of the bile
— and its consequent accumulation in the system. Like the
accumulation of urea in structural disease of the kidney,
this produces blood-poisoning ; and we have characterized
this condition by the name of Cholestercemia, a name ex-
pressing a pathological condition, but at the same time indi-
cating the physiological relations of cholesterine.

CHAPTEE X.

PRODUCTION OF SUGAR IN THE LIVER.

Evidences of a glycogenic function in the liver — Processes for the determination
of sugar — Fehling's test for sugar — Examination of the blood of the portal
system for sugar — Inosite — Examination of the blood of the hepatic veins
for sugar — Does the liver contain sugar during life ? — Characteristics of
liver-sugar — Mechanism of the production of sugar in the liver — Glyco-
genic matter — Process for the extraction of glycogenic matter — Variations
in the glycogenic function — Production of sugar in foetal life — Influence of
digestion and of different kinds of food on glycogenesis — Influence of the
nervous system, etc., on glycogenesis — Artificial diabetes — Influence of the
inhalation of anaesthetics and irritating vapors on glycogenesis — Destina-
tion of sugar — Alleged production of fat by the liver — Changes in the
albuminoid and the corpuscular elements of the blood in their passage
through the liver.

IT was formerly supposed that the chief and the only
important office of the liver was to produce bile, and all
physiological researches into the functions of this organ were
then directed to the question of the uses of the biliary secre-
tion ; but in 1848, it was announced by Bernard that he
had discovered in the liver a new and important function,
and he proceeded to show, by an ingeniously conceived
series of experiments, that the liver is constantly producing
sugar of the variety that had long been recognized in the
urine of persons suffering from diabetes mellitus. The great
physiological and pathological importance of the discovery,
attested, as it was, by experiments which seemed to be posi-
tively conclusive in their results, excited the most profound
scientific interest. During the present century, indeed, there

296 SECRETION.

have been few physiological questions that have attracted so
much attention ; and the observations of Bernard were soon
repeated, modified, and extended by experimentalists in dif-
ferent parts of the world. In 1857, Bernard discovered a
sugar-forming material in the liver, analogous in its compo-
sition and properties to starch ; and this seemed to complete
the history of glycogenesis.

Shortly after the publication of the glycogenic theory, it
was found that other changes were effected in the blood in
its passage through the liver, and physiologists then under-
stood, for the first time, how glandular organs might pro-
duce secretions, and yet not discharge them into excretory
ducts ; and this, indeed, pointed the way to the explanation
of the function of the ductless glands. It is perfectly correct
to say that the liver secretes sugar ; but the secretion, in
this instance, is carried away by the blood ; and from this
point of view, the liver is a ductless gland. It is evident,
therefore, that even after having studied fully the secre-
tion and the physiological relations of the bile, we have to
consider other glandular functions of the liver, hardly less
important.

Evidences of a Glycogenie Function in the Liver. — The
proof of the glycogenic function of the liver rests upon the
fact, experimentally demonstrated by Bernard, that in all
animals, the blood coming from the liver by the hepatic
veins contains sugar ; and that the presence of this principle
here is not dependent upon the starch or sugar of the food.
Bernard assumes to have proven that, in carnivorous ani-
mals, never having taken starch or sugar into the aliment-
ary canal, except in the milk, there is no sugar in the blood
of the portal vein as it passes into the liver ; but, under nor-
mal conditions, the blood of the hepatic veins always contains
sugar. Having examined the blood from various parts of the
body, and made extracts of all the other tissues and organs,
Bernard was unable to find sugar in any other situations

PRODUCTION OF SUGAR IN THE LIVER. 297

than the liver and the blood coming from the liver. As the
blood from the liver is mixed in the vena cava with the blood
from the lower extremities, and in the right side of the heart,
with the blood from the descending cava, the amount of sugar
is proportionately diminished in passing from the liver to the
heart. It was found that the sugar generally disappeared in
the lungs, and did not exist in the blood of the arterial sys-
tem. Assuming that these statements have been sustained
by experimental facts, there can be no doubt that the liver
produces or secretes sugar ; that this secretion is taken up
by the blood ; and that the sugar is destroyed in its passage
through the lungs.

The question of the production of sugar in the economy
has given rise to a great deal of discussion, and the experi-
ments of Bernard have been repeated very extensively.
Many physiologists of high authority have been able to
verify these observations in every particular; but others
have published accounts of experiments which seem to dis-
prove the whole theory.

There can be no doubt of the fact that sugar may, under
certain conditions, be produced de novo in the organism.
Cases of diabetes, in which the discharge of sugar by the
urine continues, to a certain extent, when no starch or sugar
is taken as food, are conclusive evidence of this- proposition.
It is a fact equally well established, that the sugar taken as
food and resulting from the digestion of starch is consumed
in the organism, and is never discharged. The fact with re-
gard to diabetes shows, then, that it is not impossible, when
no sugar or starch is taken as food, that sugar should be pro-
duced in the body ; and the failure to find the sugar of the
food in the blood or excreta shows that this principle is nor-
mally destroyed or consumed in the organism. It only re-
mains, therefore, to determine whether the production of
sugar in diabetes be a new pathological process, or merely
the exaggeration of a physiological function.

We have so often repeated and verified the observations

298 SECRETION.

of Bernard, both in experiments made for purposes of inves-
tigation and in public demonstrations, that we can entertain
no doubt with regard to the glycogenic function of the liver.
We have, however, made some late observations, which have
modified our views concerning the mechanism of glycogene-
sis ; but the fact of the production of sugar in the healthy
organism is not affected. Notwithstanding that it seems
so easy to verify these experiments, there is, particularly in
Great Britain, a pretty wide-spread conviction, that the liver
does not produce sugar during life, and that the sugar found
by Bernard and others is due to post-mortem action. This
view is based chiefly on the observations of Dr. Pavy, of
Guy's Hospital ; but it has been adopted by some authori-
ties in Germany and in France. In this state of the ques-
tion, it will not be sufficient to detail merely the experi-
ments that seem to demonstrate the glycogenic function,
but it will be necessary to examine these observations
critically, and compare them with experiments which lead,
apparently, to opposite conclusions ; for it is but fair to
admit that the observations of Pavy seem to be as accu-
rate, and, at the first blush, as conclusive as those of
Bernard.

The experiments of Bernard were published for the first
time in 1848,1 but were afterward much extended, and pub-
lished as a thesis, in 1853." The most accessible account
of the original experiments is in the first volume of his
published lectures, delivered at the College of France, in
1854-'55.8 In addition, many of the volumes of lectures
published from time to time by Bernard contain new obser-

1 BERNARD, De Vorigine du sucre dans V economic animale. — Archives generates
de medecine, Paris, 1848, 4me serie, tome xviii., p. 303, et seq.

2 BERNARD, Recherches sur une nouvelle fonction du foie, consider e comme
organe producteur de matiere sucree chez Fhomme et les animaux. These presentee d
la Faculte des Sciences de Paris pour obtenir le grade de Docteur es Sciences Naiu-
relles, Paris, 1853.

8 BERNARD, Lecons de physiologie experimentale. Cours du semestre tfhiver,
1854-'55, Paris, 1855.

PRODUCTION OF SUGAR IX THE LIVER. 299

vations upon the glycogenic function ; ' and in the Journal
de la physiologic 1859, is an account of the formation of
sugar in the foetus,2 followed by some reflections upon its
relations to the development of the tissues.3

In the account of the discovery given by Bernard, it
appears that he first sought for the situation in the body
where the sugar derived from alimentary substances is de-
stroyed. With this end in view, he fed a dog for seven days
with articles containing a large proportion of sugar and
starch. On analyzing the blood from the portal system, he
found a large proportion of sugar ; and he also found it in
the blood of the hepatic veins. As a counter-experiment,
he fed a dog for seven days exclusively on meat, and then
looked for sugar in the blood of the hepatic veins; and,
to his surprise, found it in abundance. This experiment
he repeated frequently with the greatest care, and always
with the same result; and he concluded that sugar was
formed in the liver, and was contained in the blood com-
ing from this organ independently of the diet of the ani-
mal. He afterward made extracts of the substance of the
liver and of the other tissues, and found that this organ
always contained sugar, while it was not to be detected in
any other organ or tissue in the economy.4 In subsequent
experiments, it was demonstrated that the livers of nearly all
classes of animals contained sugar, and that it existed also in
the human subject.5 He made observations, also, upon the

1 BERNARD, Lemons sur les effets des substances toxiques et medicamenteuses,
Paris, 1857, p. 445, et seq.

Leconssur la, physiologic et la pathologic du systeme nerveux, Paris, 1858,

tome i., p. 397, et seq., and tome ii., p. 544, et seq.

Lecons sur les proprittes physiologiques et les alterations palhologiques des

liquidesde Vorganisme, Paris, 1859, tome ii., p. 88, et seq.

3 BERNARD, Sur une nouvelle fonction du placenta. — Journal de la physiologic,
Paris, 1859, tome ii., p. 31, et seq.

3 Idem, p. 326, et seq.

4 BERNARD, These, Paris, 1853, pp. 13, 14.

5 BERNARD, op. cit., p. 31, et seq. The examinations of the liver of the human
subject for sugar were made by Bernard in executed criminals, soon after death,

300 SECRETION.

mechanism of its production, its disappearance in the blood
circulating through the lungs, and the various influences
which modify the glycogenic function. These points will
be considered in their appropriate place ; and we will now
proceed, after examining the processes for the determination
of sugar, to take up, seriatim, the following questions :

1. The absence of sugar from the blood of the portal
system in animals that have taken neither starch nor sugar
into the alimentary canal.

2. The presence of sugar in the blood as it comes directly
from the liver by the hepatic veins, independently of saccha-
rine or amylaceous food.

3. The mechanism of the production of sugar by the liver.

Processes for the Determination of Sugar. — In Bernard's
first observations on the liver, he applied the fermentation-
test to a simple decoction of the hepatic substance, and ob-
tained unmistakable evidences of sugar. In operating upon
perfectly fresh and normal blood, the addition of water and
nitration frequently sufficed to procure a clear solution, to
which the ordinary copper-tests could be applied ; but the
most satisfactory method of making a clear extract was to
boil the blood with water and an excess of sulphate of soda.
By this means a clear extract can be obtained, containing, it
is true, a large proportion of sulphate of soda ; but this salt,
fortunately, does not interfere with the tests. Later, Bernard
decolorized his solutions and extracts by making the liquid
into a paste with animal charcoal and filtering. We have
long been in the habit of employing both of these methods ;
but when we have simply desired to determine the presence
or absence of sugar, the process with the sulphate of soda
has proved the most convenient. In delicate examinations,

and in persons killed suddenly while in perfect health. An opportunity lately
occurred in Albany for the examination of the liver in a man killed suddenly.
The analysis was made by the late Prof. Howard Townsend, who fully confirmed
the observations of Bernard (TOWNSEND, Glycogenic Function of the Liver,
Albany, 1864).

PRODUCTION OF SUGAR IN THE LIVER. 301

however, we have generally used animal charcoal. We have
used both methods in decolorizing the decoction of the liver-
substance, as well as in operating upon the blood.

In ordinary examinations, Trommer's test is sufficiently
delicate ; but it is not so sensitive nor so convenient as some
of the standard test-solutions. We have been in the habit
of using, for the determination of sugar in the urine, a modi-
fication of Fehling's test, which is also very convenient for
examinations of the blood and liver-extract. This may also
be used for quantitative examinations ; but, like all of the
standard solutions, it presents the inconvenience of under-
going alteration by keeping, so that it is desirable to use it
freshly-made for each series of examinations. We have suc-
ceeded in obviating this difficulty, however, by the following
modification in its preparation ; and, made in this way, it is
probably the most convenient test that can be used in the
examination of any of the animal fluids for sugar.

Fehling^s Test for Sugar. — The modification in the test
consists simply in preparing three separate solutions, which
are to be mixed just before using, as follows :

Solution of crystallized sulphate of copper, 90£ grains in
an ounce of distilled water.

Solution of neutral tartrate of potash, 36i grains in an
ounce of distilled water.

Solution of caustic soda, specific gravity 1*12.

These solutions are to be kept in separate bottles, and
used as follows :

Take half of a fluidrachm of the copper-solution, add
half a fluidrachm of the solution of tartrate of potash, and
add the solution of caustic soda, to make three fluidrachms.
It is important to measure the copper-solution with especial
accuracy for quantitative analyses, as the quantity of copper
decomposed indicates the amount of sugar.1

1 The above modification of Fehling's test consists simply in making and
keeping the solutions separately, and mixing them for use in the proportions

302 SECRETION.

To apply this test in ordinary qualitative analyses, heat
a small portion of the test-liquid to the boiling point in a
test-tube, and add the suspected fluid, drop by drop. If
sugar be present in even a moderate quantity, a dense yel-
lowish precipitate of the suboxide of copper will be produced
after adding a few drops; and if the liquid be added to
about the same volume as the test, and the mixture be again
raised to the boiling point, without producing any deposit,
it is certain that no sugar is present. The estimation of the
quantity of sugar in any liquid depends upon the fact that
two hundred grains of the test-liquid is decolorized by ex-
actly one grain of glucose. To apply this test, measure off
in a glass, specially graduated for the purpose, two hundred
grains of the solution ; put this into a flask, with about twice
its volume of distilled water, and boil ; when boiling, add
the suspected solution, little by little, from a burette gradu-
ated in grains (raising the mixture to the boiling point each
time and afterward allowing the precipitate to subside), until
the blue color is completely discharged ; by then reading off
the number of grains of the saccharine solution that has been
added, the proportion of sugar may be readily calculated.
If the solution be suspected to contain a considerable quan-
tity of sugar, the estimate may be more accurately made by
diluting it to a known degree, say with nine parts of water,
and adding this diluted mixture to the test-liquid.1

Bernard, in his quantitative examinations, employed a
test-liquid known as Barreswil's solution, but the process is
essentially the same as the one we have just described. One
advantage of boiling the standard liquid before applying the

required. The original formula, given by Roberts, reduced to English grains,

is as follows :

Sulphate of copper, 90i grains ;

Neutral tartrate of potash, 364 grains ;

Solution of caustic soda, sp. gr. 112, four fluidounces.

Add water to make exactly six fluidounces.

— (ROBERTS, A Practical Treat^e on Urinary and Renal Diseases, Philadelphia,
1866, p. 147.)

1 ROBERTS, op. cit., p. 147.

PRODUCTION OF SUGAR IN THE LIVER. 303

test is that, when it is altered so as to be unreliable, the
yellow precipitate is thrown down by simple boiling. In
making delicate examinations, it is best always, when this
occurs, to make a fresh solution.1

Examination of the Blood of the Portal System for
Sugar. — If starch or sugar be taken into the alimentary
canal, it is well known that sugar is always to be found,
during absorption, in the blood of the portal system ; but
in the carnivorous animals, that have been fed entirely upon
meat, no sugar is to be found in the portal blood. Bernard
is very definite upon this point, and indicates a liability to
error when the operation of tying the portal vein has not
been skilfully performed, and when blood, containing sugar,
is allowed to regurgitate from the substance of the liver. In
taking the blood just before it enters the liver, it is necessary
to apply a ligature to the vessels as they penetrate at the
transverse fissure. This should be done quickly, and the
opening into the abdominal cavity should be small. Other-
wise, as the vessels have no valves, we are liable to have re-
flux of blood from the liver. We have frequently performed
the experiment, after the method described by Bernard,
making a small opening in the linea alba a little below the
ensiform cartilage, just large enough to admit the forefinger
of the left hand ; introducing the finger, and feeling along
the concave surface of the liver until we are able to seize
the vessels; then passing in an aneurism-needle, and con-
stricting the vessels before the abdomen is widely opened^
when a firm ligature is applied. When this step of the
operation has been satisfactorily performed, we have never
found a trace of sugar in the extract from the blood of the
portal system, in animals that have been fed upon nitrogen-
ized matter alone.

Among those who have refused to admit the glycogenic

1 The properties of the test-liquid may be restored sufficiently for ordinary
qualitative examinations by adding a little more caustic soda and filtering.

304: SECKETION.

function of the liver, there have been few who have denied
the proposition that the portal blood does not contain sugar
except during absorption of this principle from the alimen-
tary canal. Figuier, who made an elaborate series of inves-
tigations on this subject with the view of invalidating the
experiments of Bernard, assumed that this proposition was
incorrect, and that the portal blood carries sugar to the liver
during the digestion of starchy and saccharine matters, where
it is retained,1 and, furthermore, that there is sugar in the
blood of the portal vein during the digestion of raw meat.2
From these and other observations, Figuier concludes that
the liver does not produce sugar, but that the sugar, brought
to this organ by the portal blood, is here stored up, to be
passed, little by little, into the blood of the hepatic veins.3

These conclusions cannot be accepted, for the reason that
the evidence of the presence of sugar in the portal blood of
animals during the digestion of meat is far from satisfac-
tory. A commission of the French Academy of Sciences,
composed of MM. Dumas, Pelouze, and Rayer, after a careful
examination of the extracts of the portal blood presented by
M. Figuier, decided that the evidence of the presence of sugar
was insufficient, and came to the conclusion "that sugar
was not appreciable in the blood of the portal vein of a dog
fed on raw meat." * This seems to settle the question, as far
as the observations of M. Figuier are concerned, the report
of the commission being pretty generally accepted as con-
clusive.6

1 FIGUIER, Memoire sur Vorigine du sucre dans le foie et sur T existence normale
du sucre dans le sang de Vhomme et des animaux. — Comptes rendus, Paris, 1855,
tome xi, p. 228.

2 FIGUIER, Deuxieme memoire d propos de la fonction glycogenique du foie. —
Comptes rendus, Paris, 1855, tome xl., p. 674.

3 FIGUIER, Troisieme memoire sur la fonction glycogenique du foie. — Comptes
rendus, Paris, 1855, tome xli., p. 352.

4 DUMAS, Rapport sur divers memoires relatifs auxfonctions du foie. — Comptes
rendus, Paris, 1855, tome xl., p. 1281.

5 BERARD, Note additionnelle au memoire lu d V Academic dans la seance du 19
mai, 1857. — Gazette hebdomadaire, Paris, 1857, tome iv., p. 414.

PRODUCTION OF SUGAR IN THE LIVER. 305

The only other question that has been raised with regard
to the possible presence of sugar or sugar-forming matter in
the blood of the portal vein has been that inosite (C12HiaO12),
a substance discovered by Scherer in the muscular tissue of
the heart,1 might be introduced into the portal blood with
the animal food. But even if inosite should be contained
in food and be detected in the blood of the portal system,
it cannot possibly have any thing to do with the glycogenic
process, and it is not known that it has any relations to the
sugars. Anhydrous inosite is isomeric with anhydrous glu-
cose, but it does not respond to any of the copper-tests, and
is unfermentable.a

In view of all these facts, there can be no doubt that the
blood carried to the liver by the portal vein does not contain
sugar, in animals fed solely upon nitrogenized matters. The
quantity of blood carried to the liver by the hepatic artery
is insignificant ; and, although the arterial blood may tem-
porarily contain a trace of sugar, as we shall see further on,
this need not complicate the question under consideration, as
the presence of sugar in the blood of the hepatic artery is ex-
ceptional, and its proportion, when it exists, is very minute.

Examination of the Blood of the Hepatic Veins for
Sugar. — It is upon this question that the whole doctrine of
the sugar-producing function of the liver must rest. If it
can be proven that the blood, taken from the hepatic veins
during life or immediately after death, normally contains
sugar, while the blood distributed to the liver contains neither
sugar nor any substance that can be immediately converted
into sugar, the inevitable conclusion is that the liver is a
sugar-producing organ. We will, consequently, examine
this part of the question with the care which its importance
demands.

1 SCHERER, Ueber eine neue, aus dem Muskelfleische, gewonnene Zuckerart. —
Annalen der Chemie und Pkarmacie, Heidelberg, 1850, Bd. Ixxiii., S. 322, et seq.
8 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. i., p. 264.
20

306 SECRETION.

The proposition that the blood from the hepatic veins does
not contain sugar during life and health cannot be sustained
by actual experiment. Observers may say that the quantity
is very slight, but its existence in this situation, indepen-
dently of the kind of food taken, cannot be denied. Dr.
Pavy, who is the originator of the theory that the sugar
found in the liver and in the blood coming from the liver
is due to a post-mortem change, nowhere states that he has
taken the blood from the hepatic veins and failed to find
sugar. He states that he has found the blood taken from
the right side of the heart by catheterization, in a living
animal, " scarcely at all impregnated with saccharine mat-
ter," l but he does not deny its presence in small quantity.
In twelve examinations made by Dr. M'Donnell, of Dublin,
traces of sugar were found in five specimens of blood taken
from the right auricle by catheterization, in the living ani-
mal, and no sugar was detected in seven.8 It must be re-
membered, in considering these experiments, that the blood
of the right side of the heart is the mixed blood from the
entire body ; and, assuming that the hepatic blood is con-
stantly saccharine, the quantity in the blood of the right
heart would not be very great.

In opposition to these experiments, which are only par-
tially negative, we have the following results of examina-
tions of the blood of the hepatic veins and of the right side
of the heart taken as nearly as possible under normal condi-
tions.

To demonstrate the absence of sugar in the portal vein
and its constant presence in the hepatic veins in dogs fed ex-
clusively on meat, Bernard employed the following process :
The animal was killed instantly by section of the medulla
cblongata. A small opening was then made into the abdo-
men, just large enough to admit the finger and to enable

1 PAVY, Researches on the Nature and Treatment of Diabetes, London, 1862,
PP- 44, 46.

2 M'DONNELL, Observations on the Functions of the Liver, Dublin, 1865, p. 4.

PRODUCTION OF SrGAK IX THE LIVER. 307

him to seize the portal vein as it enters at the transverse
fissure, and apply a ligature. The abdomen was then freely
opened and a ligature applied to the vena cava just above the
renal veins, to shut off the blood from the posterior extremi-
ties. The chest was then opened, and a ligature was applied
to the vena cava just above the opening of the hepatic veins.
Operating in this way, blood may be taken from the portal
system before it enters the liver, and from the hepatic veins
as it passes out. In the blood from the portal system no
sugar is to be found, but its presence is unmistakable in the
blood from the hepatic veins.1 To avoid disturbing the cir-
culation in the liver, and in order to collect from the hepatic
veins as large a quantity of blood as possible, Bernard modi-
fied the experiment, in some instances, by introducing into
the vena cava in the abdomen a double sound, the extremity
of which is provided with a bulb of India-rubber. This was
pushed into the vein above the diaphragm ; and by inflating
the bulb, the vein was obstructed above the liver, and the
blood could be collected through one of the canulse, as it
came directly from the hepatic vessels. Bernard never
failed to determine the presence of sugar in these specimens
of blood, employing a number of different processes, includ-
ing the fermentation-test and even collecting the alcohol.8
To complete the proof of the existence of sugar in the blood
coming from the liver, Bernard demonstrated its presence in
blood taken from the right auricle in a living animal. He

O O

also showed that during digestion the whole mass of blood
contained sugar, but the quantity was greater in the right
side of the heart than in the arterial system.8

It is unnecessary to cite all the authorities that have
confirmed the observations of Bernard. Shortly after these

1 BERNARD, Recherches sur une nouvdle fondwn du foie, Paris, 1853, p. 56.

2 BERNARD, Lemons de physiologic experimentale, Paris, 1855, p. 494. The
reader will find here a description, with a figure, of the instrument mentioned
in the text, which is very ingenious.

3 Op. tit., p. 120.

308 SECRETION.

experiments were published, Lehmann,1 Frerichs,8 and many
others verified their accuracy. Bernard gives in full the
experiments of Poggiale8 and of Leconte,4 the results of
which were identical with his own. He gives, also, in one
of his later works, the proportions of sugar in the blood of
the hepatic veins, obtained by Lehmann, Schmidt, Poggiale,
and Leconte; no sugar being found in the blood of the por-
tal system.6 "We have ourselves made a number of experi-
ments with a view of harmonizing, if possible, the discordant
observations of Bernard and Pavy, and have examined the
blood from the hepatic veins for sugar, taking the speci-
mens under what seemed to be strictly physiological condi-
tions. In one of these published experiments, blood was
taken from the hepatic veins of a large dog, fully grown and
fed regularly every day, but not in digestion at the time of
the experiment, and the operation lasted only seventy
seconds. No anaesthetic was employed. The extract of
this specimen of blood, treated with Fehling's test-liquid,
presented a well-marked deposit of the oxide of copper,
revealing unequivocally the presence of a small quantity of
sugar.9 This has been the invariable result in numerous
experiments and class-demonstrations made since 1858 ; and
since the experiments just referred to were published, we
have verified the observation with regard to the hepatic
blood, keeping the animal perfectly quiet before the opera-

1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. i., p. 257.
9 FRERICHS, Verdauung. — WAGNER'S Handworterbuch der Physiologic, Braun-
schweig, 1846, Bd. iii., erste Abtheilung, S. 831.

3 POGGIALE, La matiere sucree se forme-t-elle par V action digestive, dans lefoie
et dans le torrent circulatoire ? in BERNARD, Lemons de physiologic experimentale,
Paris, 1855, p. 497.

4 LECONTE, Recherches sur la fonction glucogenique du foie, Idem, p. 499.

5 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 98.

6 FLINT, Jr., Experiments undertaken for the Purpose of reconciling some of
the Discordant Observations upon the Glycogenic Function of the Liver. — New
York Medical Journal, 1869, vol. viii., p. 381. These experiments will be referred
to again in treating of the question of the existence of sugar in the substance
of the liver during life.

PRODUCTION OF SUGAR IN THE LIVER. 309

tion, avoiding the administration of an anaesthetic, and
taking the blood so rapidly that no sugar could be formed
by the liver post mortem. These experiments leave no doubt
of the fact that, during life and in health, the blood, as it
passes through the liver and is discharged by the hepatic veins
into the vena cava, contains sugar, which is formed by the
liver, independently of the sugar and starch taken as food.

Does the Liver contain Sugar normally during Life f —
This is the only question upon which the results of reliable
experiments have been entirely opposite. Bernard made the
greater part of his observations by analyzing the substance of
the liver ; and he arrived at most of his conclusions with re-
gard to the variations in the glycogeuic function, from esti-
mates of the proportion of sugar in the liver under different
conditions. For many years we have been in the habit of re-
peating these experiments, with like results, and never failed
to find sugar, under normal conditions of the system. "We
were formerly in the habit of making the demonstrations of
the formation of sugar in the liver upon animals that had
been etherized ; and then we always obtained a brilliant pre-
cipitate from the clear extract of the substance of the liver
boiled with the test-liquid. The experiment was performed
in this way before we had acquired sufficient dexterity to
seize the portal vein readily and to go through with the
necessary manipulations with rapidity. "We subsequently
made the operation by first suddenly breaking up the me-
dulla oblongata, then making a small incision into the
abdominal cavity, seizing the portal vein instantly, and
following out the remaining steps of the experiment without
delay. In this way, although sugar was always found in the
blood of the hepatic veins, we frequently failed to obtain a
distinct reaction in the extract of the liver ; and it seemed,
indeed, that the more accurately and rapidly the operation
was performed, the more difficult was it to detect sugar in
the hepatic substance.

310 SECRETION.

It seems probable, in reflecting upon these facts, that,
inasmuch as no one has assumed that the actual quantity of
sugar produced by the liver is very considerable, and as a
large quantity of blood (in which the sugar is very soluble)
is constantly passing through the liver, precisely as we pass
water through its vessels to remove the sugar, the sugar
might be washed out by the blood as fast as it is formed ;
and really the liver might never contain sugar in its sub-
stance, as a physiological condition, although it is constantly
engaged in its production. We know that the characteristic
elements of the various secretions proper are produced in
the substance of the glands, and are washed out at the
proper time by liquid derived from the blood, which circu-
lates in their substance during their functional activity in
very much greater quantity than during the intervals of
secretion. ISTow, the liver-sugar may certainly be regarded
as an element of secretion ; and, possibly, it may be com-
pletely washed out of the liver, as fast as it is formed, by
the current of blood; the hepatic vein, in this regard,
serving as an excretory duct.

To put this hypothesis to the test of experiment, it was
necessary to obtain and analyze a specimen of the liver in
a condition as near as possible to that under which it exists
in the living organism ; and in carrying out this idea, we
instituted the following experiments :

Experiment I. — A medium-sized dog, full grown, in
good condition, not in digestion, was held upon the operat-
ing-table by two assistants, and the abdomen was widely
opened by a single sweep of the knife. A portion of the
liver, weighing about two ounces, was then excised and
immediately cut into small pieces, which were allowed to
fall into boiling water. The time from the first incision
until the liver was in the boiling water was twenty-eight
seconds. An excess of crystallized sulphate of soda was
then added, and the mixture was boiled for about five min-
utes. It was then thrown upon a filter, and the clear fluid

PRODUCTION OF. SUGAR IN THE LIVER. 311

that passed through was tested for sugar by Trommer's test.
The reaction was doubtful, and presented no marked evidence
of sugar.

Experiment II. — A medium-sized dog, in the same con-
dition as the animal in the first experiment, was held upon
the table, and a portion of the liver excised, as above de-
scribed. The whole operation occupied twenty-two seconds.
But ten seconds elapsed from the time the portion 'of the
liver was cut off until it was in the boiling water. It was
boiled for about fifteen minutes, made into a paste with
animal charcoal, and thrown upon a filter. The clear fluid
that passed through was tested for sugar by Trommer's test.
There was no marked evidence of sugar.

Experiment III. — A large dog, full grown, and fed regu-
larly every day, but not in digestion at the time of the
experiment, was held firmly upon the table. This dog had
been in the laboratory about a week, and was in a perfectly
normal condition. The abdominal cavity was opened, and
a piece of the liver cut off and thrown into boiling water,
the time occupied in the process being ten seconds. Be-
fore the liver was cut up into the boiling water, the blood
was rinsed off in cold water. The liver was boiled for about
seventeen minutes, mixed with animal charcoal, and the
whole thrown upon a filter.

Immediately after cutting off a portion of the liver and
throwing it into boiling water, the medulla oblongata was
broken up ; a ligature was applied to the ascending vena
cava, just above the renal veins ; the chest was opened, and
a ligature applied to the vena cava, just above the opening
of the hepatic veins. A specimen of blood was then taken
from the hepatic veins. This portion of the operation occu-
pied not more than one minute. A little water was added
to the blood, which was boiled briskly, mixed with animal
charcoal, and thrown upon a filter. The liquid that passed
through from both specimens was perfectly clear.

While the filtration was going on, Fehling's test-liquid

312 SECRETION.

was made up, so as to be perfectly fresh. The two liquids
were then carefully tested for sugar. The extract of the
liver presented not the slightest trace of sugar. The extract
from the blood of the hepatic veins presented a well-marked
deposit of the oxide of copper, revealing unequivocally the
presence of a small quantity of sugar.

Experiment IV. — This experiment was made upon a
medium-sized dog, in full digestion of meat. The medulla
oblongata was broken up ; the portal vein was tied through
a small opening in the abdomen • and the abdomen was then
widely opened, and a portion of the liver excised, rapidly
rinsed, and cut up into boiling water. The length of time
that elapsed between breaking up the medulla and cutting
up the specimen of liver into the boiling water was one
minute.

The vena cava was then tied above the renal veins, the
chest opened, and the cava again tied above the hepatic
veins. Blood was then taken from the hepatic veins, about
an equal bulk of water was added with an excess of the
crystallized sulphate of soda, and the mixture was boiled.
A portion of the portal blood and the decoction of the liver
were then treated in the same way, and the three specimens
filtered.

The clear extracts were then tested with Fehling's liquid,
with the following result :

There was no sugar in the portal blood.

There was no sugar in the extract of the liver.

There was a marked reaction in the extract of the blood
from the hepatic veins, the precipitate rendering the whole
solution bright yellow and entirely opaque.

This experiment was made in the presence of the class,
at the Bellevue Hospital Medical College, January 4, 1869.

The importance of the question under consideration and
its present unsettled condition are, we hope, sufficient to
justify the introduction of the details of the preceding
experiments. They were undertaken with the view of har-

PRODUCTION OF SUGAR IN THE LIVER. 313

monizing, if possible, the facts brought forward by different
experimentalists.

It is difficult to imagine how any observer, so well
known and accurate as Dr. Pavy, could assert positively, as
the result of personal examination, that the liver does not
contain sugar when examined immediately after its removal
from the living body, when Bernard and so many others
have demonstrated its presence in this organ in large quan-
tity. Yet such was the result of all the experiments of
Pavy,1 and the same conclusion was arrived at by M'Don-
nell,a and afterward by Meissner and Jaeger, and by Schiff.3
The elegant experiment of Bernard, showing that sugar is
formed in a liver removed from the body and washed
sugar-free by a stream of water passed through its vessels,4
demonstrated the possibility of the production of sugar post-
mortem, so strongly claimed by Pavy as the only condition
under which it is ever formed ; still, it does not seem pos-
sible to deny the sugar-producing function of the liver, in
view of the conclusive experimental proof of the constant
presence of glucose in the blood of the hepatic veins.

From our own experiments we have come to the conclu-
sion that Dr. Pavy and those who adopt his views cannot
consistently deny that sugar is constantly formed in the liver

1 PAVY, Researches on Sugar Formation in ike Liver. — Philosophical Trans-
actions, London, 1860, p. 595, and Researches on the Nature and Treatment of
Diabetes, London, 1862, p. 52, et seq.

2 M'DONNELL, Observations on the Functions of the Liver, Dublin, 1865, p. 4,
et seq.

3 SCHIFF, Nouvelles recherches sur la glycogenie animale. — Journal de Vanatomie,
Paris, 1866, tome Hi., p. 354, et seq. Meissner and Jaeger and Schiff took por-
tions of the liver from living animals and from animals at the instant they were
killed by section of the medulla oblongata, plunged the tissue immediately into
boiling water, and invariably failed to find sugar in the extract. They did not,
however, recognize sugar in the blood coming from the liver, as we did in our
own experiments.

4 BERNARD, Sur h mechanisme de la formation du sucre dans lefoie. — Comptes
rendus, Paris, 1855, tome xli., p. 461, and Lemons sur les effets des substances
toxiqucs et medicamenteuses, Paris, 1857, p. 453.

314 SECEETION.

and discharged into the blood of the hepatic veins ; nor can
Bernard and his followers ignore the fact that the liver does
not contain sugar during life ; although, as has been shown
by Pavy, and more specifically by M'Donnell,1 sugar ap-
pears in the liver in great abundance soon after death.

In the experiments that we have just detailed, which
are simply typical examples of numerous unrecorded obser-
vations, we attempted to verify the observations of Pavy
without losing sight of the facts observed by Bernard, and
to verify the experiments of Bernard in the face of the
apparently contradictory statements of Pavy. When an
animal is in perfect health, has been kept quiet before the
experiment, and a piece of the liver is taken from him by
two sweeps of the knife, the blood rinsed from it and the
tissue cut up into water already boiling, the whole operation
occupying only ten seconds ( as was the case in Experiment
III. ), the liver is as nearly as possible in the condition in
which it exists in the living organism. As this was done
repeatedly in animals during digestion and in the intervals
of digestion, and an extract thoroughly made without
finding any sugar, we regarded the experiments of Pavy as
entirely confirmed, and the fact demonstrated that the liver
does not contain sugar during life. On the other hand,
when we made the experiment on the liver as above
described, and, in addition, took specimens of the portal
blood and the blood from the hepatic veins, under strictly
physiological conditions ( as was done in Experiment IY. ),
and found no sugar in the portal blood or in the substance
of the liver, but an abundance in the blood of the hepatic
veins, it was impossible to avoid the conclusion that the
sugar was formed in the liver, and was washed out in the
blood as it passed through.

In treating of the mechanism of the formation of sugar
in the liver, we will describe more fully the glycogenic mat-
ter ; but, taking into consideration the demonstration of the

1 Loc. cit.

PRODUCTION OF SUGAR IN THE LIVER. 315

presence of sugar in the blood of the hepatic veins by Ber-
nard ; his discovery of the post-mortem production of sugar
in a liver washed sugar-free, probably from a substance re-
maining in the liver and capable of being transformed into
sugar ; the negative results of the examinations of the liver
for sugar by Pavy ; and, adding to this our own experiments
upon all of these points, we are justified in adopting the fol-
lowing conclusions :

1. A substance exists in the healthy liver, which is capa-
ble of being converted into sugar ; and inasmuch as this is
formed into sugar during life, the sugar being washed away
by the blood passing through the liver, it is perfectly proper
to call it glycogenic, or sugar-forming matter.

2. The liver has a glycogenic function, which consists in
the constant formation of sugar out of the glycogenic matter,
this being carried away by the blood of the hepatic veins,
which always contains sugar in a certain proportion. This
production of sugar takes place in the carnivora, as well as
in those animals that take sugar and starch as food ; and it
is, essentially, independent of the kind of food taken.

3. During life, the liver contains only the glycogenic
matter and no sugar, because the great mass of blood which
is constantly passing through this organ washes out the
sugar as fast as it is formed ; but after death, or when the
circulation is interfered with, the transformation of glyco-
genic matter into sugar goes on ; the sugar is not removed
under these conditions, and can then be detected in the sub-
stance of the liver.

Characteristics of the Liver-Sugar. — Very little is to be
said regarding the chemical peculiarities of liver-sugar. It
resembles glucose, or the sugar resulting from the digestion
of starch, in its composition, having for its formula, in a
crystalline form, CiaHuO14. The formula for the anhydrous
sugar is C12H12O12. This sugar, like glucose, responds
promptly to all of the copper-tests, and undergoes trans-

316 SECRETION.

formation into melassic acid on being boiled with an alkali.
One of its most marked peculiarities is that it ferments more
readily than any other variety of sugar ; and another pecu-
liarity, described first by Bernard, is that it is destroyed in
the economy with extraordinary facility. This fact has been
illustrated by the following ingenious experiment : Bernard
injected under the skin of a rabbit a little more than seven
grains of cane-sugar, dissolved in about an ounce of water,
and found sugar in the urine. Under the same conditions,
he found he could inject seven grains of milk-sugar, fourteen
and a half grains of glucose, twenty-one and a half grains
of diabetic sugar, and nearly thirty grains of liver-sugar,
without finding any sugar in the urine ; 1 showing that the
liver-sugar is consumed in the organism more rapidly and
completely than any other saccharine principle.

Mechanism of the Production of Sugar in the Liver. —
When Bernard first described the glycogenic function of the
liver, he thought that the sugar was produced from nitro-
genized principles, in some manner which he did not attempt
to explain.8 Subsequent discoveries, however, have led to
conclusions entirely different.

In 1855, Bernard first published an account of his re-
markable experiment showing the post-mortem production
of sugar. After washing out the liver with water passed
through the vessels, until it no longer contained a vestige of
sugar, it was allowed to remain at about the temperature of
the body for a few hours, and was then found to contain
sugar in abundance.3 This experiment we have already re-
ferred to, and it is one that we have frequently verified.
Bernard explained the phenomenon by the supposition, sub-

1 BERNARD, Lemons de physiologic experimentale, Paris, 1855, p. 214.

2 BERNARD, Recherches sur une nouvelle fonction du foie, These, Paris, 1853,
p. 77.

8 BERNARD, Sur h mecJianisme de la formation du sucre dans lefoie. — Comptes
rendus, Paris, 1855, tome xli., p. 461.

PRODUCTION OF SUGAR IK THE LIVER. 317

sequently shown to be correct, that the liver contains a
peculiar principle, slightly soluble in water and capable
of transformation into sugar. We have given rather a de-
tailed account of this observation, because some authors
have attributed the discovery of the glycogenic matter to
Hensen. Hensen confirmed Bernard's observations, in 1856,
and described the insoluble substance rather more fully.1
In 1857, Bernard studied the mechanism of the glycogenic
function more closely, and completed his description of the
glycogenic matter.3

Glycogenic Matter (C12HiaO12). — In its composition, re-
actions, and particularly in the facility with which it under-
goes transformation into sugar, glycogenic matter bears a
very close resemblance to starch. It is described by Pavy
under the name of amyloid matter,8 a name which is applied
to it, also, by Rouget.4 It is insoluble in water, and, by vir-
tue of this property, may be extracted from the liver after
the sugar has been washed out. The following is the method
for its extraction proposed by Bernard : 6

The liver of a small and young animal, like the rabbit,
in full digestion, presents the most favorable conditions for
the extraction of the glycogenic matter. The liver is taken
from the animal immediately after it is killed, is cut into
thin slices, and thrown into boiling water. When the tissue
is hardened, it is removed and ground into a pulp in a mor-
tar. It is then boiled a second time in the water of the

1 HENSEN, Ueber die Zucherbildung im thierischen Organismus. — SCHMIDT'S
Jahrbuther, Leipzig, 1857, Bd. xciii., S. 15; taken from Verhandlungen derphy.-
med. Gcs. zu, Wurzb., 1856, Bd. vii., S. 219.

2 BERNARD, Sur le mechanixme physiologique de la formation du sucre dans le
foie. — Comptes rendus, Paris, 1857, tome xliv., p. 578.

3 PATY, Researches on the Nature and Treatment of Diabetes, London, 1862,
p. 26, et seq.

4 ROUGET, Des substances amylo'ides ; de leur role dans la constitution dex tis-
sus des animaux. — Journal de la physiologic, Paris, 1859, tome ii., pp. 83, 308.
Rouget calls the glycogenic matter, or animal starch, zoamyline.

6 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 119.

318

•SECRETION.

FIG. 12.

E_J

first decoction, strained through a cloth, and the opaline liquid

which passes through is made into
a thin paste with animal charcoal.
The paste is then put into a dis-
placement apparatus, the end of
which is loosely filled with shreds
of moistened cotton. By success-
ive washings, the paste is ex-
hausted of its glycogenic matter,
leaving behind the albuminoid
and coloring matters. The whit-
ish liquid, as it flows, is received
into a vessel of absolute alcohol,
when, as each drop falls, the gly-
cogenic matter is precipitated in
great, white flakes. This is fil-
tered and dried rapidly in a cur-
rent of air. If the alcohol be
M pn not allowed to become too dilute,

the matter when dried is white
and easily pulverized. The ap-
paratus used by Bernard is repre-
sented in Fig. 12 : A B, displace-
ment apparatus in which the
filtration takes place ; C, animal
charcoal mixed with the decoction
of the liver ; E, glycogenic solu-
tion ; M, lamp-wicking, attached
to a thread, passing through the
carbon, and coming out at the
upper part of the apparatus ; I,
precipitating-glass ; G, glycogenic
matter precipitated ; Y, alcohol.1
The substance thus obtained may
"be held in suspension in water,
giving to the liquid a strongly

2 BERNARD, op. dt., p. 120.

PRODUCTION OF SUGAR IN THE LITER. 319

opaline appearance. It is neutral, without odor or taste,
and presents nothing characteristic under the microscope. It
reacts strongly with iodine, which produces a dark-violet or
chestnut-brown color, but rarely a well-marked blue. It
presents none of the reactions of sugar, and is entirely in-
soluble in alcohol.1 It is changed into sugar by boiling for
a long time with dilute acids, and this conversion is rapidly
effected by the saliva, the pancreatic juice, and a- peculiar
ferment found in the substance of the liver. Prepared in
the way above indicated, and pulverized, it may be preserved
for an indefinite period.

The peculiar reaction of the glycogenic matter with
iodine has led to its recognition in the substance of the liver-
cells and in some other situations. Schiff found in the
liver-cells minute granulations, which presented the peculiar
color on the addition of iodine, characteristic of glycogenic
matter.3 Bernard, a few years after his discovery of this
principle in the liver, recognized it in cells attached to the
placenta. He believes that these cells produce sugar during
the early period of foetal life, before the liver takes on this
function, and that they disappear during the later months, as
the liver becomes fully developed.3

Since the discovery of the glycogenic function of the
liver, anatomists have found amyloid corpuscles in various
of the tissues of the body. We do not propose, however, to
discuss this question in all its bearings, but only to consider
the known relations of the amyloid substances found in the
body to the formation of sugar.

In the first place, there can be no doubt of the fact, that
the liver of a carnivorous animal that has been fed exclu-
sively on meat contains an amyloid substance readily con-

1 BERNARD, Lemons sur la physiologic et la pathologic dit systeme nerveux, Paris,
1858, tome i., p. 4tO.

2 SCHIFF, De la nature des granulations qui remplissent les cellules hepatiques :
Amidon animak. — Comptes rendm, Paris, 1859, tome xlviii., p. 880.

3 BERNARD, Sur une nouvdle fonction du placenta. — Journal de la physiologic,
Paris, 1859, tome ii., p. 31, et seq.

320 SECRETION.

vertible into sugar. The experiments of Bernard, of Pavy,
and all, indeed, agree upon this point. The question of the
existence of the same amyloid matter in other tissues and
organs is only pertinent in so far as it bears upon the pro-
duction of sugar or upon the formation of the glycogenic
matter in the liver. In no tissue or organ in the adult has
it been demonstrated that there is any formation of sugar,
except the ordinary transformation of starch into sugar in
the process of digestion ; but it has been claimed that amy-
loid matter is contained in the flesh of herbivorous animals,
and is taken up by the carniv.ora and deposited in the liver.
M. Sanson has made two elaborate communications on this
subject, and concludes, from his own experiments, that the
liver has no glycogenic function.1 These experiments were
repeated by M. Sanson in the presence of a commission from
the French Academy of Medicine, composed of MM. Bouley,
Poggiale, and Longet, and were reported upon to the Acad-
emy. The conclusions of the commission were unreservedly
in favor of the glycogenic function of the liver ; and out of
a great number of observations, in only one was any amyloid
matter discovered in butcher's meat.3 It was found normally
in horse-flesh, and, as subsequent experiments showed, could
be produced in the muscular tissue of various of the her-
bivora, by feeding them upon certain articles, particularly
oats and barley.3

If the liver taken from an animal freshly killed be simply
kept at about the temperature of the body, after it has been
drained of blood, or even after it has been washed through
the vessels, sugar will be rapidly formed in its substance.

1 SANSON, De Vorigine du sucre dans feconomie animate. — Journal de la
physiologic, Paris, 1858, tome i., p. 244, et seq., and Sur Vexistence de la matiere
glycogene dans tous les organes des herbivores et sur Vinfluence de V alimentation sur
la production de cette substance. — Journal de la physiologic, Paris, 1859, tome ii.,
p. 104, et seq.

2 POGGIALE, Sur la formation de la matidre glycogene dans V economic animale.—
Journal de la physiologic, Paris, 1858, tome i., p. 549, et seq.

3 BERNARD, Liquides de Vorganisme, Paris, 1859, tomeii., p. 111.

PRODUCTION OF STJGAB IN THE LIVEK. 321

This must be due to some ferment remaining in the tissue ;
and Bernard has, indeed, been able to isolate a principle
which exerts this influence in a marked degree. If an
opaline decoction of the liver be allowed to stand until it has
become entirely clear, showing that all the glycogenic mat-
ter has been transformed into sugar, and alcohol be added
to the liquid, the hepatic ferment will be precipitated. This
may be redissolved in water, and it effects the transforma-
tion of starch into sugar with great rapidity.1

From these facts it is pretty conclusively shown that the
following is the mechanism of the production of sugar in the
liver :

The liver first produces a peculiar principle, analogous
to starch in its composition and in many of its properties,
though it contains two atoms more of water, out of which
the sugar is to be formed. The name, glycogenic matter,
may properly be applied to this substance. It is, as far as is
known, produced in all classes of animals, carnivora and
herbivora ; and though its quantity may be modified by the
kind of food, its formation is essentially independent of the
alimentary principles absorbed.

The glycogenic matter is not taken up by the blood as
it passes through the liver, but is gradually transformed, in
the substance of the liver, into sugar, which is washed out of
the organ as fast as it is produced. Thus the blood of the
hepatic veins always contains sugar, though sugar is not
contained in the substance of the liver during life.

Variations in the Glycogenic Function.

In following out the relations of the glycogenic process
to the various animal functions, Bernard studied very closely
its variations at different periods of life, with digestion, the
influence of the nervous system, and other modifying condi-
tions. He made some of his observations by examining the

1 BERNARD, op. ezz., p. 124.
21

322 SECRETION.

blood in living animals, and others, by estimating the pro-
portion of sugar in the liver. The latter method must be
considered, with an appreciation of the fact that the liver
does not normally contain sugar during life ; but it repre-
sents, to a certain extent, the activity of the glycogenic
function. Still, the facts arrived at in this way must be
taken with a certain degree of caution.

Glycogenesis in the Foetus. — In. the early months of foetal
existence, many of the tissues and fluids of the body were
found by Bernard to be strongly saccharine ; but at this
time no sugar is to be found in the liver. Taking the ob-
servations upon foetal calves as the criterion, sugar does not
appear in the liver until toward the fourth or fifth month of
intra-uterine life.1 Before this period, however, epithelial
cells filled with glycogenic matter are found in the placenta,
and these produce sugar until the liver takes on its functions.
As the result of numerous observations by Bernard upon
foetal calves, this function of the placenta appears very early
in foetal life, and, at the third or fourth month, has attained
its maximum. At about this time, when glycogenic matter
begins to appear in the liver, the glycogenic organs of the
placenta become atrophied, and are lost some time before
birth.8

Influence of Digestion, and of Different Kinds of Food.
— Activity of the digestive organs has a marked influence
upon the production of sugar in the liver. In a fasting ani-
mal, sugar is always found in the blood of the hepatic veins
and in the vessels between the liver and the heart, but it

1 BERNARD, Lemons de physiologic experimental^ Paris, 1855, p. 82.

2 BERNARD, Sur une nouvelle fonction du placenta. — Journal de la physiologie,
Paris, 1859, tome ii., p. 33. Bernard found glycogenic matter in the placenta
of animals in which the organ was single, as in the human subject ; but in ani-
mals with multiple placenta he did not at first discover the glycogenic organs,
which he subsequently found, not in the vascular portion, but attached to the
amnion.

PRODUCTION OF SUGAR IN THE LIVER. 323

never passes the lungs, and does not exist in the arterial
system. During digestion, however, even when the diet is
entirely nitrogenized, the production of sugar is so much
increased that a small quantity frequently escapes decompo-
sition in the lungs, and passes into the arterial blood.1 Un-
der these conditions, the quantity in the arterial blood is
sometimes so large that a trace may appear in the urine, as
a temporary and exceptional, but not an abnormal condition.
This physiological fact is well illustrated in certain cases of
diabetes. There are instances, indeed, in which the sugar
appears in the urine only during digestion ; a and in almost
all cases, the quantity of sugar eliminated is largely increased
after eating. Pavy mentions a very striking instance of this
kind, in which the examinations of the urine were made
with great care.8

The influence of the kind of food upon the glycogenie
function is a question of great pathological as well as physi-
ological importance. It is well known to pathologists that
certain cases of diabetes are relieved when the patient is
confined strictly to a diet containing neither saccharine nor
amylaceous principles,* and that, almost always, the quantity
of sugar discharged is very much diminished by such a course
of treatment ; but there are instances in which the discharge
of sugar continues, in spite of the most carefully-regulated
diet. Bernard does not recognize fully the influence of dif-
ferent kinds of food upon glycogenesis, and his experiments
on this point are wanting in accuracy, from the fact that the
proportion of sugar in the liver is given, without indicating
at what period after death the examinations were made. In
the observations on this point by Pavy, the examinations of

1 BERNARD, Lefons de physiologic experimentale, Paris, 1855, p. 111.

2 BERNARD, op. tit., p. 114.

3 PAVY, Researches on the Nature and Treatment of Diabetes, London, 1862,
p. 142.

4 Several very striking examples of this kind are given by Pavy (op. «*., p.
107).

324 SECRETION.

the liver were made immediately after death, and the pro-
portion of glycogenic matter, not sugar, was estimated. His
results are, consequently, much more reliable and satisfac-
tory. In a number of analyses of the livers of dogs confined
to different articles of diet, Pavy found a little over seven
per cent, of glycogenic matter, upon a diet of animal food ;
over seventeen per cent., upon a diet of vegetable food; and
fourteen and a half per cent., upon a diet of animal food and
sugar.1 These results have been confirmed by M'Donnell,
who, in addition, found that hardly a trace of amyloid sub-
stance could be detected in the liver on a diet of fat, and
none whatever upon a diet of gelatine.2 Bernard had al-
ready observed that the amount of sugar produced by the
liver on a diet of fat was the same as during total abstinence
from food.3 These facts are entirely in accordance with ob-
servations upon the effects of different kinds of food in dia-
betes, and they have an important bearing upon the dietetic
measures to be employed in this disease.

The effect of entire deprivation of food is to arrest the
production of sugar in the liver, three or four days before
death.4 This arrest of the glycogenic function has generally
been observed in cases of disease, except when death has
occurred suddenly.

Influence of the Nervous System, etc. — Bernard has
studied the influence of the nervous system upon the pro-
duction of sugar more satisfactorily than any other of the
variations of the glycogenic function, for the reason that he
has noted these modifications by determining the sugar in
the blood and the urine. Some of the points with regard
to the nervous system we will consider again in another vol-
ume ; and it is sufficient, in this connection, to mention the

1 PAVY, op. cit., p. 33, el seq.

8 M'DONNELL, Observations on the Functions of the Liver, Dublin, 1865, p. 14.

3 BERNARD, Lemons de physiologic experimentale, Paris, 1855, p. 137.

* BERNARD, op. cit., p. 129.

PRODUCTION OF SUGAR LIST THE LIVER. 325

main results of some of the most striking of the experiments
on this subject.

The most remarkable experiment upon
the influence of the nervous system on the
liver is the one in which artificial diabetes
is produced by irritation of the floor of the
fourth ventricle. This operation is not diffi-
cult, and is one that we have often repeated.
The instrument used is a delicate stilet, with
a flat cutting extremity, and a small project-
ing point, about -£% of an inch long.1 In per-
forming the operation upon a rabbit, the
head of the animal is firmly held in the left
hand, and the skull is penetrated in the
median line, just behind the superior occipi-
tal protuberance. This can easily be done
by a few lateral movements of the instrument.
Once within the cranium, the instrument is
passed obliquely downward and forward, so
as to cross an imaginary line between the
two auditory canals, until its point reaches
the basilar process of the occipital bone. The
point then penetrates the medulla oblongata,
between the roots of the auditory nerves and
the pneumogastrics, and, by its projection,
serves to protect the nervous centre from
more serious injury from the cutting edge.
The instrument is then carefully withdrawn,

-, . •• .. . i ,L i a mi • Instrument for pnnc-

and the operation is completed. This ex- turin? the floor of

. . , . -. -. . . . , , the fourth ventricle

penment is almost painless, and it is not de- (BERNARD, Leyons

, , , . . ,, , . de physiologie ex-

sirable to administer an anaesthetic, as this, pfrtmaOate^ Pan?,

1855, p. 290).

in itself, would disturb the glycogenic pro-
cess. The urine may be drawn before the operation, by
pressing the lower part of the abdomen, taking care not to

1 These instruments have been made by Messrs. Tiemann & Co., of this city.

2 BERNARD, Lemons de physiologic experimentale, Paris, 1855, p. 291, et seq.

326

SECRETION.

allow the bladder to pass up above the point of pressure,
and it will be found turbid, alkaline, and without sugar. In
one or two hours after the operation, the urine will have be-
come clear, acid, and will react readily with any of the
copper-tests. "When this operation is performed without in-
juring the adjacent organs, the presence of sugar in the
urine is only temporary, and the next day, the secretion

FIG. 14.

Section of the head of a rabbit, showing the operation of puncturing the floor of the
fourth ventricle, a, cerebellum ; J, origin of the seventh pair of nerves ; c, spinal
cord ; d, origin of the pneumogastric ; e, opening of entrance of the instrument into
the cranium : /, instrument ; g, fifth pair of nerves ; A, auditory canal ; i, extremity
of the instrument on the spinal cord after having penetrated the cerebellum ; #, oc-
cipital venous sinus ; /, tubercula quadrigemina ; m, cerebrum ; n, section of the atlas.
— (BERNARD, Lemons de physiologic experimental, Paris, 1855, p. 293.)

will have returned to its normal condition. It is best, in
performing this experiment, to operate on an animal in full
digestion, when the production of sugar is at its maximum.

The production of diabetes in this way, in animals, is
exceedingly interesting in its relations to certain cases of the
disease in the human subject, in which the affection is trau-
matic, and directly attributable to injury near the medulla.

PRODUCTION OF SUGAR IN THE LIVER. 327

Its mechanism it is difficult to explain. The irritation is
not propagated through the pneumogastric nerves, for the
experiment succeeds after both of these nerves have been
divided ; 1 but the influence of the pneumogastrics upon
gljcogenesis is curious and interesting. If both of these
nerves be divided in the neck, in a few hours or days, de-
pending upon the length of time that the animal survives
the operation, no sugar is to be found in the liver, and there
is reason to believe that the glycogenic function is arrested.
After division of the nerves in this situation, galvanization
of their peripheral ends does not affect the production of
sugar; but, by galvanization of the central ends, an impres-
sion is conveyed to the nervous centre, which is reflected to
the liver, and produces a hypersecretion of sugar.3 These
questions will be referred to again, in connection with the
physiology of the nervous system.

With regard to the influence of the sympathetic system
upon the glycogenic function, there have been few experi-
ments which lead to conclusions of any great value. Pavy
found that division of the sympathetic filaments accompany-
ing the vertebral arteries produced diabetes, but the opera-
tion was complicated by lesions of the vessels, which ren-
dered the results somewhat unsatisfactory.8

It has been observed that the inhalation of anaesthetics
and irritating vapors produces temporary diabetes;4 and
this has been attributed to the irritation conveyed by the
pneumogastrics to the nerve-centre, and reflected, in the
form of a stimulus, to the liver. It is for this reason that
we should avoid the administration of anaesthetics in all ac-
curate experiments on the glycogenic function. In illustra-
tion of this fact, Pavy has collected twenty cases, in which

1 BERNARD, loc. cit., p. 317.

3 BERNARD, op. cz7., p. 324. It has been observed by Bernard that division
of the pneumogastrics in the chest, between the lungs and the liver, does not
affect the production of sugar (p. 328).

3 PATY, op. tit., p. 87, et seq.

4 BERNARD, op. oil., p. 327.

328 SECRETION.

chloroform was administered in the human subject for surgi-
cal operations, in all of which the passage of a small quan-
tity of sugar in the urine was noted.1

Destination of Sugar. — Although sugar is constantly
produced by the liver and taken up by the circulation, it is ex-
ceptional to find it in the blood after it has passed through
the lungs. It is difficult to ascertain the precise mode of its
destruction in the lungs, and, indeed, the nutritive function
of sugar in the economy is not thoroughly understood. All
that we can say of the destination of liver-sugar is, that it
probably has the same office in nutrition as the sugar taken
as food and that resulting from the digestion of amylaceous
matters. The facts bearing upon this question will be re-
viewed under the head of nutrition.

Alleged Production of Fat Tyy the Liver. — It is stated
by Bernard, that in animals fed largely with saccharine and
amylaceous principles, the blood of the hepatic veins con-
tains an emulsive matter, which seems to be fat combined
with a proteine substance. In support of the opinion that
fat is thus produced in the liver, he brings forward that well-
known fact, that a diet of starch and sugar is particularly
favorable to the development of adipose tissue.3 But the
examinations of the matter supposed to be fatty have not
been sufficiently minute to lead to any positive conclusions
with regard to its character or composition. Rouget states,
unreservedly, that this substance is simply glycogenic or
amyloid matter.3 "While there can be no doubt of the forma-
tion of fat in the organism independently of the fat taken
as food, there is not sufficient ground for regarding the liver
as one of the organs specially concerned in its production.

1 Op. tit., p. so.

2 BERNARD, Legons de physiologic cxperimentale, Paris, 1855, p. 154.

8 ROUGET, Des substances amyloides. — Journal de la physiologic, Paris, 1859,
tome ii., p. 324.

CHANGES IN THE BLOOD IN THE LTVEB, 329

Changes in the Albuminoid and the Corpuscular Ele-
ments of the Blood in passing through the Liver. — In verify-
ing the observations of Bernard upon the presence of sugar
in the blood of the hepatic veins, Lehinann was led to observe
other differences in the composition of the blood from
these vessels, as compared with the portal blood and the
blood of the arterial system. One of the most important of
these was the absence of fibrin. While the portal blood co-
agulates strongly, like blood from any other part of the body,
the^ blood of the hepatic veins does not coagulate, and " the
fibrin is either entirely absent, or is present in mere traces." *
This observation has been confirmed by Brown-Sequard,8
and, later, by M'Donnell, who describes a peculiar caseous
matter as existing specially in the blood of the hepatic
veins.3 Lehmann also noted that the proportion of serum
to corpuscles was much less in the hepatic than in the por-
tal blood. The serum from the hepatic veins was found to
present a diminution in albumen, amounting to fully one-
third.

Some very curious observations were also made by Leh-
mann upon the blood-corpuscles in the hepatic vessels. He
estimated that the proportion of white corpuscles in the
blood of the hepatic veins was at least fivefold the propor-
tion in the portal blood. He also noted certain differences
in the appearance of the red corpuscles, which he explained
by the supposition that the liver was the seat of development
of these elements, which were formed from the white cor-
puscles, and that the blood of the hepatic veins contained a

1 LEHMAXN, Physiological Chemistry, Philadelphia, 1855, TO!, i., p. 489. Sev-
eral years before, Simon observed that fibrin was separated with difficulty from
the blood of the hepatic veins, and was not to be found in the blood of the
renal veins (SiMON, Animal Chemistry, Philadelphia, 1846, pp. 174, 178).

2 BROWN-SEQUARD, Sur des faits qui semblent montrer que plusieurs kilo-
grammes de fibrine se forment et se transformer^, chaque jour dans le corps de
Vhomme, — Journal de la physiologie, Paris, 1858, tome i., p. 300.

3 M'DONNELL, Observations on the Functions of the Liver, Dublin, 1865,
p. 34.

330 SECRETION.

greater number of "newly-formed or rejuvenescent blood-
corpuscles."

It is not our purpose, in this connection, to discuss the
development of the corpuscular elements of the blood ; but
it is interesting to note the above-mentioned changes in the
blood as it passes through the liver. The physiological sig-
nificance of the destruction of fibrin and albumen is not un-
derstood, although the fact is undoubted.

1 Op. tit., pp. 498, 499.

CHAPTER XI.

THE DUCTLESS GLANDS.

Probable office of the ductless glands — Anatomy of the spleen— Fibrous struc-
ture of the spleen (trabeculse) — Malpighian bodies — Spleen-pulp — Vessels
and nerves of the spleen — Some points in the chemical constitution of the
spleen — State of our knowledge concerning the functions of the spleen —
Variations in the volume of the spleen during life — Extirpation of the
spleen — Anatomy of the suprarenal capsules — Cortical substance — Medul-
lary substance — Vessels and nerves — Chemical reactions of the suprarenal
capsules — State of our knowledge concerning the functions of the supra-
renal capsules — Extirpation of the suprarenal capsules — Addison's disease
— Anatomy of the thyroid gland — State of our knowledge concerning the
functions of the thyroid gland — Anatomy of the thymus — Pituitary body
and pineal gland.

CERTAIN organs in the body, with a structure resem-
bling, in some regards, the true glands, but without excre-
tory ducts, have long been the subject of physiological spec-
ulation ; and the most extravagant notions concerning their
functions have prevailed in the early history of the science.
The discovery of those functions of the liver which consist
in modifications in the composition of the blood dimly
indicated the probable office of the ductless glands ; for, as
far as the production of sugar is concerned, the liver belongs
to this class. Indeed, the supposition that the ductless glands
effect some change in the blood is now regarded by physiol-
ogists as the most reasonable of the many theories that have
been entertained concerning their office in the economy;
and this view is adopted by those, even, who do not admit
the existence of a glycogenic function in the liver. Under

332 SECRETION.

this idea, these organs have been called blood-glands, or vas-
cular glands; but inasmuch as the supposition that these
parts effect changes in the blood or lymph is merely to sup-
ply the want of any definite idea of their function, and rests
mainly upon analogy with certain of the functions of the
liver, we shall retain the name, ductless glands, as indicating
the most striking of their anatomical peculiarities.

As far as presenting any definite and important physio-
logical information is concerned, we might terminate here
the history of the ductless glands. It is true that the
largest of them, the spleen, has been extensively experi-
mented upon by the earlier physiologists ; but in point of
fact, investigations have done little more than exhibit a want
of knowledge of the functions of these remarkable organs ;
and the literature of the subject is mainly a collection of
wild speculations and fruitless experiments. There are,
however, some interesting experimental facts with relation
to the spleen and the suprarenal capsules ; though they are
not very instructive, except that they indicate the extremely
narrow limits of our positive knowledge. These few facts,
with a sketch of the anatomy of the parts, will embrace all
that we shall have to say concerning the ductless glands.
Under this head are classed, the spleen, suprarenal capsules,
thyroid gland, thymus, and sometimes the pituitary body
and the pineal gland. These parts have certain anatomical
points in common with each other, but on account of our
want of knowledge of their functions, it is difficult to distin-
guish, as we have done in other organs, their physiological
anatomy.

Anatomy of the Spleen.

The spleen is found, with but few exceptions, in all ver-
tebrate animals, but does not exist in the invertebrata.1 It

1 This organ, according to Van der Hoeven, is not found in the cyclostomes
and the lepidosiren (Handbook of Zoology, Cambridge, 1858, vol. ii., p. 29); and
Milne-Edwards states that it is absent also in the amphioxus (Lemons sur la

DUCTLESS GLANDS. 333

is situated in the left hypochondriac region, next the cardiac
extremity of the stomach. Its color is of a dark bluish-red,
and its consistence is rather soft and friable. It is shaped
somewhat like the tongue of a dog, presenting above, a
rather thickened extremity, which is in relation with the
diaphragm, and below, a pointed extremity, in relation with
the transverse colon. Its external surface is convex, and its
internal surface concave, presenting a vertical fissure, the
hilum, giving passage to the vessels and nerves. It is con-
nected with the stomach by the gastro-splenic omentum, and
is still further fixed by a fold of the peritoneum passing to
the diaphragm. It is about five inches in length, three or
four inches in breadth, and a little more than an inch in
thickness. Its weight is between six and seven ounces. In
the adult it attains its maximum of development, and
diminishes slightly in size and weight in old age. In early
life it bears about the same relation to the weight of the
body as in the adult.1 It is frequently hypertrophied to an
enormous extent in disease, weighing sometimes as much
as twenty pounds.3

The external coat of the spleen is the peritoneum ; which
is very closely adherent to the subjacent fibrous struc-
ture. The proper coat is dense and resisting; but in the
human subject is quite thin and somewhat translucent. It
is composed of inelastic fibrous tissue, mixed with numerous
small fibres of elastic tissue and a few unstriped muscular
fibres.

At the hilum the fibrous coat penetrates the substance
of the spleen in the form of sheaths for the vessels and
nerves ; an arrangement entirely analogous to the fibrous

physiologic, Paris, 1862, tome vii., p. 235). According to Gray, the spleen
exists without exception in all the vertebrate animals ( Structure and Use of the
Spleen, London, 1854, p. 272).

1 Mr. Gray, in his elaborate essay on the spleen, gives a very extended table
of the weight of this organ at different periods of life (Structure and Use of the
Spleen, London, 1854, p. 76).

8 GRAY, Anatomy, Descriptive and Surgical, Philadelphia, 1862, p. 685.

334 SECRETION.

sheath in the liver. The number of the sheaths in the spleen
is equal to the number of arteries that penetrate the organ.
This is sometimes called the capsule of Malpighi.1 The
fibrous sheaths are closely adherent to the surrounding
substance, but are united to .the vessels by a loose fibrous
net-work. They follow the vessels in their ramifications to
the smallest branches, and are lost in the spleen-pulp. Be-
tween the sheath and the outer coat, are numerous bands or
trabeculse of the same structure as the fibrous coat. The
presence of elastic fibres in these structures can be easily
demonstrated, and this kind of tissue is very abundant in
the herbivora. In the carnivora the muscular tissue is par-
ticularly abundant, and can be readily demonstrated ; 2 but
in man this is not so easy, and the fibres are less numerous.
There can be no doubt, however, that muscular tissue exists
in the human subject throughout the whole extent of the
fibrous structure, and the fibres are demonstrated without
much difficulty in the trabeculse.3

These peculiarities in the fibrous structure are important
in their relation to certain physiological changes in the size
of the spleen. Its contractility can be easily demonstrated
in the dog by the application of a galvanic current to the
nerves as they enter at the hilum. This is followed by a
prompt and energetic contraction of the organ. Contrac-
tions may be produced, though they are much more feeble,
by applying the current directly to the spleen.4

The substance of the spleen is soft and friable ; and a
portion of it, the spleen-pulp, may be easily pressed out, or
even washed away by a current of water. Aside from the
vessels and nerves, it presents for study : 1. An arrange-

1 MALPIGHI, De Liene, Opera Omnia, Lugd. Batav., 1687, tomus ii., p. 294.

2 Kolliker has demonstrated the presence of muscular fibres in considerable
numbers in the dog, pig, ass, and cat ; but they were not discovered in the rab-
bit, horse, ox, hedgehog, porpoise, or bat (Handbuch dcr Gewebelchre, Leipzig,
1867, S. 449).

3 SAPPEY, Traite d'anaiomie, Paris, 1857, tome iii., p. 323.

4 BERNARD, Lefons sur les liquides deVorganisme, Paris, 1859, tome ii., p. 421.

DUCTLESS GLANDS. 335

ment of fibrous bands, or trabeculae, by which it is divided
into innumerable communicating cellular interspaces. 2.
Closed vesicles ( Malpighian bodies), attached to the walls
of the blood-vessels. 3. A soft, reddish substance, contain-
ing numerous cells and free nuclei, called the spleen-pulp.

Fibrous Structure of the Spleen (Trabeculce). — From the
internal face of the investing membrane of the spleen, and
from the fibrous sheath of the vessels (capsule of Malpighi)
are numerous bands, or trabeculse, which, by their inter-
lacement, divide the substance of the organ into irregularly-
shaped, communicating cavities. These bands are from -^
to -^ of an inch broad, and are composed, like the proper
coat, of ordinary fibrous tissue with elastic fibres and a few
smooth muscular fibres. They pass off from the capsule of
Malpighi and the fibrous coat at right angles, very soon
branch, interlace, and unite with each other, becoming
smaller and smaller, until they measure from -g-J-g- to -fa
of an inch.1 The smaller bands are cylindrical, and it is
in these that the muscular tissue can be demonstrated with
the greatest facility. As we should expect from the very
variable size of the trabeculae, the dimensions as well as the
form of the cavities are exceedingly irregular. This fibrous
net-work serves as a skeleton or a support for the softer and
more delicate parts.

Malpighian Bodies. — In the very elaborate work on the
spleen, by Malpighi, is a full account of the closed follicles,
which have since been called the Malpighian bodies.3 They
are sometimes called the splenic corpuscles or glands. They
are in the form of rounded or slightly ovoid corpuscles, about
-^j- of an inch in diameter, consisting of a delicate membrane,
generally homogeneous, but sometimes faintly striated, with
semifluid contents. In their form, size, and structure, they

1 SAPPET, Traite cTanatomie, Paris, 1857, tome iii., p. 323.

8 MALPIGHI, De Liene, Opera Omnia, Lugd. Batav., 1687, tomus ii., p. 300.

336 SECRETION.

bear a close resemblance to the closed follicles of tlie small
intestine.1 The investing membrane has no epithelial lining,
and the contents consist of an albuminoid liquid, with numer-
ous small, nucleated cells, and a few free nuclei. The cells
measure from -g-^ViF to -g-gVir of an inch in diameter. Both
the cells and the free nuclei of the splenic corpuscles bear a
close resemblance to cells and nuclei found in the spleen-
pulp. The corpuscles are surrounded by blood-vessels,
which send branches into the interior to form a delicate
capillary plexus.3

The number of the Malpighian corpuscles in a spleen
of ordinary size has been estimated by Sappey at from seven
thousand to eight thousand.3 They are readily made out in
the ox and sheep, but are frequently not to be discovered in
the human subject. In about forty examinations, in man,
Sappey found them in only four ; but in these they presented
the same characters as in the ox and the sheep, and resisted
decomposition for twelve days,4 showing that it is not neces-
sary to have recourse to perfectly fresh specimens to dis-
cover them if they exist. Kolliker notes the fact that they
are often absent in the human subject when death has taken
place from disease or long abstinence. He believes that
they are nearly always to be found in perfectly healthy per-
sons.6 The occasional absence of these bodies constitutes
another point of resemblance to the solitary glands of the
small intestine.8

The relations of the Malpighian bodies to the arterial
branches distributed through 'the spleen are peculiar. In
specimens in which these corpuscles are easily made out, if
a thin section be made, and the spleen-pulp be washed away
by a stream of water, the corpuscles may be seen attached
in some parts to the sides of the vessels, in others lying in

1 See vol. ii., Digestion, p. 321.

2 KOLLIKER, Handbuch der Gewebelehre, Leipzig, 1867, S. 456.

3 SAPPEY, op. cit., p. 326. 4 Idem., p. 325.

6 KOLLIKER, op. cit., S. 454. 6 See vol. ii., Digestion, p. 319.

DUCTLESS GLANDS. 337

the notch formed by the branching of a vessel, and in others
attached to an extremity of an arterial twig, the vessel then
breaking up into a plexus to surround the corpuscle. Ac-
cording to Sappey, the corpuscles are attached to arteries
measuring from -g^ to -^ of an inch or less in diameter.1
When the artery is enclosed in its fibrous sheath, the corpus-
cles are applied to the sheath, but in the smallest arteries
they are attached to the walls of the vessel. The attach-
ment of the Malpighian bodies to the vessels is very firm,
and they cannot be separated without laceration of the
membrane.

Spleen-pulp. — "With, regard to the constitution of the
spleen-pulp, there is considerable diversity of opinion.
While anatomists and physiologists are pretty generally
agreed concerning the structure and relations of the Mal-
pighian bodies, some minutely describe cells in the pulp, the
existence of which is denied by others of equal authority.
The pulp, however, contains the essential elements of the
spleen, and an accurate knowledge of all the structures con-
tained in it could hardly fail to throw some light on its func-
tion ; but there is so little that is definitely known of either
the anatomy or the physiology of the spleen, that we shall
refrain from discussing the views of different authors, refer-
ring the reader for full information upon these points to the
elaborate works upon general anatomy.

The pulp is a dark, reddish, semifluid substance, its color
varying in intensity in different specimens. It is so soft that
it may be washed by a stream of water from -a thin section,
and it readily decomposes, becoming then nearly fluid. It is
contained in the cavities bounded by the fibrous trabeculae,
and itself contains numerous microscopic bands of fibres
arranged in the same way. It surrounds the Malpighian
bodies, contains the terminal branches of the blood-vessels,
and probably the nerves and lymphatics. Upon microscopi-

1 Op. tit., p. 328.
22

338 SECRETION.

cal examination, it presents numerous free nuclei and cells,
like those described in the Malpighian bodies ; but the nuclei
are here relatively much more abundant. In addition are
found, blood-corpuscles, white and red, some natural in
form and size, others more or less altered, with pigmentary
granules, both free and enclosed in cells. Anatomists have
attached a great deal of importance to large vesicles en-
closing what have been supposed by some to be blood-cor-
puscles, and by others to be pigmentary corpuscles. The
state of our knowledge on these points, however, is very
unsatisfactory. Some authorities deny the existence of the
so-called blood-corpuscle-containing cells. A writer in the
British and Foreign Medico- Chirurgical JReview, in 1853,
after a thorough analysis of the various original observations
that had appeared up to that time, came to the conclusion
that the presence in the spleen-pulp of cells containing blood-
corpuscles in a transition state was extremely doubtful ; 1 and
Kolliker, who has investigated the structure of the spleen
with peculiar care, has advanced, in successive publications,
several entirely different opinions on the subject.3 "We will
therefore abstain from a discussion of these disputed ques-
tions, which are at present of a character purely anatomical.
All that we can say of the spleen-pulp is, that it contains
cells, nuclei, blood-corpuscles, and pigmentary granules, with
a yellowish-red fluid ; and that it is intersected with micro-
scopic trabeculse of fibrous and muscular tissue, and a deli-
cate net-work of blood-vessels. It is difficult to determine
whether the blood-corpuscles come from vessels that have
been divided in making the preparation, or are really free
in the pulp ; or whether the free nuclei are normal or come
from cells that have been artificially ruptured.

1 WHARTON JONES, British and Foreign Medico- Chirurgical Review, London,
1853, vol. xi., p. 32.

2 KOLLIKER, Cyclopaedia of Anatomy and Physiology, London, 1847-1849,
vol. iv., p. 771, Article, Spleen.

Manual of Human Microscopic Anatomy, London, 1860, p. 358, et seg.

Handbuch der Gewebelehre des MenscJien, Leipzig, 1867, S. 448, et seq.

DUCTLESS GLANDS. 339

Vessels and Nerves of the Spleen. — The quantity of
blood which the spleen receives is very large in proportion
to the size of the organ. The splenic artery is the largest
branch of the coeliac axis. It is a vessel of considerable
length, and is remarkable for its excessively tortuous course.
In a man of between forty and fifty years of age, the vessel
measured about five inches, without taking account of its
deflections ; and a thread placed on the vessel, so as to follow
exactly all its windings, measured a little more than eight
inches.1 The large calibre of this vessel and its tortuous
course are interesting points in connection with the great
variations in size and situation which the spleen is liable to
undergo in health and disease. The artery gives off several
branches to the adjacent viscera in its course, and as it
passes to the hilum divides into three or four branches, which
again divide so as to form from six to ten vessels. These
penetrate the substance of the spleen, with the veins, nerves,
and lymphatics, enveloped in the fibrous sheath, the capsule
of Malpighi. In the substance of the spleen the arteries
branch rather peculiarly, giving off many small ramifica-
tions in their course, generally at right angles to the parent
trunk. These are accompanied by the veins until they are
reduced to from -^j- to -fa of an inch in diameter. The two
classes of vessels then separate, and the arteries have at-
tached to them the corpuscles of Malpighi. It is also a
noticeable fact that the distinct trunks passing in at the
hilum have but few inosculations with each other in the
substance of the spleen, so that the organ is divided up into
from six to ten vascular compartments. This arrangement
was observed many years ago by Assollant.3

The veins join the fine branches of the arteries in the
spleen-pulp and pass out of the spleen in the same sheath.
They anastomose quite freely in their larger as well as their

1 SAPPEY, Tratie cTanatomie, Paris, 1857, tome iii., p. 327.

2 ASSOLLAXT, Recherche* sur la rate.— These, No. 112, Paris, an xii. (1804),
p. 36.

340 SECKETION.

smaller branches. Their calibre is estimated by Sappey as
about twice that of the arteries. This author regards the
estimates, that have put the calibre of the veins at four or
five times that of the arteries, as much exaggerated.1 The
number of veins emerging from the spleen is equal to the
number of arteries of supply.

The lymphatics of the spleen are not numerous. By
most anatomists, two sets of vessels have been recognized,
the superficial and the deep; but those who have studied
the subject practically have found it very difficult to demon-
strate the superficial layer. Sappey denies the existence of
any but the deep vessels;2 and Kolliker admits that the
superficial vessels are generally not to be found in morbid
spleens, and are very scanty in perfectly healthy specimens.3
The deep lymphatics have been demonstrated in the capsule
of Malpighi, attached to the veins and emerging with them
at the hilum. At the hilum, according to Kolliker, the
deep vessels are joined by a few from the surface of the
spleen. The vessels, numbering five or six, then pass into
small lymphatic glands, and empty into the thoracic duct
opposite the eleventh or twelfth dorsal vertebra. It was an
old idea that the lymphatics were the excretory ducts of the
spleen.4 This view was revived by Hewson,6 but it is a
speculation which does not demand any discussion at the
present day.

The nerves of the spleen are derived from the solar
plexus. They follow the vessels in their distribution, and
are enclosed with them in the capsule of Malpighi. They

1 Op. cii., p. 329.

2 SAPPEY, Traite tfanatomie, Paris, 1857, tome iii., p. 331.

3 KOLLIKER, Handbuch dcr Gewebelehre, Leipzig, 1867, S. 460.

4 In Milne-Edwards's elaborate work on physiology, now in course of publi-
cation, is an exhaustive bibliographical review of the early works on the anato-
my and physiology of the spleen. The idea that the lymphatics were its ex-
cretory ducts was advanced by Eller, in 1716. (MILNE-EDWARDS, Lemons sur la
physiologic, Paris, 1862, tome vii., p. 233, et seq.)

6 HEWSON, Works, Sydcnham Society Publication, London, 1846, p. 271.

DUCTLESS GLANDS. 341

are distributed ultimately in the spleen-pulp, but nothing
definite is known of their mode of termination. "We have
already referred to the fact that when these nerves are gal-
vanized, the non-striated muscles in the substance of the
spleen are thrown into contraction.

Some Points in the Chemical Constitution of the Spleen.
—Very little has been learned with regard to the .probable
function of the spleen, from the numerous chemical analyses
that have been made of its substance. It will therefore be
out of place to discuss its chemical constitution very fully,
and we will only refer to certain principles, the existence of
which, in the spleen-substance, may be considered as pretty
well determined. In the first place, cholesterine has been
found to exist in the spleen constantly and in considerable
quantity, and the same may be said of uric acid. In addi-
tion, chemists have extracted from the substance of the
spleen, hypoxanthine, leucine, tyrosine, a peculiar crystal-
lizable substance called, by Scherer, lienine, crystals of
hsematoidine, lactic acid, acetic acid, butyric acid, inosite,
amyloid matter, and some indefinite fatty principles.1 It
is difficult, however, to say how far some of these principles
are formed by the processes employed for their extraction,
or are due to morbid action; certainly, physiologists have
thus far been unable to connect them with any definite
views of the probable function of the spleen.

State of our Knowledge concerning the Functions of the
Spleen. — The spleen is almost universal in vertebrate ani-
mals ; it is an organ of considerable size, and is very abun-
dantly supplied with vessels and nerves ; it has a complex
structure, unlike that of any of the true glands ; its tissue
presents a variety of proximate principles ; but it has no ex-
cretory duct, and no opportunity is afforded for the study
of its secretion, except as it may be taken up by the current

1 MILSE-EDWARDS, Lemons sur la physiologic, Paris, 1862, tome vii., p. 259.

342 SECRETION.

of blood. It must be admitted, also, that up to the present
time, no definite physiological ideas have followed the elabo-
rate microscopical and chemical examinations of the spleen.
There have been only two methods of inquiry, indeed, which
have promised any such results : First, a comparison of the
blood and lymph going into and coming from the spleen,
and an examination of the variations in the volume of the
organ during life ; and second, a study of the phenomena
which follow its extirpation in living animals. A review of
the literature of the subject will show that we have gained
but little positive information from either of these methods.

The condition of the question of the influence of the
spleen upon the composition of the blood is well illustrated
in the last edition of Longet's elaborate work on physiol-
ogy.1 This author quotes opinions of the highest authori-
ties, based chiefly upon microscopical investigations, some in
favor of the view that the blood-coi*puscles are destroyed, and
others arguing that they are formed in the spleen, while he
himself oifers no opinion upon the subject.

Still there are certain established points of difference
between the blood of the splenic artery and of the splenic
vein. There can be no doubt of the fact that the blood
coming from the spleen contains a large excess of white cor-
puscles. Donne was the first to call attention to this fact,2
and his observations have been confirmed by Gray,3 and
many others.4 It can by no means be considered settled,
however, that the function of the spleen is to form white
blood-corpuscles. In pathology, although great increase in
the leucocytes of the blood frequently attends hypertrophy

1 LONGET, Traite de physiologic, Paris, 1869, p. 378.

• DONNE, Cours de microscopic, Paris, 1844, p. 99. Donne states that the
blood taken from the splenic veins presents nothing remarkable ; but on press-
ing out that contained in the tissue of the organ, the white corpuscles were
very abundant, and were even more numerous than the red.

3 GRAY, The Structure and Use of the Spleen, London, 1854, p. 150.

4 MILNE-EDWARDS, Lecons sur la physiologie, Paris, 185Y, tome i., p. 352, and
1862, tome vii., p. 256.

DUCTLESS GLANDS. 343

of the spleen, this condition is also observed when the spleen
is perfectly healthy.

Diminution in the proportion of red corpuscles in the
blood in passing through the spleen, in a very marked degree,
has been noted by Beclard,1 Gray,8 and others, and this gives
color to the supposition that the spleen is an organ for the
destruction of the blood-corpuscles ; but we know nothing
of the importance or significance of this process, and it is
not shown that the corpuscles exist in undue quantity in ani-
mals after the spleen has been removed. We learn nothing
more definite from, the fact that blood of the splenic vein
seems to contain an unusual quantity of pigmentary matter.3
In connection with the marked diminution in the proportion
of blood-corpuscles, both Beclard 4 and Gray 6 observed a
marked increase in the fibrin and albumen in the blood of
the splenic vein.

The significance of the facts just stated is so little under-
stood, that it would seem hardly necessary even to mention
them, except as an illustration of the small amount of defi-
nite information regarding the functions of the spleen that
has resulted from an examination of the blood coming from
this organ. We know nothing of any changes effected by
the spleen in the constitution of the lymph.

Variations in the Volume of the Spleen during Life. —
One of the theories with regard to the function of the spleen,
which merits a certain amount of consideration, is that it
serves as a diverticulum for the blood, when there is a ten-
dency to congestion of the other abdominal viscera. The
first attempt to formularize this idea and support it by ex-
perimental observations was made by Dobson, in 1830. He
noted the fact that the spleen was much larger in dogs, from

1 BECLARD, Recherches experimentales sur les fonctions de la rate et sur celles
de la veine porte. — Archives generates de medecine, Paris, 1848, 4me serie, tome
xviii., pp. 143, 442.

2 GRAY, op. tit., p. 156. 3 Idem., p. 147.

4 BECLARD, loc. tit., p. 443. 5 GRAY, loc. tit., p. 152.

344

SECEETION.

four to five hours after eating, than during the intervals of
digestion ; and he formally advanced the opinion that the
spleen serves as a diverticulum for the blood during the pe-
riod when there is a great afflux to the digestive organs, and
that the extent of its enlargement is in direct ratio to the
amount taken into the stomach.1 Of the accuracy of these
experiments there can be no doubt ; " but the second series
of observations, in which Dobson attempted to show that
large quantities of food cannot be taken with impunity by
animals after the spleen has been extirpated, have not been
so satisfactorily verified. "We have often removed the spleen
from dogs, the operation being followed by complete recov-
ery, and have never noted any thing unusual after feeding
the animals very largely. In one observation, an animal from
which the spleen had been removed six weeks before ate at
one time a little more than four pounds of beef-heart, nearly
one-fifth of his weight (the dog weighing twenty-two pounds),
without suffering the slightest inconvenience.

Dobson certainly established the fact that the spleen is
greatly enlarged in dogs, from four to five hours after feed-
ing, that its enlargement is at its maximum at about the
fifth hour, and that it gradually diminishes to its original size
during the succeeding twelve hours ; but it is not apparent
how far this is important or essential to the proper perform-

1 DOBSON, Structure et fonctions de la rate. — Archives generales de medecine,
Paris, 1830, tome xxiv., p. 431, et seq. The experiments and conclusions of
Dobson are here quoted in full from the original memoir. Gray, who gives in
his work upon the spleen a very full resume of the various theories with regard
to the functions of the spleen, quotes (page 23) a Gulstonian lecture by Stuke-
ley, in 1722, in which the same idea is advanced, though it eeems to be put
forward merely as a theory, without any attempt at experimental proof.
Hodgkin revived this opinion in 1822, but without presenting any positive
proof of its accuracy (HODGKIN, On the Uses of the Spleen. — Edinburgh Medi-
cal and Surgical Journal, 1822, vol. xviii., p. 90).

2 The changes in the volume of the spleen have been observed by many
physiologists. Bernard noted, in addition, that the blood of the splenic vein is
red during abstinence and dark during digestion (Liquides de Vorganisme^ Paris,
1859, tome ii., p. 420).

DUCTLESS GLANDS. 345

ance of the functions of digestion and absorption. Experi-
ments have shown that animals may live, digest, and absorb
alimentary principles perfectly well after the spleen has been
removed, and this has even been observed in the human sub-
ject ; and in view of these facts, it is impossible to assume
that the presence of the spleen, as a diverticulum for the
blood, is essential to the proper action of the other abdom-
inal organs.

Extirpation of the Spleen. — There is one experimental
fact that has presented itself in opposition . to nearly every
theory advanced with regard to the function of the spleen ;
which is, that the organ may be removed from a living ani-
mal, and yet all the functions of life go on apparently as
before. The spleen is certainly not essential to life, nor, as
far as we know, to any of the important general functions.
It has been removed over and over again from dogs, cats,
and even from the human subject, and its absence is attended
with no constant and definite changes in the phenomena of
life. If it act as a diverticulum, this function is not essen-
tial to the proper operation of the organs of digestion and ab-
sorption ; and if its office be the destruction or the formation
of the blood-corpuscles, the formation of leucocytes, fibrin,
uric acid, cholesterine, or any excrementitious matter, there
are other organs which may accomplish these functions.
What renders this question even more obscure is the fact
that we Ijave no knowledge of any constant modifications in
the size or the functions of other organs as a consequence of
removal of the spleen.1 This is not surprising, however, when
we reflect that one kidney can accomplish the function of uri-

1 Beclard mentions several authorities who have noted enlargement of the
lymphatic glands throughout the system, consequent upon removal of the
spleen, and one of these instances occurred in the human subject (Traite elemen-
taire de physiologic humaine, Paris, 1859, p. 443); but these observations have
not been confirmed sufficiently to warrant the supposition that the spleen
belongs to the lymphatic system, particularly as its connections with the blood-
vessels are very extensive, and its lymphatics are rather scanty.

346 SECEETION.

nary excretion after the other has been removed, and that
the single organ remaining probably does not undergo en-
largement.1

There are certain phenomena that sometimes follow re-
moval of the spleen from the lower animals, which are
curious and interesting, even if they do not afford much
positive information. Extirpation of this organ is an old
and a very common experiment. In the works of Malpighi,
published in 168T, we find an account of an experiment
on a dog, in which the spleen was destroyed, and tho ope-
ration was followed by no serious results.3 Since then it
has been removed so often, and the experiments have been so
universally negative in their results, that it is hardly neces-
sary to cite authorities on the subject. There are numerous
instances, also, in which it has been in part or entirely
removed from the human subject, which it is unnecessary
to refer to in detail ; but in nearly every case, when there was
no diseased condition to complicate the observation, the result
has been the same as in experiments on the inferior animals.3

One of the phenomena to which we desire to call at-
tention is the modification of the appetite. Great voracity
in animals, after removal of the spleen, was noted by the

1 See page 170.

9 MALPIGHI, De Liene, Opera omnia, Lugd. Batav., 1687, tomus ii., p. 302.

3 In the Union medicate, Paris, 1867, 21me annee, Nos. 141, 142, pp. 340,
373, a case of splenotomy followed by complete recovery is reported by M. Pean.
In succeeding numbers of the same journal, M. Magdelain has collected reports
of nine cases of splenotomy performed on account of wounds of the abdomen,
and six cases in which the spleen had been in part or entirely removed on ac-
count of disease. In all the cases of injury, the patients recovered, presenting
afterward no unusual symptoms ; but of the six cases of disease of the spleen,
four of the patients died (II union medicate, Paris, 1867, Nos. 144, 146, pp. 405,
431). Other cases of removal of the spleen in the human subject are quoted in the
New York Medical Journal, 1868, vol. vii., p. 258, et seg. In HALLER, Elementa
Physiologies, Bernse, 1764, p. 421, is a full historical account of the early ex-
periments on removal of the spleen in the lower animals ; and Prof. Dunglison
(Human Physiology, Philadelphia, 1856, vol. i., p. 583, et seg.) gives an account
of experiments on animals, and cites numerous instances of its removal or ab-
sence in the human subject.

DUCTLESS GLANDS. 347

earlier experimenters, and formed the basis of some of their
extravagant theories. Boerhaave mentions this fact in his
Animal Economy • l and Dumas advances it in support of a
theory that the spleen takes up the superabundant portion
of the gastric fluid.2 Later experimenters have observed
this change in the appetite, and have noted that digestion
and assimilation do not appear to be disturbed, the ani-
mals becoming unusually fat. Prof. Dalton has also ob-
served that the animals, particularly dogs, sometimes present
a remarkable change in their disposition, becoming unnatu-
rally ferocious and aggressive.* We have frequently observed
these phenomena after removal of the spleen ; and in the
following experiment, performed in 1861, they were particu-
larly marked :

The spleen was removed from a young dog weighing
twenty-two pounds, by the ordinary method ; viz., making
an incision into the abdominal cavity in the linea alba,
drawing out the spleen, and exsecting it after tying the
vessels. Before the operation the dog presented nothing
unusual, either in his appetite or disposition. The wound
healed rapidly, and after recovery had taken place, the
animal was fed moderately once a day. It was noticed, how-
ever, that the appetite was excessively voracious ; and the
dog became so irritable and ferocious that it was dangerous
to approach him, and it became necessary to separate him
from the other animals in the laboratory. He would eat
refuse from the dissecting-room, the flesh of dogs, faeces, etc.
On February 11, 1861, about six weeks after the operation,
having been well fed twenty-four hours before, the dog was
brought before the class at the ~New Orleans School of Medi-
cine, and ate a little more than four pounds of beef-heart,
nearly one fifth of his weight. This he digested perfectly
well, and the appetite was the same on the following day.

1 BOERHAAYE, Actio Lienis, (Economia Animalis, London, 1761, p. 80.

8 DUMAS, Principes de physiologic, Paris, 1803, tome iv., p. 611.

8 DALTON, A Treatise on Human Physiology, Philadelphia, 1867, p. 195.

34:8 SECRETION.

This dog had a remarkably sleek and well-nourished appear-
ance.

The above is a striking example of the change in the
appetite and disposition of animals after extirpation of the
spleen ; but these results are by no means invariable. We
have often removed the spleen from dogs, and kept the ani-
mals for months without observing any thing unusual ; and,
on the other hand, we have observed the change in dis-
position and the development of an unnatural appetite, in
animals after removal of one kidney ; these effects were also
very well marked in an animal with biliary fistula, that lived
for thirty-eight days. In the latter instance, the voracity
could be explained by the disturbance in digestion and as-
similation produced by shutting off the bile from the intes-
tine ; but these phenomena occurring after removal of one
kidney, which appeared to have no effect upon the ordinary
functions, are not so readily understood. "We have observed
both increase in the appetite and the development of ex-
traordinary ferocity after extirpation of one kidney almost in-
variably, since our attention has been directed to this point ;
and in those experiments of which records were preserved,
these effects were very marked. In one, a dog lived for
nearly two years with one kidney, and was finally killed.
The appetite was voracious and depraved. He would eat
dogs' flesh greedily. In another, death took place in con-
vulsions, forty-three days after removal of one kidney, the
animal having apparently recovered from the operation.
This dog was very ferocious, had an extraordinary appetite,
and would eat fasces, putrid dogs' flesh, etc., which the other
dogs in the laboratory would not touch. The other dog
entirely recovered from the operation of removing one kid-
ney, and presented the same phenomena.

In view of the above facts, it must be admitted that the
removal of the spleen in the lower animals and the human
subject has thus far demonstrated nothing, except that this
part is not essential to the proper performance of the vital

DUCTLESS GLANDS. 34:9

functions. The voracity which occasionally follows the op-
eration in animals is one of the phenomena, like the increase
in the size of animals after castration, for which physiologists
can offer no satisfactory explanation.

It is evident from the foregoing considerations that, not-
withstanding the great amount of literature on the anatomy
and functions of the spleen, physiologists have no definite
knowledge of any important office performed by this organ.
With this conclusion, we pass to a consideration of the other
ductless glands, the physiology of which is, unfortunately,
even more unsatisfactory.

Suprarenal Capsules.

The theories that have been advanced with regard to the
function of the suprarenal capsules have not, as a rule, been
based upon anatomical investigations, but have taken their
origin from pathological observations and experiments on
living animals. This fact detracts from the physiological
interest attached to the structure of these bodies, and we
shall consequently treat of their anatomy very briefly.

The suprarenal capsules, as their name implies, are situ-
ated above the kidneys. They are small, triangular, flat-
tened bodies, placed behind the peritoneum, and capping the
kidneys at the anterior portion of their superior ends. The
left capsule is a little larger than the right, and is rather
semilunar in ^ form, the right being more nearly triangular.
Their size and weight are very variable in different individ-
uals. Of the different estimates given by anatomists, we
may state, as an average, that each capsule weighs about
one hundred grains. They are about an inch and a half
in length, a little less in width, and a little less than one-
fourth of an inch in thickness.

The weight of the capsules, in proportion to that of the
kidneys, presents great variations at different periods of life ;
and they are so much larger in the foetus than after birth,
that some physiologists, in default of any reasonable theory

350 SECRETION.

of their function in the adult, have assumed that their office
is chiefly important in intra-uterine life. Meckel states that
they are easily distinguished in the foetus of two months ; at
the end of the third month, they are a little larger and heavier
than the kidneys ; they are equal in size to the kidneys (though
a little lighter) at four months ; and, at the beginning of the
sixth month, are to the kidneys as two to five. In the foetus
at term, the proportion is as one to three, and in the adult
as one to twenty-three.1 It was asserted by some of the
older writers, that the capsules are larger in the negro than
in the white races, but Meckel states that although he had
observed this in a negress, he saw nothing of it in dissecting
a negro.2 This observation did not have much significance
at that time ; but since it has been supposed that the supra-
renal capsules have some function in connection with the for-
mation of pigment, authors have quoted it as important.

The color of the capsules is whitish yellow. They are
completely covered by a thin fibrous coat, which penetrates
their interior, in the form of trabeculse. Upon section, they
present a distinct cortical and medullary substance. The
cortex is yellowish, from -£T to -fa of an inch in thickness,
surrounding the capsule entirely, and constituting about
two-thirds of its substance. The medullary substance is
whitish, very vascular, and is remarkably prone to decompo-
sition, so that it is desirable to study the anatomy of these
bodies in specimens that are perfectly fresh.

/Structure of the Suprarenal Capsules. — These bodies
have been closely studied by Frey,3 Ecker,4 Kolliker,5 Har-

1 MECKEL, Manual of General, Descriptive, and Pathological Anatomy, Phila-
delphia, 1832, vol. iii., p. 394.

2 Loc. cit.

3 FREY, Cyclopaedia of Anatomy and Physiology, London, 1849-1852, vol. iv.,
part ii., p. 827, Article, Supra-Renal Capsules.

4 ECKER, Nebennieren, in WAGNER'S Handwdrterbuch der Physiologic, Braun-
schweig, 1853, Bd. iv., S. 128, et seq.

5 KOLLIKER, Manual of Human Microscopic Anatomy, London, 1860, p. 421,
et seq., and Handbuch der Gewebelehre des Menschen, Leipzig, 1867, S. 514, et seq.

DUCTLESS GLANDS. 351

ley,1 and many others. Recently, a very elaborate account
of their minute anatomy has been given by M. Grandry.2
The parts examined by M. Grandry were taken from an
executed criminal, aged nineteen years, before they had un-
dergone any alteration, and were placed immediately in
chromic acid. We do not. propose to discuss fully all the
minute details or the mooted questions in the anatomy of
these parts, for these have very little physiological interest ;
and we refer the reader to the authorities just cited for a
more complete account of their histology. It is sufficient
for us to know that they have no excretory duct, and that
their structure resembles that of the other ductless glands.

Cortical Substance. — The cortical substance is divided
into two layers. The external is pale yellow, and is com-
posed of closed vesicles, rounded or ovoid in form, contain-
ing an albuminoid fluid, cells, nuclei, and fatty globules.
This layer is very thin. The greater part of the cortical
substance is of a reddish-brown color, and is composed of
closed tubes. On making thin sections through the cortical
substance, previously hardened in chromic acid and ren-
dered clear by means of glycerine, numerous rows of cells
are seen, arranged with great regularity, and extending,
apparently, from the investing membrane to the medullary
substance. On studying these sections with a high mag-
nifying power, it is evident that the cells are enclosed in
tubes measuring from 10100 to -3^-5- of an inch in diameter.
Harley is of the opinion that these tubes are not simply
bounded by fibrous processes from the external coat, but
are lined by a structureless membrane.3 This view is
confirmed by the more recent observations of M. Grandry,
made upon perfectly fresh specimens from the human sub-

1 HARLEY, Histology of the Supra-Renal Capsule*. — The Lancet, London, 1858,
vol. L, pp. 551, 576.

4 GRANDRY, Memoire sur la structure de la capsule surrenale de Fhomme et de
qudques animaux. — Journal de Canatomie et de la physiologic, Paris, 1867, tome
iv.j pp. 225, 389.

3 Loc. cit.

352 SECRETION.

ject ; * but it is probably the fact that the rows of cells are
enclosed in tubes through a portion only of the cortical sub-
stance, the membrane being absent in the deeper layers.
The cells are granular, with a distinct nucleus and nucleolus,
and a variable number of oil-globules. They measure from
TTTO *° TTTUTT °f an mcn m diameter. Grandry describes
three kinds of tubes in what he calls the second layer of the
cortical substance ; viz., tubes filled with a strongly-refracting
mass of needle-shaped crystals, like crystals of fat ; tubes
filled with finely-granular, nucleated cells, containing no fat ;
and tubes filled with nucleated cells containing numerous
fatty granulations.8 Between the tubes of the cortical sub-
stance are bands of fibrous tissue, connected with the cover-
ing of the capsule.

Medullary Substance. — The medullary substance is much
paler and more transparent than the cortex. In its centre
are numerous openings, marking the passage of its venous
sinuses. It is penetrated in every direction by excessively
delicate bands of fibrous tissue, which enclose blood-vessels,
nerves, and numerous elongated closed vesicles, containing
cells, nuclei, and granular matter. These vesicles, -fa of an
inch long and about ^-J-^ of an inch broad, have been demon-
strated by Grandry in the ox and in the human subject.
The cells in the human subject are from 17100 to I210o of an
inch in diameter. They are isolated with difficulty, and are
very irregular in their form. The nuclei measure about
•g-gVff- of an inch.3 The medullary substance is peculiarly
rich in vessels and nerves.

1 GRANDRY, op. tit., p. 392. M. Grandry makes three layers in the cortical
substance ; but these he found more distinct in the inferior animals than in
man. The external layer is composed of one, two, or three rows of rounded or
ovoid closed vesicles ; the second layer is formed of tubes ; and the third layer
is composed of elements like those contained in the tubes, but not enclosed
either in tubes or vesicles. This division into three zones had previously been
made by Arnold (Journal of Anatomy and Physiology, London and Cambridge,
1867, vol. i., p. 147; from YIRCHOW'S Archiv, January, 1866).

2 Loc. cit. 3 Op. cit., pp. 232, 398.

DUCTLESS GLANDS. 353

Vessels and Nerves. — The blood-vessels going to the supra-
renal capsules are very numerous, and are derived from the
aorta, the phrenic, the coeliac axis, and the renal artery. Some-
times as many as twenty distinct vessels penetrate the capsule.
In the cortical substance the capillaries are arranged in elon-
gated meshes, anastomosing freely, and surrounding the
tubes, but never penetrating them. In the medullary sub-
stance the meshes are more rounded, and here the vessels
form a very rich capillary plexus. Two large veins pass
out, to empty, on the right side, into the vena cava, and on
the left into the renal vein. Other smaller veins empty into
the cava, the renal, and the phrenic veins.

The nerves are very numerous, and are derived from the
semilunar ganglia, the renal plexus, the pneumogastric, and
the phrenic. Kolliker mentions that he has counted, in the
human subject, thirty-three nervous trunks entering the
right suprarenal capsule.1 According to Grandry, the nerves
pass directly to the medullary substance, but here their mode
of distribution is unknown. In the medullary matter, how-
ever, are two ganglia, characterized by nerve-cells of the or-
dinary form, and situated close to the central vein.3

Nothing whatever is known of the lymphatics of the
suprarenal capsules, and the existence of these vessels, even,
is doubtful.

Chemical Reactions of the Suprarenal Capsules. — A few
years ago M. Yulpian discovered in the medullary portion
of the suprarenal capsules a peculiar substance, soluble in
water and in alcohol, which gave a greenish reaction with
the salts of iron and a peculiar rose-tint on the addition of
iodine. He could not determine the same reaction with ex-
tracts from any other parts.3 Later, in conjunction with M.

1 KOLLIKER, Handbuch der Gewebelehre, Leipzig, 1867, S. 620.

2 Op. cit., p. 400.

* VULPIAN, Note sur quelques reactions propres d la substance des corps surre-
nates. — Comptes rendus, Paris, 1856, tome xliii., p. 663.
23

354: SECRETION.

Cloez, he discovered hippuric and taurocholic acid in the
capsules of some of the herbivora.1 Other researches have
been made into the chemistry of these bodies, but without
results of any great physiological importance.

State of our Knowledge concerning the Functions of tJie
Suprarenal Capsules.

In 1855, the late Dr. Addison, of Guy's Hospital, pub-
lished a remarkable memoir on a peculiar disease which he
had found connected with disorganization of the suprarenal
capsules. This disease, sometimes called Addison's disease,
is characterized by bronzing of the skin, and is accompanied
by serious disorders in nutrition. It was supposed to be in-
variably fatal. The peculiar discoloration of the surface,
attended with disorganization of the suprarenal capsules, led
physiologists to suppose that, perhaps, these bodies had some
function connected with the formation of pigment ; and, fol-
lowing the publication of Dr. Addison's memoir, we find
quite a number of experiments on animals, consisting chiefly
in extirpation of the capsules. Before this time there had
been no reasonable theory, even, of the probable function of
these bodies. As our first ideas of the relations of the supra-
renal capsules to the formation of pigment were derived from
cases of disease, it may not be out of place to consider briefly
whether there be any invariable and positive connection be-
tween structural change in these organs and the affection
known under the name of bronzed skin.

In the memoir by Dr. Addison, are reported eleven cases
of anaemia, accompanied with bronzing of the skin, termi-
nating fatally, and found, after death, to be attended with
extensive disorganization of the suprarenal capsules.2 The

1 CLOEZ ET VULPIAN, Note sur ^existence des acides hippurique et choleique
dans les corps surrenales dcs animaux herbivores. — Comptes rendus, Paris, 1857,
tome xlv., p. 340.

2 ADDISON, On the Constitutional and Local Effects of Disease of the Supra-
Renal Capsules, London, 1855.

DUCTLESS GLANDS. 355

reports of these cases attracted a great deal of attention
among physiologists as well as pathologists. A year later,
Prof. I. E. Taylor, of Bellevue Hospital, reported seven
cases of bronzed skin, in two of which the diagnosis of
disease of the suprarenal capsules was verified by post-
mortem examination.1 Attention now being directed to this
peculiar condition of the system, accompanied with discol-
oration of the skin, numerous cases were reported, from time
to time, but some of them did not fully carry out the views
of Dr. Addison. In 1858, Dr. Harley, in connection with
his elaborate researches into the anatomy and physiology of
the suprarenal capsules, cited several cases of the so-called
Addison's disease, unaccompanied with any disorganization
of the capsules, and also several instances in which the cap-
sules were seriously invaded by disease, without any bronzing
of the skin.2 Perhaps the most extensive collection of cases,
however, taken from a great number of authorities, is given
by Dr. Greenhow, in a recent work on Addison's disease.
Dr. Greenhow is apparently convinced that the connection
between the constitutional symptoms and discoloration of
the skin, described by Addison, and disorganization of the
suprarenal capsules is well established. He reports one
hundred and ninety-six cases ; and, out of these, he selects
one hundred and twenty-eight, as fair representatives of Ad-
dison's disease.3 There are several cases (ten) in which there
was bronzing of the skin, the suprarenal capsules being per-
fectly healthy ; but in only one of these were there any of the

1 TAYLOR, The Sunburnt Appearance of the Skin as an early Diagnostic Symp-
tom of Supra-Renal Capsule Disease. — Reprinted from the New York Journal of
Medicine, 1856.

2 HARLEY, An Experimental Inquiry into tftd Functions of the Supra-Renal
Capsules, and their Supposed Connexion with Bronzed Skin. — British and Foreign
Medico- Chirurgical Review, London, 1858, vol. xxi., pp. 204, 498. Shortly after
these papers appeared, we made an editorial analysis of them, in connection
with the recent observations of MM. Brown-Sequard, Martin-Magron, Gratiolet,
and Philipeaux, in the Buffalo Medical Journal (see vol. xiii., 1858, p. 575, and
vol. xiv., p. 175).

3 GREENHOW, On Addison's Disease, London, 1866, p. 47, et seq.

356 SECRETION.

characteristic constitutional symptoms.1 There are twenty-
two cases cited of cancer of the suprarenal capsules, not one
of which presented the characteristic constitutional symp-
toms, seven only presenting some slight discoloration of the
skin.8

Without discussing this subject more fully, it seems justi-
fiable to adopt the opinion, entertained by many pathologists,
that there is a connection between bronzed skin accompa-
nied with certain grave constitutional symptoms, and disor-
ganization of the suprarenal capsules, which is frequent but
not invariable ; but it is not established that the destruction
of the capsules stands in a causative relation to the discolor-
ation or to the constitutional disturbance. It is more interest-
ing to us, however, to know that the investigations into these
diseased conditions have developed little or nothing of impor-
tance concerning the physiology of the suprarenal capsules.

Extirpation of the Suprarenal Capsules. — There are two
important questions to be settled by the removal of the supra-
renal capsules from living animals. The first is, whether or
not these organs are essential to life ; and the second is, to
determine the consequences of their removal, as exhibited in
modifications of the animal functions. The first experi-
ments on this subject, by Dr. Brown-Sequard, seemed to
show, not only that the suprarenal capsules are essential
to life, but that they have an important function connected
with the development of pigment. These experiments were
in a measure complementary to the pathological observations
by Dr. Addison.

Are the suprarenal capsules essential to life ? This ques-
tion can be answered in a very few words. Dr. Brown-
Sequard,8 in his first experiments, removed one and both

1 Op. tit., p. 49. * Op. tit., p. 50.

3 BROWN-SEQUARD, Recherches experimentales sur la physiologie et la pathologic
des corps sv,rrenales. — Archives generales de medetine, Paris, 1856, 5me s6rie,
tome viii., pp. 385, 572.

DUCTLESS GLANDS. 357

capsules in rabbits, Guinea-pigs, dogs, and cats, and the ani-
mals died in the course of two or three days. He also noted
several peculiar results, as turning, and contraction of the
pupil, when one capsule had been extirpated, and the de-
velopment of peculiar crystals in the blood. M. Gratiolet
repeated these experiments, and ascertained that the left
capsule could be removed with impunity, while extirpation
of the right was always fatal.1 M. Philipeaux added a num-
ber of observations, experimenting chiefly on rats and taking
great care to disturb the adjacent organs as little as possible.
As the result of these experiments, he concluded that the
capsules were not essential to life. Of four rats operated
upon in this way, three died, as Philipeaux supposed, of
cold, the first in nine days, the second in twenty-three days,
and the third in thirty-four days. One was alive and well
when the report was made, although the capsules had been
removed for forty-nine days.3 The views first advanced by
Dr. Brown-Sequard were reiterated by him in a memoir
published in the Journal de la physiologie, in 1858, with the
modification that the capsules might have no important
functions in animals without pigment, as white rabbits and
rats, but that they were indispensable to the life of animals
not albinos.8 These views, however, were further disproved
by Dr. Harley, who made experiments upon a variety of
animals, albinos and colored, with the most satisfactory re-
sults. Two Guinea-pigs were experimented upon by Dr.
Harley, in the following way: In one the abdomen was
opened, and the amount of injury which the parts would
suffer by removal of the suprarenal capsules was inflicted,
the wound was closed, and the capsules allowed to remain ;
and the other, of the same age, sex, and development, was

1 GRATIOLET, Note sur les effete qui suivent Variation dcs capsules surrenales. —
Comptes rendus, Paris, 1856, tome xliii., p. 469.

2 PHILIPEAUX, Note sur ^extirpation des capsules surrenales chez les rats albino*.
— Comptes rendus, Paris, 1856, tome xliii., p. 904.

3 BROWN-SEQUARD, Nouvdles recherches sur ^importance des fonciions des cap?
sules surrenales. — Journal de la physiologic, Paris, 1858, tome i., p. 160, at seq.

358 SECRETION.

deprived of the capsule on the corresponding side. Both
animals died within twenty-four hours. Dr. Harley, among
other experiments, took out both capsules from a piebald rat.
The left was removed six weeks after the right. The ani-
mal entirely recovered and became fat and healthy looking.1

In such a question as this, negative experiments are of
little account ; and the instances in which animals have re-
covered and lived perfectly well after removal of both supra-
renal capsules show conclusively that they are not essential
to life. Death has probably been due, in most of the experi-
ments, to injury of the semilunar ganglia, as suggested by
Dr. Harley, and it is probably on account of the greater in-
jury, from the situation of the capsule, produced by opera-
ting on the right side, that the remoyal of the capsule on that
side is more generally fatal.

It is not necessary to take account, in this connection, of
the contraction of the pupil, " turning " and other symptoms
referable to the nervous system, which have sometimes fol-
lowed these operations. These phenomena are undoubtedly
due to injury of adjacent parts, and not to extirpation of the
capsules. The only remaining question to determine is
whether the capsules have any thing to do with the formation
or change of pigment. Notwithstanding the assertion of
Dr. Brown-Sequard, that flakes of pigment and blood-crys-
tals differing from those found in normal blood are found in
animals deprived of the suprarenal capsules, this view is
adopted by few physiological authorities. Longet cites
the observations of Martin-Magron,3 who examined daily,
with the greatest care, the blood of a cat that lived two
months after extirpation of the capsules, and could never
determine the pigmentary matters described by Brown-

1 HARLEY, An Experimental Inquiry into the Functions of the Supra-Renal
Capsules, and their Supposed Connexion with Bronzed Skin. — British and Foreign
Medico- Chirurgical Review, London, 1858, vol. xxi., p. 204, etseq.

2 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 392. It does not
appear from this quotation that the experiments of Martin-Magron were ever
published elsewhere.

DUCTLESS GLANDS. 359

Sequard. Dr. Harley, also, in one of the experiments
in which the animal died, failed to find pigmentary mat-
ter.1

In view of these facts, and in the absence of comparative
examinations of the blood going to the suprarenal capsules
by the arteries and returned from them by the veins, it is
impossible to assign any definite function to these bodies, and
it is certain that they are not essential to life. Their greater
relative size before birth has led to the supposition that they
might have an important office in intra-uterine life, but this
is a pure hypothesis, based upon no positive knowledge.

Thyroid Gland.

The history of this gland belongs almost exclusively to
descriptive anatomy ; and its only physiological interest is
in the similarity of its structure to that of the other ductless
glands. It has no excretory duct. It is attached to the
lower part of the larynx, following it in its various move-
ments. Its color is brownish-red. The anterior face is con-
vex, and is covered by certain of the muscles of the neck.
The posterior surface is concave, and is applied to the larynx
and trachea. It is formed of two lateral lobes, with a rounded,
thickened base below, and a long, pointed extremity extend-
ing upward, connected by an isthmus. Each of these lobes
is about two inches in length, three-quarters of an inch in
breadth, and about the same in thickness at its thickest por-
tion. The isthmus connects the lower portion of the lateral
lobes. It covers the second and third tracheal rings, and is
about half an inch wide and one-third of an inch thick. From
the left side of the isthmus, and sometimes from the left lobe,
is a portion projecting upward, called the pyramid. The
weight of the thyroid gland, according to Sappey, is from
three hundred and fifty to three hundred and eighty grains.
It is usually stated by anatomical writers that it is relatively

1 Loc. dt.

SECRETION.

larger in the foetus, and in early life, than in the adult ; but
Sappey, from his own researches, is disposed to believe that
its weight, in proportion to the weight of the adjacent organs,
does not vary with age.1 It is a little larger and more promi-
nent in the female than in the male.

Structure of the Thyroid Gland. — The gland is covered
with a thin but resisting coat of ordinary fibrous tissue, which
is loosely connected with the surrounding parts. From the
internal surface of this membrane are numerous fibrous bands,
or trabeculae, giving off, as they pass through the gland, sec-
ondary trabeculse, and then subdividing, until they become
microscopic. By this arrangement, the gland is divided up
into communicating cells, like a sponge. These bands are
mingled with numerous small elastic fibres. Throughout
the substance of the gland, lodged in the meshes of the tra-
beculae, are numerous rounded or ovoid closed vesicles, meas-
uring from ^-J-g- to -g-J-g- of an inch. These are formed of
a structureless membrane, and lined by a single layer of pale,
granular, nucleated cells, from 3^0 to g^ of an inch in
diameter.3 The layer of cells sometimes lines the vesicle
completely, sometimes it is incomplete, and sometimes it is
wanting. The contents of the vesicles are a clear, yellowish,
slightly viscid, albuminoid fluid, with a few granules, pale
cells, and nuclei. Robin has described in these vesicles some
curiously-shaped, translucent, feebly-refracting, colorless
bodies which he lias called sympexions ; but little is known
of their constitution or properties.3 The vesicles are arranged
in little collections or lobes, with the great veins passing be-
tween them.

Vessels and Nerves. — The blood-vessels of the thyroid
gland are very numerous, it being supplied by the superior

1 SAPPEY, Traite d'anatomie descriptive, Paris, 1857, tome iii., p. 447.

2 KOLLIKER, Handbuch der Gewebelehre des Menschen, Leipzig, 1867, S. 481.

8 LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1855, Articles, Sym-
pexion and Thyrco'ide.

DUCTLESS GLANDS. 361

and inferior thyroid arteries, and sometimes a branch of the
innominata. The arteries break up into a close capillary
plexus, surrounding the vesicles with a rich net-work, but
never penetrating their interior. The veins are large, and,
like the hepatic veins, are so closely adherent to the sur-
rounding tissue, that they do not collapse when cut across.
The veins emerging from the gland form a plexus over its
surface and the surface of the trachea, and then go to form
the superior, middle, and inferior thyroid veins. The nerves
are derived from the pneumogastric and the cervical sym-
pathetic ganglia. The lymphatics are numerous, but are
difficult to inject. The exact distribution of the nerves and
the origin of the lymphatics are not well understood.

State of our Knowledge concerning the Functions of the
Thyroid Gland. — It is generally admitted that the thyroid
gland may be removed from animals without interfering
with any of the vital functions ; and this, taken in connec-
tion with the fact that it is so often diseased in the human
subject, without producing any general disturbance, shows
that its function cannot be very important. Nothing of im-
portance has been learned from a chemical analysis of its
substance. The blood of the thyroid veins has been analyzed
by Colin and Berthelot, but the changes in its composition
in passing through the gland are slight and indefinite.1 An
instance is quoted by Longet of periodical enlargement of
the gland in a female during menstruation,* but there is no
evidence that this is of constant occurrence.

Thymus Gland.

The anatomy of the thymus assimilates it to the ductless
glands, but its function, whatever it may be, is confined to
early life. In the adult the organ is wanting, traces, only,
of fibrous tissue, with a little fat, existing after puberty in

1 COLIN, Traite de physiologic comparee, Paris, 1856, tome ii., p. 479.
8 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 398.

362 8ECKETION.

the situation previously occupied by this gland. As there
never has been a plausible theory, even, of the function of
this organ, the existence of which is confined to the first two
or three years of life, we shall abstain from all discussions
with regard to minute points in its anatomy, and give a sim-
ple sketch of its structure, as compared with the ductless
glands already considered.

The thymus appears about the third month of foetal life,
and gradually increases in size until about the end of the
second year. It then undergoes atrophy, and disappears al-
most entirely at the age of puberty. It is situated partly in
the thorax and partly in the neck. The thoracic portion is
in the anterior mediastinum, resting upon the pericardium,
extending as low as the fourth costal cartilage. The cervical
portion extends upward as far as the lower border of the
thyroid. The whole gland is about two inches in length,
one and a half inches broad at its lower portion, and about
one-quarter of an inch thick. Its color is grayish, with a
slight rosy tint. It is usually in the form of two lateral
lobes, lying in apposition in the median line, though some-
times there exists but a single lobe. It is composed of nu-
merous lobules, held together by fibrous tissue.

The proper coat of the thymus is a delicate fibrous mem-
brane, sending processes into the interior of the organ. Its
fibrous structure, however, is loose, so that the lobules can
be separated with little difficulty. Portions of the gland
may be, as it were, unravelled, by loosening the interstitial
fibrous tissue. In this way it will be found to be composed
of numerous little lobular masses, attached to a continuous
cord. This arrangement is more distinct in the inferior ani-
mals of large size than in man. The lobules are composed
of rounded vesicles, from ten to fifteen in number, and from
T2T ^0 iV °f an mcn in diameter. The walls of these vesicles
are thin, finely granular, and excessively fragile. The vesi-
cles contain a small quantity of an albuminoid fluid, with
cells and free nuclei. The cells are small and transparent,

DUCTLESS GLANDS. 363

and the nuclei, spherical, relatively large, and containing from
one to three nucleoli. The free nuclei are also rounded and
contain several distinct nucleoli. These vesicles are easily
ruptured, when their contents exude in the form of an opa-
lescent fluid, sometimes called the thymic juice.

Anatomists are somewhat divided in their opinions with
regard to the structure of the central cord and lobules. Some
adopt the view advanced by Sir Astley Cooper,1 that the cord
has a central canal, connected with cavities in the lobules ; 8
while others believe that the cavities thus described are pro-
duced artificially, by the processes employed in anatomical
investigation.3 The latter opinion is the latest, and is prob-
ably correct.

The blood-vessels of the thymus are numerous, but their
calibre is small, and the gland is not very vascular. They
are derived chiefly from the internal mammary artery, a few
coming from the inferior thyroid, the superior diaphragmatic,
or the pericardial. They pass between the lobules, surround
and penetrate the vesicles, and form a capillary plexus in
their interior. The vesicles, in this respect, bear a certain
resemblance to the closed follicles of the intestine. The veins
are also numerous, but they do not follow the course of the
arteries. The principal vein emerges at about the centre of
the gland, posteriorly, and empties into the left brachio-
cephalic. Other small veins empty into the internal mam-
mary, the superior diaphragmatic, and the pericardial. A
few nervous filaments from the sympathetic system surround
the principal thymic artery, and penetrate the gland. Their
ultimate distribution is uncertain. The lymphatics are very
numerous.4

Inasmuch as the thymus is peculiar to early life, one of

1 COOPER, Anatomy of the T/iymus Gland, London, 1832, p. 26, et seq.

8 Cyclopaedia of Anatomy and Physiology, London, 1849-1852, vol. iv., Part
ii., p. 1087, Article, Thymus.

* SAPPEY, Traite tfanatomie descriptive, Paris, 1857, tome iii., p. 456, and
LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1865, Article, Thymus.

4 KOLLIKER, ffandbuch der Gewebelehre des Menschen, Leipzig, 1867, S. 485.

364: SECRETION.

the most interesting points in its anatomical history relates
to its mode of development. This, however, does not pre-
sent any great physiological importance, and is fully treated
of in works upon anatomy.1

Pituitary Body and Pineal Gland.

These little bodies, situated at the base of the brain, are
quite vascular, contain closed vesicles and but few nervous
elements, and are sometimes classed with the ductless glands.
Physiologists have no idea of their function.

The pituitary body is of an ovoid form, a reddish-gray
color, weighs from five to ten grains, and is situated in the
sella turcica of the sphenoid bone. It is said to be larger in
the foetus than in the adult, and at that time has a cavity
communicating with the third ventricle.8 Ecker describes it
as containing the elements of a blood-gland.3 This little body
has lately been studied by M. Gran dry, in connection with
the suprarenal capsules. He regards it as essentially com-
posed of closed vesicles, with fibres of connective tissue and
blood-vessels. The vesicles measure from -g^-g- to y^-g- of an
inch in diameter. They are formed of a transparent mem-
brane, containing irregularly polygonal, nucleated cells, and
free nuclei. The cells are from ^^ to yyVg- of an inch in
diameter. The nuclei are distinct, with a well-marked nu-
cleolus, and measure about -g-jnnj- of an inch. Capillary ves-
sels surround these vesicles, without penetrating them. M.
Grandry did not observe either nerve-cells or fibres between
the vesicles.4 In old subjects he found the peculiar concre-

1 For the history of the development of the thymus, the reader is referred
to special treatises. A very full account of its development is given by Dr.
Handfield Jones, in the Cyclopaedia of Anatomy and Physiology, London, 1849-
1852, vol. iv., Part ii., p. 1087, et seq.

2 GRAY, Anatomy, Descriptive and Surgical, Philadelphia, 1862, p. 519.

3 ECKER, in WAGNER, Handworterbuch der Physiologic, Braunschweig, 1853,
Bd. iv., S. 161.

4 GRANDRY, Glande pituitaire. — Journal de V anatomic, Paris, 1867, tome iv.,
p. 400, et seq.

DUCTLES8 GLANDS. 365

tions (sympexions) already described as existing in the thy-
roid.1

The pineal gland is situated just behind the posterior
commissure of the brain, between the nates, and is enclosed
in the velum interposition. It is of a conical shape, one-
third of an inch in length, and of nearly the color of the
pituitary body. It is connected with the base of the brain
by several delicate commissural peduncles. It presents a
small cavity at its base, and frequently contains in its sub-
stance little calcareous masses, composed of phosphate and
carbonate of lime, phosphate of magnesia and ammonia, and
a small quantity of organic matter.a It is covered with a
fibrous envelope, which sends processes into its interior. As
the result of the researches of M. Grandry, it has been found
to present a cortical substance, entirely analogous in its
structure to the pituitary body, and a central portion, com-
posed of the ordinary nervous elements found in the gray
matter of the brain. Its structure is regarded by Grandry
as very like that of the medullary portion of the suprarenal
capsules.3

It is difficult to classify organs, of the function of which
we are entirely ignorant; but the structure of the little
bodies just described certainly resembles that of the duct-
less glands. We have only indicated their anatomy to show
that their function is probably analogous to that of the other
organs of the same class.

1 See page 360. 8 GRAY, op. rit., p. 528.

3 GRANDRY, Glande pineale. — Journal de fanatomie, Paris, 1867, tome iv., p.
405, et seq.

CHAPTEK XII.

NUTRITION.

Nature of the forces involved in nutrition — Protoplasm — Definition of vital
properties — Life, as represented in development and nutrition — Principles
which pass through the organism — Principles consumed in the organism —
Nitrogenized principles — Development of power and endurance by exercise
(Training) — Non-nitrogenized principles — Formation and deposition of fat
— Conditions under which fat exists in the organism — Physiological anatomy
of adipose tissue — Conditions which influence nutrition — Products of dis-
assimilation.

NUTRITION proper, in the light in which we propose to
consider it in this chapter, is the process by which the phys-
iological decay of the tissues and fluids of the body is com-
pensated by the appropriation of new matter. All of the
physiological processes that we have thus far studied, in-
cluding circulation, respiration, alimentation, digestion, ab-
sorption, and secretion, are to be viewed in the light of
means directed to a single end ; and the great function, to
which all the others are subservient, is the general process
of nutrition.

The nature of the main forces involved in nutrition, be
it in a highly-organized part, like the brain or muscles, or a
tissue called extra-vascular, like the cartilages or nails, is
unknown. The phenomena attending the general process,
however, have been studied most carefully, and certain im-
portant positive results have been attained ; but we find no
more satisfactory explanation of the nature of the causative
force of nutrition in the doctrines of to-day than in the
speculative theories of Pythagoras.

GENERAL CONSIDERATIONS. 367

We can hardly realize the vast extent of the problem of
nutrition from a review of the functions which we have al-
ready considered. We have seen that the blood contains all
the elements that enter into the composition of the tissues and
secretions, either identical with them in form and composition,
as is the case with the inorganic principles, or in a condition
which allows of their transformation into the characteristic
principles of the tissues, as we see in the organic substances
proper. These materials are supplied to the tissues, in the
required quantity, through the circulatory apparatus; and
the oxygen, which is immediately indispensable to all the
operations of life, is introduced by respiration. The great
nutritive fluid, being constantly drawn upon by the tissues
for materials for their regeneration, is kept at the proper
standard by the introduction of new matter into the system,
in alimentation, its elaborate preparation by digestion, and
its appropriation by the fluids by absorption. These pro-
cesses, many of them, require the action of certain secre-
tions. The introduction of new matter, so essential to the
continuance of the phenomena of life, is demanded, on ac-
count of the change of the substance of the tissues into what
we call effete matter ; and this is discharged from the animal
organism, to be appropriated by vegetables, and thus main-
tain the equilibrium between these two great kingdoms in
Nature.

What is it that causes the parts of a living animal organ-
ism to undergo change into effete matter, incapable of any
further animal functions ; and what is it that gives to these
parts the power of self-regeneration, when new matter is
presented under proper conditions ?

These questions are the physiological ignis fatuus, which,
it is to be feared, will forever elude the grasp of scientific in-
quiry. They constitute one of the great mysteries ever pres-
ent in the minds of the student of Nature, and one, the gran-
deur of which is so immense that it is a problem with which
our intelligence can scarcely grapple. Its greatness is com-

368 NUTRITION.

mensurate with that of the question of the soul, and its rela-
tions to the finite and the infinite ; a question which philoso-
phers have been constrained either to admit upon the faith
of revelation, or to hopelessly abandon. Little, if any, real
progress is to be made by endeavoring to cover the inscruta-
ble problem of life with a simplicity entirely artificial. This
will always be attractive, and, to a certain extent, satisfac-
tory to the minds of those unacquainted with the details of
natural laws, or willing to admit speculative theories upon
subjects concerning which it is impossible, in the present
condition of science, to have any positive information ; and,
if generally admitted by biological students, would carry
our science back to the dark periods in its history, when the
study of Nature was confined to speculation, and there ex-
isted no knowledge based upon the direct observation of
phenomena. A new name, arbitrarily applied to organic
matter, without any addition to its physiological history,
does not advance our definite knowledge. For example, it
has long been known that certain nitrogenized constituents
of the organism, classed collectively as organic principles,
seem to give to the tissues their property of self-regeneration
and development. It may seem to those not engaged in
scientific inquiry that a recital of the wonderful properties
of " protoplasm " affords some additional information con-
cerning the phenomena observed in organized bodies ; but
the true definition of the term leads us back to our former
ideas of the so-called vital properties of organic matters.1

It is a well-established fact that while nearly all of the
tissues undergo disassimilation, or conversion into effete
matter, during their physiological decay in the living organ-
ism, others, like the epidermis and its appendages, are

1 HUXLEY, The Physical Basis of Life, New Haven, 1869,— from the Fort-
nightly Review, for February, 1869. This very interesting and able discourse,
delivered originally before a popular audience, is referred to, not as a subject
for rigid scientific criticism, but as formularizing some of the prevalent ideas
concerning the properties of the so-called protoplasm.

GENERAL CONSIDERATIONS. 369

gradually desquamated, and, when once formed, do not pass
through any further changes. An attempt has been made
by Dr. Beale to distinguish in all the tissues a matter en-
dowed with the so-called vital properties, which he calls ger-
minal matter, and a "formed material," which is passive and
cannot become the seat of vital actions.1 Under this idea,
the functions of nutrition and development are performed ex-
clusively by germinal matter. This theory has been adopted
by few physiologists ; and we cannot but regard such a divi-
sion as purely anatomical and artificial, as far as the
physiology of nutrition is concerned. It is hardly more
than a new statement of the old idea of the activity of the
nucleus in the process of cell-development. TVe are not
called upon to enter into an extended discussion of this ques-
tion, until some facts are brought forward which would
render such an hypothesis probable.

The whole question of the essence and nature of the
nutritive property or force resolves itself into vitality. Life
is always attended with what we know as the phenomena of
nutrition, and nutrition does not exist except in living organ-
isms. When we can state positively what is life, we will
know something of nutrition. At present, physiologists
have only been able to define life by a recital of certain of
its invariable and characteristic attendant conditions ; and
yet there are few, if any, definitions of life — regarding it as
the sum of the phenomena peculiar to living organisms — that
are not open to grave objections.

If we regard life as a principle, it stands in the relation
of a cause to the vital phenomena ; if we regard it as the
totality of these phenomena, it is an effect.

If we study the development of a fecundated ovum, life
seems to be a principle, giving the wonderful property
of appropriating matter from without, until the germ be-
comes changed, from a globule of microscopic size and an

1 TODD, BOWMAN, AND BEALE, The Physiological Anatomy and Physiology of
Man, London, 1866, p. 87.
24

370 NUTRITION.

apparently simple structure, into a complete organism, with
highly-elaborated parts. This organism has a definite form
and size, a definite period of existence, and produces, at a
certain time, generative elements, capable of perpetuating
its life in new beings. We may say that an organism
dies physiologically because the vital principle, if we ad-
mit the existence of a principle, has a limited term of
existence. But, on the other hand, the fully-developed
living organism, which we call an animal, presents numerous
distinct parts, each endowed with an independent property
called vital, that property recognized by Haller in various
tissues, under the name of irritability ; and it is the coor-
dinated sum of these vitalities that constitutes the perfect
being. These are more or less distinct ; and we do not com-
monly observe a sudden and simultaneous arrest of the vital
properties in all the tissues, in what we call death. For
example, the nerves may die before the muscles, or the mus-
cles, before the nerves. It is also found that vital properties,
apparently lost or destroyed, may be made to return ; as in
resuscitation after asphyxia, or the restoration of muscular or
nervous irritability by injection of blood.

The life of a fecundated ovum is the property which
enables it to undergo a certain development when placed
under favorable conditions ; and, by the surrounding condi-
tions, its development may be arrested, suspended, or modi-
fied. The life of a non-fecundated ovum is like that of any
ordinary anatomical element.

The life of an anatomical element or tissue in process of
development is the property by virtue of which it arrives at its
perfection of organization, and performs certain defined func-
tions, as far as its organization will permit. This can also be
destroyed, suspended, or modified by surrounding conditions.

The life of a perfect anatomical element or tissue is the
property which enables it to regenerate itself and perform its
functions, subject, also, to modifications from surrounding
conditions.

PRINCIPLES WHICH PASS THROUGH THE ORGAXISM. 371

The life of a perfect animal organism is the sum of the
vitalities of its constituent parts ; but a being may live with
the vitality of certain parts abolished or seriously modified,
as a man exists and preserves his identity with a limb am-
putated. Life may continue for a long time without
consciousness, or with organs paralyzed or their function
destroyed ; but certain functions, such as respiration or cir-
culation, are indispensable to the nutrition of all parts, and
the vitality of the different tissues is speedily lost when
these processes are arrested, and the being then ceases to
exist.

These considerations make it evident that it is difficult,
if not impossible, to give a single comprehensive definition
of life, a study of the varied phenomena of which con-
stitutes the science of physiology.

The general process of nutrition begins with the intro-
duction of matter from without, called food. It is carried
on by the appropriation of this matter by the organism.
It is attended with the production of excrementitious prin-
ciples, and the development of certain phenomena that we
have not yet studied, the most important of which is the
production of heat. We shall have little to say about food,
beyond what we have already considered under the head of
alimentation, except to classify the alimentary principles
with reference to their relations to the general process of
nutrition.

Principles which pass through the Organism.

All of the inorganic principles taken in with the food
pass out of the organism, generally in the form in which
they enter, in the faeces, urine, and perspiration ; but it must
not be inferred from this fact that they are not useful as con-
stituent parts of the body. Some of these principles, such
as water and the chlorides, have very important functions
of a purely physical nature. It is necessary, for example,
that the blood should contain a certain proportion of the

372 NUTRITION.

chloride of sodium, this substance modifying and regulating
the processes of absorption and probably of assimilation.
In addition, however, we find the chlorides as constituent
parts of every tissue and organ of the body, and so closely
united with the nitrogenized principles, that they cannot be
completely separated without incineration. Those inorganic
matters, the function of which is so marked in their passage
through the body, are found largely as constituents of the
fluids, and are less abundant in the solids. They are con-
tained in quantity, also, in the liquid excretions ; and any
excess over the amount actually required by the system is
thrown off in this way. Other inorganic matters are espe-
cially important as constituent parts of the tissues, and are
more abundant in the solids than in the fluids. Examples
of principles of this class are the salts of lime, particularly
the phosphates. These are also in a condition of intimate
union with organic matter, and accompany these principles
in all of their so-called vital acts.

If we except certain simple chemical changes, such as the
decomposition of the bicarbonates, the inprganic elements of
food do not necessarily undergo any modification in the pro-
cess of digestion. They are generally introduced already in
combination with organic matter, and accompany it in the
changes which it passes through in digestion, assimilation
by the blood, deposition in the tissues, and the final trans-
formations that result in the various excrementitious mat-
ters ; so that we find the inorganic principles united with the
organic matter of the food as it enters the body, and what
seem to be the same principles in connection with the or-
ganic excrementitious matters; but between these two
extremes, are the various operations of assimilation and dis-
assimilation, from which inorganic matter is never absent.
We have already referred to these facts so often, under the
heads of proximate principles, alimentation, digestion, and
excretion, that it is unnecessary, in this connection, to dis-
cuss them more fully.

NTTKOGENIZED PRINCIPLES. 373

Various combinations of bases with organic acids taken
as food, as the acetates, tartrates, etc., found in fruits,
undergo decomposition in the body, and are transformed
into carbonates. In this form they behave precisely like the
other inorganic salts.1

Principles consumed by the Organism.

All of the assimilable organic matter taken as food is con-
sumed in the organism ; and none is ever discharged from the
body, in health, in the form under which it was introduced.
The principles thus consumed in nutrition have been di-
vided into nitrogenized and non-nitrogenized ; and, although
they both disappear in the organism, they possess certain
marked differences in their properties, and probably, also, in
their relations to nutrition.

Nitrogenized Principles. — The nitrogenized principles,
having for their basis, carbon, hydrogen, nitrogen, and oxy-
gen, undergo, in the process of digestion and absorption,
remarkable changes ; but these are more marked with rela-
tion to their properties than their ultimate chemical com-
position. They are all converted into the nitrogenized
elements of the blood, which, in their turn, are transformed
into the characteristic nitrogenized principles of the different
tissues, and are appropriated by these tissues, to supply the
place of worn-out matter. With the intimate nature of this
series of transformations, we are entirely unacquainted ; but
we know that the deposition of new nitrogenized matter in
the tissues, constituting one of the most important of the

1 It is a fact well established that the ingestion of certain salts of vegetable
origin produces alkaline carbonates of the same bases, which are discharged in
the excretions. The replacement of the vegetable acid in this way by carbonic
acid, which is weaker, is supposed by Milne-Edwards to be due to the action of
the oxygen in the process of respiration. This explanation is not very satis-
factory, but the fact of the production of the alkaline carbonates from the
vegetable acid salts cannot be doubted ( MILNE-EDTTARDS, Lemons sur la physio-
logic, Paris, 1862, tome vii., p. 531).

374 NUTRITION.

acts of nutrition, is attended with a corresponding loss of
matter that has become changed into the nitrogenized ele-
ments of excretion. It is the intermediate series of phe-
nomena that is so obscure.

The nutrition of the nitrogenized elements of the tissues
may be greatly modified by the supply of new matter. For
example, a diet composed of nitrogenized matter in a readily
assimilable form will undoubtedly affect favorably the devel-
opment of the corresponding tissues of the body ; and, on the
other hand, a deficiency in the supply will produce a corre-
sponding diminution in power and development. The modi-
fications in nutrition due to supply have, however, certain
well-defined limits. An excess taken as food is not discharged
in the faeces, nor does it pass out in the form in which it
entered in the urine ; but it apparently undergoes digestion,
becomes absorbed by the blood, and increases the quantity
of nitrogenized excrementitious matter discharged, particu-
larly the urea. This fact is shown by the great increase in
the elimination of urea produced by an excess of nitrogen-
ized food.1 Whether the nitrogenized matter that is not
actually needed in nutrition be changed into urea in the
blood, or whether it be appropriated by the tissues, increas-
ing the activity of their disassitnilation, is a question difficult
to determine experimentally. Certain it is, however, that
an excess of nitrogenized food is thrown off in nearly the
same way as an excess of inorganic matter ; the difference
being that the latter passes out in the form in which it has
entered, and the former is discharged in the form of nitro-
genized excrementitious matter.

Development of Power and Endurance ly Exercise and
Diet (Training). — The nutrition of the nitrogenized ele-
ments of the body is greatly influenced by functional
exercise. This is partly local and partly general in its
effects. For example, by the persistent exercise of particu-

1 See page 225.

NITEOGENIZED PRINCIPLES. 375

lar muscles, their development can be carried to a high
degree of perfection, the rest of the muscular system under-
going no change ; or the entire muscular system may, by
appropriate general exercise, be made to increase consider-
ably in volume, and a person may become capable of great
endurance, under an ordinary diet. It is surprising, some-
times, to see how small an amount of well-regulated exercise
will accomplish this end. But if it be desired to attain the
maximum of strength and endurance, it is necessary to
carefully regulate the diet as well as the exercise. Those
who are in the habit of " training " men, particularly for
pugilistic encounters, have long since demonstrated prac-
tically certain facts which physiologists have been rather
slow to appreciate. By carefully regulating the diet, con-
fining it chiefly to nitrogenized articles, eliminating fat
entirely, and reducing the starchy elements to the minimum ;
by regulating the exercise so as to increase the nutritive
activity of all the muscles to the greatest possible extent ;
by increasing the respiratory activity by running, etc., and
removing from the body all the unnecessary adipose tissue ;
by all these means, which favor nutritive assimilation by
the nitrogenized elements of the organism, a man may be
u trained " so as to be capable of immense muscular effort
and endurance.

The process of training, skilfully carried out, is in
accordance with what are now admitted as physiological
laws ; though it has been practised for years by igno-
rant persons, and its rules are entirely empirical. It is
stated that the athletes of ancient times, while vigorously
exercising the muscles, favored by their diet the development
of fat, so as to be better able to resist the blows of their an-
tagonists.1 However this may be, since the English prize-ring
has been regularly organized, or since about the middle of the
last century, the system of training has been entirely differ-
ent, and fat has been, as far as possible, removed from every

1 HARRISON, Athletic Training and Health, Oxford and London, 1869, p. 87.

376 NUTRITION.

part of the body. Fat is regarded by trainers as inert mat-
ter ; and they recognize, practically at least, the fact that
the characteristic functions of parts depend for their activity
upon their nitrogenized constituents. The contraction of a
muscle, for example, is powerful in proportion to the amount
and condition of its musculine ; and it has been found, prac-
tically, that the muscular system can be most thoroughly de-
veloped by carefully graduated exercise and a diet composed
largely of nitrogenized matter. In the regular system of
training, starch, sugar, fat, and liquids are avoided ; and
the diet is confined almost entirely to rare meats, eggs, and
stale bread or toast, with oatmeal-gruel. The oatmeal has
been used from time immemorial, and is supposed to be
useful in keeping the bowels in good condition. A very
small amount of alcohol and other nervous stimulants,
chiefly in the form of home-brewed ale, sherry wine, and
tea, are allowed. Sexual intercourse and all unusual ner-
vous excitement are interdicted.

Those who adopt absolutely the classification of food into
plastic, or tissue-forming, and calorific, or respiratory, would
regard this course of diet as eminently plastic ; but during
the severe habitual exercise, which is most rigid after the
man has been " trained down " so that his fat is reduced to
the minimum, the respiratory power and the exhalation of
carbonic acid are immensely increased, while the proportion
of hydro-carbons in the food is very small.

"We do not, of course, propose to discuss from a scientific
point of view all of the minutiae of training. Many of its
traditional rules are trivial and unimportant j l but it is cer-

1 A very curious account of training, the more interesting as it contains the
essentials of the methods employed at the present day, is to be found in a book
on pugilism, called JBoxiana. This work is attributed to the celebrated Captain
Barclay (T/ie Art of Training. — JBoxiana ; or Sketches of Modern Pugilism, con-
taining all the Transactions of note connected with the Prize-Ring, during the
Years 1821, 1822, 1823, London (no date). The subject of training has at-
tracted considerable attention within the last few years in connection with
boating; but the brutal practice of prize-fighting affords, probably, the best
examples of strength, endurance, and nervous energy.

NITBOGKSnZED PRINCIPLES. 377

tainly a question of great physiological interest to study the
processes by which the muscular strength' and endurance
of a man may be brought to the highest point of devel-
opment.

One of the most remarkable of the results of thorough
training is the development of immense endurance and
" wind." This is accomplished by running and prolonged
exercise, not so violent as to be exhausting, and always fol-
lowed by ablutions and frictions, so as to secure a full re-
action. The surprising faculty of endurance thus developed
must be due in a great measure to nervous power as well as
to gradual, careful, and perfectly physiological development
of the muscular system. A man may be brought into the
ring in what would appear to be perfect condition ; but if he
be trained down too much or too rapidly, he is liable to
give out after comparatively slight exertion. A man who
does not possess the required constitutional stamina and ner-
vous power is likely to break down in training, and can-
not be brought to proper condition. On the other hand,
a man in perfect condition is capable of the maximum of
muscular exertion for an hour, or can walk a hundred miles
in a day.

It is a question of great importance, in connection with
the subject of nutrition, to determine whether the extraordi-
nary muscular power developed by severe training be, in the
end, beneficial or deleterious. This can be answered very
easily upon practical as well as theoretical grounds. A fully-
grown, well-developed man, in perfect health, may be trained
so as to be brought to what is technically called fine condi-
tion, and he will present at that time all the animal func-
tions in their perfection. He is then a model of a physical
man ; and the only consequences that can result from such
a course are beneficial. The argument that professional
pugilists are short-lived is fallacious ; for it is well known
that almost all of them, after training for and passing
through an encounter, immediately relapse into a course of

378 NUTRITION.

life, in which all physiological laws are habitually violated.
During training, even of the most severe character, not only is
great attention paid to diet and exercise, but all of the func-
tions are scrupulously watched. Tranquillity of mind, avoid-
ance of exhaustion, of artificial excitement, stimulants, tobac-
co, etc., are strictly enjoined ; and the process is always very
gradual, especially at its commencement, and is continued
for several months. The cases in which training has been
followed by bad effects are entirely different. Undeveloped
boys are frequently trained for boating, in the most reckless
manner, until they break down. An attempt is made to
accomplish in a few weeks what can only be done physio-
logically in several months ; and the result is, that some of
the vital organs, particularly the heart, are liable to become
permanently injured. To improve the " wind " and endur-
ance, a person undergoes the most violent exercise, which is
followed by great exhaustion, intense respiratory distress,
and disturbance of the action of the heart, these vital parts
being suddenly forced far beyond their functional capacity.
This cannot be done without danger of permanent disturb-
ances of the system, such as have been frequently observed ;
and it is all the more liable to be followed by bad results,
from the fact that amateurs are trained together, five or six
under one man, and are more or less independent, while the
professional is never out of the sight of his trainer for months,
and during that time is under complete control. There is,
it seems, every physiological reason to believe that it is bene-
ficial to the general system to bring it to the highest point
of functional activity by training ; but if this be not done
with great caution and judgment, it is liable to be followed
by serious results.

Non-Nitrogenized Principles. — The non-nitrogenized
principles present a marked contrast to the alimentary sub-
stances we have just considered. In the first place, they are
not indispensable to the nutrition of all animals. The car-

NON-XITROGEXIZED PRINCIPLES. 379

nivora, for example, may be well nourished upon a diet com-
posed exclusively of nitrogenized matter ; and the remarks
we have just made upon training show that the human
subject may be brought to a high condition of physical
development, when starch, sugar, and fat are almost en-
tirely eliminated from the food. This shows conclusively
that the division of the food into plastic and calorific ele-
ments is not absolute, and that the animal temperature
may be maintained without the hydro-carbons. The nitro-
genized principles certainly are the only class of alimentary
substances capable of forming muscular tissue ; but, by cer-
tain transformations, with the exact nature of which we are
imperfectly acquainted, this class of substances is capable of
producing heat and of furnishing the carbonic acid elimi-
nated in respiration. The non-nitrogenized principles are
incapable in themselves of meeting the nutritive demands
of the system, and they are either consumed without form-
ing part of the tissues, or are deposited in the form of fat.
These questions we have already considered fully under the
head of alimentation ; and it will be remembered that, with
a few exceptions, fat always exists in the body uncombined,
either in the form of adipose tissue or fatty granulations in
the substance of other tissues.

The non-nitrogenized elements taken up by the blood
may be divided into two varieties : one, the sugars, com-
posed of carbon with hydrogen and oxygen in the propor-
tions to form water, constituting the true hydro-carbons ;
and the other, the fats, in which the hydrogen and oxygen
do not exist in the proportion to form water. "We speak of
the sugars only, because starch and all varieties of sugar
taken as food are transformed into glucose.

In connection with the study of proximate principles, ali-
mentation, and glycogenesis, we have already referred to the
destination of the true hydro-carbons in the organism. They
are taken as food to a considerable extent, particularly in the
form of starch, and are formed constantly by the liver, in all

380 NUTRITION.

classes of animals. Sugar is never discharged from the body
in health,1 nor is it deposited in any part of the organism, even
as a temporary condition. It generally disappears in the pas-
sage of the blood through the lungs. How is sugar destroyed,
and what relation does it bear to nutrition ? In studying the
changes which it is capable of passing through, it has been
found that it may be converted into lactic acid, or be changed
into carbonic acid and water ; but precisely to what extent the
sugars undergo these changes, or how they are acted upon by
the inspired oxygen, it has been impossible thus far to deter-
mine. "We must be content to say that the exact changes
which the sugars undergo in nutrition are unknown. They
seem very important in development, being abundant in the
food and formed largely in the system in early life.2 They
certainly do not enter into the composition of the tissues ;
and it would seem that they must be important in the two
remaining phenomena of nutrition, namely, the formation
of fat and the development of animal heat. The relations
of sugar to these two processes will be taken up under their
appropriate heads.

The fats taken as food are either consumed in the organ-
ism, or are deposited in the form of adipose tissue. That
the fats are consumed, there can be no doubt ; for, in
the normal alimentation of man, fat is a constant article,
and it is never discharged from the body. We are forced
to admit, however, that the changes which fat undergoes in
its process of destruction are not thoroughly understood.
All that we positively know is, that the fatty principles
of the food are formed into a fine emulsion in the small in-
testine, and are taken up, chiefly by the lacteals, and dis-
charged into the venous system. For a time, during ab-

1 We have already noted the exceptional discharge of sugar, fat, and nitro-
genized matter in the milk.

2 We have already noted these facts, as well as the production of glyco-
genic matter and sugar in animals deprived entirely of starch and sugar in their
food, when it seems that the formation must take place from the albuminoid
principles.

NON-NITKOGKSTZED PRINCIPLES. 381

sorption, fat may exist in certain quantity in the blood;
but it soon disappears, and is either destroyed directly in the
circulatory system, or is deposited in the form of adipose
tissue to supply a certain amount of this substance con-
sumed. That it may be destroyed directly is proven by the
consumption of fat in instances where the amount of adipose
matter is insignificant ; and that the adipose tissue of the
organism may be consumed is shown by its rapid disappear-
ance in starvation.

The question of the relations of fat to nutrition is im-
portant, but somewhat obscure. It does not take part in the
nutrition of. the parts that are endowed, to an eminent de-
gree, with the so-called vital functions; and when these
tissues are brought to their highest point of functional de-
velopment, the fat is entirely removed from their substance.
If fat be not a plastic material, it would seem to have no func-
tion remaining but that of keeping up, by its oxidation, the
animal temperature. But it is not proven that fat, or fat and
sugar, are the sole principles concerned in the production of
carbonic acid and the generation of heat ; for both of these
phenomena occur in the carnivora, and in man, when fat and
sugar are eliminated from the food and the fat in the body has
been reduced to the minimum. Fat is undoubtedly destroyed
in the organism, and probably assists in the formation of the
carbonic acid eliminated; it is also taken in much larger
proportion in cold than in temperate or warm, climates;1
but we cannot, with our present information, say without
reserve, that fats and sugar are oxidized directly, by a pro-
cess with which we are familiar under the name of com-
bustion, and that their exclusive function is the production
of animal heat.

It is a curious fact that fat is generally deposited in tissues
during their retrograde processes. The muscular fibres of
the uterus, during the involution of this organ after partu-
rition, become the seat of a deposit of fatty granulations.

1 See vol. ii., Alimentation, p. 128.

382 NUTRITION.

Long disuse of any part will produce such changes in its
power of appropriating nitrogenized matter for its regenera-
tion, that it soon becomes atrophied and altered. Instead
of the normal nitrogenized elements of the tissue, we have,
under these circumstances, a deposition of fatty matter.
The fat is here inert, and takes the place of the substance
that gives to the part its characteristic function. These phe-
nomena are strikingly apparent in muscles that have been
long disused or paralyzed, or in nerves that have lost their
functional activity. If the change be not too extensive, the
fat may be made to disappear, and the part will return to its
normal constitution, by appropriate exercise ; but frequently
the alteration has proceeded so far as to be irremediable and
permanent. This condition is known in pathology under
the name of fatty degeneration — a term which implies that
the nitrogenized elements of the part are changed or degen-
erated into fat, and which is not strictly correct. During the
ordinary process of nutrition, the nitrogenized elements are
removed by disassimilation, and new matter, of the same
kind, is deposited ; but when the so-called fatty degenera-
tion ocures, fat is substituted for the nitrogenized substance.
This change, then, should rather be called fatty substitution.1
Accurate observations have shown that, in young ani-
mals, rapidly fattened, all the adipose matter in the body
cannot be accounted for by what is taken in as food ; and it
is certain that fat may be produced de novo in the organism.

Formation and Deposition of Fat. — The question of the
generation of fat in the economy is one of great importance.
Whatever the exact nature of the changes accompanying
the destruction of non-nitrogenized matter may be, it is
certain that the fat stored up in the body is consumed,
when there is a deficiency in any of the elements of food, as
well as that which is taken into the alimentary canal. It is

1 LITTRK ET ROBIN, Dictionnaire de medecine, Paris, 1865, p. 1444, Article,
Substitution graisseusc.

FORMATION AND DEPOSITION OF FAT. 383

rendered probable, indeed, by the few experiments that have
been made on the subject, that obesity increases the power
of resistance to inanition.1 At all events, in starvation, the
fatty constituents of the body are the first to be consumed,
and they almost entirely disappear before death. As we
have already seen, sugar is never deposited in any part of
the organism, and is only a temporary constituent of the
blood. If the sugars and fats have, in certain regards', simi-
lar functions in nutrition, and if, in addition to the mechani-
cal functions of fat, it may be retained in the organism for
use under extraordinary conditions, it becomes very impor-
tant to ascertain the mechanism of its production and depo-
sition.

The production of fatty matter by certain insects, in ex-
cess of the fat supplied with the food, was established long
ago by the researches of Huber, whose experiments were
fully confirmed by Dumas and Milne-Edwards.3 A little
later, similar observations were made upon birds, by Persoz,8
and upon birds and mammals, by Boussingault.4 Some of
the experiments of Boussingault are peculiarly interesting,
as they were made upon pigs, in which the digestive appa-
ratus closely resembles that of the human subject. They
showed conclusively that, under certain circumstances, more
fat exists in the bodies of animals than can be accounted for
by the total amount of fat taken as food added to the fat ex-
isting at birth. In some very interesting experiments with
relation to the influence of different kinds of food upon the
development of fat, it was ascertained that fat could be pro-
duced in animals upon a regimen, sufficiently nitrogenized,
but deprived of fatty matters ; but the fact should be recog-

1 See vol. ii., Alimentation, p. 26.

8 MILNE-EDWARDS, Lemons sur la physiologic., Paris, 1862, tome vii., p. 653.

3 PERSOZ, Experiences sur Fengrais des oies. — Comptes rendus, Paris, 1844,
tome xviii., p. 245.

4 BOUSSINGAULT, Reckerches experimentales sur le developpement de la. graissi
pendent V alimentation des animaux. — Memoire* de chimie agricole ct de physiologic,
Paris, 1854, p. 105, et seq.

384 NUTRITION.

nized " that the nutriment which produces the most rapid
and pronounced fattening is precisely that which joins to the
proper proportion of albuminoid substances the greatest pro-
portion of fatty principles."

Animals cannot be fattened without a certain variety in
the regimen. We have already discussed the necessity of a
varied diet, and have shown that an animal will die of star-
vation when confined exclusively to one class of principles,
even if this be of the most nutritious character ; a and it is
not necessary to refer again to the experiments which have
demonstrated that a diet confined exclusively to starch,
sugar, or fat, or even pure albumen or fibrin, cannot sus-
tain life, much less fatten an animal. We are prepared,
then, to understand why, in the pigs experimented upon by
Boussingault, a regimen confined to potatoes did not prove
to be fattening, notwithstanding the large proportion of
starch,3 and that fat was produced in abundance only when
the food presented the proper variety of principles.

Yery little is known concerning the precise mechanism
of the production of fat. The experiments of Boussingault
seem to leave no doubt that it may be formed from any kind
of food, even when it is exclusively nitrogenized ; 4 but it is,
nevertheless, a matter of common observation that certain
articles of diet are more favorable to its deposition than
others ; and it is also true that the herbivora are fattened
much more readily, as a rule, than the carnivora.

Theoretical considerations would immediately point to
starch and sugar as the elements of food most easily con-
vertible into fat, as they contain the same elements, though
in different proportions ; and it is more than probable that

1 BOUSSINGAULT, op. cit., p. 16Y.

2 See vol. ii., Alimentation, p. 128.

3 Op. cit., p. 122.

4 The researches of Wurtz have shown that certain of the albuminoid prin-
ciples can be converted into fatty acids by the action of an alkali and heat, and
that this may also occur spontaneously (WURTZ, Sur la transformation de la
fibrine en acide butyrlque. — Comptes rendus, Paris, 1844, tome xviii., p. 704).

FORMATION AND DEPOSITION OF FAT. 385

this view is correct. It is said that in sugar-growing sec-
tions, during the period of grinding the cane, the laborers
become excessively fat, from eating large quantities of the
saccharine matter. We cannot refer to any exact scientific
observations on this point, but the fact is pretty generally
admitted by physiologists. Again, it has been frequently a
matter of individual experience that sugar and starch are
favorable to the deposition of fat, especially when there is a
constitutional tendency to obesity. A most remarkable ex-
ample of this, and one which has met with considerable
notoriety, is worthy of mention, though not reported by a
scientific observer. We refer to the letter on corpulence, by
Mr. Banting.1 The writer of this curious pamphlet, in 1862,
was sixty-six years old, five feet and five inches in height,
an,d weighed two hundred and two pounds. Under the ad-
vice of Mr. William Harvey, F. R. C. S., of London, he con-
fined himself to a diet containing no sugar, and as little
starch and fat as possible. Continuing this regimen for one
year, he gradually lost weight, at the rate of about one
pound each week, until he was reduced to one hundred and
fifty-six pounds. At the time the last edition of the pam-
phlet was published, in 1864, he enjoyed perfect health and
weighed one hundred and fifty pounds, his weight varying
only to the extent of one pound, more or less, in the course
of a month. This little tract is very interesting, both from
the importance of its physiological relations and its quaint
literary style. It has had an immense circulation, and many
persons suffering from excessive adipose development have
adopted the system here advised, with results more or less
favorable. A study of the course of diet here prescribed
shows it be a pretty rigid training system, with the excep-
tion of succulent vegetables and liquids, which are allowed
without restriction. It is proper to remark, however, that
some enthusiastic advocates of the plan have exceeded the
limits prescribed, and neglected the caution of the author

1 BANTING, Letter on Corpulence, London, 1864.
25

386 NUTRITION.

always to employ it under the advice of a physician ; and
its too rigid enforcement has been followed by serious dis-
turbances in general nutrition. Others, however, have veri-
fied the favorable results obtained by Mr. Banting.

It is difficult to explain the remarkable constitutional
tendency to obesity observed in some individuals, which is
very often hereditary. Such persons will become very fat
upon a comparatively low diet, while others deposit but lit-
tle adipose matter, even when the regimen is abundant. It
is to be noted, however, that the former are generally ad-
dicted to the use of starchy, saccharine, and fatty elements
of food, while the latter consume a greater proportion of
nitrogenized matter.

It is not an uncommon remark that the habit of taking
large quantities of liquids favors the formation of fat ; but
it is not easy to find any scientific basis for such an opinion.
As to the formation of fat by any particular organ or organs
in the body, no positive scientific view has been advanced,
except the proposition by Bernard, that the liver had this
function, in addition to its glycogenic office. This we have
already discussed, and have shown that such a function is
far from being positively established.1

Condition under which Fat exists in the Organism. — It
is said that fat combined with phosphorus is united with ni-
trogenized matter in the substance of the nervous tissue ; but
its condition here is not well understood, as we shall see when
we come to treat of the nervous system. A small quantity of
fat is contained in the blood-corpuscles, and a little is held
in solution in the bile ; but with these exceptions, fat always
exists in the body isolated and uncombined with nitrogen-
ized matter, in the form of granules or globules and of adipose
tissue. The three varieties of fat are here combined in
variable proportions, which is the cause of the differences in
its consistence in different situations. The ultimate ele-

1 See page 328.

ANATOMY OF ADIPOSE TISSUE. 387

ments of fat are, carbon, hydrogen, and oxygen, the two
latter in unequal proportions. It has been found very diffi-
cult, however, to obtain either stearin e, margarine, or oleine
in a condition of sufficient purity to ascertain their exact
ultimate composition.1

Physiological Anatomy of Adipose Tissue. — Adipose
tissue is found in abundance in the interstices of the sub-
cutaneous areolar tissue, where it is sometimes known as the
panniculus adiposus. It is not, however, to be confounded
with the so-called cellular or areolar tissue, and is simply
associated with it without being one of its essential parts ;
for the areolar tissue is abundant in certain situations, as the
eyelids and scrotum, where there is no adipose matter, and
adipose tissue exists sometimes, as- in the marrow of the
bones, without any areolar tissue.

Adipose tissue is widely distributed in the body, and has
important mechanical functions.2 Its anatomical element is
a vesicle, from -g-i-g- to -g-fj of an inch in diameter, composed
of a delicate, structureless membrane, 2g^00 of an inch
thick, enclosing fluid contents.3 The form of the vesicles is
naturally rounded or ovoid ; but in microscopical prepara-
tions they are generally compressed so as to become irregu-
larly polyhedrical. The membrane sometimes presents a
small nucleus attached to its inner surface. The contents
are a minute quantity of an albuminoid fluid moistening the
internal surface of the membrane, and a mixture of oleine,
margarine, and stearine, liquid at the temperature of the
body, but becoming harder on cooling.* Little rosettes
formed of acicular crystals of margarine are frequently ob-
served in the fat- vesicles, when the temperature is rather low.

1 ROBIN* ET VERDEIL, Traite de chimie anatomique et phwiologique, Paris, 1853,
tome iii., p. 105.

2 See vol. i., Introduction, p. 65.

3 LITTRE ET ROBIN*, Didionnaire de medecine, Paris, 1865, Article, Adipeiix.

4 TODD AND BOWMAN, Physiological Anatomy and Physiology of Man, Phila-
delphia, 1857, p. 89.

388 NUTRITION.

The adipose vesicles are collected into little lobules, from
-£% to J of an inch in diameter,1 which are surrounded by a
rather wide net-work of capillary blood-vessels. Close ex-
amination of these vessels shows that they frequently sur-
round individual fat-cells, in the form of single loops.
There is no distribution of nerves or lymphatics to the ele-
ments of adipose tissue.

It is seen by this sketch of the structure of adipose tis-
sue, that there is no anatomical reason for classing these
vesicles with the ductless glands, as is done by some physi-
ologists. They undoubtedly, under certain conditions, have
the power of filling themselves with fat ; but it would be
no more appropriate to call this a secretion than to apply this
term to the development and nutrition of the muscular sub-
stance within the sarcolemma.

Conditions which influence Nutrition. — We know more
concerning the conditions that influence the general pro-
cess of nutrition than about the nature of -the process itself.
It will be seen, for example, when we come to study the ner-
vous system, that there are nerves which regulate, to a
certain extent, the nutritive forces. We do not mean to
imply that nutrition is effected through the influence of the
nerves, but it is the fact that certain nerves, by regulating
the supply of blood, and perhaps by other influences, are
capable of modifying the nutrition of parts to a very consid-
erable extent.

In discussing the influence of exercise upon the develop-
ment of parts, we have shown that this is not only desirable
but indispensable ; and the proper performance of the func-
tions of all parts involves the action of the nervous system.
It is true that the separate parts of the organism and the
organism as a whole have a limited existence ; but it is not
true that the change of nitrogenized, living substance into
effete matter, a process that is increased in activity by phys-

1 LITTRE ET ROBIN, loc. cit.

CONDITIONS WHICH INFLUENCE NUTK1T1ON. 389

iological exercise, consumes, so to speak, a definite amount
of the limited life of the part. Physiological exercise
increases disassimilation, but it also increases the activity of
nutrition and favors development. It is a favorite sophism
to assert that bodily or mental effort is made always at the
expense of a definite amount of vitality and matter consumed.
This is partly true, but mainly false. Work involves change
into effete matter ; but when restricted within physiological
limits, it engenders a corresponding activity of nutrition,
assuming, of course, that the supply from without be suffi-
cient, Other things being equal, a man will live longer
under a system of physiological exercise of every part, than
if he made the least effort possible. It is, indeed, only by
such use of parts that they can undergo proper development
and become the seat of normal nutrition. But notwith-
standing all these facts, life is self-limited. Unless subjected
to some process which arrests all changes, such as cold, the
action of preservative fluids, etc., organic substances are con-
stantly undergoing transformation. In the living body, their
disassimilation and nutrition are unceasing ; and after they
are removed from the influence of what is called life, they
change, first losing irritability, or becoming incapable of
performing their functions, and afterward decomposing into
matters which, like the results of their disassimilation, are
destined to be appropriated by the vegetable kingdom.
Nutrition sufficient to supply the physiological decay of
parts cannot continue indefinitely. The wonderful forces
in the fecundated ovum lead it through a process of develop-
ment that requires, in the human subject, more than twenty
years for its completion ; and when development ceases, no
one can say why it becomes arrested, nor can we give any
sufficient reason why, with a sufficient and appropriate sup-
ply of material, a man should not grow indefinitely. After
the being is fully developed, and during what is known as
the adult period, the supply seems to be about equal to the
waste. But after this, nutrition gradually becomes deficient,

390 NUTRITION.

and the deposition of new matter in progressive old age is
more and more inadequate to supply the place of the living
nitrogenized substance. We may at this time, as an excep-
tion, have a considerable deposition of fat, but the nitrogen-
ized matter is always deficient, and the proportion of inert
inorganic matter combined with it is increased.

There can be little if any doubt that the forces which
induce the regeneration or nutrition of parts reside in the
organic nitrogenized substance, and that they give to the
parts their characteristic functions, which we call vital ; the
inorganic matter being passive, or having, at the most,
purely physical functions. If, therefore, as age advances,
the organic matter be gradually losing the power of com-
pletely regenerating its substance, and if its proportion
be progressively diminishing, while the inorganic matter is
increasing in quantity, a time will come when some of the
organs necessary to life will be unable to perform their
office. When this occurs we have death from old age, or
physiological dissolution. This may be a gradual failure of
the general process of nutrition, or it may attack some one
organ or system. Why death is thus certain to occur, we do
not know, any more than we can explain why and how
animals live.

The modifications in nutrition due to the very varied in-
fluences that may be brought to bear upon it present a most
extended subject for discussion ; but we shall not touch upon
any of these influences that are not purely physiological.
Among the most interesting of these modifications, are those
due to age, constituting, as they do, in early life, the process
of development. They will be treated of fully in connection
with the subject of generation. It is evident, also, from
what we have already said, that each tissue and organ has
its own conditions of nutrition and development ; and this
constitutes another interesting division of the subject, the
more so, because the nutrition and development of the indi-
vidual tissues are closely connected with the processes of

PRODUCTS OF DISASSIMILATTON. 391

regeneration and repair after injury. We have stated, as
far as possible, all that is positively known of the nutrition
of the fully-formed tissues of the body ; but their develop-
ment belongs to embryology. If we were to attempt to
follow the processes of regeneration after injury in nerves,
muscles, bone, etc., we would be compelled to pass almost
immediately into the domain of pathology. The influences
of climate, respiratory activity, food, etc., have already been
considered under the heads of respiration, alimentation, and
excretion, and will be touched upon again in connection
with animal heat.

Products of Disassimilation. — It only remains now to
recapitulate briefly the mode of production of the excretions.
The process of disassimilation, we are aware, always accom-
panies nutrition, and the substances thus formed are the
result of the final changes of the organic constituents of the
tissues. As we have seen in studying the urine, the excre-
mentitious principles proper are always associated with in-
organic matter, which has passed through the organism ;
and while there are many effete substances that we have
been able to recognize, there are probably others which have
thus far escaped observation. It is almost futile to specu-
late upon the probable bearing which the discovery of new
excrementitious principles will have upon pathological con-
ditions, while there are so many, which we now know only
by name, their relations to the different tissues being still
obscure ; but if we reason from the light thrown upon cer-
tain diseased conditions by the fact that urea, the urates, and
cholesterine are liable to be retained in the blood and produce
certain symptoms, we may safely infer that the description of
new effete principles will have an important influence upon
our pathological knowledge as well as our comprehension of
physiological processes. The following are the most impor-
tant excrementitious matters, the relations of which to nutri-
tion and disassimilation are more or less fully understood :

392 NUTRITION.

Products of Disassimilation.

Name of principle. How excreted.

f Principally by the

lungs ; but also

Carbonic acid (C02) ................................ •< by the skin, and

in solution in the
[ excreted fluids.
Alkaline sudorates (Sudoric acid, CioH8Oi3N) ........... Perspiration.

f Principally in the

urea(c2H4N2o2).. .

tain quantity in
I the perspiration.
Urate of soda (Uric acid, C6HIST202+HO) ................. Urine.

Urate of ammonia

Urate of potassa

Urate of lime

Urate of magnesia

Hippurate of soda (Hippuric acid, Ci8H8N06)

Hippurate of potassa

Hippurate of lime

Creatine (C8H904N3+ 2HO) ............................ "

Creatinine (C8H702N3) ................................. "

Oxalate of lime (CaO,C203+2HO) ....................... "

Xanthine (C10H6N404) ................................. "

Stercorine (changed from Cholesterine, C25II220, of bile). . . Faeces.
Excretine (C78H7802S) ................................. "

In the above list we have omitted all doubtful excremen-
titious principles, as well as the inorganic compounds found
in the excreted fluids ; and we can safely assume that the
substances therein enumerated represent, as far as we are
now able to determine, the physiological wear of the organ-
ism. We shall not again discuss the fact that the life of
tissues involves physiological waste or decay, and that the
excrementitious principles proper represent the final changes
of the organic substance. We know that this process goes
on without necessarily involving exercise of the peculiar
functions of the parts ; but it is no less true that exercise,
or work, increases the activity both of nutrition and wear.
This is one of the great principles underlying all our ideas

PRODUCTS OF DISASSIMILATION. 393

of the process of nutrition. We shall not discuss here the
influence of work upon the elimination of some of the nitro-
genized compounds, particularly urea, for we have already
examined that subject most carefully in another place ; x but
we have no hesitation in stating, as a general law, that has
yet to find its exceptions, that physiological work increases
excretion.

1 See page 226.

CHAPTER XIII.

ANIMAL HEAT.

General considerations — Limits of variation in the normal temperature in man
— Variations with external temperature — Variations in different parts of
the body — Variations at different periods of life — Diurnal variations — Rela-
tions of animal heat to digestion — Influence of defective nutrition and in-
anition— Influence of exercise, mental exertion, and the nervous system,
upon the heat of the body.

THE process of nutrition in animals is always attended
with the development of heat, and produces a temperature
more or less independent of external conditions. This is true
in the lowest as well as the highest animal organizations ;
and analogous phenomena have even been observed in plants.
In cold-blooded animals, nutrition may be suspended by a
diminished external temperature, and certain of the functions
become temporarily arrested, to be resumed when the animal
is exposed to a greater heat. This is true, to some extent,
in certain warm-blooded animals that periodically pass into
a condition of stupor, called hibernation ; but in man, and
nearly all the warm-blooded animals, the general tempera-
ture of the body can undergo but slight variations. The
animal heat is essentially the same in the intense cold of the
frigid zones and under the burning sun of the tropics ; and
if, from any cause, the body become incapable of keeping up
its temperature when exposed to cold, or moderating it when
exposed to heat, death is the invariable result.

The production of animal heat is so closely connected
with nutrition, that in serious pathological modifications of

ANIMAL HEAT. 395

this process, as in the essential fevers or extensive inflamma-
tions, the temperature of the body becomes an important
guide, particularly in prognosis. The clinical value of a
recognition of the temperature in disease has only been fully
appreciated within a few years, especially since the very
elaborate observations of Wunderlich, and other German
observers.1

The study of the temperature in different classes of ani-
mals presents very great interest, but the limits of a work
on pure human physiology restrict us to the phenomena as
observed in man, and in animals in which the processes of
nutrition are similar, if not identical. We shall therefore
treat of the subject from one point of view, and consider it
as follows :

1. The normal temperature in the human subject, with
its variations in different parts of the body and at different
periods of life.

2. The diurnal variations in the animal temperature, and
the relations of alimentation, digestion, respiration, nutri-
tion, exercise, and the nervous system.

3. The means by which the temperature of the body is
kept within the limits necessary to the preservation of life
and health.

Limits of Variation in the Normal Temperature in
jlfan. — A great number of observations have been made
upon the normal temperature in the human subject under
different conditions ; but we shall cite those only in which all
sources of error in thermoinetry seem to have been avoided,
and in which the results present noticeable peculiarities.
One of the most common methods of taking the general tem-
perature has been to introduce a delicate thermometer, care-
fully protected from all disturbing conditions, into the axilla,
reading off the degrees after the mercury has become abso-

1 HIRTZ, Chaleur dans Fetal de maladie. — Nouveau dictionnaire de medecine,
Paris, 1867, tome vi., p. 772, et seq.

396 NUTRITION.

lutely stationary. Nearly all observations made in this way
agree with the results obtained by Gavarret,1 who estimates
that the temperature in the axilla, in a perfectly healthy
adult man, in a temperate climate, ranges between 97*7°
and 99*5°.a Dr. Davy, from a large number of observa-
tions on the temperature under the tongue, estimates the
standard, in a temperate climate, at 98°. 3 When we ex-
amine the temperature of the blood in the deeper vessels
and the variations in different parts, we shall see that the
axilla and the tongue, being more or less exposed to external
influences, do not exactly represent the general heat of the
organism ; but these are the situations, particularly the axilla,
in which the temperature is most frequently taken, both in
physiological and pathological examinations. As a standard
for comparison, we may assume that the most common tem-
perature in these situations is 98°, subject to variation within
the limits of health of about 0*5° below and 1*5° above.

Variations with External Temperature. — There can be
no doubt that the general temperature of the body varies,
though within very restricted limits, with extreme changes
in climate. The results obtained by Davy, in a large num-
ber of observations in temperate and hot climates, show an
elevation in the tropics of from 0*5° to 3°.4 It is well known,
also, that the human body, the surface being properly pro-
tected, is capable of enduring for some minutes a heat much
greater than that of boiling water. Under these conditions,
the general temperature is raised but very slightly, as com-
pared with the intense heat of the surrounding atmosphere.
According to the observations of Dr. Dobson, the tempera-
ture was only raised to 99*5° in one instance, 101*5° in an-

1 GAVARRET, De la chaleur produite par Us etres vivants, Paris, 1855, p. 100.

2 All the temperatures, unless it be otherwise stated, are given according to
the Fahrenheit scale.

3 DAVY, Researches, Physiological and Anatomical, London, 1839, vol. i., p.
196.

4 DAVY, loc. tit.

HEAT. 397

other, and 102° in a third, when the body was exposed to a
heat of more than 2120.1 MM. Delaroche and Berger, how-
ever, found that the temperature in the mouth could be in-
creased by from 3° to 9°, after sixteen minutes' exposure to
intense heat.3 This was for the external parts only ; but it
is not at all probable that the temperature of the internal
organs ever undergoes such extensive variations.

It is very difficult to estimate the temperature in persons
exposed to intense cold, as in Arctic explorations, because
the greatest care is always taken to protect the surface of the
body as fully as possible ; but experiments have shown that
the animal heat may be considerably reduced, as a tempo-
rary condition, without producing death. In the. latter part
of the last century, Dr. Currie caused the temperature in
a man to fall 15° by immersion in a cold bath; but he
could not bring it below 83°. This extreme depression,
however, lasted only two or three minutes, and the tem-
perature afterward returned to within a few degrees of
the normal standard.3 Nearly the same results were ob-
tained by Hunter, in a series of experiments on a mouse.
With an external temperature of 60°, he found the tempera-
ture in the upper part of the abdomen 99°, and in the pelvis
• 96°. The animal was then exposed for an hour to a cold

1 DOBSON, Experiments in an Heated Room. — Philosophical Transactions, Lon-
don, 1775, p. 463, et seq.

2 DELAROCHE, Experiences sur les effets qu'une forte chaleur produit dans Tecono-
mie animale. — Theses de Paris, 1806, tome i., No. xi. M. Delaroche, in connec-
tion with M. Berger, made a number of very interesting experiments upon the
influence of high temperatures upon the general heat of the body. Delaroche
remained for eight minutes exposed to a temperature of 176°, and the tempera-
ture under the tongue was raised from a little over 98° to nearly 107°. In an
experiment of the same kind by Berger, the temperature was raised, in sixteen
minutes, from 98° to nearly 105°. Enclosed in a hot steam-bath of from 100°
to 120°, the temperature, in one instance, was raised, in thirteen minutes, to
over 103°, and in another, in fifteen minutes, to 101° (Loc. cit., pp. 43, 44).

3 CURRIE, An Account of the remarkable Effects of a Shipwreck on the Mari-
ners ; with Experiments and Observations on the Influence of Immersion in fresh
and salt Water, hot and cold, on the Powers of the living Body. — Philosophical
transactions, London, 1792, p. 204, et seq.

398 NUTEITION.

atmosphere of 13°, and there was a diminution of the tem-
perature at the diaphragm of 16°, and at the pelvis of 180.1
These results show that while the normal variations in
temperature in the human subject, even when exposed to
great climatic changes, are very slight, generally not ranging
beyond two degrees, the body may be exposed for a time to
excessive heat or cold, and the extreme limits, consistent
with the preservation of life, may be reached. As far as
lias been ascertained by direct experiment, these limits are
83° and 107° ; giving a range of about 15° below and 9°
above the average standard under normal conditions.2

Variations in different Parts of the Body. — It is to be
expected that the temperature of the internal organs should
be higher and more constant than that of parts, like the axilla
or mouth, more or less exposed to loss of heat by evaporation
and contact with the cool air ; and the differences observed
in the blood in certain parts, as in the two sides of the heart,
have important bearings, as we shall hereafter show, upon
the various theories of animal heat. We shall here simply
note the variations observed in the blood in different situa-
tions, and confine ourselves chiefly to late observations,
which have generally been made with apparatus much more
reliable and delicate than was formerly employed.

A great number of experiments have been made upon
modifications in temperature accompanying the general
change of the blood from arterial to venous ; but perhaps
the most exact and elaborate are those by M. Claude Ber-
nard. For measuring the temperature in different parts of
the vascular system, he used the exceedingly delicate " me-

1 HUNTER, Observations on certain Parts of the Animal (Economy, London,
1792, p. 114.

2 We have referred only to observations upon the influence of the surround-
ing temperature in man and mammals generally. Certain important peculiari-
ties in this regard have been observed in hibernating animals, and in reptiles,
fishes, and insects, the consideration of which belongs to comparative physi-
ology.

ANIMAL HEAT. 399

tastatic " thermometers of M. "Walferdin ; 1 and in all com-
parative observations lie employed the same instrument, in-
troduced successively into different parts, frequently revers-
ing the order, and employing every precaution so as to insure
perfectly physiological conditions. The preeminent skill of
this distinguished observer in experimenting upon living ani-
mals is almost in itself a sufficient guarantee of the accuracy
of his results.

It is universally admitted that the blood becomes slightly
lowered in its temperature in passing through the general
capillary circulation ; 3 but the amount of difference is ordi-
narily not more than a fraction of a degree, and is dependent,
in all probability, upon external conditions and the evapora-
tion constantly going on from the surface of the body. This
fact is not at all opposed to the proposition that the animal heat
is generated in greatest part in the general capillary system,
as one of the results of nutritive action ; for the blood circu-
lates with such rapidity that the heat acquired in the capil-
laries of the internal organs, where little or none is lost, is
but slightly diminished before the fluid passes into the arte-
ries, even in circulating through the lungs ; and the evapora-
tion from the surface simply moderates the heat acquired in
the tissues, and keeps it at the proper standard. We know
that the heat of the body is equalized by means of the circu-
lation and cutaneous transpiration ; and all comparative ob-
servations on the temperature in different parts show that,
where it is not subjected to refrigerating influences, the blood
is warmer in the veins than in the arteries.

The elaborate investigations of Bernard have demon-
strated that the blood is, as the rule, from 0'36° to 1-8°
warmer in the hepatic veins than in the aorta. The tem-
perature in the hepatic veins is from 0*18° to 1*44° higher

1 BERNARD, Liquides de Forganisme, Paris, 1859, tome i., p. 67, et seq. Ber-
nard here gives a full description of this instrument. With it he has been able
to note accurately variations of ^ of a degree cent.

8 BERNARD, op. cit., p. 58, and LOXGET, Traite de phyeioloffie, Paris, 1869, tome
ii., p. 517.

400 NUTRITION:

than in the portal veins. These figures are the result of
numerous experiments made on dogs. The maximum of
thirty-three observations upon the temperature in the aorta
was 105*8°, and the minimum, 98*78° ; the maximum of
thirty-two observations upon the portal vein was 106*34r°,
and the minimum, 100*04° ; the maximum of thirty-five ob-
servations upon the hepatic veins was 107°, and the mini-
mum, 99*86V Compared with the aorta, the temperature
of the portal vein was generally found to be higher (maxi-
mum of differencej 0*9°) ; but in a few instances, five out of
fifteen, it was a very little lower, which is explained by Ber-
nard by the supposition that the intestinal canal is not en-
tirely removed from external modifying influences. These
results show that the blood coming from the liver is warmer
than in any other part of the body.

The general fact that the superficial parts are cooler than
those less exposed to loss of heat by evaporation, observed
by Hunter,3 Davy,8 and others, does not demand extended
discussion ; but in a series of experiments by Breschet and
Becquerel,4 who were among the first to employ thermo-
electric apparatus in the study of animal heat, it was found
that the cellular tissue was from 2*5° to 3*3° cooler than the
muscles. This difference will be readily understood when
we consider the production of heat in the general system,
and more especially in the highly-organized parts.

A most interesting question, in this connection, relates

1 BERNARD, op. cit., p. 84. We have calculated these results from an elabo-
rate table given by Bernard, but have disregarded two observations (Nos. 17
and 18, table in.), made on animals after death, the circulation being kept up
by artificial respiration.

2 HUNTER, Experiments and Observations on Animals, with respect to the Power
of producing Heat. — Observations on certain Parts of the Animal (Economy ', Lon-
don, 1792, pp. 108, 115.

3 DATY, Researches, Physiological and Anatomical, London, 1839, vol. i., p.
150, et seq. The paper here referred to first appeared in the Philosophical
Transactions, in 1814.

4 BRESCHET ET BECQUEREL, Premier memoire sur la chaleur animate. — Annales
de chimie et de physique, Paris, 1835, tome lix., p. 129.

ANIMAL HEAT. 401

to the comparative temperature of the blood in the two
sides of the heart. Upon this point there have been several
conflicting observations, the results favoring two opposite
theories of calorification. By some it has been thought that
the blood gains heat in passing through the lungs, and this
is explained by the theory of the direct union, in these organs,
of oxygen with the hydro-carbons ; while others suppose that
the blood is slightly refrigerated in the air-cells. The ques-
tions here involved will be fully discussed in connection with
the theories of animal heat ; and we shall confine ourselves
at present to a study of the experimental facts.

An excellent review of all the important direct observa-
tions upon the temperature of the two sides of the heart in
living animals is given by Bernard, as an introduction to his
original experiments. It appears from this that Golem an,
Astley Cooper, Saissy, Davy, Thackrah, and Nasse, found
the blood warmer in the left side of the heart than in the
right. Mayer did not find any difference in animals re-
cently killed. Autenreith found the blood warmer in the
right side in an animal recently killed, the circulation being
kept up by artificial respiration. Berger, Collard de Mar-
tigny, Magendie and Bernard, Hering, Georg von Liebig,
and Fick found a marked difference in favor of the right
side.1 This being the state of the question in 1859, it re-
mains to see how far the conditions under which these re-
sults were obtained are capable of explaining their contra-
dictory character.

It is evident that, when the chest is opened, the external
refrigerating influences might act differently upon the two
sides of the heart, particularly as the right ventricle is much
thinner than the left. It would not be improper, indeed, to
exclude all observations made in this way, and depend en-
tirely upon experiments in which the physiological condi-
tions are not so palpably violated. Magendie and Bernard
introduced delicate thermometers into the two sides of the

1 BERNARD, Liquides de Vorganisme, Paris, 1859, tome i., p. 55, el seq.

402 NUTRITION.

heart, through the vessels in the neck, without opening the
chest. These experiments were made upon a horse, and the
right heart was always found considerably warmer than the
left. Hering introduced a thermometer into the cavities
of the heart in a living calf affected with cardiac ectopia.
The temperature of the right side was 102'74°, and the left
side, IGI'790.1 Georg von Liebig illustrated one of the
sources of error in all examinations made after opening the
chest, by filling the cavities of the heart of a dog with warm
water, placing the organ in a water-bath, and bringing the
two sides to precisely the same temperature. After five
minutes' exposure to the air, the temperature in the right
ventricle was sensibly lower than in the left, which was un-
doubtedly due to the difference in the thickness of the walls.3
The observations by Bernard himself upon dogs and sheep
are very conclusive, as far as these animals are concerned.
In dogs he found a difference of from 0*1° to 0*2°, always
in favor of the right side ; and the results in sheep were
nearly the same.3

A series of experiments recently instituted by Colin
shows pretty conclusively that there are other conditions
that may account, in a measure, for the opposite results of
observations on the temperature of the two sides of the
heart, besides exposure of the parts to the air. In one hun-
dred and two experiments, he found the blood warmer in
the right side in thirty-one ; in fifty-one, it was warmer on
the left side ; and in twenty-one, there was no difference.4
He finds that in animals covered with a thick fleece, like
sheep, where there is but little loss of temperature by the
general surface, the blood in the right heart is generally

1 BERNARD (op. cit., p. 106, et seq.) gives a full account of this very interest-
ing observation.

2 BERNARD, op. cit., p. 65.

3 Op. cit., pp. 11Q, 116.

4 COLIN, Experiences sur la chaleur animale, in the report by LONGET. — Comp-
tcs rendus, Paris, 1867, tome Ixiv., p. 464. The error in the figures quoted is
in the original report. .

AKIMAL HEAT. 4:03

warmer than in the left ; while in horses, dogs, and probably
in man, where there is considerable loss of heat by the skin,
the blood is warmer on the left side. It is difficult to ex-
plain how the blood can pass through the lungs without
losing a certain amount of heat, but the experiments just
detailed, taken in connection with some of the earlier ob-
servations, leave little doubt as to the fact.

These experiments are only indirectly applicable to the
human subject ; and if it be proven that in animals, the con-
ditions vary with " the state of the skin, the digestive appa-
ratus, and the muscular system," * it is impossible, in the
absence of positive demonstration, to say what change in
temperature, if any, takes place in the blood in its passage
through the lungs. The only reliable observations upon
this point in man are those lately made by Prof. Lombard,
of Boston. Prof. Lombard used in his experiments a very
ingenious and delicate thermo-electric apparatus, capable
of indicating a difference of -^-^ of a degree cent.8 With
this instrument, he was able to determine very slight
variations in the temperature of the blood in the arterial
system, by simply placing the conductors over any of the
superficial vessels, like the radial. Of course it is impossible
to note the actual temperature in the two sides of the heart
in the human subject during life ; but Prof. Lombard en-
deavored to arrive at the same end, by calculating that if all
the sources of refrigeration in the lungs were artificially
removed, the blood in the arteries should gain about the
same amount of heat that would be lost under ordinary con-
ditions. To effect this object, he breathed air saturated
with moisture and of the same temperature as the circulating
blood. " If, then, when respiration takes place under ordi-
nary circumstances, the blood is cooled one-third of a degree
(cent.) in passing through the lungs, the temperature should

1 COLIN, loc. tit.

2 LOMBARD, Description d'un nouvel appareil thermo-electrique pour P etude de
la chaleur animale. — Archives de physiologic, Paris, 1868, tome i., p. 498.

404 NUTRITION.

be raised so much ; that is to say, one-third of a degree,
when we respire air at the temperature of the blood and
saturated with the vapor of water, all loss of heat then being
impossible." l In numerous experiments performed on this
principle, Prof. Lombard failed to observe a sufficiently
marked elevation of temperature to justify the conclusion
that the blood is ordinarily cooled in passing through the
lungs. These experiments cannot be so positive as those
made by introducing thermometers into the heart in living
animals without opening the chest or disturbing the circu-
lation ; but they are important, in connection with such
observations, as failing to prove that the blood is either
cooled or heated in the lungs.

From these facts it appears that there is no positive evi-
dence of any change in the temperature in the blood in pass-
ing through the lungs in the human subject. In animals there
probably exist no constant differences in temperature in the
two sides of the heart. "When the loss of heat by the gen-
eral surface is active, as in animals with a slight covering of
hair, the blood is generally cooler in the right cavities ; but
in animals with a thick covering, that probably lose a great
deal of heat by the pulmonary surface, the blood is cooler on
the left side. There can be no doubt that there are refri-
gerating influences in the lungs, both from the low tempera-
ture of the inspired air and evaporation ; but these are
equalized and sometimes overcome by processes in the blood
itself; although, as we shall see hereafter, the lungs are by
no means the most important organs of calorification.

Variations at different Periods of Life. — The most im-
portant variations in the temperature of the body at different
periods of life are observed in infants just after birth. Aside
from one or two observations, which are admitted to be ex-

1 LOMBARD, RechercJm experimentales sur V influence de la respiration sur la
temperature du sang dans son passage d travers le poumon. — Archives de physi'
ologie, Paris, 1869, tome ii., p. 7.

ANIMAL HEAT. 405

ceptional, the body of the infant and of young mammalia
and birds, removed from the mother, presents a diminution
in temperature of from one to nearly four degrees. This
important fact was established by "W. F. Edwards,1 who
made, also, a number of curious and instructive experiments
upon the power of young warm-blooded animals to resist
cold. In infancy the ability to resist cold is less than in
later years ; but after a few days the temperature of the
child nearly reaches the standard in the adult, and the
variations produced by external conditions are less consid-
erable. These facts have been fully confirmed by the re-
searches of Despretz,3 Roger,8 and others.

The experiments of W. P. Edwards have an important
bearing upon our ideas of nutrition during the first periods
of extra-uterine life. He found that in certain animals, par-
ticularly dogs and cats, that are born with the eyes closed
and in which the foramen ovale remains open for a few days,
the temperature rapidly diminished when they were removed
from the body of the mother, and that they then become
reduced to a condition approximating that of cold-blooded
animals ; but after about fifteen days, this change in tem-
perature could not be effected. In dogs just born, the
temperature fell after three or four hours' separation from
the mother to a point but a few degrees above that of the
surrounding atmosphere.* The views advanced by Edwards
are fully illustrated in instances of premature birth, when
the animal heat is much more variable than in infants at

1 W. F. EDWARDS, De V influence des agens physiques sur la vie, Paris, 1824,
p. 234.

8 DESPRETZ, Recherches experimentales sur les causes de la chaleur animate. —
Annales de chimie et de physique, Paris, 1824, tome xxvi., p. 338. Despretz
found the temperature in three infants, between one and two days old, only
95-1°.

3 ROGER, De la temperature chez les enfants d Vetat phyxiologique et patho-
logique. — Archives generates de medecine, Paris, 1845, 4me serie, tome ix.,
p. 264.

4 Op. tit., p. 132, et seq.

4:06

term,1 and in cases of persistence of the foramen ovale. In
certain instances in which life has been prolonged under this
abnormal condition, the individual is nearly in the condition
of a cold-blooded animal. We can also understand the re-
markable power of resistance to asphyxia in newly-born
animals observed by Buffon, Legallois, and Edwards ; a for
it is well known that cold-blooded animals will bear de-
privation of oxygen much better than the higher classes.

In adult life there does not appear to be any marked and
constant variation in the normal temperature; but in old
age, according to the observations of Davy, while the ac-
tual temperature of the body is not notably reduced, the
power of resisting refrigerating influences is diminished
very considerably.3

There are no positive observations showing any constant
differences in the temperature of the body in the sexes ; and
it may be assumed that in the female, the animal heat is
modified by the same influences and in the same way as in
the male.

Diurnal Variations in the Temperature of the Body. —
Although the limits of variation in the animal temperature
are not very extended, certain fluctuations are observed, de-
pending upon repose or activity, digestion, sleep, etc., which
it is necessary to take into account. These conditions, which
are of a perfectly normal character, may produce changes in
the temperature amounting to from one to three degrees. It
has been ascertained that there are two well-marked periods
iii the day when the heat is at its maximum. These, according
to the most recent observations in Germany, are at eleven
A. M. and four p. M. ; and it is a curious fact, that while all

1 W. F. Edwards noted a temperature in the axilla, of a little loss than 90°,
two or three hours after birth, in an infant born at the seventh month ( Op. tit.,
p. 236).

2 See vol. i., Respiration, p. 420, et seq.

3 DAVY, On the Temperature of Man in advanced Age. — Physiological Re-
searches, London, 1863, p. 4, et seq.

ASTRAL HEAT. 407

observations agree upon this point, the .very elaborate ex-
periments of Lichtenfels and Frohlich show that these
periods are well-marked, even when no food is taken.1
Barensprung and Ladame further show that the fall in tem-
perature during the night takes place sleeping or waking ;
and that when sleep is taken during the day it does not
disturb the period of the maximum, which occurs at about
four p. M.*

According to these experiments, at eleven in the morn-
ing, the animal heat is at one of its periods of maximum ; it
gradually diminishes for two or three hours and is raised
again to the maximum at about four in the afternoon, when
it again undergoes diminution until the next morning. The
variations amount to from about 1° to 2*16.° The minimum
is always during the night.

The relations of the animal temperature to digestion are
still somewhat indefinite. It is well known that activity
of the digestive organs increases the consumption of oxygen,
and, to a corresponding degree, the exhalation of carbonic
acid ; but we have to assume that the production of heat is
in direct ratio to the respiratory action in order to establish
any relation between calorification and the digestion of
ordinary food. It is easy to calculate that a given amount
of oxygen will produce a definite quantity of carbonic acid,
and will, by its union with carbon and hydrogen, generate a
certain number of " units of caloric ; " but the mechanism of
the production of animal heat is too complex and not well
enough understood to admit of such positive reasoning.
There is, indeed, no experimental evidence of any marked
and constant change in the general temperature of the body
during the ordinary process of digestion ; but it is none
the less true that the quantity and quality of food bear

1 LICHTEXFELS UNO FROHLICH, Beobacldungen uber die Gesetze des Ganges der
Pulzfrequenz und Korperwdrme in den normalen Zustanden. — Denkschriften der
kaiserlichen Akad. der Wissenschaften, maihematiscli-naturwissenschaftliche Classe,
Wien, 1852, Bd. iii., Zweite Abth., S. 113, et seq.

2 LOXGET, Traite de physiologic, Paris, 1869, tome ii., pp. 499, 534.

408 NUTRITION.

a certain relation to calorification. This is inevitable from
the connection of animal heat with the general process
of nutrition ; but this relation is expressed in the con-
nection of calorification with nutrition of the tissues, and
not in the process of preparation or absorption of food. We
shall see that when nutrition is modified by alimentation,
the general temperature is always more or less affected ; and
when the requirements of the system, as far as the genera-
tion of heat is concerned, are changed, by climate or other-
wise, alimentation is modified. One of the objects of ali-
mentation and nutrition is to maintain the body at a nearly
constant temperature.

The influence of defective nutrition or inanition upon
the heat of the body is very marked. John Hunter, in his
experiments upon animal heat, made a few observations upon
this point, and noted a decided fall in temperature in a
mouse kept fasting.1 The same phenomena were also ob-
served by Collard de Martigny ; a but Chossat, to whose
memoir we have so fully referred in another volume under
the head of inanition, noted the effects of deprivation of
food upon the power of maintaining the animal temperature,
in the most exact and satisfactory manner. This point has
already been so fully considered that it is only necessary in
this connection to note the general results. In pigeons, the
extreme diurnal variation in temperature, under normal con-
ditions, was found by Chossat to be 1'3.° During the prog-
ress of inanition, the daily variation was increased to 5 '9,°
with a slight, but well-marked diminution in the absolute
temperature ; and the periods of minimum temperature were
unusually prolonged. Immediately preceding death from
starvation, the diminution in temperature became very
rapid, the rate, in the observations on turtle-doves, being

1 Op. tit., p. 114.

* COLLARD DE MARTIGNY, RecJierches experimentales sur les effete de I ^abstinence
complete d'alimens solides et liquides. — Journal de physiologic, Paris, 1828, tomo
viii., p. 163.

ANIMAL HEAT. 409

from 7° to 11° per hour. Death usually occured when the
diminution had amounted to about 30°. x

When the surrounding conditions call for the develop-
ment of an unusual amount of heat, the diet is always
modified, both as regards the quantity and kind of food ; but
when food is taken in sufficient quantity and is of a kind
capable of maintaining proper nutrition, its composition
does not affect the general temperature. If we were to
adopt without reserve the view that the non-nitrogenized
alimentary principles are the sole agents in the production
of heat, we should certainly be able to determine either an
increase in the animal heat or a greater loss of heat from
the surface, in persons partaking largely of this kind of
food. This, however, has not been shown to be true ; and
the temperature of the body seems to be uniform in the
same climate, even in persons living upon entirely different
kinds of food. The elaborate observations of Dr. Davy are
very conclusive on this point: "The similarity of tem-
perature in different races of men is the more remarkable,
since between several of them whose temperatures agreed,
there was nothing in common but the air they breathed —
some feeding on animal food almost entirely, as the Yaida —
others chiefly on vegetable diet, as the priests of Boodho —
and others, as Europeans and Africans, on neither exclu-
sively, but on a mixture of both." a

Xevertheless, the conditions of external temperature
have a remarkable influence upon the diet. It is well
known, for example, that in the heat of summer, the
amount of meats and fat taken is small, and the succulent,
fresh vegetables and fruits, large, as compared with the diet
in the winter. But although the proportion of starchy mat-
ters in many of the fresh vegetables used during a short season
of the year is not large, these articles are equally deficient

1 CHOSSAT, Recherches experimentales sur ^inanition, Paris, 1843, p. 123.

2 DATY, Researches, Physiological and Anatomical, London, 1839, vol. i., p.
197.

410 NUTRITION.

in nitrogenized matter. During the winter, the ordinary
diet, composed of meat, fat, bread, potatoes, etc., contains a
large amount of nitrogenized substance, as well as a con-
siderable proportion of the hydro-carbons; and in the
summer, we instinctively reduce the proportion of both of
these varieties of principles, the more succulent articles
taking their place. This is even more strikingly illus-
trated by a comparison of the diet in the torrid or tem-
perate and the frigid zone. Under the head of alimentation,
we have already rioted the prodigious quantities of food con-
sumed in the Arctic regions, and the effect of the continued
cold upon the habits of diet of persons accustomed to a tem-
perate climate. It is stated, on undoubted authority, that
the daily ration of the Esquimaux is from twelve to fifteen
pounds of meat, about one-third of which is fat. Dr. Hayes,
the Arctic explorer, noted that with a temperature ranging
from — 60° to — 70,° there was a continual craving for a
strong, animal diet, particularly fatty substances. Some of
the members of the party were in the habit of drinking the
contents of the oil-kettle with evident relish.1

Under such conditions as those which surround inhabit-
ants of temperate regions, in passing into the frigid zones a
change in diet is imperatively demanded, in order to keep
the animal temperature at the proper standard ; but when
the climate is changed from the temperate to the torrid, the
habits of life frequently remain the same. It is a pretty
general opinion among physicians who have studied the sub-
ject specially, that many of the peculiar disorders that affect
those who have changed their residence from a temperate to
a very warm climate are due, in a great measure, to the fact
that the diet and habits of life are unchanged.

The influence of alcoholic beverages upon the animal
temperature has been studied chiefly with reference to the

1 HAYES, An Arctic Boat-Journey, Boston, 1860, pp. 257, 259, and American
Journal of the Medical Sciences, Philadelphia, 1859, New Series, vol. xxxviii.,
p. 114, et seq.

ANIMAL HEAT. 411

question of their use in enabling the system to resist exces-
sive cold. Davy states that " the effect of wine, unless used
in great moderation, is commonly lowering, that is, as to
temperature, while it accelerates the heart's action, followed
after a while by an increase of temperature." 1 We have
already discussed somewhat fully the physiological effects
of alcohol, and have shown that its use does not enable men
to endure a very low temperature for a great length of time.
This is the universal testimony of scientific Arctic explorers ;
and Dr. Hayes particularly states, that " in almost any shape,
it is not only completely useless, but positively injurious."2

The relations of animal heat to respiration and nutrition
constitute a most interesting and important division of the
subject, which will be more fully considered in discussing the
various theories of calorification. As a rule, when the respira-
tory activity is physiologically increased, as it is by exercise,
bodily or mental, ingestion of food, or diminished external"
temperature, the generation of heat in the body is correspond-
ingly augmented ; and, on the other hand, it is diminished
by conditions which physiologically decrease the absorption
of oxygen and the exhalation of carbonic acid. The only
positive experiments upon the influence of simple increase in
the number and extent of the respiratory acts are those of
Prof. Lombard. He found that when the respirations were
increased in depth and frequency for ten minutes, there was
a diminution of two degrees in the temperature over the
radial artery. There was also a very slight lowering of the
temperature, from '001 to *01 of a degree cent., in from a
minute to a minute and a half after suspension of respiration.
Prof. Lombard explains these phenomena by the mechani-
cal effects of the condition of the lungs upon the arterial
pressure.3

1 DAVY, Physiological Researches, London, 1863, p. 57.

2 HAYES, Observations on the Relations existing between Food and the Capabilities
of Men to resist Low Temperatures. — American Journal of the Medical Sciences,
Philadelphia, 1859, Xew Series, vol. xxxviii., p. 117.

3 LOMBARD, Recherches experimentales sur quetguts influences non etudiees

412 NUTRITION.

The relations of animal heat to the general process of
nutrition are most intimate. Any condition that increases
the activity of nutrition and of disassimilation, or even any
thing that increases disassimilation alone, will increase the
production of heat. The reverse of this proposition is equally
true. In pathology, the heat of the body may be increased
by a deficient action of the skin in keeping down the tem-
perature, without any increase in the activity of calorification.

Influence of 'Exercise, etc., upon the Heat of the Body. —
The influence of muscular activity upon animal heat is pecu-
liarly interesting in connection with the theories of calorifi-
cation, from the fact that the muscular system constitutes the
greatest part of the organism ; and, as has repeatedly been
shown by experiment, a muscle taken from a living animal
is not only capable of contraction upon the application of a
stimulus, but will perform for a time certain of the acts of
nutrition and disassimilation, such as the appropriation of
oxygen and the generation and exhalation of carbonic acid.

The most complete repose of the muscular system is ob-
served during sleep, when hardly any of the muscles are
brought into action, except those concerned in tranquil respi-
ration. There is always a notable diminution in the general
temperature at this time. John Hunter found a difference,
in man, of about one degree and a half.1 This fact has been
confirmed by all who have studied the question experimen-
tally. In the diurnal variations in the temperature of the
body, the minimum is always during the night ; and, as we
have already seen, this is not entirely dependent upon sleep,
for a depression in temperature is constantly observed at that
time, even when sleep is avoided.8

It is a matter of common observation, that one of the

jusqu'ici de la respiration sur la temperature du corps humain. — Archives de
physiologic, Paris, 1868, tome i., p. 496.

1 HUNTER, Observations on certain Parts of the Animal (Economy, London,
1792, p. 114.

2 See p. 407.

ANIMAL HEAT.

most effective methods of resisting the depressing influence
of cold is to constantly exercise the muscles ; and it is well
known, that after long exposure to intense cold, the tendency
to sleep, which becomes almost irresistible, if indulged in, is
followed by a very rapid loss of heat and almost certain
death. It is not necessary to cite the accounts of travellers
and others in support of these facts. In some animals, the
amount of increase in the temperature during muscular
activity is very great, and this is notably marked in the
class of insects. In the experiments of Newport, on bees
and other insects, a difference of about 27° was noted be-
tween the conditions of complete repose and great muscular
activity.1 The same facts were observed by Dutrochet, but
he operated upon single insects, and observed an elevation
of only a fraction of a degree.2 These facts are interesting,
as showing the very great elevation of temperature that can
be produced in the lower order of beings during violent ex-
citement ; but in man, the differences, though distinct, are
never very considerable, for the reason that violent mus-
cular exertion is generally attended with greatly-increased
action of the skin, which keeps the heat of the body within
very restricted limits. In the experiments of Newport, the
loss of heat from the surface was arrested by confining the
insects in small glass bottles.

The effects of active exercise, as in fast walking or riding,
were very well observed by Dr. Davy. He found a con-
stant elevation in the general temperature (taken under the
tongue), amounting to between one and two degrees ; 3 but
the most marked effects were observed in the extremities,
especially when they were cold before taking the exercise.4

1 XEWPORT, On the Temperature of Insects, and its Connexion with the Func-
tions of Respiration and Circulation in this Class of Invertebrate Animals —
Philosophical Transactions, London, 1837, p. 281.

8 DUTROCHET, Recherches sur la chaleur propre des etres vivans d basse tempera-
ture— Annales des sciences naturelles, Zoologie, Paris, 1840, 2me serie, tome xiii.,
p. 43, et seq.

3 DATY, Physiological Researches, London, 1863, p. 16. 4 Ibid., p. 11.

414 NUTRITION.

The elevation in temperature that attends muscular
action is produced directly in the substance of the muscle.
This important fact was settled by the very interesting and
ingenious experiments of Becquerel and Breschet. Intro-
ducing a thermo-electric needle into the biceps of a man
who used the arm in sawing wood for five minutes, these
physiologists noted an elevation of temperature of one de-
gree centigrade J (nearly two degrees Fahr.). The produc-
tion of heat in the muscular tissue was even more strikingly
illustrated by Matteucci, in experiments with portions of
muscle from the frog. Not only did he observe absorption
of oxygen and exhalation of carbonic acid and water after
the muscle had been removed from the body of the animal,
but he noted an elevation in temperature of about one de-
gree Fahr., following contractions artificially excited.3

It is useless to multiply citations of experiments illus-
trating the facts above noted, or to discuss elaborately the
theoretical transformation of a given quantity of caloric into
a definite and invariable amount of work. The conditions
in the animal economy are such that we cannot exactly ap-
preciate the loss of heat by the cutaneous and respiratory
surfaces ; nor can we follow the processes in the body which
involve the disappearance of oxygen and the evolution of
carbonic acid ; the exact changes undergone by the hydro-
carbonaceous elements of food and constituents of the body ;
the amount of heat involved in the changes of the nitro-
genized elements ; and, in short, we cannot make the correc-
tions that are absolutely necessary before we can hope to re-
duce the question of the oxidation of certain principles in the
body, the development of heat, and the generation of mechan-
ical force, to exact mathematical calculation. This has been
attempted by Beclard 3 and others, who have endeavored to

1 BECQUEREL ET BRESCHET, Premier memoire sur la chaleur animale. — Annales
de chimie et de physique, Paris, 1835, tome lix., p. 113.

2 MATTEUCCI, Recherches sur les phenomenes physiques et chimiques de la con-
traction musculaire. — Comptes rendus, Paris, 1856, tome xlii., p. 651.

3 BECLARD, DC la contraction musculaire dans ses rapports avec la temperature

ANIMAL HEAT. 4:15

establish the numerical value of" certain acts in what are
called "mechanical equivalents of heat," or "heat-units."
The observations of Beclard possess considerable physiolo-
gical interest, but they are useful chiefly, if not entirely, in
their positive results.

Observations upon the influence of mental exertion on
the temperature of the body have not been so numerous, but
they are, apparently, no less exact in their results. Dr. Davy
was the first to make any extended experiments on this
point, and has noted a slight but constant elevation during
" excited and sustained attention." x More lately, the same
line of observation has been followed by Prof. Lombard, who
employed much more exact methods of investigation. Prof.
Lombard noted an elevation of temperature in the head
during mental exertion of various kinds, but it was slight,
the highest rise not exceeding the twentieth of a degree.8

It is stated, also, that the temperature of the body is in-
creased by the emotions of hope, joy, anger, and all exciting
passions; while it is diminished by fear, fright, and mental
distress. Burdach, from whom the foregoing statement is
taken, cites an example of an elevation of temperature from
96° to 99*5° in a violent access of anger, and a descent to
92*75° under the influence of fear, but the temperature soon
returned to 9T'25°.3

The nervous system exerts a most important influence
over the animal temperature, as it modifies the circulation
and the nutritive processes in particular parts. The most
interesting of these influences are transmitted through the
sympathetic system. These will be discussed, to a certain
extent, in connection with the theories of calorification ; but
they cannot be taken up fully until we come to consider the

animale. — Archives generates de medecine, Paris, 1861, 5me serie, tome xvii.
The conclusions in this interesting memoir are to be found on page 277, et seq,

1 DATY, Physiological Researches, London, 1863, pp. 19, 51.

2 LOMBARD, Experiments on the Relations of Heat to Mental Work. — New York
Medical Journal, 1867, vol. v., p. 198, et seq.

3 BURDACH, Traite de physiologic, Paris, 1841, tome is., p. 645.

416 inTTRITION.

functions of the sympathetic system and its relations to nu-
trition. In this connection, we will simply allude to certain
phenomena manifested through the nervous system, without
attempting to fully explain their mechanism.

It is well known that when the sympathetic nerves going
to a particular part are divided, the arterial coats are para-
lyzed and dilated, the supply of blood is increased, nutrition
is locally exaggerated and more or less modified, and the
temperature of that particular part is increased by from five
to ten degrees. An illustration of these facts in the ear of
the rabbit, after division of the sympathetic in the neck, is a
very common observation, which we have often verified in
public demonstrations. All of these unnatural phenomena
disappear on galvanizing the divided extremity of the nerve.
These local modifications in the temperature have been fre-
quently observed pathologically in the human subject.

A number of curious local variations of temperature can
be explained by direct or reflex action through the sympa-
thetic nerves. Brown-Sequard and Lombard observed that
pinching of the skin was soon followed by an elevation in
temperature, and was attended also with a diminution in the
temperature in the corresponding member on the opposite
side. Sometimes the irritation of the upper extremities pro-
duced changes in temperature in the lower limbs.1 Exam-
ples of reflex action through the sympathetic nerves are
given by Tholozan and Brown-Sequard, in a very interest-
ing series of experiments. These physiologists found that
lowering the temperature of one hand produced a considera-
ble diminution in the temperature of the other hand, without
any great depression in the general heat of the body ; and
Brown-Sequard showed that by immersing one foot in water
at 41°, the temperature of the other foot was diminished
about 7° in the course of eight minutes.2

1 BROWN-SEQUARD ET LOMBARD, Experiences sur F influence de V irritation des
nerfs de la peau sur la temperature des membres. — Archives de physiologic, Paris,
1868, tome i., p. 691.

8 THOLOZAN ET BROWN-SEQUARD, Recherche* experimentales sur quelqu'uns des

AXIMAL HEAT. 4:17

' The influence of the cerebro-spinal system upon the animal
temperature is illustrated in cases of paralysis, when there
is generally a very considerable diminution in the heat of
the affected part. This fact was noted, many years ago, by
Earle, who also observed that the temperature was in part
restored under the influence of electricity. In one case of
paralysis, he found the temperature of the hand of the af-
fected side 70°, while the hand of the sound side was 92°.
After the use of electricity for ten minutes, the temperature
of the paralyzed hand was raised to 74°. Ten days after,
the temperature of the hand on the paralyzed side was 71°
before, and 77° after electricity had been employed.1

It is evident that if animal heat be one of the necessary
attendant phenomena of nutrition, it must be greatly influ-
enced by the state of the circulation. It has been a ques-
tion, indeed, whether the modifications in temperature pro-
duced by operating upon the sympathetic system of nerves
be not due entirely to changes in the supply of blood. It is
certain that whatever determines an increased supply of
blood to any part raises the temperature ; and whenever the
quantity of blood in any organ or part is considerably dimin-
ished, the temperature is reduced. This fact is constantly
illustrated in operations for the delegation of large arteries.
It is well known that after tying a large vessel, the utmost
care is necessary to keep up the temperature of the part to
which its branches are distributed, until the anastomosing
vessels become enlarged sufficiently to supply blood enough
for healthy nutrition. In the experiments of Becquerel and
Breschet, simple compression of the artery supplying the
arm was sufficient to produce an immediate fall in the tem-
perature.3

effete du froid sur Vliomme. — Journal de la physiologic, Paris, 1858, tome i., pp.
502, 505.

1 EARLE, Cases and Observations, illustrating the Influence of the Nervous Sys-
tem in regulating Animal Heat. — Medico- Chirurgical Transactions, London, 1816,
vol. vii., p. 176.

2 Loc. tit.

CHAPTER XIY.

SOURCES OF ANIMAL HEAT.

THE most interesting question connected with calorifica-
tion relates to the sources of heat in the living organism ;
and a careful estimate of the physiological value of all the
facts that have been positively established with reference to
this point places the following proposition beyond any
reasonable doubt :

The generation of heat in the living animal organism is
connected, more or less intimately, with all of the processes
of nutrition and disassimilation, including, of course, the
consumption of oxygen and the production of carbonic acid ;
and this function is modified, to a greater or less degree, by
all conditions that influence the general process of nutrition
or the operation of the nutritive forces in particular parts.

This proposition is not contradicted by any well-settled
physiological facts or principles. Every one of the functions
of the body bears more or less closely upon nutrition ; and
all of the physiological modifications of the various func-
tions, without exception, affect the process of calorification.
AVe must bear in mind the fact, that in man and the warm-

SOURCES CF AXMAL HEAT. 4:19

blooded animals generally, the maintenance of the tem-
perature of the organism at a nearly fixed standard is a
necessity of life and of the physiological action of the dif-
ferent parts ; and that while heat is generated in the
organism with an activity that is constantly varying, it is as
constantly counterbalanced by physiological loss of heat
from the cutaneous and respiratory surfaces. Variations in
the activity of calorification are not to be measured by cor-
responding changes in the temperature of the body, but are
to be estimated by calculating the amount of heat lost. The
ability of the human race to live in all climates is explained
by the adaptability of man to different conditions of diet
and exercise, and to the power of regulating loss of heat
from the surface by appropriate clothing.

Our proposition regarding the production of animal heat
is in no wise opposed to the so-called combustion-theory, as
it is received by most physiologists of the present day ; but
it must be admitted that it is an unfortunate use of terms to
apply the name combustion to the general process of nutri-
tion, as is done by those who attempt to preserve, not only the
ideas of the great author of this theory, but certain modes of
expression, which were in accordance only with his limited
knowledge of the phenomena of nutrition. If we speak of
animal heat as the result of combustion of certain elements,
it will be necessary constantly to refer to the difference
between combustion as it occurs in the organism, and mere
oxidation out of the body ; or to start with a full definition
of what is to be understood by the term physiological
combustion, which reduces itself simply to a definition of
nutrition.

Regarding calorification, then, as connected with all of
the varied processes of nutrition, it remains for us to deter-
mine the following questions :

1. In what part or parts of the organism is heat gen-
erated ?

2. What is the relative importance in calorification, as

420 NUTKITION.

regards the amount of heat generated, of the processes of
nutrition, as we can study them separately ?

3. What are the principles invariably and of necessity
consumed and produced in the organism in calorification ;
and what is the relative importance of the principles thus
consumed and the products thus generated and thrown off?

4. How far have we been able to follow those material
transformations in the organism, which involve the consump-
tion of certain principles, the production of new compounds,
and the generation of heat ?

Seat of the Production of Animal Heat. — Few if any
physiologists at the present day hold to the opinion that
there is any part or organ in the body specially and exclu-
sively concerned in the production of heat. In the early his-
tory of the oxidation-theory of Lavoisier, it was thought by
some that the inspired oxygen combined with the hydro-
carbons of the blood in the lungs, and that the heat of
the body was generated almost exclusively in these organs ;
but this idea has long since been abandoned. We have
already f ally considered the question of loss or gain in the
temperature of the blood in its passage through the lungs,
and have seen that there is, to say the least, no constant
elevation showing a generation of heat in these organs, suffi-
cient to warm the blood, and through it the different parts
of the body. If we find that the blood in coming from
the lungs has about the same temperature as when it en-
tered, it must be admitted that there is a certain generation
of heat to compensate the loss by evaporation from the pul-
monary surface. As far as we know, the heat that results from
the mere physical solution of oxygen in the blood is all that
is produced in the lungs. It is, indeed, estimated by Mar-
chand, that the fixation of oxygen in this way is marked by
an elevation of nearly 2° Fahr.1 There is no sufficient evi-

1 MARCHAND, Ueber die Einwirkung des Sauerstoffs auf das Blut und seine
Bcstandtheile. — Journal fur praktische CJiemie, Leipzig, 1845, Bd. xxxv., S. 400.

SOURCES OF ASTMAL HEAT. 421

deuce to show that the lungs are special organs of calorifi-
cation ; and any generation of heat that takes place here is
due, probably, to purely physical phenomena in the blood.

The theory that all the respiratory changes, involving
the consumption of oxygen, the production of carbonic acid,
and the evolution of heat, take place in the blood as it cir-
culates, was advanced many years ago by Lagrange and
Hassenfratz ; 1 but recent investigations, showing the ap-
propriation of oxygen and the evolution of carbonic acid by
the tissues deprived of blood, and the evident production of
heat in the muscular substance and in other parts, have
completely overthrown this hypothesis.

It is only necessary to refer back to the pages treating
of the variations in the temperature of the blood in different
parts, to show that heat is produced in the general system,
and not in any particular organ, or in the blood as it circu-
lates. The experiments of Matteucci, showing an elevation
of temperature in a muscle excited to contraction after it
had been removed from the body, and the observations of
Becquerel and Breschet, showing increased development of
heat by muscular contraction, are sufficient evidence of the
production of heat in the muscular system ; 2 and, inasmuch
as this constitutes by far the greatest part of the weight of
the body, it is a most important source of animal heat.

It has been demonstrated, by the experiments of Bernard,
that the blood becomes notably warmer in passing through
the abdominal viscera. This is particularly marked in the
liver, and it shows that the large and highly-organized vis-
cera are also important sources of caloric.3

As far as it is possible to determine by experimental
demonstration, not only is there no particular part or organ

1 HASSENFRATZ, Memoire sur la combination de Foxygene avec le carlone et Vhy-
drogene du sang, mr la dissolution de I'oxygene dans le sang, et sur la maniere dont
le calorique se dfyage. — Annales de chimie, Paris, 1791, tome ix., p. 261.

2 See page 414.

3 See page 399.

422 NUTRITION.

in the body endowed with the special function of calorifica-
tion, but every part in which the nutritive forces are in
operation produces a certain amount of heat; and this is
probably true of the blood-corpuscles and other anatomical
elements of this class. The production of heat in the body
is general, and is one of the necessary consequences of the
process of nutrition; but, with nutrition, it is subject to
local variations, as is strikingly illustrated in the effects of
operations upon the sympathetic system of nerves, and the
phenomena of inflammation.

Relations of Animal Heat to the different Processes of
Nutrition. — Nutrition involves the appropriation of matters
taken into the body, and the production and elimination of
effete substances. In its widest signification, this includes
the consumption of oxygen and the elimination of carbonic
acid ; and, consequently, we may strictly regard respiration
as a nutritive act. All of the nutritive processes go on to-
gether, and they all involve, in most warm-blooded animals
at least, a nearly uniform temperature. During the first
periods of embryonic life, the heat derived from the mother
is undoubtedly necessary to the development of tissue by a
change of substance, analogous to nutrition, and even supe-
rior to it in activity. During adult life, animal heat and the
nutritive force are coexistent. It now becomes a question
to determine whether there be any class of nutritive prin-
ciples specially concerned in calorification, or any of the nu-
tritive acts, that we have been able to study by themselves,
which are exclusively or specially directed to the mainte-
nance of the temperature of the body. These questions
simply involve a review of considerations with regard to the
relations of various of the functions to the production of
heat.

The supply of the waste of tissue being effected by meta-
morphosis of alimentary matter — a process, the exact nature
of which we have not been able to determine — it has thus

RELATIONS OF ANIMAL HEAT TO NUTRITION.

far been possible, only, to divide the food into different
classes. Of these — leaving out oxygen — we will consider,
in this connection, the organic matters, divided into nitro-
genized and non-nitrogenized. The inorganic salts are al-
ways combined with nitrogenized matter, and seem to pass
through the organism without undergoing any considerable
change ; and there is no evidence that they have any connec-
tion, of themselves, with the production of heat.

What is the relation to calorification of those processes of
nutrition which involve the consumption of nitrogenized
matter and the production of the nitrogenized excrementi-
tious principles ?

We cannot study these phenomena alone, isolated from
the other acts of nutrition. We may confine an animal to
a purely nitrogenized diet, and the heat of the body will be
maintained at the proper standard ; but at all times there
is a certain quantity of non-nitrogenized matter (sugar and
perhaps fat) produced in the system, which is only formed to
be consumed. We may starve an animal, and the tempera-
ture will not fall to any very great extent until a short time
before death. Here we may suppose that the process of de-
position of nutritive matter in the tissues from the blood is
inconsiderable, as compared with the transformation of the
substance of these tissues into effete matter ; and it is almost
certain that non-nitrogenized matter is not produced in the
organism in quantity sufficient to account, by its destruction
in the lungs, for the carbonic acid exhaled. It seems beyond
question that there must be heat evolved in the body by oxi-
dation of nitrogenized matter. When the daily amount of
food is largely increased for the purpose of generating the
immense amount of heat required in excessively cold cli-
mates, the nitrogenized matters are taken in greater quan-
tity, as well as the fats, although their increase is not in the
same proportion. When, however, we endeavor to assign
to the nitrogenized matters a definite proportion of heat-pro-
ducing power, we are arrested by a want of positive knowl-

424 NUTRITION.

edge with regard to the metamorphoses which these prin-
ciples undergo ; and it is equally impossible to fix the rela-
tive calorific value of the deposition of new material in repair
of the tissues, and the change of their substance into eifete
matter in disassimilation.

From these facts, and other considerations that have
already been fully discussed under different heads, it is evi-
dent that the physiological metamorphoses of nitrogenized
matter bear a certain share in the production of animal
heat ; although, in connection with inorganic matter, their
chief function seems to be the repair of the tissues endowed
with the so-called vital properties.

What is the relation of the consumption of non-nitro-
genized matter to the production of animal heat ?

It has been impossible to treat of the relations of the
non-nitrogenized elements to nutrition without considering
more or less fully the part these principles bear in the pro-
duction of heat ; and we must refer the reader to the pre-
vious chapter for a discussion of certain of these points.1
In this connection, we will simply state the relations that
this class of principles is known to bear to calorification, and
the facts upon which our statements are based.

It has been pretty clearly shown that both sugar and fat
are actually produced in the organism, even when the diet
is strictly nitrogenized in its character; but we will only
consider the relations of the non-nitrogenized elements in-
troduced into the body, assuming that the principles of this
class appearing de novo in the organism are the result of
transformation of nitrogenized substances.

As far as the destination of the amylaceous, saccharine,
and fatty elements of food are concerned, we only know that
they are incapable, of themselves, of repairing muscular tis-
sue, and that they cannot sustain life. They are never dis-
charged from the body in health in the form under which
they enter ; but are in part or completely destroyed in nutri-

1 See page 378, et seq.

RELATIONS OF ANIMAL HEAT TO NUTRITION. 425

tion. They are. completely destroyed in persons who, from
habitual muscular exercise, have very little adipose tissue.
"When their quantity in the food is large, they are not of
necessity entirely consumed, but may be deposited in the
form of adipose tissue. This, however, may be made to dis-
appear by violent exercise, or under an insufficient diet.

There can be no doubt that the non-nitrogenized class of
alimentary principles is craved by the system in long-con-
tinued exposure to extreme cold. This is particularly marked
with regard to the fats. In all cold climates, fat is a most im-
important element of food ; and in excessively cold regions,
while the nitrogenized elements are largely increased, there is
a very much larger proportional increase in the quantity of
fat. These facts are very significant. If the non-nitrogen-
ized elements of food — which are not always indispensable,
though often very necessary articles — do not form tissue, are
not discharged from the body, and are consumed in some of
the processes of nutrition, it would seem that their change
must involve the production of carbonic acid, perhaps also of
water, and the evolution of heat. It is so difficult to ascer-
tain the exact quantities of carbonic acid, watery vapor, etc.,
thrown off by the lungs, skin, and other emunctories, and to
estimate the exact amount of heat produced and lost, that it
is not surprising that calculations of the calorific power of
different articles of food should be frequently erroneous;
particularly as we have no means of knowing the exact calo-
rific value of the nitrogenized principles.

Though we may assume that the non-nitrogenized ele-
ments of food are particularly important in the production
of animal heat, and that they are not concerned in the repair
of tissue, it must be remembered that the animal tempera-
ture may be kept at the proper standard upon an exclu-
sively nitrogenized diet ; and we cannot, indeed, connect
calorification exclusively with the consumption of any sin-
gle class of principles, nor with any single one of the acts
of nutrition.

426 NUTRITION.

Relations of Calorification to Respiration. — Respiration
is one of the nutritive processes that can be closely studied
by itself, as it involves the appropriation by the system of a
single principle (oxygen), and that simply in solution in the
blood. There can be no doubt that, of all the nutritive acts,
respiration is, far more than any other, intimately connected
with calorification. As far as the general process is con-
cerned, the production of heat is usually in direct ratio to
the consumption of oxygen and the exhalation of carbonic
acid. In the animal scale, wherever we have the largest
amount of heat produced, we observe the greatest respiratory
activity. In man, whatever increases the generation of heat
increases as well the consumption of oxygen and the elimina-
tion of carbonic acid. The production of heat in warm-
blooded animals is constant, and cannot be interrupted, even
for a few minutes. The same is true of respiration. The
tissues may waste for wrant of nourishment, but the heat of
the body must be kept near a certain standard, which is almost
always much higher than the surrounding temperature ; and
there is no other nutritive act so constant and so immediately
necessary to existence as the appropriation of oxygen. It is
not surprising, then, that early in the history of the physi-
ology of nutrition, before we knew, even, the exact condition
and proportion of the gases in the blood, it should have, been
thought that animal heat was the result of slow combustion
of the hydro-carbons.

The physiological history of respiration and of animal heat
dates from the same series of discoveries. In the latter part
of the last century, the great chemist, Lavoisier, discovered
the intimate nature of the respiratory process, and applied
the theory of the consumption of oxygen and the evolution
of carbonic acid to calorification. We have already followed
out the progress of this discovery in connection with respira-
tion ; 1 and like nearly all of the great advances in physiologi-
cal science, the distinctly-enunciated idea was foreshadowed

1 See vol. i., Respiration, p. 409, et seq.

RELATIONS OF ANIMAL HEAT TO RESPIRATION. 427

by earlier writers. The most remarkable of these was Mayow,
who, in 1667, and afterward in 1674, published a work on
the Spiritua Nitro-aereus, and on respiration, in which he
attributed to the nitro-aereous gas (oxygen) the property of
combining with the blood in the lungs, producing the red
color, and generating heat.1 These ideas, as well as those
advanced by Crawford, near the time of the publication of
the first observations of Lavoisier, were crude and indefinite,
and contributed but little to our positive knowledge of the
mechanism of calorification.2

It will not be necessary to treat, from a purely historical
point of view, of the discoveries made by Lavoisier, as this
has already been done sufficiently under the head of respi-
ration.3 He undoubtedly went as far in his explanations of
the phenomena of animal heat as was possible in the condi-
tion of the science at the time. his investigations were made;
and although he inevitably fell into some errors in his calcu-
lations and deductions, he must forever be regarded as the
-author of the first reasonable theory of the generation of
heat by animals.

The Consumption of Oxygen and Production of Car-
bonic Acid in Connection with the Evolution of Heat. — As
far as it has been possible to determine by actual experiment,

1 MAYOW, Tradatiis quinque Jfedico-physici. Quorum primus agit de Salnitro,
et Spiritu Nitro-aereo. Secundus de Respiratione, etc., Oxonii, 1674, p. 151, et seq.
The first edition of the work on Respiration was published in 1767.

2 CRAWFORD, Experiments and Observations on Animal ffeat, London, 1788,
second edition, p. 354, et seq. Crawford published the first edition of his work
in 1779, but the second edition, in which his views are avowedly made to cor-
respond with the observations of Lavoisier, is the only one at all accessible.
From all we can learn of the matter contained in the first edition, from extracts
and references in other treatises, Crawford's ideas were not in advance of those
presented by Lavoisier to the Academy of Sciences, in 1777.

3 The various papers published by Lavoisier and Seguin, and Lavoisier and de
la Place, are scattered through the volumes of memoirs of the French Academy
of Sciences, from ITTTto 1790. An exhaustive analytical review of these memoirs
is given by Gavarret (De la chaleur produite par les etres vivants, Paris, 1855, p.
165, et seq.).

428 NUTRITION.

all animals, even those lowest in the scale, appropriate oxy-
gen and eliminate carbonic acid ; and this is equally true of
all living tissues. In 1775, Lavoisier noted the fact that the
gas obtained by decomposing the oxide of mercury was more
active than the air in maintaining the respiration of animals.1
Two years later, he compared oxidation by respiration in
animals to ordinary combustion, and advanced the hypothe-
sis that this action was the cause of the constant temperature
of animals of about 32|-° Reaumur.2 A little later, he pub-
lished the remarkable experiments in which he estimated
the amount of " combustion " in a Guinea-pig, by collecting
the carbonic acid exhaled, and compared it with the amount
of heat lost by the same animal in a definite time.3 Here
he met with some difficulty, and found that the heat pro-
duced, according to his calculations, did not quite equal the
heat lost. In later memoirs he ascertained positively that
the carbonic acid exhaled in respiration did not represent
the totality of the oxygen consumed ; and he attributed the
production of heat in part to the union of oxygen with hy-
drogen.4 Since it has been ascertained that oxygen is dis-
solved, as oxygen, in the arterial blood, that it disappears in
part or entirely in the capillary circulation, that carbonic
acid is taken up by the venous blood, both in solution and in
feeble combination in the bicarbonates, to be discharged in
the lungs by displacement and the action of the pneumic

1 LAYOISIER, Memoire sur la nature du principe qui se combine avec les metaux
pendant leur calcination, et qui en augmente lepoids. — Histoire de V academic royale
des sciences, annee, 1775, Paris, 1778, pp. 521, 525.

2 LAVOISIER, Memoire sur la combustion en general. — Histoire de V academic
royale des sciences, annee, 1777, Paris, 1780, p. 599.

3 LAVOISIER ET DE LA PLACE, Memoire de la ckaleur. — Histoire de Vacademie
royale des sciences, annee, 1780, Paris, 1784, p. 407.

4 LAVOISIER, Memoire sur les alterations qui arrivent d Fair dans plusieurs
circonstances ou se trouvent les Jiommes reun'ts en societe. — Histoire de la societe
royale de medecine, annees, 1782 et 1783, Paris, 1787, p. 574.

SEGUIN ET LAVOISIER, Premier memoire sur la respiration des animaux. —
Histoire de Vacademie royale des sciences, annee, 1789, Paris, 1793, p. 566,
et seq.

RELATIONS OF ANIMAL HEAT TO RESPIRATION. 429

acid, and that the tissues themselves have the property of
appropriating oxygen and exhaling carbonic acid, those who
adopt the theory of Lavoisier have simply changed the seat
of oxidation from the lungs to the general system.

It has been proven beyond question that oxygen, of all
the principles introduced from without, is the one most im-
mediately necessary to nutrition; and it differs from the
class of substances ordinarily known as alimentary, only in
the fact that it is consumed more promptly and constantly.
In the same way, carbonic acid is to be regarded as an ele-
ment of excretion, like urea, creatine, etc., differing from
them only in the immediate necessity for its elimination.1
As the comparatively slow excretion of urea and other nitro-
genized matters is connected with the ingestion of ordinary
alimentary substances that are slowly appropriated by the
tissues, so the rapid elimination of carbonic acid is connected
with the equally rapid appropriation of oxygen. There is
no reason why we should not regard carbonic acid, like other
effete substances, as an excretion, the result of disassimila-
tion of the tissues generally ; but, more closely than any, it
is connected with the rapid and constant evolution of heat.
This view is proven by the experiments of Spallanzani,3
W. F. Edwards,3 and Collard de Hartigny.4 All of these
eminent observers demonstrated, beyond a doubt, that car-
bonic acid may be formed in the system and exhaled, in
animals deprived of oxygen, and that its exhalation will
take place from a piece of tissue freshly removed from a

1 Collard de Martigny, who was one of the most powerful opponents of
the combustion-theory of animal heat, concludes the account of his experi-
ments on the production of carbonic acid with the statement that it " is a prod-
uct of assimilative decomposition, secreted hi the capillaries, and excreted by the
lungs" (Journal de physiologic, Paris, 1830, tome x., p. 161).

8 SPALLAXZAXI, Jfemoires sur la respiration, Geneve, 1803, pp. 86, 343.

3 EDWARDS, De linfluen.ee, des agens physiques sur la vie, Paris, 1824, p.
443, et seq., and p. 455, et seq.

* COLLARD DE MARTIGNY, Recherches experimentales et critiques sur fabsorption
et sur F exhalation respiratoires. — Journal de physiologic, Paris, 1830, tome x., p.
124.

430 NUTRITION.

living animal and placed in an atmosphere of hydrogen or
nitrogen.

Experiments on the influence of the sympathetic nerves
upon the temperature of particular parts have completed the
chain of evidence in favor of the localization of the heat-
producing function in the tissues. It is not our purpose to
discuss the relations of the sympathetic system to nutrition,
deferring this subject until we come to treat specially of the
nervous system ; but the facts bearing on calorification are
briefly as follows :

If the sympathetic nerve be divided in the neck of a
rabbit, or any other warm-blooded animal, the side of the
head supplied by this nerve will become from flve to eight
or ten degrees warmer than the opposite side, or than the
rest of the body. This observation we have repeatedly veri-
fied. The conditions under which this local exaggeration of
the animal heat is manifested are, dilatation of the arteries
of supply of the part,- so that it receives very much more blood
than before, and increased activity of the general process of
nutrition. It also has been observed, in experiments upon the
horse, that the blood coming from the part is red, and con-
tains very much more oxygen than ordinary venous blood.1

The recent observations of MM. Estor and Saint-Pierre
show that the blood coming from inflamed parts, in which
there is a considerable elevation above the normal temper-
ature, is red, and contains from fifty to two hundred and
fifty per cent, more oxygen than ordinary venous blood.2
These facts are regarded as inconsistent with the view that
the temperature of parts is due chiefly to oxidation; but
when we consider the fact that, in the conditions above
mentioned, the actual quantity of blood circulating in these

1 BERNARD, Sur la quantite d'oxygene que contient le sang veneux dcs organes
glandulaires, d Petal def auction et d Tetat de repos. — Comptes rendus, Paris, 1858,
tome xlvii., p. 398, note.

2 ESTOR ET SAINT-PIERRE, Recherches experimentales sur les causes de la colora-
tion rouge des tissus enflammes. — Journal de Panatomie, Paris, 1864, tome i., p.
412, and Du siege dcs combustions respiratoires. — Ibid., 1865, tome ii., p. 314.

RELATIONS OF ANIMAL HEAT TO RESPIRATION. 431

parts is increased many times, the error in the deduction is
palpable enough. It is not sufficient to show that the blood
coming from an inflamed tissue, with an abnormally high
temperature, contains more oxygen than under ordinary
conditions, but it is indispensable to demonstrate that the
absolute quantity of oxygen consumed is diminished. For
example, if the venous blood should contain double the normal*
proportion of oxygen, but the quantity coming from the part
should be increased threefold, it is evident that the actual
consumption of oxygen would be doubled. As an illustra-
tion, let us assume that, in one minute, 100 parts of blood,
containing 10 parts of oxygen, circulate through a member,
losing in its passage 7*5 parts of oxygen, thus leaving a pro-
portion of 2*5 of oxygen for the venous blood ; if the part
become inflamed, let us suppose that during the same period,
300 parts of blood, with 30 parts of oxygen, pass through, but
that the venous blood contains five per cent, of oxygen, or 15
parts. That would show an actual consumption of 15 parts of
oxygen in inflammation, against 7'5 under normal nutrition.
Estor and Saint-Pierre do not state the amount of increase in
the quantity of blood circulating through inflamed tissues, but
they admit that, " in inflammation, the vessels are dilated, and
the current of blood is more rapid." * An increase in the
absolute quantity of blood passing through parts after divi-
sion of the sympathetic nerves distributed to the coats of the
blood-vessels has been observed by all who have experi-
mented on the subject ; and the increase is probably greater
than that which we have assumed in our argument. An
additional argument in favor of our interpretation of the
experiments of Estor and Saint-Pierre is the fact, noted by
them, that the blood from inflamed parts contains more
carbonic acid than ordinary venous blood.9

Taking into account all the facts bearing upon the ques-
tion, there can be little doubt, that while the processes of

1 Journal de V anatomic, Paris, 1865, tome ii., p. 314.
1 Idem., Paris, 1864, tome i., p. 412.

432 NUTRITION.

nutrition and disassimilation, involving changes in the nitro-
genized constituents of the blood and the tissues, are not
disconnected with calorification, the production of heat by
animals is most closely related to the appropriation of oxygen
and the formation of carbonic acid.

Intimate Nature of the Calorific Processes. — A compre-
hension of the intimate nature of the calorific processes
involves simply an answer to the question, how far we can
follow the material transformations in the organism, which
involve the consumption of certain principles, the production
of new compounds, and the evolution of heat. As regards
the nature of the intermediate processes connecting the dis-
appearance of oxygen with the production of carbonic acid,
we can only explain it by reciting the simple facts. Oxygen
disappears, carbonic acid is formed, and the carbon is fur-
nished, perhaps by the tissues, perhaps by the blood, probably
by both. It is probable that the intermediate changes are
more simple and rapid than those which intervene between the
appropriation of nitrogenized nutritive matter and the forma-
tion of the nitrogenized excretions ; but we have never been
able to follow either of these processes through all of their
different phases. We must be content, in the present con-
dition of our positive knowledge, to regard calorification as
one of the attendant phenomena of nutrition ; and we have
only to study as closely as possible the facts with regard to
the disappearance of certain principles and the formation of
effete matters, that are always and of necessity associated
with the development of heat.

Equalization of the Animal Temperature. — A study of
the phenomena of calorification in the human subject has
shown that under all conditions of climate the general heat
of the body is equalized. Nearly always, the surrounding
temperature is below the standard of the body, and there is,
of necessity, an active production of caloric. Under all con-

EQUALIZATION OF THE ANIMAL TEMPERATURE. 433

ditions, there is more or less loss of heat by evaporation from
the general surface, and when the surrounding atmosphere is
very cold, it becomes desirable to reduce this loss to the mini-
mum. This is done by appropriate clothing, which must
certainly be regarded as a physiological necessity. The
proper kind of clothing, the conducting power of different
materials, their porosity, etc., form important questions in
practical hygiene, and their full discussion belongs to special
treatises. Clothing protects from excessive heat as well
as cold. Thin, porous articles moderate the heat of the
sun, equalize evaporation, and afford great protection in
hot climates. In excessive cold, clothing is of the greatest
importance in preventing the escape of heat from the body.
When the body is not exposed to currents of air, the gar-
ments are chiefly useful as non-conductors, imprisoning many
layers of air, warmed by contact with the person. It is fur-
ther very important to protect the body from the wind,
which increases so greatly the loss of heat by evaporation.
It is wonderful, however, how intense a cold may be resisted
by healthy men under proper conditions of alimentation and
exercise and with the protection of appropriate clothing, as
in Arctic explorations, when the thermometer has for days
ranged from —60° to —70° Fahr.1

When from any cause there is a tendency to undue ele-
vation of the heat of the body, cutaneous transpiration is
increased, and the temperature is kept at the proper stand-
ard. We have already considered this question in treating
of the action of the skin, and have noted facts showing that
men can work when exposed to a heat much higher than
that of the body itself. The amount of vapor that is lost
lender these conditions is sometimes enormous, amounting to
from two to four pounds in an hour.2 We have often noted a
loss of between two and three pounds after exposure for less

1 HAYES, An Arctic Boat-Journey, Boston, 1860, pp. 257, 259, and American
Journal of the Medical Sciences, Philadelphia, 1859, Xew Series, vol. xxxviii.,
p. 114, et seq. 2 See page 140.

434 NUTRITION.

than an hour to a steam-bath of from 110° to 116° ; and a
much greater elevation of temperature, in dry air, can be
tolerated with impunity. We have alluded to some of the ob-
servations on the temperatures that could be borne without
bad results, in connection with the question of variations in
the heat of the body. In the experiments of Delaroche and
Berger, the temperature was considerably under 200°. 1 Tillet
recorded an instance of a young girl who remained in an oven
for ten minutes without inconvenience, at a temperature of
130° Reaumur, or 324*5° Fahr.2 Dr. Blagden, in his noted
experiments in a heated room, made in connection with
Drs. Banks, Solander, Fordyce, and others, found in one
series of observations, that a temperature of 211° could be
easily borne ; and at another time, the heat was raised to
260°. 3 Chabert, who exhibited in this country and in
Europe under the name of the " fire-king," is said to have
entered ovens at from 400° to 6000.4 Under these extraor-
dinary temperatures, the body is protected from the radiated
heat by clothing, the air is perfectly dry, and the animal
heat is kept down by excessive exhalation from the surface.
It is a curious fact, that after exposure of the body to an
intense dry heat or to a heated vapor, as in the Turkish and
Russian baths, when the general temperature is somewhat
raised and the surface is bathed in perspiration, a cold
plunge, which checks the action of the skin almost imme-
diately, is not injurious, and is rather agreeable. This pre-
sents a striking contrast to the effects of sudden cold upon
a system, heated and exhausted by long-continued exertion.
In the latter instance, when the perspiration is suddenly
checked, serious disorders of nutrition, inflammations, etc.,

1 See page 397.

2 TILLET, Memoire sur les degres extraordinaires de chaleur auxquelles les
hommes et les animaux sont capables de resister. — Histoire de Vacademie rot/ale des
sconces, annee, 1764, Paris, 1767, p. 188.

3 BLAGDEN, Experiments and Observations in an heated Room. — Philosophical
Transactions, London, 1775, pp. 196, 484.

4 DUNGLISON, Human Physiology, Philadelphia, 1856, vol. i., p. 598.

EQUALIZATION OF THE ANIMAL TEMPERATUBE. 435

are very liable to occur. The explanation of this, as far as
we can present any, seems to be the following : When the
skin acts to keep down the temperature of the body in sim-
ple exposure to external heat, there is no modification in
nutrition, and the tendency to an elevation of the animal
temperature comes from causes entirely external. It is a
practical observation that no bad effects are produced, under
these circumstances, by suddenly changing the external con-
ditions; but when the animal temperature is raised by a
modification of the internal nutritive processes, as in pro-
longed muscular effort, these changes cannot be suddenly
arrested ; and a suppression of the compensative action of
the skin is apt to produce disturbances in nutrition, very
often resulting in inflammations.

CHAPTEK XV.

MOVEMENTS GENERAL PROPERTIES OF CONTRACTILE TISSUES.

THE organic, or vegetative functions of animals involve
certain movements ; and almost all animals possess, in addi-
tion, the power of locomotion. "Very many of these move-
ments have, of necessity, been considered in connection with
the different functions ; as the action of the heart and ves-
sels in the circulation ; the uses of the muscles in respira-
tion ; the ciliary movement in the air-passages ; the muscular
acts in deglutition ; the peristaltic movements ; and the me-
chanism of defecation and urination. There remain, how-
ever, certain general facts with regard to various kinds of
movement and the mode of action of the different varieties
of muscular tissue, that will demand more or less extended
consideration. As regards the exceedingly varied and com-
plex acts concerned in locomotion, it is difficult to fix the
limits between anatomy and physiology. A full compre-
hension of such movements must be preceded by a complete

AMORPHOUS CONTRACTILE SUBSTANCE. 437

descriptive anatomical account of the passive and active or-
gans of locomotion ; and special treatises on anatomy almost
invariably give the uses and actions, as well as the structure
and relations of these parts.

Amorphous Contractile Substance. — In some of the very
lowest orders of beings, in which hardly any thing but amor-
phous matter and a few granules can be recognized by the
microscope, certain movements of elongation and retraction
of their amorphous substance have been observed. In the
higher animals, similar movements have been noticed in cer-
tain of their structures, such as the leucocytes, the contents
of the ovum, epithelial cells, and connective-tissue cells.
These movements are generally simple changes in the form
of the cell, nucleus, or whatever it may be. They are sup-
posed to depend upon an organic principle called sarcode, or
protoplasm ; 1 but it is not known that such movements are
characteristic of any one definite proximate principle, nor is
it easy to determine their cause and their physiological im-
portance. In the anatomical elements of adult animals of
the higher classes, the sarcodic movements usually appear
slow and gradual, even when viewed with high magnifying
powers; but in some of the very lowest orders of* being,
where these movements serve as the means of progression,
they are more rapid.

It does not seem possible, in the present condition of our
knowledge, to explain the nature and cause of the move-
ments of homogeneous contractile substance ; and it must

J5 J

be excessively difficult, if not impossible, to observe directly
the effects of different stimuli, in the manner in which we
study the movements of muscles. As far as we can judge,

1 KUHXE, Untersuchungen uber das Protoplasma und die Contractilitat, Leipzig,
1864. In this very elaborate memoir almost all varieties of contraction are re-
ferred to the action of the single principle, protoplasm. The chief physiological
interest, however, is attached to this explanation of muscular contraction ; but
there are few writers of authority who accept the view that it is entirely due to
the presence of the so-called protoplasm.

438 MOVEMENTS.

they are analogous to the ciliary movements, the cause of
which is equally obscure.

Ciliary Movements. — The epithelium covering certain
of the mucous membranes is provided with little hair-like
processes upon the free portion of the cells, called cilia.
These are in constant motion, from the beginning to the end
of life, and produce currents on the surfaces of the mem-
branes to which they are attached, the direction being always
from within outward. In many of the infusoria, the ciliary
motion serves as a means of progression, effects the intro-
duction of nutriment into the alimentary canal, and, indeed,
is almost the sole agent in the performance of the func-
tions involving movement. Even in higher classes, as the
mollusca, the movements of the cilia are of great impor-
tance. In man, and the warm-blooded animals generally,
the ciliated or vibratile epithelium is of the variety called
columnar, conoidal, or prismoidal. The cilia are attached to
the thick ends of the cells, and form on the surface of the
membrane a continuous sheet of vibrating processes.

It is unnecessary to describe in detail the size and form of
the cells provided with cilia, as their variations in different
situations have been and will be considered in connection with
the physiological anatomy of different parts. In general
structure, the ciliary processes are entirely homogeneous, and
gradually taper from their attachment to the cell to an ex-
tremity of excessive tenuity. Although anatomists, from
time to time, have described striae at the bases of the cilia,
and have attempted to explain their motion by a kind of
muscular action, no well-defined structure has ever been
actually demonstrated in their substance.

Certain currents were observed in the infusoria, mollusca,
and other of the lower order of animals, long before the
structure of the cilia had been accurately described ; but in
1835, Purkinje and Yalentin, in a very elaborate memoir,
described these structures fully, and noted the situations

CILIAHY MOVEMENTS. 439

in which they are to be found in the human subject.1
Their presence has been demonstrated on the following
surfaces : The respiratory passages, including the nasal fos-
sae, the pituitary membrane, the summit of the larynx, the
bronchial tubes, the superior surface of the velum palati,
and the Eustachian tubes ; the sinuses about the head ; the
lachrymal sac and the internal surface of the eyelids ; the geni-
tal passages of the female, from the middle of the neck of the
uterus to the extremities of the Fallopian tubes ; and the ven-
tricles of the brain. They probably exist also at the neck of
the capsule of Miiller, in the cortical substance of the kid-
ney. In these situations, to each cell
of conoidal epithelium are attached
from six to twelve prolongations,2
about ssooo of an inch in thickness' at
their base, and from yoW *° ToVrr °f
an inch in length.3 The appearance
of the cilia in detached cells is repre-
sented in Fig. 15. When seen in situ,
they appear regularly disposed on the
surface, are of nearly equal length,
and are all slightly inclined in the

-,. .. f» . T . «,, . , Ciliated epithelium. (LOKGET,

direction Ot the Opening OI the Cavity Tralte de physiologic, Paris,
•,.-,,,, 1869, tome ii., p. 579.)

lined by the membrane.

The ciliary motion is one of the most beautiful physio-
logical demonstrations that can be made with the micro-
scope. By scraping the roof of the mouth of a living frog,
the mucous membranes of the respiratory passages in a
warm-blooded animal just killed, the beard of the oyster or
clam, and placing the preparation, moistened with a little
serum, under a magnifying power of about two hundred and

1 PURKINJE AND VALENTIN*, Discovery of Continual Vibratory Motions, pro-
duced by Cilia, as a general Phenomenon in Reptiles, Birds, and Mammiferous
Animals. — Edinburgh New Philosophical Journal, 1835, vol. xix., p. 118,
et seq.

* BECLARD, Traite elementaire dt physiologic humaine, Paris, 1859, p. 497.

3 POUCHET, Precis d?histologie humaine, Paris, 1864, p. 189.

440 ' MOVEMENTS.

fifty diameters, the currents produced in the liquid will be
strikingly exhibited. The movements may be studied in de-
tached cells, in the human subject, by introducing a feather
into the nose, when a few cells will be removed with the
mucus, and can be observed in the same way.1 This demon-
stration serves to show the similarity between the movements
in man and in the lower orders of animals. When the move-
ments are seen in a large number of cells in situ, the ap-
pearance is very graphically illustrated by the apt comparison
of Henle to the undulations of a field of wheat agitated by
the wind.2 In watching this movement, it is usually seen
to gradually diminish in rapidity, until what at first ap-
peared simply as a current, produced by movements too
rapid to be studied in detail, becomes revealed as distinct
undulations, in which the action of individual cilia can be
readily studied. Purkinje and Valentin describe several
kinds of movement,3 but the most common is a bending of
the cilia, simultaneously or in regular succession, in one di-
rection, followed by an undulating return to the perpendicu-
lar. The other movements, such as the infundibuliform, in
which the point describes a circle around the base, the pen-
dulum-movement, etc., are not common, and are unimpor-
tant.

The combined action of the cilia upon the surface of a
mucous membrane, moving as they do in one direction, is to
produce currents of considerable power. This may be illus-
trated under the microscope by covering the surface with a
liquid holding little solid particles in suspension. In this case
the granules are tossed from one portion of the field to another
with considerable force. It is not difficult, indeed, to meas-
ure in this way the rapidity of the ciliary currents. In the
frog it has been estimated at from ^-g- to T^ of an inch per
second, the number of vibratile movements being from

1 BECLARB, op. cit., p. 497.

2 HENLE, Traite tfanatomie generate^ Paris, 1843, tome i., p. 263.

3 Loc. cit.

CILIAEY MOVEMENTS. 441

seventy-five to one hundred and fifty per minute. In the
fresh water polyp the movements are more rapid, being from
two hundred and fifty to three hundred per minute.1 There
is no reliable estimate of the rapidity of the ciliary currents
in man, but they are probably more active than in animals
low in the scale.a

The movements of cilia, like those observed in fully de-
veloped spermatozoids, seem to be entirely independent of
nervous influence, and are affected only by purely local con-
ditions. They will continue, under favorable circumstances,
for more than twenty-four hours after death, and can be seen
in cells entirely detached from the body when they are moist-
ened with proper fluids. Beclard states that in the tortoise,
the movement may be preserved for several weeks after the
death of the animal.3 When the cells are moistened with
pure water, the activity of the movement is at first increased ;
but it soon disappears as the cells become swollen. Acids
arrest the movement, but it may be excited by feeble alka-
line solutions. All abnormal conditions have a tendency
either to retard or to abridge the duration of the ciliary mo-
tion. It is true that when the movement is becoming feeble,
it may be temporarily restored by very dilute alkaline solu-
tions, but the ordinary stimuli, such as are capable of exciting
muscular contraction, are without effect. Purkinje and
Valentin, Sharpey, and others have attempted to excite
the movements of cilia by galvanic stimulus, but without
success.4 Anaesthetics and narcotics, which have such a
decided effect upon muscular action, have no influence upon
the cilia.

It is useless to follow the speculations that have been

1 BECLARD, Traite elementaire de physiologic, Paris, 1859, p. 498.

8 A pupil of M. Bernard, M. Calliburces, has devised a very ingenious in-
strument for measuring the rapidity of the ciliary motion (BERNARD, Lemons sur
les proprietes &s tissus vivants, Paris, 1866, p. 139, et seg.).

3 Zoo. cit.

4 SHARPEY, Cyclopaedia of Anatomy and Physiology, London, 1835-'36, vol. i.,
p. 634, Article, Cilia.

442 MOVEMENTS.

advanced to account for the movement of cilia. There is no
muscular structure, no connection with the nervous system,
and there seems to be no possibility of explaining the move-
ment except by a bare statement of the fact that the cilia
have the property of moving in a certain way so long as they
are under normal conditions. As regards the physiological
uses of these movements, it is sufficient to refer to the physi-
ology of the parts in which cilia are found, where the pecu-
liarities of their action are considered more in detail. In
the lungs and the air-passages generally, and the genital
passages of the female, the currents are of considerable im-
portance ; but it is difficult to imagine the use of these move-
ments in certain other situations, as the ventricles of the
brain.

Movements due to Elasticity. — There are certain impor-
tant movements in the body that are due simply to the action
of elastic ligaments or membranes. These are entirely distinct
from muscular movements, and are not even to be classed
with the movements produced by the resiliency of muscular
tissue, in which that curious property, called muscular toni-
city, is more or less involved. Movements of this kind are
never excited by nervous, galvanic, or other stimulus, but
consist simply in the return of movable parts to a certain
position after they have been displaced by muscular action,
and the reaction of tubes after forcible distention, as in the
walls of the large arteries.

Elastic Tissue. — Most writers of the present day adopt
the division of the elastic tissue, first made by Henle,1 into
three varieties. This division relates to the size of the
fibres ; and all varieties are found to possess essentially the
same chemical composition and general properties, includ-
ing the elasticity for which they are so remarkable. On
account of the yellow color of this tissue, presenting, as it
does, a strong contrast to the white, glistening appearance

1 HENLE, Traite & anatomic generale, Paris, 1843, tome i., p. 430.

MOVEMENTS DUE TO ELASTICITY. 443

of the inelastic fibres, it is frequently called the yellow elas-
tic tissue.

The first variety of elastic tissue is composed of small
fibres, generally intermingled with fibres of the ordinaiy
inelastic tissue. These are sometimes called by the French,
dartoic fibres. They possess all the chemical and physical
characters of the larger fibres, but are excessively minute,
measuring from 25i00 to ^^ or -^^ of an inch in diame-
ter.1 If we add acetic acid to a preparation of ordinary
connective tissue, the inelastic fibres are rendered semitrans-
parent, but the elastic fibres are unaffected and become very
distinct. They are then seen isolated — that is, never arranged
in bundles — always with a dark, double contour, branching,
brittle, and when broken, their extremities curled and pre-
senting a sharp fracture, like a piece of India-rubber. These
fibres pursue a wavy course through the bundles of inelastic
fibres in the areolar tissue and in most of the ordinary fibrous
membranes, and here they exist as an accessory anatomical
element. They are found in greater or less abundance in the
situations just mentioned ; also in the ligaments (but not the
tendons) ; in the layers of involuntary muscular tissue ; the
true skin ; the true vocal cords ; the trachea, bronchial tubes,
and largely in the parenchyma of the lungs ; the external
layer of the large arteries ; and, in brief, in nearly all situa-
tions in which the ordinary connective tissue exists.

The second variety of elastic tissue is composed of fibres,
larger than the first, ribbon-shaped, with well-defined out-
lines, anastomosing, undulating or curved in the form of the
letter S, presenting the same curled ends and sharp fracture
as the smaller fibres. These measure from g^ to ^Vfr of
an inch in diameter.2 Their type is found in the ligamenta
subflava and the ligamentum nuchse. They are also found

1 POUCHET, Freds cCJustologie humaine, Paris, 1864, p. 62. In order to
secure as much uniformity as possible in our measurements of microscopic
structures, we have generally followed the French school of histologists.

2 POUCHET, loc. cit.

444 MOVEMENTS.

in some of the ligaments of the larynx, the stylo-hyoid liga-
ment, and the suspensory ligament of the penis. The form
and arrangement of these fibres may be very beautifully
demonstrated by tearing off a portion of the ligamentum
nuchse and lacerating it with needles in a drop of acetic
acid. The action of the acetic acid renders the accessory
structures of the ligament transparent, and the elastic fibres
become very distinct. The same may be accomplished by
boiling the tissue for a short time in caustic soda.

The third variety of elastic tissue can hardly be said to
consist of fibres, their branches are so short and their anas-
tomoses so frequent. This kind of structure is found form-
ing the middle coat of the large arteries, and has already
been described in connection with the vascular system.1
The fibres are very large, flat, with numerous short
branches, " which unite again with the trunk from which
they originate or with adjacent fibres. In certain situ-
ations, the interstices are considerable, in proportion to the
diameter of the fibres, and the anastomosing branches are
given off at acute angles, so that they follow pretty closely
the direction of the trunks, and the anastomoses do not dis-
turb the longitudinal direction and parallelism of the fibres.
Indeed, the anastomoses are so numerous, and the intervals
so small, proportionally to the fibres, that we would believe
we had under observation a reticulated membrane, present-
ing openings, rounded and oval, some large and others
small." 2 These anastomosing fibres, forming the so-called
fenestrated membranes, are arranged in layers, and the struc-
ture is sometimes called the lamellar elastic tissue.

The great resistance which the elastic tissue presents to
chemical action serves to distinguish it from nearly every
other structure in the body. "We have already seen that it

1 See vol. i., Circulation, p. 244.

2 The above description, taken from Henle's general anatomy, conveys a
very clear idea of the arrangement of the large elastic fibres in the " fenestrated
membranes" (HENLE, Traite d'anaiomie generate, Paris, 1843, tome i., p. 431).

MUSCULAR MOVEMENTS. 445

is not affected by acetic acid or by boiling with caustic soda.
It is not softened by heat, by prolonged boiling in water,
but is slowly dissolved, without decomposition, by sulphuric,
nitric, and hydrochloric acid, the solution not being precipi-
table by potash. Its organic base is a nitrogenized sub-
stance called elasticine ; l containing carbon, hydrogen, oxy-
gen, and nitrogen, without sulphur. This is supposed to be
identical with the sarcolemma of the muscular tissue.8

The purely physical property of elasticity plays an im-
portant part in many of the animal functions. TVe have
already had an example of this in the action of the large
arteries in the circulation, and in the resiliency of the paren-
chyma of the lungs ; and we will have occasion, in treating
of the functions of other parts, to refer again to the uses of
elastic membranes and ligaments. The ligamenta subflava
and the ligamentum nuchse are important in aiding to main-
tain the erect position of the body and head, and to restore
this position when flexion has been produced by muscular
action. Still, the contraction of muscles is also necessary to
keep the body in the vertical position.

Muscular Movements.

Muscular movements are observed only in the higher
classes of animals. Low in the scale of animal life, we have
the contractions of amorphous substance and ciliary mo-
tion ; and in some vegetables, movements, even attended
with locomotion, have been observed. These facts make the
absolute distinction between the two kingdoms a question of
some difficulty ; but in animals only do we have separate
muscular systems.

The muscular movements capable of being excited by
stimulus of various kinds are divided into voluntary and
involuntary ; and generally there is a corresponding divi-

1 See vol. i., Introduction, p. 91

9 ROBIN ET YERDEIL, Traite de chimie anatomique, Paris, 1853, tome iii.,
p. 364.

446 MOVEMENTS.

sion of the muscles as regards their minute anatomy. The
latter, however, is not absolute ; for there are certain invol-
untary functions, like the action of the heart or the move-
ments of deglutition, that require the rapid, vigorous con-
traction characteristic of the voluntary muscular tissue ; and
here we do not find the structure of the involuntary mus-
cles. With a few exceptions, however, the anatomical
division of the muscular tissue into voluntary and involun-
tary is sufficiently distinct.

Physiological Anatomy of the Involuntary Muscles.—
We have so often described this tissue, as it is found in the
vascular system, the digestive organs, skin, and other situ-
ations, that it will not be necessary, in this connection,
to give more than a sketch of its structure and mode of
action.

The involuntary muscular system presents a striking
contrast to the voluntary muscles, not only in its minute
anatomy and mode of action, but in the arrangement of its
fibres. While the voluntary muscles are almost invariably
attached by their two extremities to movable parts, the in-
voluntary muscles form sheets or membranes in the walls of
hollow organs, and by their contraction simply modify the
capacity of the cavities which they enclose.

Various names have been given to this tissue to denote
its distribution, mode of action, or structure. The name
involuntary muscle indicates that its contraction is not
under the control of the will; and this is the fact, these
muscles being chiefly animated by the sympathetic system
of nerves, while the voluntary muscles are supplied mainly
from the cerebro-spinal system. On account of the peculiar
structure of these fibres, they have been called muscular
fibre-cells, smooth muscular fibres, pale fibres, non-striated
fibres, fusiform fibres, and contractile cells. The distribu-
tion of these fibres to parts concerned in the organic or
vegetative functions, as the alimentary canal, has given

INVOLUNTARY MUSCLES.

them the name of organic muscular fibres, or fibres of
organic, or vegetative life.

It is difficult to isolate the individual fibres of this tissue
in microscopical preparations ; and when seen in situ, their
borders are faint, and we can make out their arrangement
best by the appearance of their nuclei. Robin recommends
soaking the tissue for a few days in a mixture of one part of
ordinary nitric acid to ten of water.1 This renders the
fibres dark and granular, makes their borders very distinct,
and frequently some of them become entirely isolated. The
nuclei, however, are obscured. In their natural condition,
the fibres are excessively pale, very finely granular, flat-
tened, and of an elongated spindle-shape, with a very long,
narrow, almost linear nucleus in the centre. The nucleus
generally has no nucleolus, and it is sometimes curved,
or shaped like the letter S. The ordinary length of these
fibres is about -g-J-g-, and their breadth about ^nnnr °f an
inch. In the gravid uterus they undergo remarkable hyper-
trophy, measuring here from -§V to -^ of an inch in length,
and 20*0 0 of an inch in breadth.8 The peculiarities of their
structure in the uterus will be fully considered under the
head of generation.

In the contractile sheets formed of the involuntary mus-
cular tissue, the fibres are arranged side by side, closely ad-
herent, and their extremities, as it were, dove-tailed into
each other. Generally the borders of the fibres are regular
and their extremities simple; but sometimes the ends are
forked, and the borders present one or more little projec-
tions. It is very seldom that we see the fibres in a single
layer, except in the very smallest arterioles. Usually the
layers are multiple, being superimposed in regular order.
The action of acetic acid is to render the fibres pale, so that
their outlines become almost indistinguishable, and to bring

1 ROBIN, Recherches sur quelques particularites de la structure des capittaires de
Fencephale. — Journal de la physiologic, Paris, 1859, tome ii., p. 541.

2 POUCHET, op. cit., p. 65.

448 MOVEMENTS.

out the nuclei more strongly. If we have an indistinct
sheet of this tissue in the field of view, the addition of acetic
acid, by bringing out the long, narrow, and curved nuclei
arranged in regular order, and rendering the fibrous and
other structures more transparent, will often enable us to
recognize its character.

Contraction of the Involuntary Muscular Tissue. — The
mode of contraction of the involuntary muscles is peculiar.
It does not take place immediately upon the reception of a
stimulus, applied either directly or through the nerves, but
is gradual, enduring for a time and then followed by slow
and gradual relaxation. A description of the peristaltic
movements of the intestines gives a perfect idea of the mode
of contraction of these fibres, with the gradual propagation
of the stimulus along the alimentary canal, as the food makes
its impression upon the mucous membrane.1 An equally
striking illustration is afforded by labor-pains. These are
due to the muscular contractions of the uterus, and last
from a few seconds to one or two minutes.3 Their gradual
access, continuation for a certain period, and gradual disap-
pearance coincide exactly with the history of the contrac-
tions of the involuntary muscular fibres.

The strong points of contrast between the mode of
action of the striated and the smooth muscular fibres are
very well brought out in a recent paper by MM. Legros and
Onimus. These observers, after carefully studying the
structure and properties of the " muscles of vegetative life,"
give, in substance, the following resume of their physio-
logical action :

The contraction is slow, and the fibres return slowly to a
condition of repose. The movements are always involun-
tary. Peristaltic action is the rule ; and the contraction
takes place progressively and without oscillations. Con-

1 See vol. ii., Digestion, p. 376, et seq.

2 CAZEAUX, A Theoretical and Practical Treatise on Midwifery, Philadelphia,
1857, p. 123.

VOLUNTARY MUSCLES. 4:49

tractility persists for a long time after death. Arrest of
function is followed by little or no atrophy, and hyper-
trophy is very marked as the result of exaggerated action.
Excitation of the nerves has less influence upon contraction
of these fibres than direct excitation of the muscles. The
involuntary muscular tissue is regenerated very rapidly,
while the structure of the voluntary muscles is restored with
great difficulty after destruction or division.1

Physiological Anatomy of the Voluntary Muscles. — A
voluntary muscle is the most highly organized, and is
possessed of the most varied endowments, of all living
structures. It contains, in addition to its own peculiar
contractile substance, fibres of inelastic and elastic tissue,
adipose tissue, numerous blood-vessels, nerves, and lym-
phatics, with certain nuclear and cellular anatomical ele-
ments. The muscular system constitutes by far the greatest
part of the organism, and its nutrition consumes a large pro-
portion of the reparative material of the blood, while its
clisassimilation furnishes a corresponding quantity. of excre-
mentitious matter. The condition of the muscular system,
indeed, is an almost unfailing evidence of the general state
of the body, allowing, of course, for peculiarities in different
individuals. Among the characteristic properties of the
muscles are, elasticity, a constant and insensible tendency to
contraction, called tonicity, the power of contracting forci-
bly on the reception of a proper stimulus, called irritability,
a peculiar kind of sensibility, and the faculty of generating
galvanic currents. The relations of particular muscles, as
taught by descriptive anatomy, involve special functions ;
but the most interesting physiological points connected with
this system relate to the general properties and functions of
the muscles, and must necessarily be prefaced with a sketch
of their general anatomy.

1 LEGROS ET OXIMUS, De la contraction des muscles de la vie vegetative. — Jour'
nal de Tanaiomie, Paris, 1869, tome vi., p. 435.
29

450 MOVEMENTS.

It has been demonstrated by minute dissection that all
of the red, or voluntary muscles are made up of a great
number of microscopic fibres, known as the primitive mus-
cular fasciculi. These are called red, striated, or voluntary
fibres, or the fibres of animal life. Their structure is com-
plex, and they may be subdivided longitudinally into fibril-
lae, and transversely into disks, so that it is somewhat
doubtful as to what is, strictly speaking, the ultimate ana-
tomical element of the muscular tissue.

A primitive muscular fasciculus runs the entire length
of the muscle, and is enclosed in its own sheath, without
branching or inosculation. This sheath contains the true
muscular substance only, and is not penetrated by blood-
vessels, nerves, or lymphatics. If we view with the micro-
scope a thin transverse section of a muscle, the divided ends
of the fibres will present an irregularly polygonal form with
rounded corners. They seem to be cylindrical, however,
when viewed in their length and isolated. Their color by
transmitted light is a delicate amber, resembling somewhat
the color of the blood-corpuscles.

The primitive fasciculi vary very much in size in dif-
ferent individuals, and in the same individual under different
conditions and in different muscles. As a rule they are
smaller in young persons and in females than in adult males.
They are comparatively small in persons of slight muscular
development. In persons of great muscular vigor, or when
the general muscular system or particular muscles have been
increased in size and power by exercise, the fasciculi are
relatively larger. It is probable that the physiological in-
crease in the size of a muscle from exercise is due to an
increase in the size of the preexisting fasciculi, and not to
the formation of any new elements. In young persons the
fasciculi are from 17100 to 12*00 of an inch in diameter. In
the adult they measure from ^-J-0- to -^^ of an inch.1

The appearance of the primitive muscular fasciculi

1 LITTRE ET ROBIN, Dictionnaire de Medecine, Paris, 1865, Article, Musculaire.

VOLUNTARY MUSCLES. 451

under the microscope is characteristic and unmistakable.
They present regular transverse striae, formed of alternating
dark and clear bands about 25^0() of an inch wide. These
are generally very distinct in healthy muscles. In addition
we frequently observe longitudinal striae, not so distinct,
and quite difficult to follow to any extent in the length of
the fasciculus, but tolerably well marked, particularly in
muscles that are habitually exercised. The muscular sub-
stance, presenting this peculiar striated appearance, is en-
closed in an excessively thin but elastic and resisting
tubular membrane, called the sarcolemma, or myolemma.
According to Robin,1 the sarcolemma is composed of the
same substance as the elastic tissue. This envelope cannot
be seen in ordinary preparations of the muscular tissue ; but
it frequently happens that the contractile muscular sub-
stance is broken, leaving ths sarcolemma intact, which
gives a good view of the membrane and conveys an idea of
its strength and elasticity. Attached to the inner surface of
the sarcolemma, are numerous small, elongated nuclei with
their long diameter in the direction of the fasciculi. These
are not usually well seen in the unaltered muscle, but the
addition of acetic acid renders the muscular substance pale
and destroys the striae, when the nuclei become very
distinct.

Water, after a time, acts upon the muscular tissue, ren-
dering the fasciculi somewhat paler and larger. Acetic acid
and alkaline solutions efface the striae, and the fibres become
semitransparent.

In fasciculi that are slightly decomposed, there is fre-
quently a separation at the extremity into numerous smaller
fibres, called fibrillae. These, when isolated, present the same
striated appearance as the primitive fasciculus ; viz., alter-
nate dark and light portions. They measure about 2g^o6
of an inch in diameter, and their number, in the largest
primitive fibres, is estimated by Kolliker at about two thou-

1 Loc. tit.

452 MOVEMENTS.

sand.1 The structure of the fibrillae, which are regarded by
many as the anatomical elements of the muscular tissue, has
been very closely studied by Rouget ; and, although all of
his observations, particularly those with regard to the spiral
form of the fibrillae, have not been confirmed, there can be
hardly any doubt that their structure is uniform, the appear-
ance of alternate dark and light segments being due to dif-
ferences in thickness.2 In fact, it is well known that water,
by its simple mechanical action, swells the fibrillge, and
causes the striae to disappear.

Late researches have shown that the interior of each prim-
itive fasciculus is penetrated by an excessively delicate mem-
brane, closely surrounding the fibrillse. This arrangement
may be distinctly seen in a thin section of a fibre treated
with a solution of salt in water in the proportion of five
parts per thousand.3 The arrangement of this membrane,
which is nothing more nor less than a series of tubular
sheaths for the fibrillae, is a strong argument in favor of the
view that the fibrilla is the anatomical element of the mus-
cular tissue.

By the action of certain reagents, such as alcohol, hydro-
chloric acid, or gastric juice, the primitive fasciculi may
be separated into disks corresponding to the transverse striae.
Bowman, in his elaborate investigations into the structure
of the muscles, noted this fact, and concluded that the cleav-
age in this direction was as easily effected as the separation
into fibrillae. He regarded the primitive fasciculi as com-
posed of fibrillae, and these as made up of little particles,
alternately dark and light, wrhich he called sarcous ele-
ments.4 Subsequent investigations, however, have not en-

1 KOLLIKER, Elements tFhistologie humaine, Paris, 1868, p. 207.

2 ROUGET, Sur les phenomenes de polarization qui s'observent dans quelqucs tis-
sus. — Journal de la physiologic, Paris, 1862, tome v., p. 263, et seq., and Memoire
sur les tissus contractile^ et la contractilite. — Id., 1863, tome vi., p. 647, et scq,

3 KOLLIKER, Elements d}histologie humaine, Paris, 1868, p. 201.

4 BOWMAN, On the Minute Structure and Movements of Voluntary Muscle. —
Philosophical Transactions, London, 1840, p. 457, et seq.

VOLUNTAEY MUSCLES.

453

FIG. 16.

tirely confirmed this view ; and the separation into disks is

now pretty generally regarded as artificial.

When we come to
the question of the real
anatomical element of
the muscular tissue,
there are only two
reasonable yiews that
present themselves.
One is that all subdi-
vision of the primitive
fasciculus is artificial,
and that it, with its
investing membrane,
the sarcolemma, is the
true element. An ar-
gument in favor of

Voluntary muscular fibre*. A. Transverse striae and tlllS Opinion IS that
nuclei of a primitive fasciculus (maeuified 250 di-
ameters); B. Longitudinal stria? and fibrillse of a flip tissue is lllOSt read-
primitive fasciculus in which the sarcolemma has l

been lacerated at one point by pressure. (SAPPET, 1]^ ipnirfltpfl into "Pn«i-
Traite d'anatomie, Paris, 1868, tome it, p. 22.)

ciculi, each enclosed in

its own membrane, and not penetrated by vessels, nerves,
or lymphatics ; while the fibrillae are situated in a reticulum
of canals, from which they cannot readily be isolated. The
other opinion, that the fibrillse are the ultimate elements, is
based on the fact that these little fibres present the striae and
all the anatomical characteristics of the primitive fasciculi,
and that by far the most natural and easy mode of separa-
tion of these fasciculi is in a longitudinal direction. The
question of adopting one or the other of these views is not
of very great physiological importance.

Fibrous and Adipose Tissue in the Voluntary Muscles.
-The structure of the muscles strikingly illustrates the re-
lations between the principal and the accessory anatomical
elements of tissues. The characteristic or principal element

454: MOVEMENTS.

is, of course, the muscular fibre or fibrilla ; but we also find
in the substance of the muscles certain anatomical elements,
not peculiar to the muscles, and merely accessory in their
function, but none the less necessary to their proper consti-
tution. For example, every muscle is composed of a number
of primitive fasciculi ; but these are gathered into secondary
bundles, which in turn are collected into bundles of greater
and greater size, until, finally, the whole muscle is enveloped
in its sheath, and is penetrated by a fibrous connective sub-
stance. We find, probably, in the muscles, the best illustra-
tion of the structure of what is known as the connective
tissue.

Connective Tissue. — We have already had occasion to
refer to certain of the elements of connective tissue, more
especially the inelastic and elastic fibres. In this connection
we shall treat specially of the connective tissue of the mus-
cles ; but our description will answer for almost all situations
in which fibrous tissue exists merely for the purpose of hold-
ing parts together. In the muscles we have a membrane
holding a number of the primitive fasciculi into secondary
bundles. This is known as the perimysium. The fibrous
membranes that connect together these secondary bundles
with their contents are enclosed in a sheath enveloping the
whole muscle, sometimes called the external perimysium.
The peculiarity of these membranes, and their distinction
from the sarcolemma, is that they have a fibrous structure
and are connected together throughout the muscle, while
the tubes forming the sarcolemma are structureless, and each
one is distinct.

The name now most generally adopted for the tissue un-
der consideration is connective tissue. It has been called
cellular, areolar, or fibrous, but most of these names were
given to it without a clear idea of its structure. Its prin-
cipal anatomical element is a fibre of excessive, almost im-
measurable, tenuity, wavy, and with a single contour. These

VOLUNTARY MUSCLES. 4:55

fibres are collected into bundles of very variable size, and are
held together by an adhesive amorphous substance. The
wavy lines that mark the bundles of fibres give them a very
characteristic appearance.

The direction and arrangement of the fibres in the vari-
ous tissues present marked differences. In the loose areolar
tissue beneath the skin and between the muscles, and, in the
loose structure surrounding some of the glands and connect-
ing the sheaths of blood-vessels and nerves to the adjacent
parts, the bundles of fibres form a large net-work, and are
very wavy in their course. In the strong, dense membranes,
as the aponeuroses, the proper coats of many glands, the
periosteum and perichondrium, and the serous membranes,
the waves of the fibres are shorter, and the fibres themselves
interlace much more closely. In the ligaments and tendons,
the fibres are more nearly straight, and are all arranged
longitudinally.

On the addition of acetic acid, the bundles of inelastic
fibres swell up, become semitransparent, and the nuclei and
elastic fibres are brought out. The proportion of elastic
fibres differs very much in different situations, but they are
all of the smallest variety, and present a striking contrast to
the inelastic fibres in their form, and size. Though they
are still very small, they always present a double contour.

Certain cellular and nuclear elements are always found
in the connective tissue. The cells have been described
under the name of connective-tissue cells. They are very
irregular in size and form, some of them being spindle-shaped
or caudate, and others star-shaped. They possess one, and
sometimes two or three clear, ovoid nuclei, with distinct nu-
cleoli. On the addition of acetic acid the cells disappear,
but the nuclei are unaffected. These are the fibro-plastic ele-
ments of Lebert,1 and the embryo-plastic elements of Eobin.2

1 LEBERT, Physiologic pathologique, Paris, 1845, tome ii., page 120.
8 LITTBE ET ROBIN*, Didionnaire de medecine, Paris, 1865, Article, Embryo-
plastique.

456

MOVEMENTS.

It is impossible to give any accurate measurements of the
cells, on account of their great variability in size. The
length of the nuclei is from -g-gVo" to ^-^Vo- °f an inch, and
their diameter, from -g^Vo" to ^Vo of an inch.1 The appear-
ance of the connective tissue, with a few cells and nuclei, is
represented in Fig. 1Y.

FIG. 17.

Loose net-work of connective tissue from the liaraan subject, showing the fibres and
cells, a, a, a capillary blood-vessel. (ROLLETT, in STBICKER, Handbuch der Lehre
von den Geweben, Leipzig, 1868, S. 57.)

Between the muscles, and in the substance of the mus-
cles between the bundles of fibres, there always exists a
greater or less quantity of adipose tissue in the meshes of
the fibrous structure.

Blood-vessels and Lymphatics. — The muscles are abun-
dantly supplied with blood-vessels, generally by a number
of small arteries, with two satellite veins. The capillary ar-

1 ROBIN, loc. cit.

VOLUNTARY MUSCLES. 457

rangement in this tissue is peculiar. From the smallest
arterioles, capillary vessels are given off, arranged in a net-
work with tolerably regular, oblong, rectangular meshes,
their long diameter following the direction of the fibres.
These envelop each primitive fasciculus, enclosing it com-
pletely, the artery and vein being on the same side. The ca-
pillaries are the smallest in the whole vascular system.. When
distended with blood they are from -^Yo" to 31l$Q of an inch
in diameter ; and when empty their diameter is from 7010()
to -g-gVo °f an inch.1

The arrangement of the lymphatics in the muscles has
never been definitely ascertained. There are numerous lym-
phatics surrounding the large vascular trunks of the extremi-
ties and of the abdominal and thoracic walls, which, it would
appear, must come from the substance of the muscles ; but
they have never been traced to their origin. Sappey has
succeeded in injecting lymphatics upon the surface of some
of the larger muscles, but never has been able to follow them
into the muscular substance.3

Connection of the Muscles with the Tendons. — It is now
generally admitted that the primitive muscular fasciculi
terminate in little conical extremities, which are received
into corresponding depressions in the bundles of fibres com-
posing the tendons ; but this union is so close, that the muscle
or the tendon may be ruptured without a separation at the
point of juncture. In the penniform muscles this arrange-
ment is quite uniform and elegant. In other muscles it is
essentially the same, but the perimysium seems to be contin-
uous with the loose areolar tissue enveloping the correspond-
ing tendinous bundles.

Chemical Composition of the Muscles. — We are as yet so
little acquainted with the exact constitution of the nitrogen-
ized constituents of the body, that we cannot appreciate the

1 KOLLIKER, Elements (Fhistologie humaine, Paris, 1868, p. 220.

2 SAPPEY, Traite cTanatomie descriptive, Paris, 1868, tome ii., p. 27.

458 MOVEMENTS.

nature of all the proximate principles that exist in the mus-
cular substance. The most important of these is musculine.
This resembles the fibrin of the blood, but presents certain
points of difference in its behavior to reagents, by which it
may be readily distinguished. One of its peculiar properties
is that it is dissolved at an ordinary temperature by a mix-
ture of one part of hydrochloric acid and ten of water.

The muscular substance is permeated by a fluid, called
the muscular juice, which contains a peculiar coagulable
principle called myosine.

Combined with the organic principles, we find a great
variety of mineral salts in the muscular substance, that can-
not be separated without incineration. Certain excrementi-
tious matters have also been found in the muscles ; and
probably nearly all of those eliminated by the kidneys exist
here, though they are taken up by the blood as fast as they
are produced, and are consequently detected with difficulty.
The muscles also contain inosite, inosic acid, lactic acid, and
certain other acids of fatty origin. During life the muscular
fluid is slightly alkaline, but it becomes acid soon after death.
The muscle itself, during contraction, has an acid reaction.1
According to Gavarret, the muscular juice is alkaline or
neutral after moderate exercise, as well as during complete
repose ; but ne states that when a muscle is made to un-
dergo excessive exercise, the lactic acid exists in greater
quantity, and the reaction becomes acid.3

Physiological Properties of the Muscles.

The general properties of the striated muscles, as distin-
guished from all other tissues except the involuntary muscles,
are as follows : 1. elasticity ; 2. tonicity ; 3. sensibility of a
peculiar kind ; 4. contractility, or irritability. These are all
necessary to the physiological action of the muscles. Their

1 BUDGE, Lehrbuch derspecieV.cn Physiologic des Memchen, Leipzig, 1862, S. 534.

2 GAVARRET, Les phenomenes physiques de la vie, Paris, 1869, p. 125.

PHYSIOLOGICAL PROPERTIES OF THE MUSCLES. 459

elasticity is brought into play in opposing muscles or sets of
muscles ; one set acting to move a part and extend the
antagonistic muscles, which, by virtue of their elasticity,
retract when the extending force is removed. Their tonicity
is an insensible, and more or less constant contraction, by
which the action of opposing muscles is balanced when both
are in the condition of what we call repose. Their sensibil-
ity is peculiar, and is expressed chiefly in the sense of fatigue,
and in the appreciation of weight and resistance to contrac-
tion. Their contractility, or irritability is the property which
enables them to contract and exert a certain amount of
mechanical force under the proper stimulus. All of these
general properties strictly belong to physiology, as do some
special acts that are not necessarily involved in the study
of ordinary descriptive anatomy.

Elasticity of Muscles. — The true muscular substance
contained in the sarcolemma is eminently contractile ; and
though it may possess a certain degree of elasticity, this
property is most strongly marked in the accessory anatomi-
cal elements. The interstitial fibrous tissue is loose and pos-
sesses a certain number of elastic fibres, and, as we have
seen, the sarcolemma is very elastic. It is probably the sar-
colemma that gives to the muscles their retractile power after
simple extension.

It is unnecessary to follow out in detail all of the numer-
ous experiments that have been made upon the elasticity
of muscles. There is a certain limit, of course, to their
perfect elasticity (understanding by this the degree of ex-
tension that is followed by complete retraction), and this
cannot be exceeded in the human subject without dislocation
of parts. In some late experiments by Marey, it was found
that the gaetrocnemius muscle of a frog, detached from the
body, could be extended about one-fiftieth of an inch by a
weight of a little more than three hundred grains. This
weight, however, did not extend the muscle beyond the

460 MOVEMENTS.

limit of perfect elasticity. The muscle of a frog of ordinary
size was extended beyond the possibility of complete resto-
ration by a weight of about seven hundred and fifty grains.1
Marey also showed that fatigue of the muscles increased
their extensibility and diminished their power of subsequent
retraction. This fact has its application to the physiological
action of muscles ; for it is well known that they are un-
usually relaxed during fatigue after excessive exertion ; and,
as we should expect, they are at that time more than ordi-
narily extensible.

Muscular Tonicity. — The healthy muscles have an in-
sensible and constant tendency to contract, which is more
or less dependent upon the action of the motor nerves. If,
for example, a muscle be cut across in a surgical operation,
the divided extremities become permanently retracted ; or
if the muscles be paralyzed on one side of the face, the mus-
cles upon the opposite side insensibly distort the features.
It is difficult to explain these phenomena by assuming that
tonicity is due to reflex action, for there is no evidence that
the contraction takes place as the consequence of a stimu-
lus. All that we can say is, that a muscle, not excessively
fatigued, and with its nervous connections intact, is con-
stantly in a state of insensible contraction, more or less
marked, and that this is an inherent property of all of the
contractile tissues.

Sensibility of the Muscles. — The muscles possess to an
eminent degree that kind of sensibility which enables us to
appreciate the powrer of resistance, immobility, and elasticity
of substances that are grasped, on which, we tread, or which,
by their weight, are opposed to the exertion of muscular
power. It is by the appreciation of weight and resistance
that we regulate the amount of force required to accomplish
any muscular act. These properties refer chiefly to simple

1 MAREY, Du mouvement dans lesfondions de la vie, Paris, 1868, pp. 289, 301.

MTJSCTJLAK CONTRACTILITY. 461

muscular efforts. After long-continued exertion, we appre-
ciate a sense of fatigue that is peculiar to the muscles. It is
difficult to separate this entirely from the sense of nervous
exhaustion, but it seems to be, to a certain extent, distinct ;
for when suffering from the fatigue that follows over-exer-
tion, it seems as though we could send a nervous stimulus to
the muscles, to which they are, for the time, unable to
respond. When we come to consider fully the subjects of
muscular and nervous irritability, we shall see that these
two properties are entirely distinct, and that we may ex-
haust or destroy the one without influencing the other.

When the muscles are thrown into spasm or tetanic con-
traction, a peculiar sensation is produced, entirely different
from painful impressions made upon the ordinary sensitive
nerves. In the cramps of cholera, tetanus, or the convul-
sions from strychnine, these distressing sensations are very
marked. The so-called recurrent sensibility of the anterior
roots of the spinal nerves is probably due to the tetanic con-
tractions produced by galvanizing these filaments. This
question, however, will be taken up again in connection
with the nervous system.

If the muscles possess any general sensibility, it is very
faint. A muscle may be lacerated or irritated in any way
without producing actual pain, though we always can ap-
preciate the contraction produced by irritants, and the sense
of tension when the muscles are drawn upon.

Muscular Contractility, or Irritability. — Physiologists
now regard muscular irritability as synonymous with con-
tractility ; and perhaps the latter term more nearly expresses
the fact, though the term irritability, applied to the nerves,
and even of late years to the glands, is one very generally used.

By irritability we understand a property belonging to
highly-organized parts, which enables them to perform cer-
tain peculiar and characteristic functions in obedience to a
proper stimulus. In the sense in which the term is gen-

462 MOVEMENTS.

erally received, it is proper to apply it to any tissue or organ
that performs its vital function, so-called, under a natural
or artificial stimulus. The nerves receive impressions and
carry a stimulus to the muscles, causing them to contract.
This property, which is always present during life under
normal conditions, and persists for a certain period after
death, is called nervous irritability. It has lately been
shown that the application of a proper stimulus will induce
secretion by the glands ; and Bernard has called this glandular
irritability.1 The application of a stimulus to the muscular
tissue causes the fibres to contract ; and this is muscular irri-
tability. As it always involves contraction, and is extinct
only when the muscles can no longer act, it is equally proper
to call this property contractility. 'No property, such as we
understand by this definition of irritability, is manifested
by tissues or organs that have purely passive or mechanical
functions, such as bones, cartilages, and fibrous or elastic
membranes. Irritability can only be applied properly to
nerves or nerve centres, contractile structures, and glands.

During life and under normal conditions, the muscles
will always contract in obedience to a proper stimulus ap-
plied either directly or through the nerves. In the natural
action of the organism, this contraction is always induced by
nervous influence through reflex action or volition. Still, a
muscle may be living and yet have lost its contractility.
For example, after a muscle has been for a long time par-
alyzed and disused, the application of the most powerful
galvanic excitation will fail to induce contraction. But
when we examine such a muscle with the microscope, it is
found that the nutrition has become profoundly affected,
and that the contractile substance has disappeared, giving
place to inert fatty matter. Muscular contractility persists
for a certain time after death and in muscles separated from
the body ; and this fact has been taken advantage of by phys-
iologists in the study of the so-called vital properties of the

1 See page 24.

MUSCULAR CONTRACTILITY. 463

muscular tissue. We have already seen that a muscle de-
tached from the living body continues for a time to respire,
and probably undergoes some of the changes of disassimila-
tion observed in the organism. So long as these changes are
restricted to the limits of physical and chemical integrity of
the fibre, contractility remains. As these processes are very
slow in the cold-blooded animals, the irritability of all the
parts persists for a considerable time after death. We have
repeatedly demonstrated muscular contractility, several days
after death, in alligators and turtles.

In the human subject and the warm-blooded animals, the
muscles cease to respond to excitation a few hours after
death, though the time of disappearance of irritability is
very variable. Xysten, in a number of experiments upon
the disappearance of contractility in the human subject after
decapitation, found that different parts lost their con-
tractility at different periods, but that generally this de-
pended upon exposure to the air. With the exception of
the right auricle of the heart, the muscles of the voluntary
system were the last to lose their irritability. In one in-
stance, certain of the voluntary muscles that had not been
exposed retained their contractility seven hours and fifty
minutes after death.1 The observations of Longet and Mas-
son show that a galvanic shock, sufficiently powerful to pro-
duce death, instantly destroys the irritability of the mus-
cular tissue and of the motor nerves.2

One of the most important questions to determine with
regard to muscular irritability is whether it be a property
inherent in the muscular tissue or derived from the nervous
system. The fact that muscles can be excited to more pow-
erful and regular contractions by stimulating the motor
nerves than by operating directly upon their substance and
the great difficulty in tracing the nerves to their termination

1 XYSTEX, De la cotitractitite des organes musculaires. — Eecherches de physiologie
et de chimie pathologiques, Paris, 1811, p. 306, et seg.

2 LOXGET, Tratte. de physiologie, Paris, 1869, tome ii., p. 602.

464 MOVEMENTS.

in the muscles have led to the view that muscular contrac-
tility is dependent upon nervous influence, and consequently
that the muscles have no irritability or contractility, as a
property inherent in their own substance. This doctrine,
however, cannot be sustained. Bowman, in the course of his
researches into the structure and movements of voluntary
muscles, speaks of seeing the individual fibres contract after
they had been isolated and removed from all connection with
the nervous system ; and this has been frequently observed.1

The experiments of Longet, published in 1841, presented
almost conclusive proof of the independence of muscular
irritability. He resected the facial nerve, and found that it
ceased to respond to mechanical and galvanic stimulus, or,
in other words, lost its irritability, after the fourth day. Op-
erating, however, upon the muscles supplied exclusively with
filaments from this nerve, he found that they responded
promptly to mechanical and galvanic irritation, and con-
tinued to contract, under stimulation, for more than twelve
weeks.8 In some further experiments it was shown that
while the contractility of the muscles could be seriously in-
fluenced through the nervous system, this was effected only
by modifications in their nutrition. "When the mixed nerves
were divided, the nutrition of the muscles was generally dis-
turbed ; and although muscular irritability persisted for some
time after the nervous irritability had disappeared, it be-
came very much diminished at the end of six weeks.

These experiments are very striking and satisfactory ; but
the whole question was definitively settled by the observations
of Bernard on the peculiar influence of the woorara poison
and the sulphocyanide of potassium. As the result of these
experiments, it was ascertained that some varieties of woorara
destroy the irritability of the motor nerves, leaving the sen-
sitive filaments intact. If a frog be poisoned by introducing

1 BOWMAN, The Minute Structure and Movements of Voluntary Muscle. —
Philosophical Transactions, London, 1840, p. 488, et seq.

2 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 606.

MUSCULAR CONTRACTILITY. 465

a little of this agent under the skin, irritation, galvanic or
mechanical, applied to an exposed nerve, fails to produce
the slightest muscular contraction ; but if the stimulus be
applied directly to the muscles, they will contract vigorously.
In this way the nerves are, as it were, dissected out from the
muscles ; and the discovery of an agent that will paralyze
the nerves, without affecting the muscles, is conclusive proof
that the irritability of these two systems is entirely distinct.
A curious effect of the woorara, that we may note in passing,
is that in an animal under its influence, the muscular irrita-
bility is intensified, and persists much longer after death than
in animals not poisoned.1 If a frog be poisoned with sulpho-
cyanide of potassium, precisely the contrary effect will be
observed ; that is, the muscles will become insensible to ex-
citation, while the nervous system is unaffected. This fact
may be demonstrated by applying a tight ligature around
the body in the lumbar region, involving all the parts except
the lumbar nerves. If the poison be now introduced beneath
the skin of the parts above the ligature, the anterior parts
only are affected, because the vascular communication with
the posterior extremities is cut off. If the exposed nerves be
now galvanized, the muscles of the legs are thrown into con-
traction, showing that the nervous irritability remains. Re-
flex movements in the posterior extremities may also be pro-
duced by irritation of the parts above the ligature.2

These experiments, most of which we have frequently re-
peated, taken in connection with the observations of Longet,
and the fact that isolated muscular fibres have been seen to
contract, leave no doubt of the existence of an inherent and
independent irritability in the muscular tissue. Contractions
of muscles, it is true, are normally excited through the ner-
vous system, and artificial stimulation of a motor or mixed
nerve is the most efficient method of producing the simul-

1 BERNARD, Lemons sur Us e/ets des substances toxiyues et medicamentemes,
Paris, 1857, pp. 277, 320, 353,

2 BERNARD, loc. oil., p. 354, et seq.

4:66 MOVEMENTS.

taneous action of all the fibres of a muscle, or set of muscles ;
but galvanic, mechanical, or chemical irritation of the mus-
cles themselves will produce contraction, after the nervous
irritability has been abolished.

The conditions under which muscular irritability exists
are simply those of normal nutrition of the muscular tissue.
When the muscles have become profoundly affected in their
nutrition, as the result of section of the mixed nerves, or after
prolonged paralysis, the irritability disappears and cannot
be restored. The determination of the presence or absence
of muscular contractility, in cases of paralysis, is one of the
methods of ascertaining whether treatment directed to the
restoration of the nervous power will be likely to be followed
by favorable results. If the muscular irritability have en-
tirely disappeared, it is almost useless to attempt to restore
the functions of the part.

A great many experiments have been made upon the in-
fluence of the circulation on muscular irritability, chiefly
with reference to the effects of tying large vessels. Among
the most recent are those of Longet. He tied the abdominal
aorta in five dogs, and found that voluntary motion ceased
in about a quarter of an hour, and that the muscular irrita-
bility was extinct in two hours and a quarter. When the
blood was restored, after three or four hours, by removing the
ligature, the irritability and finally voluntary movement re-
turned.1 These experiments show that the circulation of the
blood is necessary to the contractility of the muscles. Tying
the vena cava did not affect the irritability of the muscles.
In dogs in which this experiment was performed, the lower
extremities preserved their contractility, and the voluntary
movements were unaffected up to the time of death, which
took place in twenty-six hours.3

The relations of muscular irritability to the circulation
have been further illustrated, in some very curious and in-

1 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 616.

2 LONGET, op. tit., p. 618.

MUSCULAR CONTRACTILITY. 4:67

teresting experiments, by Dr. Brown-Sequard. The first
observations were made upon two men executed by decapi-
tation. Thirteen hours and ten minutes after death, when
the muscular irritability had entirely disappeared and was
succeeded by cadaveric rigidity, a quantity of fresh, defi-
brinated, venous blood, from the human subject, was in-
jected into the arteries of one hand, and returned by the
veins. It was afterward reinjected several times during a
period of thirty-five minutes. The whole time occupied in
the different injections was from ten to fifteen minutes. Ten
minutes after the last injection, and about fourteen hours
after death, the irritability was found to have returned, in a
marked degree, in twelve muscles of the hand. There were
only two muscles out of the nineteen in which the irritability
could not be demonstrated. Three hours after, the irritability
still existed, but it disappeared a quarter of an hour later.
The second observation was essentially the same, except that
defibrinated blood from the dog was used, and the experiments
were made upon the muscles of the arm. The irritability
was restored in all of the muscles, and was present, the
cadaveric rigidity having disappeared, twenty hours after
decapitation.1

These experiments are exceedingly interesting, as showing
the dependence of irritability upon certain of the processes
of nutrition, which are probably restored, though temporarily
and imperfectly, by the injection of fresh blood. They are
also important in connection with the cadaveric rigidity of
muscles, a condition which follows the loss of their so-called
vital properties. The subject of cadaveric rigidity will be
fully discussed as one of the phenomena of death.

1 BROWX-SEQUARD, Proprietes physiologiques et les usages du sang rouge et du
sang noir. — Journal de la physiologic, Paris, 1858, tome i., p. 108, et seg.

CHAPTEE XYI.

MTJSCULAK COISTTEACTION. — PASSIVE OKGANS OF LOCOMOTION.

Changes in the form of the muscular fibres during contraction — Secousse,
Zuckung, or spasm — Spasm produced by artificial excitation — Mechanism
of prolonged muscular contraction — Tetanus — Electric phenomena in the
muscles — Muscular effort — Passive organs of locomotion — Physiological
anatomy of the bones — Fundamental substance — Haversian rods — Haver-
sian canals — Lacunse — Canaliculi — Bone-cells, or corpuscles — Marrow of
the bones — Medullocells — Myeloplaxes — Periosteum — Physiological anat-
omy of cartilage — Cartilage-cavities — Cartilage-cells — Fibro-cartilage.

THE stimulus of the will, conveyed through the conduct-
ors of motor influences from the brain to a muscle or set of
muscles, produces an impression upon the muscular fibres and
causes them to contract. In parts where the muscles have
been exercised and educated, this action is regulated with ex-
quisite nicety, so that the most delicate, rapid, as well as
powerful contractions may be produced. Certain movements,
not under the control of the will, are produced as the result of
unconscious reflection from a nervous centre, along the motor
conductors, of an impression made upon sensitive nerves.
During this action, certain important phenomena are ob-
served in the muscles themselves. They change in form,
consistence, and, to a certain extent, in their constitution ;
the different periods of their stimulation, contraction, and re-
laxation are positive and well-marked ; their nutrition is for
the time modified ; they develop galvanic currents ; and, in
short, present a number of general phenomena, distinct from
the results of their action, that are more or less interesting
and important to the physiologist.

MUSCULAR CONTRACTION. 469

The most striking of the phenomena accompanying mus-
cular action is shortening and hardening of the fibres. It is
only necessary to observe the action of any well-developed
muscle to appreciate these changes. The active shortening
is shown by the approximation of the points of attachment,
and the hardening is sufficiently palpable. The latter phe-
nomenon is marked in proportion to the development. of the
true muscular tissue and its freedom from inert matter, such
as fat. "We have already seen that it is the muscular sub-
stance alone that has the property of contraction ; and we
have shown that this action increases the consumption of
oxygen and probably of other matters, the production of
carbonic acid and some other excrementitious principles, and
develops heat.

Notwithstanding the marked and constant changes in the
form and consistence of the muscles during contraction, the
actual volume is unchanged, or it undergoes modifications so
slight that they may practically be disregarded. Experi-
ments on this point have been so uniform in their results,
that it is hardly necessary to refer to them in detail. All
modern observers accept the results of the older experiments
in which muscles have been made to contract in a vessel of
water connected with a small upright tube, showing that
when the muscles are in active contraction as the result of
a galvanic stimulus, the elevation of the liquid in the tube
is unchanged. These old experiments have been recently
repeated by Marey 1 and others, with more delicate and sen-
sitive apparatus, and have been followed by the same results.
It is evident, therefore, that a muscle, while it hardens and
changes in form during contraction, does not sensibly change
in its actual volume.

1 MAREY, Du mouvement dans ksfondions de la vie, Paris, 1868, p. 269. The
earlier experiments of this kind were made by Glisson, Elaine, Carlisle, Barzel-
lotti, Prevost, and Dumas, and some others. Prevost and Dumas used several
large pieces of muscle, and their results were very satisfactory. (Memoire sur
les phenomenes qui accompagnent la contraction de la fibre musculaire. — Journal
de physiologic, Paris, 1823, tome iii., p. 310.)

470 MOVEMENTS.

Changes in the Form of the Mitscular Fibres during
Contraction. — It lias been found exceedingly difficult to de-
termine a question apparently so simple as that of the change
in form which the muscular fibres undergo during contrac-
tion ; and it is only of late years that this single point has been
definitively settled. The idea that the fibres do not shorten,
but that they assume a zigzag arrangement during contraction,
which was entertained by some of the earlier physiologists,
and was supported very strongly by Prevost and Dumas,1 is
not adopted by any modern writers. All are now agreed, that
in muscular contraction there is an increase in the thickness
of the fibre, exactly compensating its diminution in length.
This has been repeatedly observed in microscopical exami-
nations, by Bowman,3 Donne,3 and many others ; and the
only points now to determine are the exact mechanism of
this transverse enlargement, its duration, the means by
which it may be excited, and its physiological modifica-
'tions. These questions, within the last few years, have been
made the subjects of elaborate investigations by Helmholtz,
Du Bois-Reymond, Aeby, Marey, and others ; and although
it is hardly necessary to follow these experimenters through
all of their investigations, many points have been developed,
particularly by the system of registering the muscular move-
ments, that possess considerable physiological importance.

One essential condition in the study of the mechanism
of muscular contraction is to imitate, in a muscle or part of
a muscle that can be subjected to direct observation, the
force that naturally excites it to contraction. The applica-
tion of electricity to the nerve is beyond all question the
most perfect method that can be employed for this purpose.
We can in this way excite a single contraction, or, by em-
ploying a rapid succession of currents, can excite continuous,

1 Journal de physiologic, Paris, 1823, tome iii., p. 301, et seq.

2 BOWMAN, On the Minute Structure and Movements of Voluntary Muscle. —
Philosophical Transactions, London, 1840, p. 488.

3 DONNE, Cours de microscopie, Paris, 1844, p. 114.

MUSCULAR CONTRACTION. 471

or tetanic action. While the electric current is not identi-
cal with the nervous force, it is the best substitute we can
employ in experiments on muscular contractility, and has
the advantage of not affecting the physical and chemical
integrity of the nervous and muscular tissue. In studying
this subject, we will first follow some of the experiments
upon muscular contraction excited artificially, and then
apply them, as far as possible, to the strictly physiological
actions of muscles.

There are two classes of phenomena that may be pro-
duced by electrical excitation of motor nerves: 1. When
the stimulus is applied in the form of a single discharge, it
is followed by a single muscular contraction. 2. Under a
rapid succession of discharges, the muscle is thrown into a
state of permanent, or tetanic contraction. It will greatly
facilitate our comprehension of the subject to study these
phenomena separately and successively.

The muscular contraction produced by a single stimulus
applied to the nerve is called, by the French, secousse (shock),
and by the Germans, Zilckung (convulsion). It will be con-
venient for us to employ some term that will express this
sudden action of the muscular fibres, as distinguished from
the contraction that takes place on repeated stimulation, or
in continued muscular effort ; and we will designate a single
muscular contraction, then, as spasm, applying the term
tetanus, to continued action.

Spasm Produced ~by Artificial Excitation. — If an elec-
tric discharge, even very feeble, be applied to a motor nerve
connected with a fresh muscle, it is followed by a sudden
contraction, succeeded by a rapid relaxation. Under this
stimulation, the muscle shortens by about three-tenths of its
entire length.1 The form of the contraction, as registered
by the apparatus of Helmholtz, Marey, and others who have
applied the so-called graphic method to the study of muscu-

1 BECLARD, Traite elemental™ de physiologic, Paris, 1859, p. 507.

472 MOVEMENTS.

lar action, presents certain interesting peculiarities. "We
will give, however, only the general characters of this ac-
tion, without discussing in detail the complicated apparatus
employed.1

According to Helmholtz, the whole period of a single
contraction and relaxation of the gastrocnemius muscle of a
frog is a little less than one-third of a second. The muscles
of mammals and birds contract more rapidly, but with this
exception, the essential characters of the contraction are the
same. The following are the periods occupied by these dif-
ferent phenomena:2

Interval between stimulation and contraction 0"'020

Contraction 0"'180

Kelaxation 0"'105

0"-305

The duration of the electric current applied to the nerve
is only 0"*0008. Contraction, however, does not follow im-
mediately, there being an interval, called pose, of about one
fiftieth of a second. The contraction then follows, suc-
ceeded by gradual relaxation, the former being a little
longer than the latter.

This description represents the contraction of an entire
muscle, but does not indicate the changes in form of the in-
dividual fibres, a point much more difficult to determine
satisfactorily. It is pretty well established, however, that a
single fibre, with its irritability unimpaired, becomes con-
tracted and swollen at the point where the stimulation is
applied. Now, the question is whether, in normal contrac-
tion of the fibres in obedience to the natural nervous
stimulus, there be a uniform shortening of the whole fibre,
a shortening of those portions only that are the seat of the

1 A very good resume of the general characters of a single muscular con-
traction (secousse musculaire) is given by Bernard, in his recent work on the
properties of living tissues. (Le$om sur les proprietes des tissus vivants, Paris,
1866, p. 193, et seq.)

2 BERNARD, op. cit., p. 196.

MUSCULAR CONTRACTION.

terminations of the motor nerves, or a peristaltic shortening
and swelling, rapidly running the length of the fibre.

The recent experiments of Aeby, which have been repeated
and extended by Marey, demonstrate beyond a doubt that
when one extremity of a muscle is excited, a contraction occurs
at that point, and is propagated along the muscle in the form of
a wave, exactly like the peristaltic action of the intestines, ex-
cept that it is more rapid. Both Aeby and Marey have suc-
ceeded in measuring the rapidity of this wave, and find it to
be about forty inches per second.1 Applying this principle
to the physiological action of muscles, Aeby advances the
theory that shortening of the fibres takes place wherever
a stimulus is received, and that this is propagated in the
form of a wave, which meets in its course another wave
starting from a different point of stimulation. As we know

FIG. 18.

Diagram of the muscular wave after Aeby. (MABEY, Du mouvement dans les fonctions
de la vie, Paris, 1868, p. 282.)

that the motor nerves terminate at different points by be-
coming fused, as it were, with the sarcolemma, we can readily
comprehend, under this theory, how the simultaneous con-
traction of all the fibres of a muscle is produced by stimula-
tion of its motor nerve. This idea is expressed in the ac-
companying diagram.

1 MAREY, Du mouvement dans lesfonctions de la, vie, Paris, 1868, p. 280.

474: MOVEMENTS.

Although this view of the physiological action of the
muscular fibres is extremely probable, it cannot be assumed
that it has been absolutely demonstrated ; but it is certainly
more satisfactory and better sustained by experimental facts
than any theory that has hitherto been advanced.

Mechanism of prolonged Muscular Contraction. — By a
voluntary effort we are able to produce a muscular contrac-
tion of a certain duration, and of a power, within certain
limits, proportionate to the amount of force we may desire
to produce ; but after a certain time, the muscle becomes fa-
tigued, and it may become exhausted to the extent that it
will not respond to the normal stimulus. This is the kind
of muscular action most interesting to us as physiologists.

The experiments of Marey seem to show precisely how
far the nervous action that gives rise to a powerful and con-
tinuous muscular contraction can be imitated by electricity.
Calling the movement produced by a single electric dis-
charge, secousse, which we have translated by the word
spasm, he calls the persistent contraction, tetanus. We will
adopt this name to distinguish persistent muscular action
from the single contraction that we have just described.

It is a curious fact that a continued current of galvanic
electricity passed through a nerve or a muscle does not induce
muscular contraction; and it is only when the current is
closed or broken that any action is observed. But if we
employ statical electricity, a muscular spasm occurs at every
discharge, proportionate, in some degree, to the power of the
excitation. If the discharges be very frequently repeated, or
if a galvanic current be applied, broken by an interrupting
apparatus, the spasms follow each other in quick succession.
In experimenting upon the muscles of the frog with a regis-
tering apparatus, Marey has found that with a gradual
increase in the rapidity of the electric shocks, the individual
muscular spasms become less and less distinct, and that
finally the contraction is permanent. His diagrams show

MUSCULAR CONTRACTION. 475

well-marked spasms under ten excitations per second, a
more complete fusion of the different acts with twenty per
second, and a complete fusion, or tetanus, with twenty-seven
per second. When the contraction had become continuous
that was an elevation in the line, showing increased power,
as the excitations became more and more frequent.1

This is precisely the kind of contraction that occurs in
the physiological action of muscles. Although the ner-
vous force is not by any means identical with electricity,
either the interrupted galvanic current or a series of statical
discharges is capable of producing a muscular action very
like that which is involved in voluntary movements. The
observations of Marey, showing that the intensity of what
he terms artificial tetanic contraction is in proportion to
the rapidity with which the electric discharges succeed each
other, are exceedingly interesting in their practical applica-
tions ; and an important question at once arises regarding
the nervous force that excites voluntary motion. Is this a
series of discharges, as it were, producing a power of mus-
cular contraction in exact proportion to their rapidity ? In
view of the experiments just cited, this theory is very prob-
able ; and it is certain that a rapid succession of electric dis-
charges almost exactly simulates the normal action. That
vibrations, more or less regular, actually occur in muscular
contraction has been settled beyond a doubt by the re-
searches of Wollaston, Haughton, and more lately by Helm-
lioltz, the latter having recognized a musical tone in con-
tracting muscles, exactly corresponding with the number of
impressions per second made upon the nerve. He further
devised an ingenious method of recognizing the tone, by fill-
ing the ears with wax and contracting the temporal and
masseter muscles. Marey has found, in repeating this
experiment, that the tone may be changed by modifying the
intensity of the muscular action. With the jaws feebly con-
tracted, a grave sound is produced, and this can be raised

1 MAREY, op. cit., p. 373, et seq

476 MOVEMENTS.

one-fifth, by contracting the muscles as forcibly as pos-
sible.1

The nerves are not capable of conducting an artificial
stimulus for an indefinite period, nor are the muscles able
to contract for more than a limited time upon the reception
of such an impression. The electric current may be made
to destroy for a time both the nervous and muscular irrita-
bility ; these properties becoming gradually extinguished,
the parts becoming fatigued before they are completely
exhausted. Precisely the same phenomena are observed in
the physiological action of muscles. When a muscle is
fatigued artificially, a tetanic condition is excited more and
more easily, but the intensity of the contraction proportion-
ally diminishes.2 Muscles contracting in obedience to the
will pass through the same stages of action. It is probable
that constant contraction is excited more and more easily as
the muscles become fatigued, because the nervous force is
gradually diminishing in intensity. It is certain that the vigor
of contraction at the same time progressively diminishes.

Electric Phenomena in the Muscles. — It was ascertained
a number of years ago, by Matteucci, that all living muscles
are the seat of electric currents ; not very powerful, it is true,
but still sufficiently marked to be detected by ordinary gal-
vanometers. It is difficult, in the present state of our
knowledge, to appreciate the physiological significance of
this fact, and we will therefore merely allude to the chief
electric phenomena that are ordinarily observed, without at-
tempting to follow out the elaborate and curious experi-
ments since made by Du Bois-Reymond and others. One
of the most simple methods of demonstrating this current is
to prepare the leg of a frog with the crural nerve attached,
and apply one portion of the nerve to the deep parts of an
incised muscle and the other to the surface. As soon as the
connection is made, a contraction of the leg takes place.

1 MAREY, op. cit., p. 455. 2 Idem., p. 378, et scq.

MUSCULAE EFFORT. 477

The same fact may be demonstrated with an ordinary gal-
vanometer; but the evidence obtained by the frog's leg,
when the experiment is properly performed, is sufficiently
conclusive.

Matteucci constructed out of the fresh muscles from the
thigh of the frog, what is sometimes called a frog-battery ;
which exhibits these currents in the most striking manner,
their intensity being in direct ratio to the number of elements
in the pile. To do this, he takes the muscles of the lower
half of the thigh from several frogs, removing the bones, and
arranges them in a series, each with its conical extremity
inserted into the central cavity of the one below. In this
way the external surface of each thigh except the last is in
contact with the internal surface of the one below. If the
two extremities of the pile be now connected with a gal-
vanometer, quite a powerful current from the internal to
the external surface of the muscle may be demonstrated. In
a pile formed of ten elements, the needle of a galvanometer
was deviated to from 30° to 40V '

Electric currents are observed in all living muscles, but
are most marked in the mammalia and warm-blooded ani-
mals. They exist, also, for a certain time after death.
Artificial tetanus of the muscles, however, instead of intensi-
fying the current, causes the galvanometer to recede. If,
for example, the needle of the instrument show a deviation
of 30° during repose, when the muscle is excited to tetanic
contraction, it will return so as to mark only 10° or 15°.
This phenomenon is observed only during a continued mus-
cular contraction, and does not attend a single spasm.

Muscular Effort. — The mere voluntary movement of
parts of the body, when there is no obstacle to be overcome

1 MATTEUCCI, Lemons sur les phenomenes physiques dfs corps vivante, Paris,
1847, p. 175, et seq. For a fuller exposition of these interesting phenomena,
the reader is referred to the elaborate treatise on physiology, by Prof. Longet
(Traite de physiologic, Paris, 1869, pp. 620, 639).

478 MOVEMENTS.

or no great amount of force is required, is very different from
a muscular effort. For example, in ordinary progression there
is simply a movement produced by the action of the proper
muscles, almost without our consciousness, and this is unat-
tended with any modification in the circulation or respira-
tion; but if we attempt to lift a heavy weight, to jump, to
strike a powerful blow, or to make any vigorous effort, the
action is very different. In the latter instance, we prepare
for the muscular action by inflating the lungs, closing the
glottis, and contracting more or less forcibly the expiratory
muscles, so as to render the thorax rigid and unyielding ;
and by a concentrated effort of the will, the proper muscles
are then brought into action.

This remarkable action of the muscles of the thorax
and abdomen, due to simple effort, and independent of
the particular muscular act that is to be accomplished,
compresses the contents of the rectum and bladder, and
obstructs very materially the venous circulation in the
large vessels. It is well known that hernia is frequently
produced in this way; the veins of the face and neck be-
come turgid ; the conjunctiva may become ecchymosed ; and
sometimes aneurismal sacs are ruptured. An effort of this
kind is generally of short duration, and cannot, indeed, be
prolonged beyond the time during which respiration can be
conveniently arrested. At its conclusion there is commonly
a prolonged expiration, which is audible and somew;hat vio-
lent at its commencement.

There are degrees of effort which are not attended with
this powerful action of the muscles of the chest and abdo-
men, and in which the glottis is not completely closed ; and
an opening into the trachea or larynx, rendering immobility
of the thorax impossible, does not interfere with certain acts
that require considerable muscular power. If we examine a
dog with the glottis exposed, when he makes violent efforts
to escape, we can see that the opening is firmly closed. This
fact is indicated by Longet, and we have often observed it

PASSIVE OK&ANS OF LOCOMOTION. 479

in vivisections ; but Longet has further shown 'that dogs
with an opening into the trachea are frequently able to run
and leap with " astonishing agility." He also saw a horse,
with a large canula in the trachea, that performed severe
labor and drew heavily-loaded wagons in the streets of
Paris.1

Passive Organs of Locomotion.

It would be out of place to describe fully and in detail
all of the varied and complex movements produced by mus-
cular action. Many of these, such as the movements of deg-
lutition and of respiration, are necessarily considered in con-
nection with the functions of which they form a part ; but
others are purely anatomical questions. Associated and an-
tagonistic movements, automatic and reflex movements, etc.,
belong to the history of the motor nerves, and will be fully
considered under the head of the nervous system.

The study of locomotion involves a knowledge of the
physiological anatomy of certain passive organs, the bones,
cartilages, and ligaments. Though a complete history of the
structure of these parts trenches somewhat upon the domain
of anatomy, we are tempted to give a brief description of
their histology, as it will complete our account of the tissues
of the body, with the exception of the nervous system and
the organs of generation, which will be taken up hereafter.

Locomotion is effected by the muscles acting upon cer-
tain passive, movable parts. These are the bones, cartilages,
ligaments, aponeuroses, and tendons. We have already de-
scribed the fibrous structures, and it only remains for us to
study the bones and cartilages.

Physiological Anatomy of the Bones. — The number, clas-
sification, and relations of the bones are questions belonging
to descriptive anatomy ; and the only points we propose to
consider refer to their general or microscopic structure.

1 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 669.

480 MOVEMENTS.

Every bone, be it long or short, is composed of what is
called the fundamental substance, marked by microscopic
cavities and canals of peculiar form. The cavities contain
corpuscular bodies, called bone-corpuscles. The canals of
larger size serve for the passage of blood-vessels, while the
smaller canals (canaliculi) connect the cavities with each
other, and finally with the vascular tubes. Many of the
bones present a medullary cavity, filled with a peculiar
structure, called marrow. In almost all bones there are two
distinct portions : one, which is exceedingly compact, and
the other, more or less spongy or cancellated. The bones
are also invested with a membrane, containing vessels and
nerves, called the periosteum.

The method usually employed in the study of the bones
is by thin sections made in various directions, and examined
either in their natural condition or with the calcareous mat-
ter removed by maceration in weak acid solutions. By the
first method, we can make out the relations of the funda-
mental substance, the direction and relations of the vascular
canals, and the form, size, relations, and connections of the
bone-cavities and small canals. By the latter method we
can isolate and study the organic and corpuscular elements.

Fundamental Substance. — This constitutes the true bony
substance, the medullary contents, vessels, nerves, etc., being
simply accessory. It is composed of a peculiar organic mat-
ter, called osteine, combined with various inorganic salts, in
which the phosphate of lime largely predominates. In ad-
dition to the phosphate of lime, the bones contain carbonate
of lime, fluoride of calcium, phosphate of magnesia, soda,
and the chloride of sodium. The relative proportions of the
organic and inorganic matters are somewhat variable ; but
the average is about one-third of the former to two-thirds of
salts. This proportion is necessary to the proper consistence
and toughness of the bones.

Anatomically, the fundamental substance is arranged in
the form of regular, concentric lamellae, about -^^ of an

ANATOMY OF THE BONES. 481

inch in thickness.1 This matter is of an indefinitely and
faintly-striated appearance, but it cannot be reduced to dis-
tinct fibres. In the long bones the arrangement of the
lamellae is quite regular, surrounding the Haversian canals,
and forming what are sometimes called the Haversian rods,
following in their direction the length of the bone. In the
short, thick bones the lamellae are more irregular, frequently
radiating from the central portion to the periphery. These
peculiarities in the disposition of the fundamental substance
will be more readily understood after a description of the
Haversian canals.

Haversian Canals. — These canals exist in the compact
bony structure. They are absent, or very rare, in the spongy
and reticulated portions. Their form is rounded or ovoid,
the larger ones being sometimes quite irregular. In the
long bones their direction is generally longitudinal, although
they anastomose by lateral branches. Each one of these ca-
nals contains a blood-vessel, and their disposition constitutes
the vascular arrangement of the bones. They are all con-
nected with the opening on the surface of the bones, by
which the arteries penetrate and the veins emerge. Their
size, of course, is variable. According to Sappey, the largest
are about -fa and the smallest -g^-g- of an inch in diameter.
Their average size is from -^-g- to -g-J-g- of an inch.a In a
transverse section of a long bone the Haversian canals may
be seen cut across and surrounded by from twelve to fifteen
lamellae. In a longitudinal section the course and anasto-
moses may be studied.

Lacunae. — The fundamental substance is everywhere
marked by irregular, microscopic excavations, of a peculiar
form, called lacunae, or osteoplasts. These were at one time
supposed to be corpuscles of calcareous matter, and were
known as the bone-corpuscles ; but it has since been ascer-
tained that this appearance is due to the imperfect methods

1 SAPPEY, Traite tfanatomie, Paris, 1866, tome i., p. 84.

2 SAPPEY, op. cit., p. 76.

482

MOVEMENTS.

of preparation of the thin sections of bone. They are con-
nected with numerous little canals, giving them a stellate
appearance. These are most numerous at the sides. The
lacunae measure from y^^rr to -g-J-g- of an inch in their long
diameter, by about -^Vo °f an ^ncn *n width.1 They contain
the true bone-corpuscles, which we will presently describe.

Canaliculi. — These are little wavy canals, connecting
the lacunae with each other and presenting a communication
between the first series of lacunae and the Haversian canals.
Each osteoplast presents from eighteen to twenty canaliculi
radiating from its borders. Their length is from -^ to ^-J-g-
of an inch, and their diameter about ^-g-^oir °f an inch.2 The
arrangement of the Haversian canals, lacunae, and canaliculi
is shown in Fig. 19.

Fia. 19.

Vascular canals and lacunae, seen in a transverse section of the dianhysis of the hn-
merus. Magnified two htindred diameters.— 1, 1. 1, Section of the Haversian canals •
2, Section of a longitudinal canal divided at the point of its anastomosis with a
transverse canal. Around the canals, cut across perpendicularly, are seen the lacunrc
(with their canaliculi), forming concentric rings. (SAPPEY, Traite d'anatomie Paris
1866, tome i., p. 79.)

.Bone-cells or Corpuscles. — By treating perfectly-fresh
specimens of bone with weak acid solutions, Virchow has

1 SAPPEY, op. cit., p. 80.

2 Idem., p. 81.

ANATOMY OF THE BOXES. 483

demonstrated the presence of stellate cells, or corpuscles,
exactly filling up the lacunae, and sending prolongations into
the canaliculi.1 These structures have since been studied
by Rouget, who has succeeded in demonstrating them in
fresh bones from the foetus, without using any reagent.2
They are stellate, granular, with a large nucleus and several
nucleoli, and are of exactly the size and form of the lacunae.
They send out prolongations into the canaliculi, but it has
been impossible to ascertain positively whether or not they
form membranes lining the canaliculi through their entire
length.

Marrow of the Bones. — The peculiar -structure called
marrow is found in the medullary cavities of the long bones,
filling them completely and moulded to all the irregulari-
ties of their surface. It is also found filling the cells of the
spongy portion. In other words, with the exception of the
vascular canals, lacunaB, and canaliculi, the marrow fills all
the spaces in the fundamental substance. We know very
little of the functions of the marrow, and will therefore pass
it over with a brief description.

It is now settled that the cavities of the bones are not
lined with a membrane corresponding to the periosteum, and
that the marrow is applied directly to the bony substance.
In the foetus and in very young children, the marrow is red
and very vascular. In the adult it is yellow in some bones,
and gray or gelatiniform in others. It contains certain pecu-
liar cells and nuclei, with amorphous matter, adipose vesi-
cles, connective tissue, blood-vessels, and nerves.

Medullocells. — Robin has described little bodies, existing
both in the form of cells and free nuclei, called medullocells.
These are found in greater or less number in the bones at

, Cellular Pathology, Philadelphia, 1863, p. 112. Virchow's first
observations were made in 1850.

2 ROUGET, Note sur les corpuscles des os. — Journal de la physiologic, Paris,
1858, tome i., p. 764, etseq.

484: MOVEMENTS.

all ages, but are more abundant in proportion as the amor-
phous matter and fat-cells are deficient. The nuclei are
spherical, with borders sometimes irregular, generally with-
out nucleoli, finely granular, and from ^^Q-Q to -g-gVo of an
inch in diameter. They are insoluble in acetic acid.1 The
cells are less numerous than the free nuclei. They are
spherical or slightly polyhedric, contain a few pale granu-
lations, are rendered pale, but are not dissolved by acetic
acid, and measure about 17100 of an inch in diameter.2

Myelopldxes. — These are irregular, nucleated patches,
also described by Robin, more abundant in the spongy por-
tions of the bones than in the medullary canals, and are
applied to the internal surfaces of the bones. They are ex-
ceedingly irregular in size and form (measuring from 12100
to -^Q of an inch in diameter), are finely granular, and pre-
sent from two to twenty or thirty nuclei. The nuclei are
clear, ovoid, generally with a nucleolus, and are from %^Q
to innnr of an incn long> by -g^ to ^^ of an inch broad.
The myeloplaxes are rendered pale by acetic acid, and the
nuclei are then brought out more distinctly.8

In addition to the anatomical elements just described,
the marrow contains a few very delicate bundles of connec-
tive tissue, most of which accompany the blood-vessels. In
the foetus the adipose vesicles are few or may be absent ;
but in the adult they are quite numerous, and in some bones
seem to constitute the whole mass of the marrow. They do
not differ materially from the fat-cells in other situations.
Holding these different structures together, is a variable
quantity of semitransparent, amorphous, or slightly granu-
lar matter.

The nutrient artery of the bones sends branches to the
marrow, generally two in number for the long bones, which
are distributed between the various anatomical elements, and

1 LITTRE ET ROBIN, Dictionnaire demedecinc, Paris, 1865, Article, Medullocelle.

2 POUCHET, Precis d'histologie humaine, Paris, 1864, p. 106.

3 LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1865, Article, Myeloplaxe.

ANATOMY OF THE BONES. 4:85

finally surround the fatty lobules and the fat-vesicles with a
delicate capillary plexus. The veins correspond to the arte-
ries in their distribution. The nerves follow the arteries,
and are lost when these vessels no longer present a muscular
coat.1 Nothing is known of the presence of lymphatics in
any part of the bones, or in the periosteum.

The only point of physiological interest connected with
the marrow is, that it has been found to possess, in common
with the periosteum, but in a less degree, the property
of generating true bony substances. TVe shall see further
on, that the periosteum is not only very important to the
nutrition of the bones, but that it will generate bone when
transplanted into vascular parts. M. Oilier, who has made
a very extended series of experiments upon the physiological
properties of the periosteum, endeavored to produce bone by
transplanting portions of marrow, but was unsuccessful.
M. Goujon, however, has lately been more fortunate. He
has found that frequently, but not always, marrow trans-
planted into the muscular tissue will generate bone, particu-
larly the marrow taken from young bones, but the bony
tissue thus formed is soon absorbed.3

Periosteum. — In most of the bones the periosteum pre-
sents a single layer of fibrous tissue ; but in some of the long
bones two or three layers may be demonstrated. This mem-
brane adheres to the bone, but can generally bs separated
without much difficulty. It covers the bones completely,
except at the articular surfaces, where its place is supplied
by cartilaginous incrustation. It is composed mainly of
fibres of the white inelastic variety, with numerous small
elastic fibres, blood-vessels, nerves, and a few adipose
vesicles.

The arterial branches ramifying in the periosteum are

1 SAPPET, op. czV., p. 95.

2 GOUJOX, Recherches experimentales sur les proprieles physiologiqiies de la
moelle des os. — Journal de T anatomic, Paris, 1869, tome vi., p. 399, el seq.

486 MOVEMENTS.

quite numerous, forming a close, anastomosing plexus, which
sends numerous small branches into the bony substance.
There is nothing peculiar in the arrangement of the veins.
The distribution of the veins in the bony substance has been
very little studied.

The nerves of the periosteum are very abundant, and
form in its substance quite a close plexus.

The adipose tissue is very variable in quantity. In some
parts it forms a continuous sheet, and in others the vesicles
are scattered here and there . through the substance of the
membrane.

The importance of the periosteum to the nutrition of the
bones is very great. Instances are on record where bones
have been removed, leaving the periosteum, in which the
entire bone has been regenerated. The importance of the
periosteum has been still further illustrated by the remark-
able experiments of M. Oilier, upon transplantation of this
membrane in the different tissues of living animals.1

Physiological Anatomy of Cartilage. — In this connec-
tion the structure of the articular cartilages presents the
chief physiological interest. The articular surfaces of all the
bones are encrusted with a layer of cartilage, varying in
thickness from -fa to -^ of an inch. The cartilaginous sub-
stance is white, opaline, and semitransparent when examined
in thin sections. It is not covered with any membrane, but
in the non-articular cartilages it has an investment analo-
gous to the periosteum.

Examined in thin sections, cartilage is found to consist
of a homogeneous fundamental substance, marked with
numerous excavations, called cartilage-cavities, or chondro-
plasts. The intervening substance has a peculiar organic

1 The original memoirs of M. Oilier were published in the Journal de la phys-
iologie, Paris, 1859-1863, tome ii., pp. 1, 169, 468, tome iii., p. 88, tome iv., p.
87, tome v., p. 59, and tome vi., pp. 466, 517. He has since published an elabo-
rate work on the subject, in two volumes. (Traite experimentale et dinique de
la generation des os, Paris, 1867.)

ANATOMY OF CARTILAGE.

48T

FIG

base, called cartilagine. By prolonged boiling this is
changed into a new substance, called chondrine. The or-
ganic matter is united with a certain proportion of inorganic
salts. This fundamental substance is elastic and resisting.
The cartilages are closely united to the subjacent bony tis-
sue. The free articular surface has already been described.1

Cartilage- Cavities. —
These cavities are round-
ed or ovoid, measuring
from Y^VF to -g-J-g of an
inch in diameter.2 They
are generally smaller in
the articular cartilages
than in other situations,
as in the costal carti-
lages. They are simple
excavations in the funda-
mental substance, have
no lining membrane, and
contain a small quantity
of a viscid liquid, with
one or more cells. They
are entirely analogous
to the lacunse of the
bones.

Cartilage -Cell s. —
Xear the surface of the
articular cartilages the
cavities contain each a

single cell; -but in the gection of a diarttaodiai cartilage;

deeper portions the cav-
ities are long and con-
tain from two to twenty
cells arranged longitu-
dinally. The cells are of about the size of the smallest

1 See page 40. 2 POUCHET, Precis tfhistologie humaine, Paris, 1864, p. 117-

488 MOVEMENTS.

cavities. They are ovoid, with, a large, granular nucleus.
They often contain a few small globules of oil. In the
costal cartilages the cavities are not numerous, but are
rounded and quite large. The cells contain generally a
certain amount of fatty matter. The appearance of the or-
dinary articular cartilage is represented in Fig. 20.

The ordinary cartilages have neither blood-vessels, lym-
phatics, nor nerves, and are nourished exclusively by imbibi-
tion from the surrounding parts. Their function has already
been sufficiently considered in treating of the synovial mem-
branes. In the development of the body, the anatomy of
the cartilaginous tissue possesses peculiar interest, from the
fact that the deposition of cartilage precedes the formation
of bone ; but we have here only to do with the permanent
cartilages.

Fibro-Cartilage. — This variety of cartilage presents cer-
tain important peculiarities in the structure of its funda-
mental substance. It exists in the synchondroses, the car-
tilages of the ear, of the Eustachian tabes, the interarticular
disks, the intervertebral cartilages, the cartilages of Santorini
and of Wrisberg, and the epiglottis. Its structure has been
very closely and successfully studied by Sappey, who has
arrived at results differing considerably from those obtained
by other observers.

According to Sappey,1 the fibre-cartilage is composed of
true fibrous tissue with a great predominance of elastic fibres,
fusiform, nucleated fibres, a certain number of adipose vesi-
cles, cartilage-cells, and numerous blood-vessels and nerves.
The presence of cartilage-cells assimilates this tissue to the
ordinary cartilage, though its structure is very much more
complex. The fibrous elements above mentioned take the
place of the homogeneous fundamental substance of the true
cartilage. The most important peculiarity in the structure
of this tissue is that it is abundantly supplied with blood-
vessels and nerves.

1 SAPPEY, Traite tfanatomie, Paris, 1867, tome i., p. 458, et seq.

ANATOMY OF CARTILAGE. 489

The reader is referred to works upon anatomy for a his-
tory of the action of the muscles. In some works upon
physiology, will be found descriptions of the acts of walking,
running, leaping, swimming, etc. ; but we have thought it
better to omit these subjects, rather than to enter as mi-
nutely as would be necessary into anatomical details,
and to give elaborate descriptions of movements, so simple
and familiar.

CHAPTER XVII.

VOICE AND SPEECH.

Sketch of the physiological anatomy of the vocal organs — Vocal chords — Mus-
cles of the larynx — Crico-thyroid muscles — Arytenoid muscle — Lateral
crico-arytenoid muscles — Thyro-arytenoid muscles — Mechanism of the pro-
duction of the voice — Appearance of the glottis during ordinary respira-
tion— Movements of the glottis during phonation — Variations in the quality
of the voice, depending upon differences in the size and form of the larynx
and the vocal chords — Action of the intrinsic muscles of the larynx in
phonation — Action of the accessory vocal organs — Mechanism of the dif-
ferent vocal registers — Mechanism of speech.

THERE are few subjects connected with human physiology
of greater interest than the mechanism of voice and speech.
In common with most of the higher classes of animals, man
is endowed with voice ; but, in addition, he is able to express,
by speech, the ideas that are the result of the working of the
brain. In this regard there is a difference between man
and all other animals. It is the remarkable development
and the peculiar properties of the brain that enable him
to acquire the series of movements that constitute articulate
language ; and this faculty is always impaired pari passu
with deficiency in the intellectual endowment. Language
is one of the chief expressions of intelligence ; and its study,
in itself, constitutes almost a distinct science, inseparably
connected with psychology. In connection with the study
of movements, therefore, it is not necessary to discuss the
origin and construction of language, but simply to indicate
the mechanism, first, of the formation of the voice, and

PHYSIOLOGICAL ANATOMY OF THE YOCAL ORGANS. 4:91

afterward the manner in which the voice is modified so as
to admit of the production of articulate sounds.

The voice in the human subject, presenting, as it does, a
variety of characters as regards intensity, pitch, and quality,
and susceptible of great modifications by habit and culti-
vation, affords a very extended field for physiological study.
Of late years this has been the subject of careful investiga-
tion by the most eminent physicists and physiologists ; but
to follow it out to its extreme limits requires a knowledge
of the physics of sound and the theory of music, a full con-
sideration of which would be inconsistent with the scope
and objects of this work. AVe shall content ourselves, there-
fore, with a sketch of the physiological anatomy of the parts
concerned in the formation of the voice, and the mechanism
by which sounds are produced in the larynx, without treat-
ing fully of their varied modifications in quality. It will
not be necessary to treat of the different theories of the voice
that have been presented from time to time, except in so far
as they have been confirmed by more recent and complete
observations, particularly those in which the vocal organs
have been studied in action by means of the laryngoscope.

Sketch of the Physiological Anatomy of the Vocal Organs.

The principal organ concerned in the production of the
voice is the larynx. The accessory organs are the lungs,
trachea, and expiratory muscles, and the mouth and reso-
nant cavities about the face. The lungs furnish the air by
which the vocal chords are thrown into vibration, and the
mechanism of this action is only a modification of the pro-
cess of expiration. By the action of the expiratory muscles
the intensity of vocal sounds is regulated. The trachea not
only conducts the air to the larynx, but, by certain varia-
tions in its length and calibre, may assist in modifying the
pitch of the voice. Most of the variations in the tone and
quality, however, are effected by the action of the larynx
itself and the parts situated above it.

492 VOICE AND SPEECH.

It is impossible to give a complete account of the structure
of the larynx, without going more fully than is desirable into
purely anatomical details. Some anatomical points have
already been referred to under the head of respiration, in
connection with the respiratory movements of the glottis ; 1
and we propose here only to refer to the situation of the
vocal chords, and to indicate the modifications that they
can be made to undergo in their relations and tension by
the action of certain muscles.

The vocal chords are stretched across the superior open-
ing of the larynx from before backward. They consist of
two pairs. The superior, called the false vocal chords, are
not concerned in the production of the voice. They are less
prominent than the inferior chords, though they have nearly
the same direction. They are covered by an excessively thin
mucous membrane, which is closely adherent to the sub-
jacent tissue. The chords themselves are composed of
fibres of the white inelastic variety, mixed with a few elas-
tic fibres.

The true vocal chords are situated just below the superior
chords. Their anterior attachments are near together, at the
middle of the thyroid cartilage, and are immovable. Pos-
teriorly they are attached to the movable arytenoid carti-
lages ; and by the action of certain muscles, their tension
may be modified, and the chink of the glottis may be opened
or closed. These ligaments are much larger than the false
vocal chords, and contain a very great number of elastic
fibres. Like the superior ligaments, they are covered with
an excessively thin and closely adherent mucous membrane.
According to M. Fournie, the author of a very elaborate and
recent work on the voice, the mucous membrane over the
borders of the chords is covered with pavement-epithelium,
without cilia.2 There are no mucous glands in the mem-
brane covering either the superior or the inferior chords.

1 See vol. i., Respiration, p. 358.

2 FOURNIE, Physiologie de la voix et de la parole, Paris, 1866, p. 129.

MUSCLES OF THE LAKY^X. 493

It has been conclusively shown, particularly by the ex-
periments of Longet, that the inferior vocal chords are alone
concerned in the production of the voice. This author, who
has made numerous experiments on phonation, has demon-
strated, by operations on dogs, that the epiglottis, the supe-
rior vocal chords, and the ventricles of the larynx, may be
injured, without producing any serious alteration jn the
voice ; but that phonation becomes impossible after serious
lesion of the inferior chords.1 This being the fact, as far
as the mere production of the voice in the larynx is con-
cerned, we have only to study the mechanism of the action
of the inferior ligaments and the muscles by which their
tension and relations are modified.

Muscles of the Larynx. — Anatomists usually divide the
muscles of the larynx into extrinsic and intrinsic. The ex-
trinsic muscles are attached to the outer surface of the larynx
and to adjacent organs, such as the hyoid bone and the
sternum. They are concerned chiefly in its movements of
elevation or depression. The intrinsic muscles are attached
to the different parts of the larynx itself, and, by their action
upon the articulating cartilages, are capable of modifying
the condition of the vocal chords. The number of the in-
trinsic muscles is nine, four pairs and a single muscle. In
studying the situation and attachments of these muscles, it
will be useful at the same time to note their mode of action.
This has been experimentally demonstrated by Louget, who
has studied the isolated action of the different muscles by
galvanizing the nervous filament distributed to each one,
either in the living animal, or in animals recently killed.
In this way he has been able to show the mechanism of dila-
tation of the larynx during inspiration, and to indicate the
precise action by which the vocal chords are rendered tense
or are relaxed.3 These experiments, by the positive charac-

1 LOXGET, Traite de physiologic , Paris, 1869, tome ii., p. 728, et seq.
8 Op. cit., p. 727.

VOICE AND SPEECH.

tcr of their results, have done much to simplify the study of
the muscular acts concerned in the production of the voice.

Bearing in mind the relations and attachments of the
vocal chords, we can understand precisely how they can be
rendered tense or loose by muscular action. Their fixed
point is in front, where their extremities, attached to the
thyroid cartilage, are nearly or quite in contact with each
other. The arytenoid cartilages, to which they are attached
posteriorly, present a movable articulation with the cricoid
cartilage ; and the cricoid, narrow in front, and wide behind,
where the arytenoid cartilages are attached, presents a mov-
able articulation with the thyroid cartilage. It is evident,
therefore, that muscles acting upon the cricoid cartilage can
cause it to swing upon its two points of articulation with the
inferior cornua of the thyroid, raising the anterior portion
and approximating it to the lower edge of the thyroid ; and,
as a consequence, the posterior portion, which carries the
arytenoid cartilages and the posterior attachments of the
vocal chords, is depressed. This action would, of course, in-
crease the distance between the arytenoid cartilages and the
anterior portion of the thyroid, elongate the vocal chords,
and subject them to a certain degree of passive tension.
Experiments have shown that such an effect is produced
by the contraction of the cri co-thyroid muscles.

The articulations of the different parts of the larynx
are such that the arytenoid cartilages may be approximated
to each other posteriorly, though perhaps only to a slight
extent, thus diminishing the interval between the posterior
attachments of the vocal chords. This action can be effected
by contraction of the single muscle of the larynx, the aryte-
noid, and also by the lateral crico-arytenoid muscles. The
thyro-arytenoid muscles, the most complicated of all the in-
trinsic muscles in their attachments and the direction of
their fibres, according to Longet, give rigidity and increased
capacity of vibration to the vocal chords.1

1 Op. tit., p. 730.

MUSCLES OF THE LARYNX. 495

The posterior crico-arytenoid muscles, arising from each
lateral half of the posterior surface of the cricoid cartilage,
passing upward and outward to be inserted into the outer
angle of the inferior portion of the arytenoid cartilages,
rotate these cartilages outward, separate them, and act as
dilators of the chink of the glottis. These muscles are
chiefly concerned in the respiratory movements during in-
spiration.

The muscles mainly concerned in the modifications of
the voice by their action upon the vocal chords are the crico-
thyroids, the arytenoid, the lateral crico-arytenoids, and the
thyro-arytenoids. The following is a sketch of their attach-
ments and mode of action :

Crico-thyroid Muscles. — These muscles are situated on
the outside of the larynx at the anterior and lateral por-
tions of the cricoid cartilage. Each muscle is of a triangular
form, the base of the triangle looking posteriorly. It arises
from the anterior and lateral portions of the cricoid cartilage,
and its fibres diverge to be inserted into the inferior border
of the thyroid cartilage, extending from the middle of this
border posteriorly, as far back as the inferior cornua. Longet,
after dividing the nervous filaments distributed to these mus-
cles, noted hoarseness of the voice, depending upon relaxation
of the vocal chords ; and by imitating its action mechanically,
he approximated the cricoid and thyroid cartilages in front,
carried back the arytenoid cartilages, and rendered the chords
tense.1

Arytenoid Muscle. — This single muscle fills up the space
between the two arytenoid cartilages and is attached to
their posterior surface and borders. Its evident action is
to approximate the posterior extremities of the chords and
constrict the glottis, as far as the articulations of the
arytenoid cartilages with the cricoid will permit. In any
event, this muscle is important in phonation, as it serves
to fix the posterior attachments of the vocal chords and

1 LONGET, loc. dt.

496 VOICE AND SPEECH.

to increase the efficiency of certain of the other intrinsic
muscles.1

Lateral Crico-arytenoid Muscles. — These muscles are
situated in the interior of the larynx. They arise from
the sides and superior borders of the cricoid cartilage, pass
upward and backward, and are attached to the base of the
arytenoid cartilages. By dividing all of the filaments of the
recurrent laryngeal nerves except those distributed to these
muscles, and then galvanizing the nerves, Longet has shown
that they act to approximate the vocal chords and constrict
the glottis, particularly in its interligamentous portion.2
These muscles, with the arytenoid, act as constrictors of the
larynx.

Thyro-arytenoid Muscles. — It is sufficiently easy to indi-
cate the relations and attachments of these muscles, but their
mode of action is more complex and difficult of comprehen-
sion. When we come to study the conditions of the vocal
chords involved in certain modifications of the voice, we will
refer more in detail to the action of different fasciculi of
these muscles. In this connection we will only describe
very briefly their situation and attachments, and the general
results of their contraction.

The thyro-arytenoid muscles are situated within the
larynx. They are broad and flat, and arise in front from
the upper part of the crico-thyroid membrane and the lower
half of the thyroid cartilage. From this line of origin, each
muscle passes backward in two fasciculi, both of which are
attached to the anterior surface and outer border of the
arytenoid cartilages. The application of galvanism to the
nervous filaments distributed to these muscles has the effect

1 A very interesting case of aphonia, reported by Dr. Knight, of Boston, in
which the appearances were carefully studied with the laryngoscope, seems to
show that the arytenoid muscle is not capable of producing any considerable
amount of movement, in totality, of the arytenoid cartilages. (KNIGHT, Two
Cases of Paralysis of Intrinsic Muscles of the Larynx. — Boston Medical and Sur-
gical Journal, 1869, New Series, vol. in., p. 49, et seq.)

2 LONGET, loc. tit.

PRODUCTION OF THtf VOICE. 497

of rendering the vocal chords rigid and increasing the in-
tensity of their vibrations.1 The great variations that may
be produced in the pitch and quality of the voice by the
action of muscles operating directly or indirectly on the
vocal chords render the problem of determining the precise
mode of action of the intrinsic muscles of the larynx exceed-
ingly complicated and difficult. It is certain, however, that,
in these muscular acts, the thyro-arytenoids play an impor-
tant part. Their contraction regulates the thickness and
rigidity of the vocal chords, while at the same time it modi-
fies their tension. Fournie regards the swelling of the chords,
which may be rendered regular and progressive under the
influence of the will, as one of the most important agents in
the formation of the tones of the voice.3

Mechanism of the Production of the Voice.

It will save much unprofitable discussion to dismiss
quite briefly most of the theories that have been advanced
to explain the production of the voice, and to avoid com-
parisons of the larynx with different kinds of musical instru-
ments. Before the larynx had been studied in action by
means of the laryngoscope, physiologists, having the anatom-
ical structure of the parts for their only guide, presented
various speculations with regard to the mechanism of phona-
tion, which were frequently utterly opposed to each other in
principle. The vocal apparatus was compared to wind or
brass instruments, to reed-instruments, to string-instruments,
to the flute, etc., and some even refused to the vocal chords
any share in the sonorous vibrations. An apparatus was de-
vised to imitate the vocal organs, experiments were made with
the larynx removed from the body, and every thing seemed
to be done, except to observe the organs in actual function.3

1 LONGET, op. cit., p. 730.

2 FOURNIE, Physiologic de la voix et de la parole, Paris, 1866, p. 121.

3 Perhaps the most elaborate of the observations made before the discovery
of the laryngoscope are those of J. Miiller, who experimented very extensively

498 VOICE AND SPEECH.

A short time, however, after the laryngoscope came into use,
the larynx was examined during the production of vocal
sounds. The true value of previous theories was then
positively demonstrated ; and while it has not been possible
to settle all disputed points with regard to the precise mode
of action of certain muscles, the appearances of the larynx
itself during phonation and the results of the action of cer-
tain of the intrinsic muscles have been quite accurately
described. One of the first elaborate series of investigations
of the subject by means of tLje laryngoscope was made by
Manuel Garcia.1 These observations were chiefly directed
to the changes of the glottis in singing, and were made by
Garcia upon his own person. The essential points devel-
oped by these experiments have since been confirmed by
Battaille,2 and many other observers.

Appearance of the Glottis during Ordinary Respiration.
— If the glottis be examined with, the laryngoscope during
ordinary respiration, the wide opening of the chink during
inspiration, due to the action of the crico-arytenoid muscles,
can be observed without difficulty. This action is effected
by a separation of the posterior points of attachment of the
vocal chords to the arytenoid cartilages. During ordinary
expiration, none of the intrinsic muscles seem to act, and the
larynx is entirely passive ; while the air is gently forced out
by the elasticity of the lungs and of the thoracic walls. But
as soon as an effort is made to produce a vocal sound, the ap-
pearance of the glottis undergoes a remarkable change, and
becomes modified in the most varied and interesting man-
ner, with the different changes in pitch and intensity that

with artificial vocal apparatus and with the larynx itself removed from the
body. Many of the ideas of Miiller have been carried out by recent laryn-
goscopic researches (Manuel de physiologic, Paris, 1851, p. 127, el seq.).

1 GARCIA, Observations on the Human Voice. — Proceedings of the Royal Society,
London, 1856, vol. vii., p. 399, et scq.

2 BATTAILLE, Nouvellcs recherches sitr la phonation. — Comptes rendus, Paris,
1861, tome Hi., p. 716, et scq.

PRODUCTION OF THE VOICE. 499

the voice can be made to assume. Although it is suffi-
ciently evident that a sound may be produced, and even
that words may be articulated with the act of inspiration,
true and normal phonation is effected during expiration
only. It is evident, also, that the inferior vocal chords are
the only ones concerned in the act. The changes in the
position and tension of the chords we shall study, first
with reference to the general act of phonation, and after-
ward as the chords act in the varied modifications of the
voice, as regards intensity, pitch, and quality.

Movements of the Glottis during Phonation.

It is somewhat difficult to observe with the laryngoscope
all of the vocal phenomena, on account of the epiglottis,
which hides a considerable portion of the vocal chords ante-
riorly, especially during the production of certain tones;
but the patience and skill of Garcia enabled him to over-
come most of these difficulties, and to settle, by autolaryngo-
scopy, the most important questions with regard to the move-
ments of the larynx in singing. It is fortunate that these ob-
servations, which are models of scientific accuracy and the re-
sult of most persevering study, were made by one profoundly
versed, theoretically and practically, in the knowledge of
music, and possessed of great control over the vocal organs.1

Garcia, after having observed the respiratory movements
of the larynx, as we have briefly described them, noted that
as soon as any vocal effort was made, the arytenoid carti-
lages were approximated, so that the glottis appeared as a
narrow slit, formed by two chords of equal length, firmly
attached posteriorly as well as anteriorly. The glottis thus

1 Manuel Garcia, the author of these observations, is the son of Garcia, the
great composer and singer, and the brother of Mme. Malibran. He now enjoys
a great reputation in London, as a singing-master ; and his experiments were
made with a view, if possible, of reducing the art of singing, which had always
been taught according to purely empirical methods, to scientific accuracy. It
is evident that this could be accomplished only through an exact knowledge of
the mechanism of the production of vocal sounds.

500 VOICE AND SPEECH.

undergoes a marked change. A nearly passive organ, open-
ing widely for the passage of air into the lungs, because the
inspiratory act has a tendency to draw its edges together,
and entirely passive in expiration, it has now become a sort
of musical instrument, presenting a slit with borders capable
of accurate vibration.

The approximation of the posterior extremities of the
vocal chords and their tension by the action of certain of
the intrinsic muscles are accomplished just before the vocal
effort is actually made. The glottis being thus prepared for
the emission of a particular sound, the expiratory muscles
force air through the larynx with the required power. It
seems wonderful how a carefully-trained voice can be modu-
lated and varied in all its qualities, including the intensity of
vibration, which is so completely under control ; but when we
consider the changes in its quality, we must remember, in
explanation, the varying conditions of tension and length
of the vocal chords, the differences in the size of the larynx,
trachea, and vocal passages generally, and the different
relations that the accessory vocal organs can be made to
assume. The power of the voice is simply due to the force
of the expiratory act, which is regulated chiefly by the antag-
onistic relations of the diaphragm and the abdominal muscles.
From the fact that the diaphragm, as an active inspiratory
muscle, is exactly opposed to the muscles which have a ten-
dency to push the abdominal organs, with the diaphragm
over them, into the thoracic cavity, and thus diminish the
pulmonary capacity, the expiratory and inspiratory acts can
be balanced so nicely that the most delicate vocal vibrations
can be produced. It is unnecessary to refer more in detail
to the action of these muscles, as we have already treated of
this subject fully in another volume.1

The glottis, thus closed as a preparation to a vocal act,
presents a certain amount of resistance to the egress of air.
This is overcome by the action of the expiratory muscles,

1 See vol. i., Respiration, p. 385, et seq.

PRODUCTION OF THE VOICE. 501

and with the passage of air through the chink, the edges of
the opening, which are formed by the true vocal chords, are
thrown into vibration. Many of the different qualities
that are recognized in the human voice are due to differ-
ences in the length, breadth, and thickness of the vibrat-
ing ribbons ; but, aside from what is technically known as
quality, the pitch is dependent chiefly upon the length of
the opening through which the air is made to pass, and the
degree of tension of the chords. The mechanism of these
changes in the pitch of vocal sounds is well illustrated by
Garcia in the following passage, which relates to what is
known as the chest-voice : 1

" If we emit veiled and feeble sounds, the larynx opens
at the notes p/jiv ^^1, and we see the glottis

agitated by r *~~j [ d large and loose vibrations
throughout do, re, mi. its entire extent. Its lips

comprehend in their length the anterior apophyses of the
arytenoid cartilages and the vocal chords ; but, I repeat it,
there remains no triangular space.

" As the sounds ascend, the apophyses, which are slightly
rounded on their internal side, by a gradual apposition com-
mencing at the. back, encroach on the length of the glottis ;
and as soon as we reach the sounds pi? ~], thev fin-

i VT, I ' v

ish by touching each other through- ESzzzztzzEij out their
whole extent ; but their summits are ^ do. onV s°l~
idly fixed one against the other at the notes p^jr-- ^ .
In some organs these summits are a little bLj!__^_^j:z3
vacillating when they form the posterior do, re.
end of the glottis, and two or three half-tones which are
formed show a certain want of purity and strength, which
is very well known to singers. From P-J2- i the vi-
brations, having become rounder and EfcSi 1—^3 purer,

9J £&'

are accomplished by the vocal liga- do, re. ments

alone, up to the end of the register.

1 GARCIA, op. cit., p. 401. We have indicated the notes in the following
paragraphs by the method most commonly used by musicians, as is done by
Mrs. Seiler, in the same quotation.

502 VOICE AND SPEECH.

" The glottis at this moment presents the aspect of a line
swelled toward its middle, the length of which diminishes
still more as the voice ascends. We shall also see that the
cavity of the larynx has become very small, and that the
superior ligaments have contracted the extent of the ellipse
to less than one-half."

These observations, have been in the main confirmed by
Battaille,1 Emma Seiler,8 and all who have applied the la-
ryngoscope to the study of the voice in singing. A few
years ago we had an opportunity of observing the changes
in th'e form of the glottis during the production of vocal
sounds of different degrees of pitch, through the kindness of
Dr. Ephraim Cutter, of Boston. In these experiments the
various points to which we have alluded were illustrated by
autolaryngoscopy in the most marked manner ; and nothing
could be more striking than the changes in the form of the
glottis in the transition from low to high notes. We have
also frequently observed the general appearance of the glottis
in phonation in experiments upon animals in which the glottis
has been exposed to view.

Variations in the Quality of the Voice, depending upon
differences in the Size and Form of the Larynx and the
Vocal Chords. — We are all sufficiently familiar with the
characters of the male as distinguished from the female
voice, and what are known as the different vocal registers.
In childhood, the general characters of the voice are essen-

1 Loc. cit.

2 EMMA SEILER, TJie Voice in Singing, translated from the German, Phila-
delphia, 1868. This little work contains the results of a series of observations
on the voice, made after the method employed by Garcia. These are peculiarly
interesting, as they are applied particularly to the study of the female voice,
and elucidate certain disputed points with regard to the production of the fal-
setto and the head-voice. The whole subject of the voice is treated in an
eminently scientific manner, and the author professes to correct many faults in
the methods of teaching the art of singing, that have had their origin in the
employment of purely empirical methods.

PRODUCTION OF THE VOICE. 503

tially the same in both sexes. The larynx is smaller than
in the adult, and the vocal muscles are evidently more feeble ;
but the quality of the vocal sounds at this period of life is
peculiarly pure and penetrating. While there are peculiari-
ties that distinguish the voices of boys before the age of
puberty, they present, as in the female, the different quali-
ties of the soprano and contralto. At this age the voices of
boys are capable of considerable cultivation, and their pecu-
liar quality is sometimes highly prized in church-music.
After the age of puberty, the female voice does not com-
monly undergo any very marked change, except in the de-
velopment of additional strength and increased compass, the
quality remaining the same ; but in the male there is a rapid
change at this time in the development of the larynx, and
the voice assumes an entirely different quality of tone. This
change does not usually take place if castration be performed
in early life ; and this barbarous operation was frequently
resorted to in the seventeenth century, for the purpose of
preserving the qualities of the soprano and contralto, par-
ticularly for church-music. It is only of late years, indeed,
that this practice has fallen into disuse in Italy.

The ordinary range of all varieties of the human voice
is given by Miiller as equal to nearly four octaves ; but it is
rare that any single voice has a compass of more than two
and a half octaves. There are examples, however, in which
singers have acquired a compass of three octaves, and even
more. The celebrated singer, Mme. Parepa-Rosa, has a
compass of voice that touches three full octaves, from so!2
to sol5. In music, the notes are written the same for the
male as for the female voice, but the actual value of the
female notes, as reckoned by the number of vibrations in the
second, is always an octave higher than the male.1

In both sexes there are differences, both in the range and
the quality of the voice, which it is impossible for a culti-
vated musical ear to mistake. In the male, we have the

1 FOURXIE, Physiologic de la voix et de la parole, Paris, 1866, p. 531.

504: VOICE AND SPEECH.

bass and the tenor, with an intermediate voice, called the
barytone. In the female, we have the contralto and the
soprano, with the intermediate, or mezzo-soprano. In the
bass and barytone, the lower and middle notes are the most
natural and perfect; and while the higher notes may be
acquired by cultivation, they are not easy, and do not possess
the same quality as the corresponding notes of the tenor.
The same remarks apply to the contralto and soprano. The
mezzo-soprano is regarded by many as an artificial division.

The following scale, proposed by Miiller, gives the ordi-
nary ranges of the different kinds of voice ; but it must be
remembered that there are individual instances in which
these limits are very much exceeded : 1

CONTRALTO

mi fa sol la si do re mi fa sol la si do re mi fa sol la si do re mi fa sol la si do

11 111 22 2'2 2223333 333444444

There is really no great difference in the mechanism
of these different kinds of voice, and the differences in pitch
are due chiefly to the greater length of the vocal chords in
the low-pitched voices, and their shortness in the higher
voices. The differences in quality are due to peculiarities
in the conformation of the larynx, to differences in its size,
and in the size and form of the auxiliary resonant cavities.
Great changes in the quality of the voice may be effected
by practice. A cultivated note, for example, has an entirely
different sound from a harsh, irregular vibration ; and, by
practice, a tenor may imitate the quality of the bass, and
vice versa, although the effort is unnatural. It is not at all
unusual to hear male singers imitate very closely the notes

1 MUELLER, Manuel de physiologic, Paris, 1851, tome ii., p. 198.

PRODUCTION OF THE VOICE. 505

of the female, and the contralto will sometimes imitate the
voice of the tenor in a surprisingly natural manner. These
facts have a somewhat important bearing upon certain dis-
puted points with regard to the mechanism of the different
vocal registers, which will be considered further on.

Action of the Intrinsic Muscles of the Larynx in Pho-
nation. — It is much more difficult to find an entirely satis-
factory explanation of the different tones produced by the
human larynx in the action of the intrinsic muscles than to
describe the changes in the tension and relations of the vocal
chords. These muscles are concealed from view, and the
only idea that we can have of their action is by reasoning
from a knowledge of their points of attachment, and by oper-
ations upon the dead larynx, either imitating the contrac-
tion of special muscles or galvanizing the nerves in animals
recently killed. In this way, as we have seen, some of the
muscular acts have been studied very satisfactorily ; but the
precise effect of the contraction of certain of the muscles,
particularly the thyro-arytenoids, is still a matter of dis-
cussion.

In the production of low chest-tones, in which the vocal
chords are elongated and at the minimum of tension that
will allow of regular vibrations, the crico-thyroid muscles are
undoubtedly brought into action, and are assisted by the
arytenoid and the lateral crico-arytenoids, which combine to
fix the posterior attachments of the vibrating ligaments. It
will be remembered that the crico-thyroids, by approximat-
ing the cricoid and thyroid cartilages in front, have a ten-
dency to remove the arytenoid cartilages from the anterior
attachment of the chords.

As the tones produced by the larynx become higher in
pitch, the posterior attachments of the chords are approxi-
mated more firmly, and at this time the lateral crico-aryte-
noids are probably brought into vigorous action.

The function of the thyro-arytenoids is more complex ;

506 VOICE AND SPEECH.

and it is probably in great part by the action of these mus-
cles that the varied and delicate modifications in the rigidity
of the vocal chords are produced.

The remarkable differences in singers in the purity of
their tones are undoubtedly due in greatest part to the un-
swerving accuracy with which some put the vocal chords
upon the stretch ; while in those in whom the tones are of
inferior quality, the action of the muscles is more or less
vacillating, and the tension is frequently incorrect. The
fact that some celebrated singers can make their voice heard
above the combined sounds from a large chorus and orchestra
is not due entirely to the intensity of the sound, but in a
great measure to the absolute mathematical equality of the
sonorous vibrations, and the comparative absence of discord-
ant waves.1 Musicians who have heard the voice of the
celebrated basso, Lablache, all bear testimony to the re-
markable quality of his voice, which could be heard at times
above a powerful chorus and orchestra. A grand illustration
of this occurred at the musical festival at Boston, in 1869.
In some of the solos by Mine. Parepa-Rosa, accompanied by
a chorus of nearly twelve thousand, with an orchestra of
more than a thousand and largely composed of brass instru-
ments, we distinctly heard the pure and just notes of this
remarkable soprano, standing alone, as it were, against the
entire choral and instrumental force ; and this in an im-
mense building containing an audien.ce of forty thousand
persons. The absolute accuracy of the tone was undoubt-
edly an important element in its remarkably penetrating

1 Immense progress has been made in the analytical study of different
sounds by the celebrated German physicist, Hehnholtz. By means of his in-
geniously-constructed resonators, taking advantage of the laws of consonance,
in accordance with which the quality as well as the pitch of different tones is
reproduced, he has been able to separate sounds into their different component
parts as accurately as a ponderable compound is resolved into its constituent
elements in the laboratory of the chemist. — (HELMHOLTZ, Theorie physiologique
de la musique fondee sur V etude des sensations auditives, Paris, 1868, p. 48, etseq.)
This subject will be fully considered under the head of audition.

ACTION OF THE ^ACCESSORY VOCAL OEGANS. 507

quality. In the same way we explain the fact that the flute,
clarinet, or the sound from a Cremona violin, may be heard
soaring above the chords of a full orchestra.

Action of the Accessory Vocal Organs. — A correct use
of the accessory organs of the voice is of the greatest im-
portance in singing ; but the manner in which these parts
perform their function is exceedingly simple, and does not
require a very extended description. The human vocal
organs, indeed, consist of a vibrating instrument, the larynx,
and certain tubes and cavities by which the sound is reen-
forced and modified.

The trachea serves not only to conduct air to the larynx,
but to reenforce the sound to a certain extent by the vibra-
tions of the column of air in its interior. When a powerful
vocal effort is made, it is easy to feel, with the finger upon
the trachea, that the air contained in it is thrown into vibra-
tion. The structure of this tube is such that it may be
elongated and shortened at will. In the production of low
tones, the trachea is shortened and its calibre is increased,
the reverse obtaining in the higher notes of the scale.

Coming to the larynx itself, we find that the capacity of
its cavity is capable of certain variations. In fact, both the
vertical and the bilateral diameters are diminished in the
high notes and increased in low tones. The vertical diame-
ter may be modified slightly by ascent and descent of the true
vocal chords, and the lateral diameter may be reduced by
the inferior constrictors of the pharynx, acting upon the sides
of the thyroid cartilage.

The epiglottis, the superior vocal chords, and the ventri-
cles are by no means indispensable to the production of vo-
cal sounds. In the formation of high tones, the epiglottis is
somewhat depressed, and the superior chords are brought
nearer together ; but this only affects the character of the
resonant cavity above the glottis. In low tones the su-
perior chords are separated. It was before the use of the

508 VOICE AND SPEECH.

laryngoscope in the study of vocal phenomena that the
epiglottis and the ventricles were thought to be so important
in phonation. Undoubtedly the epiglottis has something to
do with the character of the voice ; but its function in this
regard is not absolutely necessary, or even very important,
as has been clearly shown by Longet in his experiments of
excising the part in living animals.1

The most important modifications of the laryngeal sounds
are produced by the resonance of air in the pharynx, mouth,
and nasal fossae. This resonance is indispensable to the
production of the natural human voice. Under ordinary
conditions, in the production of low notes the velum palati
is fixed by the action of its muscular fibres, so that there is a
reverberation of the bucco-pharyngeal and naso-pharyngeal
cavities ; that is, the velum is in such a position that neither
the opening into the nose or the mouth is closed, and all of
the cavities resound. As the tones are raised, the isthmus
contracts, the part immediately above the glottis is also con-
stricted, the resonant cavity of the pharynx and mouth is
reduced in size, until finally, in the highest tones of the
chest-register, the communication between the pharynx and
the nasal fossse is closed, and the sound is reenforced entirely
by the pharynx and mouth. At the same time the tongue,
a very important organ to singers, particularly in the pro-
duction of high notes, is drawn back into the mouth. The
point being curved downward, its base projects upward pos-
teriorly, and assists in diminishing the capacity of the cav-
ity. In the changes which the pharynx thus undergoes in
the production of different tones, the uvula acts with the
velum and assists in the closure of the different openings.
In singing up the scale, this is the mechanism, as far as the
chest-tones extend. When, however, we pass into what is
known as the head-voice, the velum palati is drawn forward
instead of backward, and the resonance takes place chiefly
in the naso-pharyngeal cavity.

1 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 727.

VOCAL REGISTERS. 509

Mechanism of the different Vocal Registers. — There has
been a great deal of discussion, even among those who have
studied the voice with the laryngoscope, with regard to the
exact mechanism of the different vocal registers. It is now
pretty well settled how the ordinary tones of what is known
as the chest-register are produced ; but with regard to the
falsetto, the difficulties in the way of direct observation are
so great, that the question of its mechanism cannot be said
to be definitively established.

The following are the vocal registers now recognized by
most physiologists :

1. The chest-register, most powerful in male voices and
in contraltos, and, indeed, almost characteristic of the male.

2. The falsetto register, which is the most natural voice
of the soprano ; though this voice is capable of chest-tones,
not so full, however, as in the contralto or in the male. In
the female this is known as the middle register.

3. The head-register, produced by a peculiar action of
the glottis and the resonant cavities above the larynx. This
is cultivated particularly in tenors and in the female.

Aside from the three registers, which belong to every
voice, a practised ear can find no difficulty in distinguishing
the different voices in nearly any part of the scale, both in
the male and the female, by the following peculiarities : In
the bass the low tones are full, natural, and powerful, and
the higher tones nearly always seem more or less artificial.
In singing, the passage from the natural to the artificial
tones in the scale is generally more or less apparent. In
the tenor the full, natural tones are higher in the scale, the
lower tones being almost always feeble and wanting in
roundness. Corresponding peculiarities enable us to distin-
guish between the contralto and the soprano.

Chest-Register. — We will simply recapitulate briefly the
mechanism of the chest-tones, to enable us to study more
easily the transitions to the different upper registers. This

510 VOICE AND SPEECH.

is the voice commonly used in speaking, and is the most nat-
ural, the vocal ligaments vibrating according to their ten-
sion, as the air is forced through the larynx from the chest,
and the air in the pharynx, mouth, and nasal fossae pro-
ducing a resonance without any artificial division of the
different cavities. As the tones are elevated the vocal
chords are simply rendered more tense, and the parts above
the larynx are more or less constricted, without any other
change in the mechanism of the sound. But the chest-voice
in the male cannot pass certain well-defined limits ; and in
the very highest notes it must be merged, either into the
head-voice or the falsetto. The falsetto, however, is now
but little cultivated, though some tenor singers, after long
practice, succeed in making the change from one register to
the other so nicely that it is hardly perceptible, even to a
cultivated ear. The head-voice has essentially the same
mechanism in the male as in the female, and will be consid-
ered after we have discussed the falsetto, which is the natu-
ral voice of soprano singers.

Falsetto Register. — The difference of opinion among
laryngoscopists with regard to the mechanism of the falsetto
is probably in great part due to the fact that when these
tones are produced, the isthmus of the fauces is so power-
fully contracted that it becomes exceedingly difficult to
study the action of the vocal chords. There is no reason
for supposing that the mechanism of this register does
not involve vibration of the true vocal chords, as in the
chest-voice, the difference being in the tension and in the
extent of the vibrating portion. According to the observa-
tions of Fournie, in the falsetto the tongue is pressed
strongly backward and the epiglottis is forced over the
larynx.1 Mrs. Emma Setter, from an extended series of
autolaryngoscopic observations, has arrived at the conclu-
sion that this voice involves vibrations of the fine, thin edges

1 Op. dt., p. 463.

VOCAL REGISTEKS. 511

of the chords only, a greater width vibrating in the produc-
tion of the chest-voice. She is particularly careful to insist
upon the distinction between the falsetto and the head-
register, the latter being produced by an entirely different
mechanism.1 On the whole, this explanation seems to be
the most satisfactory.

It must be remembered that the distinction between the
chest-register or the head-register and the falsetto, as far as
pitch is concerned, is not absolute. Certain of the high
notes of the chest or the head-voice, for example, may be
produced in the falsetto. In the cultivation of the female
voice, Mrs. Seller considers that it is exceedingly important
not to strain the chest-voice to its highest point, but to use
each register in its normal place in the scale, taking care, by
practice, to render the transition from one to the other natu-
ral and agreeable. We have heard male singers, probably
endowed with peculiar vocal powers, who were able, by the
use of the falsetto, to imitate almost exactly. the soprano
voice, though without the sweetness and purity of tone char-
acteristic of the perfect female organ. In the same way, by
straining the chest-voice beyond its normal limits, some fe-
males, particularly contraltos, are able to produce a very-
good imitation of the tenor quality.

Head- Register. — This voice is highly cultivated, particu-
larly in tenors and in the best female singers. It is not to be
confounded, however, with the falsetto, as was done by some
physiologists, before the invention of the laryngoscope.2
Head-tones may be produced by cultivated male singers,
bass and barytone, as well as tenor ; but the former seldom
have occasion for any but the chest-notes. Still, there are
musical passages in which the sotto-voce head-notes of the
bass have an exquisite softness, and are used with great
effect. Mrs. Seiler has studied this voice by autolaryngo-

1 EMMA SEILER, The Voice in Singing, Philadelphia, 1868, p. 56, ft seq.
• MUELLER, Manuel de physiologic, Paris, 1851, tome ii., p. 199.

512 VOICE AND SPEECH.

scopy with the greatest success, and has confirmed her
views with regard to the mechanism of its production by
numerous observations upon other singers. We have already
stated that Fournie has shown that, in the transition to the
head-voice, the velum palati is applied to the base of the
tongue, and the sound is reenforced by resonance from the
naso-pharyngeal cavity.1 If this be its mechanism, its study
with the laryngoscope must be exceedingly difficult.

The most important theory of the mechanism of the
head-voice has been proposed by Mrs. Seiler. After long
and patient effort, she was able to expose the glottis during
the production of these tones, when it was found that the
vocal chords were firmly approximated posteriorly, leaving
an oval opening, with vibrating edges, involving only one-
half or one-third of the vocal ligaments. This orifice con-
tracted progressively with the higher tones. This peculiar
division of the vocal ligaments is due, according to Mrs.
Seiler, to the action of a muscular bundle, called the inter-
nal thyro-arytenoid, upon little cartilages, the cuneiform,
extending forward from the arytenoid cartilage, in the sub-
stance of the vocal ligaments, as far as the middle of the
glottis.3

"With proper cultivation, the transition from the middle re-
gister to the head- voice in the female may be effected almost
imperceptibly, thereby increasing the compass from three to
six tones, and even more ; and in the male the same may be
accomplished without difficulty, particularly in tenors. There
can be hardly any doubt of the fact that the naso-pharyngeal
space is chiefly concerned in the resonance that takes place in
head-tones, though its actual demonstration is very difficult.
The distinction between the head and the chest-notes is
fully as marked in the male as in the female ; but it must be
remembered that one of the great ends to be accomplished
in the cultivation of the human voice is to make the three

1 FOURNIE, op. cit., p. 421. 2 Op. cit., p. 60.

MECHAXISM OF SPEECH. 513

registers pass into each other so that they shall appear as
one.1

Mechanism of Speech.

Articulate language consists in a conventional series of
sounds made for the purpose of conveying certain ideas.
There being no universal language, we must confine our
description of the faculty of speech to the mode of produc-
tion of the language in which this work is written. Lan-
guage, as it is naturally acquired, is purely imitative,
and does not involve of necessity the construction of an
alphabet, with its combinations into syllables, words, and
sentences ; but as civilization has advanced, we have been
taught to associate certain differences in the accuracy and
elegance with which ideas are expressed, with the degree of
development and cultivation of the intellectual faculties.
Philologists have long since established a certain standard,
varying, to some extent, it is true, with usage and the
advance of knowledge, but still sufficiently definite, by
which the correctness of modes of expression is measured.
We do not propose to discuss the science of language, or to
consider, in this connection, at least, the peculiar mental
operations concerned in the expression of ideas, but to take
our own tongue as we find it, and describe briefly the
mechanism of the production of the most important articu-
late sounds.

Almost every language is imperfect, as far as an exact
correspondence between its sounds and written characters is
concerned. Our own language is full of incongruities in
spelling, such as silent letters and arbitrary and unmeaning

1 In studying the mechanism of the voice in singing, we have received great
assistance in many practical points from Mme. Parepa-Rosa, to whose remark-
able power as a vocalist we have already alluded, and Sig. A. Bendelari, of this
city, the eminent singing-master. These distinguished artists, thoroughly
skilled both in the science as well as the art of music, have elucidated several
difficult questions, by their practical knowledge of the art of blending and modi-
fying the different vocal registers.
33

514 VOICE AND SPEECH.

variations in pronunciation ; but these do not belong to the
subject of physiology. There are, however, certain natural
divisions of the sounds as expressed by the letters of the
alphabet.

Vowels. — Certain articulate sounds are called vowel, or
vocal, from the fact that they are produced by the vocal
chords, and are but slightly modified as they pass out of the
mouth. The true vowels, a, e, i, o, u, can all be sounded
alone, and may be prolonged in expiration. These are the
sounds chiefly employed in singing. The differences in
their characters are produced by changes in the position of
the tongue, mouth, and lips. The vowel-sounds are neces-
sary to the formation of a syllable, and although they are
generally modified in speech by consonants, each one may,
of itself, form a syllable or a word. In the construction of
syllables and words, the vowels have many different quali-
ties, the chief differences being as they are made long or
short. In addition to the modifications in the vowel-sounds
by consonants, two or three may be combined so as to be
pronounced by a single vocal effort, when they are called
respectively, diphthongs and triphthongs. In the proper
diphthongs, as oi, in voice, the two vowels are sounded. In
the improper diphthongs, as ea, in heat, and in the Latin
diphthongs, as se, in Caesar, one of the vowels is silent. In
triphthongs, as eau, in beauty, only one vowel is sounded.
Y, at the beginning of words, is usually pronounced as a con-
sonant ; but in other situations it is pronounced as e or i.

Consonants. — Some of the consonants have no sound in
themselves, and only serve to modify vowel-sounds. These
are called mutes. They are b, d, k, p, t, and c and g hard.
Their office in the formation of syllables is sufficiently
apparent.

The consonants known as semi-vowels are, f, 1, m, n, r,
s, and c and g soft. These have an imperfect sound of

MECHAOTSM OF SPEECH. 515

themselves, approaching in character the true vowel-sounds.
Some of these, 1, m, n, and r, from the facility with which
they flow into other sounds, are called liquids. Orthoepists
have further divided the consonants with reference to the
mechanism of their pronunciation : d, j, s, t, z, and g soft,
being pronounced with the tongue against the teeth, are
called dentals ; d, g, j, k, 1, n, and q are called palatals ; b,
p, f, v, and m are called labials ; m, n, and ng are called
nasals ; and k, q, and c and g hard are called gutturals.1
After the full description we have given of the voice, it is
not necessary to discuss further the mechanism of these sim-
ple acts of articulation.

For the easy and proper production of articulate sounds,
absolute integrity of the mouth, teeth, lips, tongue, and
palate is required. We are all acquainted with the modifi-
cations in articulation, in persons in whom the nasal cavities
resound unnaturally, from imperfection of the palate ; and
the slight peculiarities observed after loss of the teeth and
in hare-lip are sufficiently familiar. The tongue is gen-
erally regarded, also, as an important organ of speech, and
this is the fact in the great majority of cases ; but instances
are on record in which distinct articulation has been pre-
served after complete destruction of this organ.8 These
cases, however, are unusual, and do not invalidate the great
importance of the tongue in ordinary speech.

It is thus seen that speech consists essentially in a modi-
fication of the vocal sounds by the accessory organs, or parts
situated above the larynx ; the latter being the true vocal in-
strument. "While the peculiarities of pronunciation in differ-
ent persons and the difficulty of acquiring foreign languages
after the habits of speech have been formed show that the

1 WORCESTER, Dictionary of the English Language, Boston, 1864, p. xvii.

2 Numerous instances of preservation, more or less complete, of the faculty
of speech after loss of the tongue, are quoted in works on physiology, among
the most remarkable of which are those referred to by Dr. Elliotson (Human
Physiology, London, 1840, p. 507).

516 VOICE AND SPEECH.

organs of articulation must perform their function with great
accuracy, their movements are simple, and vary with the
peculiarities of different languages. The most interesting
question, in its general physiological relations, is that to
which the greatest part of this chapter has been devoted ;
and that is the mechanism of the production of the voice.

INDEX.

Addison's disease, 354

Adipose tissue, anatomy of, 387

Albumen, diminution of, in the

blood in the liver, 329

in milk, 95

Amyloid matter, in the liver,. . . . 320
Arytenoid muscle, 494, 495

Barreswil's test for sugar, 302

Barytone voice, X 504

Bas= voice, 504

Bellini, tubes of, 148

Bertin, columns of, 145

Bile, mechanism of the secretion

and discharge of, 250

secretion of, from venous or

arterial blood, 253

quantity of, 255

variations in the flow of, ... 256

influence of the nervous sys-
tem upon the secretion of 257

mechanism of the discharge

of, 257

general properties of, 258

specific gravity of, 259

reaction of, 259

coloration of the tissues by, . 259

composition of, 260

proportion of solid constitu-
ents in, 261

inorganic constituents of,. . . 262

fatty and saponaceous con-
stituents of, 262

lecithene of, 262

choline of, 262

peculiar salts of, 262

taurocholate of soda of, 263

process for the extraction of

the biliary salts, 264

glycocholate of soda of, 266

Bile, origin of the peculiar salts of, 266
the biliary salts do not accu-
mulate in the blood after extir-
pation of the liver, 267

cholesterine of, 267

coloring matter of (biliver-

dine),... 273

tests for, 274.

Pettenkofer's test for, 275

excrementitious function of, 277

Bile-ducts, arrangement of, in the

lobules of the liver, 241

Biliary passages (see liver), 245

Biliverdine, test for, 275

Bladder, mucous membrane of, 49, 181

anatomy of, 179

sphincter of, ^ 181

corpus trigonum, 181

blood-vessels, nerves, and

lymphatics of, 182

influence of the nervous sys-
tem on the movements of, ...".. 184
Blood-corpuscles, changes of, in

passing through the liver, 329

Bones, physiological anatomy of, 479

fundamental substance of, . . 480

Haversian rods of, 481

Haversian canals of, 481

lacunae of, 481

canaliculi of, 482

marrow of, 483

generation of, by transplanta-
tion of marrow, 485

periosteum of, 485

generation of, by transplanta-
tion of periosteum, 486

Bone-corpuscles, 482

Bursae, 39, 42

Butter, 96

Buty rine, 96

518

INDEX.

Canaliculi, of bone, 482

Capriline, in milk, 96

Caprine, in milk, 96

Caproine, in milk, 96

Carbonic acid, in the urine, 218

Cartilage, anatomy of, 486

Cartilage-cavities, 487

Cartilage-cells, 487

Cartilage, fibro-, 488

Caseine, 94

Cerumen, 69

Ceruminous glands, 60

Chest-register of the voice, 509

Chlorides, in the urine, 211

daily elimination of, in the

urine, 212

Choleic acid, 265

Cholesterine, in the bile, 267

situations of, in the organism, 268

chemical properties of, 269

crystals of, 269

extraction of, from gall-
stones, 271

extraction of, from the ani-
mal tissues or fluids, 271

functions of, 277

origin of, in the economy,.. . 279

experiments showing forma-
tion of, in the nervous tissue,. . 280

presence of, in the spleen, . . 280

experiments showing absence

of, in the blood from paralyzed

parts,.. ...'.• 284

elimination of, by the liver, . 286

experiments showing dimi-
nution of, in the blood passing

through the liver, 287

examination of the blood for,

in simple icterus, cirrhosis, etc., 292

Cholesteraemia, 294

Cholic acid, 265

Choline, 262

Chordae vocales,. 492

Cilia, where found, 439

Ciliary glands, 63

motion, 438

Colostrum,. 102

corpuscles of, 103

composition of, 104

quantity of, as an indication of

the probable quantity of milk, . 105

Connective tissue, ....." 454

Connective-tissue cells, 455

Consonants, 514

Contralto voice, 504

Corium (see skin), 114

Cream, separation of, from milk, . 89

• specific gravity of, 89

Creatine and c'reatinine, 204

daily elimination of, 207

Crico-arytenoid muscles, lateral,. .

494, 496

posterior, 495

Crico-thyroid muscles, 494, 495

Cytoblastions, in the skin, 115

Derma (see skin), 114

Diabetes, artificial, 173, 325

production of, by the in-
halation of anaesthetics and irri-
tating vapors, 327

Diphthongs, 514

Disassimilation, enumeration of
products of, 391

Ear, fluid of labyrinth of, 46

ceruminous glands of,,

sebaceous glands of, 61

cerumen, 69

Elastic tissue, 442

Embryo-plastic elements, 455

Epidermis, 116

layers of, 116

Malpighian, or mucous layer

of,.. 116

horny layer of, 116

desquamation and formation

of cells of, 117

appendages of (nails and

hair) 117

Epiglottis, action of, in phonation, 507

Epithelium, glandular, 18

pavement, 47

columnar, conoidal, or pris-

moidal, 49

ciliated, situations of, 48

Excretion, general considerations

of, 108

vicarious action in, 26

Excretions, distinction from secre-
tions, 16, 108

enumeration of, 391

mechanism of the production

of, 25

Eye, aqueous humor of, 46

Meibomian glands of, 62

Meibomian secretion, 70

Falsetto register of the voice, 509, 510
Fat, alleged production of, by the

liver, 328

office of, in nutrition, 380

ESTDEX.

519

Fat, formation and deposition of, . 382
influence of food upon the

deposition of, 384

condition of existence of, in

the organism, 386

physiological anatomy of,. . . 387

Fatty degeneration (substitution), 382

Fehfing's test for sugar, 301

Ferrein, pyramids of, 146, 148

Fibrin, destruction of, in the liver, 329 |

Fibro-cartilage, 488

Fibro-plastic elements, 455

Fibrous tissue, elastic, 442

inelastic , 454

Foetus, composition of the urine of, 221
formation of sugar in, 322

Gall-bladder, 248

Genito-spinal centre, 185

Germinal matter, 369

Glands, epithelium of, 18

condition of circulation in,

during functional activity, 21

elimination of foreign sub-
stances by, 27

motor nerves of, 31

effects of destruction of the

nerves upon, 33

follieular, 35

tubular, 35

racemose (simple and com-
pound), 35

ductless, or blood-glands, 36, 331

Glandular organs, classification of, 35
Glisson, capsule of, in the liver,.. 234
Glottis, appearance of, during or-
dinary respiration, 498

• movements of, during pho-

nation, 499

Glycine, 266

Glycocholate of soda, 266

Glycocholic acid, 266

Glycocoll, 266

Glycogenesis (see liver), 295

Glycogenic matter, 317

Hairs, situations of, 121

varieties of, 121

courses of, 121

length of, 122

number of, on the head,. . . . 122

elasticity and tenacity of,. . . 122

hygrometric and electric

properties of, 123

Hairs, roots of, 123

follicles of, 123

summary of anatomy of the

hair-follicles, 125

structure of, 126

growth of, 127

sudden blanching of, 127

Haversian rods and canals of

bone, ' 481

Head-register of the voice,. . 509, 511
Heart, variations in the tempera-
ture in the two sides of, 401

Heat, animal, 394

limits of normal variation of, 395

variations of, with external

temperature, 396

variations of, hi different

parts of the body, 398

variations of, in the two

sides of the heart, 401

yariations of, at different pe-
riods of life, 404

diurnal variations of, 406

influence of inanition upon, . 408

influence of diet upon, 409

influence of alcohol upon,. . . 410

influence of respiration upon, 411

influence of exercise upon,.. 412

development of, observed in

a detached muscle, artificially

excited to contraction, 414

influence of mental exertion

upon, 415

influence of the nervous sys-
tem upon, 415

variations in, due to reflex

action, 416

influence of paralysis upon,. 417

sources of, 418

seat of the production of,. . . 420

relations of, to nutrition,... 422

relations of, to the consump-
tion of nitrogenized matter and
the production of nitrogenized
excrementitious principles,.... 423
relations of, to the consump-
tion of non-nitrogenized mat-
ter, 424

relations of, to respiration,.. 426

consumption of oxygen and

production of carbonic acid, in
connection with the evolution

of, 427

influence of the sympathetic

system of nerves upon, 430

520

INDEX.

Heat, increase of, in inflamed

parts, 430

animal, intimate nature of

the processes involved in the

production of, 432

equalization of, 432

effects of clothing in the

equalization of, 433

influence of cutaneous exha-
lation upon, 433

Henle, tubes of, in the kidney,.. . 154

Hepatic artery (see liver), 236

secretion of bile after oblit-
eration of, 253

Hepatic duct (see liver), 4 236

Hepatic veins (see liver), 238

Hippurates, in the urine, 202

in the blood, 203

Inelastic tissue, 454

Inorganic matters, office of, in nu-
trition, 3*71

Inosates, in the urine, 204

Irritability of tissues, 462

Kidneys, effects of removal of,. 25, 163

differences in the color of

the blood in the renal artery

and vein, 26

effects of destruction of the

nerves of, 33, 174

mucous membrane of the

pelvis of, 49

physiological anatomy of, . . 144

weight of, 145

adipose capsule of, 145

pelvis of, 145, 178

: calices of, 145, 178

infundibula of, 145

cortical substance of, . 145, 149

columns of Bertin, 145

pyramids of ( Malpighi, Fer-

rein), 146

• secreting and excreting por-
tion of, 147

tubes of pyramidal substance

of (tubes of Bellini), 148

Malpighian bodies of, 152

tubes of the cortical sub-
stance of, 153

narrow tubes of Henle, 154

intermediate tubes in the

cortical substance of, 155

blood-vessels of,. 1 56

blood-vessels in the Malpig-
hian bodies, 157

Kidneys, stars of Verheyen, 159

lymphatics and nerves of,. . 159

summary of the anatomy

of, 160

effects of extirpation of one

kidney, 179

change in appetite and dis-
position of animals after remov-
al of one kidney, 170, 348

non-enlargement of the re-
maining kidney after removal
of one, 170

separation of foreign matters

from the blood by, 175

— — alternation in the action
of, 176

changes in the composition

of the blood in, 176

absence of fibrin in the blood

of the renal veins, 177

red color of the blood of the

renal veins, 177

Lactates in the urine, 204

Lactation (see milk), 72

unusual cases of, 74

condition of mammary glands

during the intervals of, 75

structure of the mammary

glands in activity, 76

Lactose, 97

Lacunae of bone, 481

Language, 490, 513

Larynx, muscles of, 493

arytenoid muscle of, ... 494, 495

crico-thyroid muscles of, 494, 495

lateral crico-arytenoid mus-
cles of, 494, 496

posterior crico-arytenoid mus-
cles of, 495

thyro-arytenoid muscles of,

494, 496

Lecithene, 262

Lienine, 341

Life, definition of, 369

Liver, physiological anatomy of,.. 232

weight of, 233

ligaments and coverings of,. 233

lobules, or acini of, 234

capsule of Glisson, 234

blood-vessels of, 235

vaginal plexus of, 235

interlobular vessels of, 236

lobular vessels of, 237

intralobular veins of, 239

structure of a lobule of,. . . . 240

IXDEX.

521

Liver, arrangement of the bile-
ducts in the lobules of, 241

excretory biliary passages,.. 245

racemose glands in, 247

vasa aberrantia of, 247

gall-bladder, hepatic, cystic,

and common ducts of, 248

nerves and lymphatics of,. . 249

excretory function of, 277

elimination of cholesterine

by,. 286

examinations of blood going

to and from the liver, for choles-
terine, 287

production of sugar by, 295

evidences of the glycogenic

function of, " 296

discovery of the glycogenic

function of, 298

examination of the blood of

the portal system for sugar,. . . 803

examination of the blood of

the hepatic veins for sugar, 305

experiments showing the ab-
sence of sugar in, during life, . . 309

mechanism of the formation

of sugar by, 316

glycogenic matter in, 317

extraction of glycogenic mat-
ter from, 317

variations in the glycogenic

function of, 321

non-formation of sugar by,

in the early months of foetal life, 322

influence of digestion and of

different kinds of food upon the
glycogenic function of, 322

effects of the deprivation of

food upon the glycogenic func-
tion of, 1 324

influence of the nervous sys-
tem upon the glycogenic func-
tion of, 324

supposed action of, in the

production of fat, 328

changes in the albuminoid

and corpuscular elements of the
blood of, 329

Liver-cells, 240

Liver-sugar, characteristics of,... 315

Locomotion, passive organs of,.. . 479

Malpighi, pyramids of, 146

corpuscles of, in the kidney,. . 1 52

blood-vessels in the corpus-
cles of, in the kidney, 157

Malpighi, capsule of, in the spleen,

334, 335

corpuscles of, hi the spleen,. 335

Mammary glands, 72

— «- number and position of,. ... 73
condition of, during the inter-
vals of lactation, 75, 80

structure of, during lactation, 76

nipple and areola of, 76

lactiferous or galactophorous

ducts of, 77, 78

areolar muscle of, 77

lobes and lobules of, 78

acini of, 79

secreting vesicles of, 79

epithelium of the secreting

vesicles of, 79

Margarine in milk, 96

Marrow of the bones, 483

generation of bony tissue

from, by transplantation, 485

Medulloce'lls,. 483

Meibomian glands, 62

secretion, 70

Mezzo-soprano voice, 504

Middle register of the female

voice, 509

Milk, mechanism of the secretion

of 80

disappearance of epithelium

during the secretion of, 82

proper diet during lactation, 83

influence of liquid ingesta

upon the secretion of, 84

influence of alcohol upon the

secretion of, 84

elimination of foreign sub-
stances in, 85

influence of mental emotions

upon the secretion of, 85

influence of the nervous sys-
tem upon the secretion of, 86

quantity of, 86

general properties of, 88

specific gravity of, 88

reaction of, 88

coagulation of, 89, 95

separation of the cream from, 89

microscopical characters of, 89

composition of, 93

nitrogenized constituents of, 94

albumen of, 95

non-nitrogenized constituents

of, 96

sugar of, 97

inorganic constituents of, ... 97

522

INDEX.

Milk, gases of, 98

variations in the composition

of, 98

composition of, at different

periods of lactation, t 99

influence of menstruation

and pregnancy upon the com-
position of, 100

comparative composition of,

in fair and dark women, and in

different races, 100

influence of the quantity se-
creted upon the composition of, 102
— : — secretion of, in the newly-
born, 106

Milk-globules, 90

Movements, general considerations

of, 436

of amorphous contractile sub-
stance, 437

of cilia, 438

due to elasticity, 442

muscular, 445

Mucous membranes, anatomical di-
vision of, 46

general anatomy of, 47

follicular and racemose

glands of, 48

of the bladder, ureters, and

pelvis of the kidney, 49

action of, in resisting the ab-
sorption of venoms, 57

Mucus, mechanism of the secre-
tion of, 49

general properties of, 51

microscopical characters of, 52

composition of, 52

nasal, composition of, 53

bronchial and pulmonary,

composition of, 54

secreted by the mucous mem-
brane of the alimentary canal, . 54

from the urinary passages, 55, 217

from the generative passages, 55

conjunctival, 56

general function of, 56

in the urine, 217

Muscles, involuntary, anatomy of, 446

action of, 448

voluntary, anatomy of, 449

« primitive fasciculi of, 450

sarcolemma of, 451

fibrillse of, 451

sarcous elements of, 452

fibrous and adipose tissue in, 453

perimysium of, 454

Muscles, connective tissue of, .... 45-i

blood-vessels and lymphatics

of, 456

connection of, with the ten-
dons, 457

chemical composition of,. . . 457

physiological properties of, . 458

elasticity of, 459

tonicity of, 460

sensibility of, 460

contractility, or irritability of, 461

persistence of contractility in,

after death, 462

distinction between muscular

and nervous irritability, 463

influence of woorara upon

the irritability of the nerves of, 464

influence of sulphocyanide

of potassium upon the contrac-
tility of, 465

influence of the nervous sys-
tem upon the irritability of, ... 466

influence of the circulation

upon the irritability of, 466

restoration of the contractil-
ity of, by injection of blood, . . . 467

contraction of, 468

shortening and hardening of

the fibres of, 469

no variation in the absolute

volume of, during contraction, . 469

changes in the form of the

fibres of, during contraction,. . . 470

contraction of, excited by

electricity applied to the nerve, 470

single contraction of (spasm), 471

period of a single contrac-
tion and relaxation of, 472

mechanism of prolonged con-
traction of (tetanus), 474

sound produced by contrac-
tion of, 475

fatigue of, 476

electric phenomena in, 476

Muscular effort, 477

Musculine, 458

Myeloplaxes, 484

Myolemma, 451

Myosine, 458

Nails, anatomy of, 118

connections of, with the epi-
dermis, 120

growth of, 120

Nerves, motor nerves of the
glands, 31

IXDEX.

523

Nervous system, influence of, upon

secretion, 24, 28

exci to-secretory, 29

influence of, upon nutrition, . 388

Xeurine, synthesis of, 195

Xitrogen in the urine, 218

Xitrogenized principles, office of,

in nutrition, 373

Xon-nitrcgenized principles, office

of, in nutrition, 378

Xutrition, general considerations, 366
office of principles (inorgan-
ic) that pass through the organ-
ism, 371

office of principles consumed

in the organism, 373

office of nitrogenized princi-
ples in, 373

effects of systematic diet and

exercise upon, 374

office of non-nitrogenized

principles in, 378

influence of the nervous sys-
tem upon, 388

influence of exercise upon, . 388

influence of age upon, 390

Oleine, in milk, 96

Oxalate of lime, in the urine, 208

Oxygen, in the urine, 218

Parotid gland, motor nerve of, ... 32

Pericardial secretion, 42

Perimysium, 454

Periosteum, 485

generation of bony tissue

from, by transplantation, 486

Peritoneal secretion, 44

Perspiration (see sweat), 131

effects of covering the entire

surface with an impermeable
• coating, 132

Phonation (see voice), 490

movements of the glottis in,. 499

Phosphates in the urine, 213

derivation of, 214

influence of food upon the

elimination of, 214

comparative proportion of, in

the carnivora and the herbivora, 214

connection of elimination of,

with disassimilation of the ner-
vous tissue, 215, 231

variations in the elimination

of, 216

Phosphates, daily elimination of, . 216

Picromel, 262

Pineal gland, 365

Pituitary body, 364

Pleural secretion, 44

Portal vein (see liver), 235

secretion of bile after oblit-
eration of, 253

Protoplasm, 368, 437

Purpurine, ; 217

Sarcode, movements of, 437

Sarcolemma, 451

Sarcous elements, 452

Sebaceous fluids, varieties of, .... 57
Sebaceous glands, structure of,. . . 58
connection of, with the hair-
follicles, 58

Sebaceous matter, 63

microscopical appearances of, 64

composition of, 65

Sebum, 63

Secreting organs, general struc-
ture of, 33

classification of, 35

Secreting membranes, 35

Secretion, condition of the circula-
tion in, 20

intermittent character of,. . . 22

action of the nerves in,.. . 24, 28

influence of the composition

of the blood upon, 27

influence of blood-pressure

upon, 27

modifications of the influence

of pressure, through the nerves, 28

excito-secretory system of

nerves, 29

reflex action in, 32

influence of pain, mental

emotions, etc., upon, 33

distinction from transuda-

tion, 34

Secretions, general considera-
tions, 13

relations of, to nutrition,. . . 14

definition of, 14

division of, 15

distinction from excretions,. 16

fluids produced by simple

transudation, sometimes called

secretions, 17

mechanism of the production

of, 18, 22, 23

action of epithelium in the

production of, 18

524

INDEX.

Secretions, formation of charac-
teristic elements of, 19

elimination of foreign sub-
stances in, 27

classification of, 37

Semivowels, 514

Serous membranes, 39

structure of, 40

Serous secretions, 43, 44

Silicic acid, in the urine,. 216

Skin, general function of, 110

general appearance of,. .... Ill

extent and thickness of,.. . . 112

layers of, 113

muscles of, 113

true skin, or corium, 114

contraction of non-striated

muscles in the substance of, . . . 114

reticulated layer of, 114

papillary layer of, 115

epidermis of (see epider-
mis), 116

effects of covering the entire

surface with an impermeable

coating, 132

amount of exhalation from,

139, 433

discoloration of, accompany-
ing disorganization of the supra-
renal capsules, 354

Smegma preputiale,. 66

of labia minora, 66

Soprano voice, 504

Speech, mechanism of, 513

action of the tongue in, .... 515

Spleen, anatomy of, 332

capsule of Malpighi, 334

fibrous structure of (trabecu-

IBB), 335

Malpighian corpuscles of, ... 335

blood - corpuscle - containing

cells of, 338

vessels and nerves of, 339

• chemical constitution of, ... 341

functions of, 341

increase of the white corpus-
cles of the blood in, 342

diminution of the red corpus-
cles of the blood in, 343

variations in the volume of,

during life, 343

extirpation of, 345

action of, as a diverticulum

for the blood, 344

voracity in animals after ex-
tirpation of, 346

Spleen, ferocity in animals after

extirpation of, 347

Spleen-pulp, 337

Stercorine in the faeces, 291

Submaxillary gland, difference in
the color of the blood in the ar-
tery and vein of, 20

motor nerve of, 31

Sudoric acid, 142

Sudoriparous glands, anatomy of, 134

length of coil of, 137

Sugar, production of, in the liver, 295
process for the determina-
tion of, in the liver and blood, . 300

Fehling's test for, 301

BarreswiPs test for, 302

examination of the blood of

the portal system for, 303

examination of the blood of

the hepatic veins for, 305

— : — examination of the blood

from the right heart for, 306

characteristics of sugar pro-
duced by the liver, 315

mechanism of the production

of, in the liver, 316

effects of the inhalation of

anaesthetics and irritating va-
pors on the production of, 327

destination of, in the econ-
omy, 328

office of, in nutrition, 379

Sugar of milk, 97

Sulphates, in the urine, 213

Sulphocyanide of potassium, in-
fluence of, upon the muscles, . . 465

Suprarenal capsules, 349

structure of, 360

vessels and nerves of, 353

chemical reactions of, 353

functions of, 354

discoloration of the skin ac-
companying disorganization of, 354

extirpation of, 356

Sweat, mechanism of the secre-
tion of, 137

influence of the nervous sys-
tem on the secretion of, 138

quantity of, 139

general properties of, 140

composition of, 141

peculiarities of, in certain

parts, 142

urea in, 142

Sympexions, 360, 365

Synovial membranes, 40

INDEX.

525

Synovial fringes, 42

Synovial fluid, 44

— — composition of, 45

Taurine, 265

Taurocholate of soda, 263

Taurocholic acid, 265

Tendons, connection of, with mus-
cles 457

Tenor voice, 504

Thymus gland, 361

Thyro-arytenoid muscles, 494, 496

Thyroid gland, 359

structure of, 360

functions of, 361

Tongue, action of, in phonation, . . 508

action of, in speech, 515

Trachea, action of, in phona-
tion, 507

Training, 374

Transudation, distinction from se-
cretion, 34

Trigone, 181

Tiiphthongs, 514

Tunica vaginalis, secretion of,... 44

Unites, formation of, 202

Urea, accumulation of, in the cir-
culation, after removal of the

kidneys, 25, 163

proportion of, in the renal

artery and renal vein, 164

presence of, in the lymph

and chyle, 164

presence of, in the blood,

after tying both ureters, 167

situations of, in the economy, 194

chemical formula of, 195

synthesis of, 195

change of, into carbonate of

ammonia, 195

crystals of, 196

origin of, 196

alleged formation of, from

other excrementitious matters, 199

daily elimination of, 200

influence of muscular exer-
cise upon the elimination of, . . . 226
Ureters, mucous membrane of, 49, 178

anatomy of, 178

movements of, on the appli-
cation of galvanism, 182

Urethra, 182

Uric acid, compounds of, in the
urine, . . ... 200

Uric acid, daily elimination of, ... 202
Urina potus, urina cibi, and urina

sanguinis, 224

Urinary passages, anatomy of,. . . 178
Urine, mechanism of the formation

of, 162

influence of Ksntal emotions

on the secretion of, 172

influence of blood-pressure

on the secretion of, . .' 172

influence of special nerves

on the secretion of, 173

effects of irritation of the

floor of the fourth ventricle up-
on the secretion of, 173

arrest of the secretion of, by

division of the spinal cord,. . . . 173

effects of division of all the

nerves of the kidney on the se-
cretion of, 174

passage of foreign matters

from the blood, 175

constant formation of, .... 175

alternation in the secretion

of, on the two sides, 176

mechanism of the discharge

of, 182

general properties of, 187

temperature of, 188

quantity of, 188

specific gravity of, 189

reaction of, 189

cause of acidity of, 191

composition of, 191

urea of (see urea), 194

urates of, 200

hippurates of, 202

lactates of, 204

inosates of, 204

creatine and creatinine of, . . 204

oxalate of lime of, 208

xantbine of, 209

fatty matter of, 210

inorganic constituents of,.. 210

chlorides of, 211

sulphates of, 213

phosphates of, 213

silicic acid of, 216

coloring matter and mucus

of, 217

gases of, 218

variations in the composition

of, 219

variations of, with age and

sex, 220

composition of, in the foetus, 221

526

EST)EX.

Urine, variations of, at different
seasons, and at different periods
of the day, 222

variations of, with food, 223

influence of muscular exer-
cise upon the composition of,. . 226

influence of mental exertion

upon the composition of, 229

Urrosacine, urochrome, urohaema-
tioe, uroxanthine, 217

Uvula, action of, in phonation, . . . 608

Velum palati, action of, in phona-
tion, 508

Tenoms, non-absorption of, by

mucous membranes, 67

Verheyen, stars of, 159

Vernix caseosa, 67

composition of, 67

microscopical characters of, . 68

function of, 68

Vocal chords, 492

appearance of, during phona-
tion, 499

Vocal organs, physiological anato-
my of, 491

Voice, 490

mechanism of the produc-
tion of, 497

characters of, in childhood,. 502

range of, 503, 504

different kinds of, 504

action of the intrinsic mus-
cles of the laryux in, 505

action of the accessory or-
gans in, ." 507

action of the trachea in, . . . 507

action of the epiglottis in, . . 507

action of the velum palati in, 508

action of the uvula in, 508

action of the tongue in,. ... 508

mechanism of the different

registers of, 509

Vowels, 514

Woorara, influence of, upon the
motor nerves, 464

Xanthine, in the urine, 209

2>. APPZWrON A CO.'S PUBLICATIONS.

THE PHYSIOLOGY

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PATHOLOGY OF THE MIND.

By HEI^-RY MIATJDSLEY, ]MI. r>., London.
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CONTEXTS :

Part I.— The Physiology of the Mind.

CHAPTER 1. On the Method of the Study of the Mind.
u 2. The Mind and the Nervous System.

" 3. The Spinal Cord, or Tertiary Nervous Centres ; or, Nervous Centres of Reflex Action.
" 4. Secondary Nervous Centres ; or Sensory Ganglia ; Sensorinm Commune.
" 5. Hemispherical Ganglia; Cortical Cells of the Cerebral Hemispheres: Ideational

Nervons Centres ; Primary Nervous Centres ; Intellectorinm Commune.
" 6. The Emotions.
". 7. Tolition.

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u 9. Memory and Imagination.

Part II.— The Pathology of the Mind.

CHAPTER 1. On the Causes of Insanity.
" 2. On the Insanity of Early Life.
" 3. On the Varieties of Insanity.

CHAPTER 4. On the Pathology of Insanity.
- 5. On the Diagnosis of Insanity.
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CHAPTER 7. On the Treatment of Insanity.

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"A BOOK WHICH 18 AS READABLE AS A NOVEL:

HISTORY OF EUROPEAN MORALS,

FROM AUGUSTUS TO CHARLEMAGNE.

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The Utilitarian School — Objections to the School — Consequence of acting on
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THE PAGAN EMPIRE.

Stoicism — Growth of a Gentler and more Cosmopolitan Spirit in Rome — Rise
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THE CONVERSION OF ROME.

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Pagan Moralists to Christian Influence — Theory which attributes the Conversion
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FROM CONSTANTINE TO CHARLEMAGNE

First Consequence of Christianity, a New Sense of the Sanctity of Human
Life — The Second Consequence of Christianity, to teach Universal Brotherhood —
Two Qualifications of our Admiration of the Charity of the Church — The Growth
of Asceticism — The Saints of the Desert — Decline of the Civic Virtues — General
Moral Condition of the Byzantine Empire — Distinctive Excellences of the Ascetic
Period — Monachism — Relation of Monachism to the Intellectual Virtues — The
Monasteries the Receptacles of Learning — Moral Condition of "Western Europe —
Growth of a Military and Aristocratic Spirit — Consecration of Secular Rank.

THE POSITION OF WOMEN.

The Courtesans — Roman Public Opinion much purer — Christian Influence —
Relation of Christianity to the Female Virtues.

D. APPLETON & CO., Publishers,

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