AN ABSTRACT 
OF 
PHYSIOLOGY 
FOR 
MEDICAL STUDENTS 
AND 
PRACTITIONERS. 
BY 
PAUL B. BARRINGER, M. D., LL. D., 
Professor of Physiology, 
University of Virginia. 
(Second Edition.) 
ANDERSON BROS., PUBLISHERS: 
University of Virginia. 
1899. Copyrighted in 1899, by Paul B. Barringer, 
University of Virginia. CONTENTS. 
Chapter I. 
General l-26 
Chapter 11. 
The Animal Tissues 26-52 
Chapter 111. 
The Chemistry of the Body 54-64 
Chapter IV. 
The Function of Circulation 66-98 
Chapter V. 
The Blood and Lymph Glands 98-114 
Chapter VI. 
The Function of Respiration 116-158 
Chapter VII. 
The Function of Digestion 158-206 
Chapter VIII. 
The Skin and its Functions 206-226 
Chapter IX. 
The Kidney and its Functions. 228-258 
Chapter X. 
Metabolic Phenomena 260-278 
Chapter XI. 
The Contractile Tissues 280-294- Chapter XII. 
The General Nervous System 294-312 
The Spinal Cord 314-330 
Chapter XIII. 
The Cranial Nerves 332-360 
Chapter XIV. 
The Brain and its Functions 360-380 
Chapter XV. 
Perversions of the Cord, etc.. ..' 380-394 
Chapter XVI. 
The Minor Senses 396-414 
Chapter XVII. 
Chapter XVIII. 
The Sense of Hearing- 416-436 
Chapter XIX. 
The Sense of Sight 438-468 PREFACE TO THE SECOND EDITION. 
This little work was originally written to take the 
place of the usual students’ notes in the course of lec- 
tures on medical physiology in this University. The 
great difficulty experienced by students, even good 
students, in following lectures when compelled to take 
notes, and the utter inability of others to take notes at 
all, was my only excuse for presenting in this abridged 
form the elementary principles of Medical Physiology. 
From time to time there has been added to this work 
practical suggestions which pertain to therapeutics, 
practice, surgery, etc., with the result that the writer 
now believes it to be, as far as it goes, a practical 
physiology. The work presupposes a knowledge of 
chemistry, anatomy and histology, and is written pri- 
marily for the student, at the same time the writer has 
endeavored not to forget that the student of to-day is 
the practitioner of the morrow and to shape his in- 
struction accordingly. To allow the student the exer- 
cise of his own powers, and to give him room for the 
insertion of such notes as a rapidly growing science 
demands, alternate pages are left blank. 
My obligations to the standard text books of the day 
are palpable and are hereby acknowledged. 
University of Virginia, P. B. Barringer. 
October ist, iSgg. Physiology 
CHAPTER I. 
Physiology, meaning literally, a “discourse on 
nature,” is practically for the medical man a study of 
the functions or actions of the various organs and 
tissues that make up the living body, in contradistinc- 
tion to the study of the forms and structure of these 
organs and tissues, as given in anatomy and histology. 
The appropriate work of each organ is here spoken of 
as its function. Hence we speak of physiology as the 
“science of the functions of life.” Naturally the 
question arises, “what is life?” No satisfactory 
answer to this question can be given. All that we 
know is that, so long as there is a harmonious perform- 
ance of the functions in organized bodies, we observe 
in them a series of continuous manifestations of activity, 
which from experience we recognize as peculiar to 
living things, and hence call these manifestations vital 
phenomena. When, however, there is serious disturb- 
ance or lack of harmony in the performance of certain 
of these functions, they all soon cease, never to begin 
again ; and we call such bodies no longer living. In 
short, the harmonious performance of function is what 
we call life, and its antithesis, death. The more per- 
fect the harmony of action the better the physiological 
state, i. e., the health, of the individual ; while serious 
lack of harmony soon gives rise to those perverted 
states of body condition to which we apply the terms 
ill health or disease, and which continued gives death. PHYSIOLOGY 
7 8 
PHYSIOLOGY 
From another standpoint, life may be described as 
“the adjustment of internal actions to meet changes in 
external conditions”. This definition takes cognizance 
of the fact that life first appeared upon the earth in 
simple form, that it has been transmitted by inherit- 
ance through countless generations to all forms now 
found upon the earth, and that the status of any present 
living form in the scale of life is fixed by the capacity 
of its antecedents to meet the diurnal, seasonal, meteo- 
rological and other changes necessarily encountered. 
This means that man, the chief subject of our discus- 
sion, as he stands to-day, is physically, at least, the 
resultant of a series of progressive changes induced 
by varying environment. A very natural inquiry is 
“whence comes this simple initial life on earth ?” 
The experience of mankind is limited to the continua- 
tion of life from antecedent life. The most careful 
scientific investigation demonstrates the present impos- 
sibility of “spontaneous generation”. The logical 
result of these facts is that life first appeared upon the 
earth as the result of some force more potent than any 
now known as acting in this field and under conditions 
which, as nature is now constituted, seem impossible. 
A good scientific name for such a force would be the 
OMNIPOTENT and for the act the Creation. 
“Mathematics and dynamics fail us when we contem- 
plate the earth fitted for life but lifeless and try to 
imagine the commencement of life upon it. This cer- 
tainly did not take place from any action of chemistry 
or electricity or crystalline grouping of molecules 
under the influence of force, or by any possible kind of 
fortuitous concourse of atoms. We must pause face to 
face with the mystery and miracle of the creation of 
living creatures. ” Ford Kelvin. PHYSIOLOGY 
9 10 
PHYSIOLOGY 
The Evidences of Life, briefly put, are as follows: 
(1.) A peculiar chemical composition. 
(2.) Peculiar structural aad physical properties. 
We find, however, that the above evidences of life 
are not peculiar to animal organisms, but are presented 
with almost equal force by vegetable forms. Before 
taking up the evidence of life in detail, we will note the 
relations between animal and vegetable life. While 
nothing could be more dissimilar than, for example, a 
horse and a tree, the two kingdoms which these rep- 
resent gradually blend, until we reach a point at which 
it becomes impossible to determine to which kingdom 
a certain representative belongs. It has been proposed 
to establish an intermediate kingdom, to which all these 
doubtful forms shall be assigned ; but so gradually do 
these forms merge one into the other, that this would 
be but the formation of two doubtful boundaries in 
place of one. There are, however, certain principles 
of differentiation that will enable us to compare the two 
forms of life in g-eneral terms, leaving detail to special 
works on the subject. 
(3.) Activities during life. {Vital phenomena.) 
Comparing animal and vegetable life, we find that 
as regards the substances required for nutrition, ani- 
mals require organic matter (primarily vegetable) while 
plants can subsist on inorganic matter alone, only the 
higher forms requiring organic food. There is more- 
over a great diiference in the physical state of the foods 
used by the two types, the animal takes into its body 
cavity solid or semisolid matter, to be later dissolved 
by digestive processes, while plants use only foods in 
solution. As regards the gaseous elements of met- 
abalism we find that animals take in O and give olf 
CO-,, while plants, at least in the sun-light, take in CO> 
and give off O. The complex organic pigment, chlo- PHYSIOLOGY 
11 12 
PHYSIOLOGY 
rophyll, is found in almost all plants ; while its 
presence among- animals is unknown except among the 
.very lowest. As rep-ards the suf porting framework of 
animal bodies as compared with plants, we find that, 
in the one, it is usually central and composed chiefly of 
the carbonates and phosphates of the earthy bases ; 
while in the latter, as a rule, it is more externally dis- 
posed, and consists of cellulose. Upon looking at the 
relative power possessed of forming complex chemical 
bodies, we find that plants under the influence of the 
sun’s rays can form highly- complex chemical sub- 
stances, among others albumin; while animals are 
incapable of forming these complex bodies and must 
obtain them secondarily from plants, or, as in the case of 
carnivorous animals, indirectly from animals that are 
vegetable feeders. When we come to compare the 
progress in development, we find that animal life 
is far advanced beyond plant life, in that it shows 
the almost universal evidence of a digestive system, 
a nervous system, and a complex circulatory system. 
The first can hardly be said to exist in plants ; 
while the two latter exist, if at all, in a very 
rudimentary form, (Mimosa sensitiva). Kven the 
more advanced forms of plant life, in this line, 
(Venus fly trap, etc.) are far behind the simpler animal 
forms, having,— as a rule, the functions only of cir- 
culation, respiration, and digestion well developed. 
These functions hence are often called the “vegetative 
functions.” The lack of symmetry in the disposition 
of the organs performing these so called vegetative 
functions among animals is striking, as compared with 
the beautiful bilateral symmetry of the nervous and 
muscular systems. Lastly, we see that, as regards 
their relative position as conservators or cxpcndcrs of 
energy, they differ widely. Plants, from simple ele- PHYSIOLOGY 
13 14 
PHYSIOLOGY 
mentary bodies, or their binary forms, build up elaborate 
chemical substances of great potentiality ; while the 
life history of animals requires that they receive and 
break down these bodies of complex molecular form 
into simpler types, with ceaseless evolution of energy. 
In other words, plants are accumulators, and animals 
dissipators of energy. Having seen wherein animal and 
plant life differ, we pass on to consider the evidences 
and manifestations of life in both forms. 
I. Chemical composition of living bodies.—Only 
about fifteen of the seventy or more elements enter into 
the composition yof living- bodies. Of these elements 
four, viz. Carbon, Hydrogen, Oxygen, and Nitrogen 
form about 97 or 98 per cent of the total weight of 
such bodies. They are hence of ten called the “organic 
elements.” You will observe that these four represent 
the extremes of physical condition, chemical affinity, 
chemical inertia, mobility, etc. Considered in detail 
we find, (1) Carbon, is a solid, allotropic, stable, and 
with chemical affinities almost nil, at ordinary temper- 
atures, except in organic bodies. In organic bodies, 
however, we find this element to combine so freely and 
in such variety of form, that we often call organic 
chemistry the “chemistry of the carbon compounds.” 
(2) Hydrogen, is the ideal gas, the perfect type 
of mobility. Its chemical union with O, outside 
the living body, is accompanied by the evolution 
of intense energy, as in the oxyhydrogen blow- 
pipe. In the organism, its union is less free and 
less energetic. (3) Oxygen is also a gas, less mobile 
than the above, but infinitely more intense in its 
chemical affinities. A large part of the energies of the 
human race are directed toward the solution of the 
problems of properly starting, regulating, and con- 
trolling the chemical affinities of this element. The PHYSIOLOGY 
15 16 
PHYSIOLOGY 
flint and steel of olden days, and the lucifer of to-day, 
are as it were, but condiments to whet the appetite of 
this omnivorous monster for the special food we wish 
him to use. (4) Nitrogen, again a gas, is the most 
indifferent of all in its chemical attachment. Even 
when united, its bonds of union are very unstable ; and 
it is this ease of separation from its attachments that 
makes it a component part of all explosives. These 
elements unite among themselves in all forms, binary, 
ternary, quarternary, and beyond even this, with 
addition of some secondary elements, usually Sulphur 
and Phosphorus. The latter element is particularly 
abundant in the class of nucleo-proteids. Not only do 
these elements form the bulk of our bodies, but their 
combinations furnish us all of our true foods. The 
binary forms give us H>o, our water ; ternary forms 
C«H10OB and CriHI 20(;, our starches, sugars, and also 
(CaiH3Bo2)3, our fats ; While the more elaborate com- 
position, CSOH8N18O235., furnishes our flesh. Give us 
but the salts, and we have our foods. Aside from the 
four elements above named, we have the following 
elementary bodies, as more or less constant constituents 
of living matter ; viz;., calcium, phosphorus, sulphur, 
sodium, chlorine, fluorine, potassium, magnesium, iron, 
and silicon, in the order of their abundance. 
11. Structural properties of living bodies.—All 
living bodies, from highest to lowest, are composed of 
cells. Pven the highest and most complex organisms, 
including man, begin life as a single cell. Some, 
during their entire existence as perfect organisms, free 
and independent creatures, never reach a stage higher 
than a single cell. This group of unicellular organ- 
isms, called the Protozoa, is of great interest to the 
physiologist in that it shows how undifferentiated cells 
can perform all the functions necessary to a more or PHYSIOLOGY 
17 18 
PHYSIOLOGY 
less perfect life. The amoeba and its kind are the best 
examples for study. In the great majority of cases, 
however, by the multiplication of cells, and by the 
formation of cells especially adapted to the performance 
of certain functions, (differentiation,) the original 
unicellular type becomes a complex, highly differenti- 
ated living body, bearing little or no resemblance to 
the lower type, but differing in degree rather than in 
kind. The name Metazoa is applied to this group of 
multicellular forms ; and it includes infinitely the 
greater number of living creatures with which we are 
familiar, including man. Turning from the cell as an 
organism to the cell as a basis of histological or 
tissue structure, find it primarily to consist of “a 
mass of protoplasm enclosing one or more vesicular 
bodies called nuclei.” It is this protoplasm, “the 
active principle of life,” that gives rise to all those 
activities during life which we call “vital phenomena. ” 
The vital phenomena, are (1) The power of volun- 
tary and reflex motion, with all that this implies ; (2) 
the power of nutrition ; (3) the power of reproduction ; 
and (4) the power of passing in time through a series 
of changes in condition, which we call the cycle of life. 
These changes are birth, growth, developement, de- 
cline, and death. 
As regards the first of these, voluntary motion, it is 
the most commonly observed manifestation of life. 
This even to the child, is a manifestation of life. At 
first thought one is not disposed to consider plant life 
as endowed with motion. But the tons of weight in a 
large tree have been raised above the earth against 
gravitation. More active, but less forcible, evidences 
of motion among plants are seen in the movements of 
the evening primrose, sensitive plant, etc. The sim- 
plest form of motion in animal life is seen in the amoeba. PHYSIOLOGY 20 
PHYSIOLOGY 
The protoplasmic processes, or pseudopodia it throws 
out, are but the result of a contraction in one diame- 
ter and extension in another. The same changes taking- 
place in each unit of the multitude of cells in the mus- 
cular tissues of hig-her forms, bring- about a result, 
greater only in degree. The movement of the cilia, 
thoug-h less understood, is probably but an alternate 
action of the contractile elements of the opposite sides 
of the hair-like processes. In addition to the coarser 
phases of motion here referred to, which are due to 
the action of contractile tissues only, living- bodies 
have other and more subtle evidences of energ-y in 
response to stimuli, as conduction, secretion, etc., 
embraced under this head. 
Under the head of nutrition we usually recogmize a 
series of most complex chemico-physical processes; 
the complexity of which however is in larg-e measure 
dependent upon the wide differentiation of the cells 
set apart for this work. If we take one of the simpler 
forms of life, and study its functions, we will see it 
presenting- only the essentials. In the amoeba, we 
see the org-anism live by a mere exposure of its surface 
to the oxyg-en of the medium around it ; we see the 
flow or “streaming-” of its protoplasmic body, by 
which this exposure is constantly renewed. We see 
it receive into its clear, jelly-like body, madder, g-am- 
bog-e or other foods fed to it, we see these slowly dis- 
solve and disappear, and we cannot but perceive the 
utility of the streaming-, as a means by which all parts 
are equally supplied with the nutriment obtained. 
Last but not least, we see it by a simple protoplasmic 
extension free itself of any undig-ested remains. In 
this we have an epitome of the complex nutritive 
functions, respiration and dig-estion with their mechan- 
ical auxiliary circulation; and also have a forecast of PHYSIOLOGY 
21 22 
PHYSIOLOGY 
that mystic series of phenomena, embraced under the 
head of metabolism. 
The next of the vital phenomena, reproduction, 
(propagation) is that function, the consummation of 
which is the goal of individual existence. Simple in 
certain forms of animal and plant life, it is in others a 
most varied and elaborate process. The general plan of 
reproduction may be divided into two forms ; viz. one. 
in which there is a division of an organism into two or 
more parts, which henceforth develop independently, 
but equally, the other,-—the separation of a part which 
develops individually, from an older organism, which 
continues to exist, although but for a time. The former 
is the rule among the protozoa, the latter the rule 
among the metazoa. In the first form there is little 
or no differentiation into sexes, in the latter there is a 
differentiation into female and male forms. The former 
produces the germ cell or ovum, and the latter the 
sperm cell or spermatozoon, which is necessary for the 
fertilization of the ovum. As this differentiation into 
sexes proceeds, we have more or less evidence of sexual 
contact, preceding the reproductive process. When we 
reach the higher forms, the complex act of coitus 
forms an essential preliminary. 
Of the Cycle of Life, we may say that all organisms, 
both plant and animal, when not interrupted by 
premature death, pass through all its phases. The 
first of these phases, birth, means but a separation 
from the parent organism, with the power of independ- 
ent life. We thus see that life is obtained by inheri- 
tance, (Omne vivurn ex vivo.) The next of these 
phases, growth, is the power of increasing in size and 
substance. We must be careful to differentiate between 
the true interstitial growth of an organism, embodying 
as it does the nutritive functions of digestion, absorp- PHYSIOLOGY 24 
PHYSIOLOGY 
tion, etc., and the superficial growth of a crystal, 
which constantly encloses unchanged the crystal of 
yesterday in the larger crystal of to-day. While 
development is a constant accompaniment of growth, 
it differs in kind rather than in degree, and may be 
said to be that change in condition by which all living 
bodies become more capable of performing their 
respective functions, till maturity and “the prime of 
life,’’ is reached. The next phase, decline, presents 
no sharp limit of differentiation either in time or func- 
tional activity, from the preceding phase. While up 
to maturity there is a constant (receding it is true) 
increment of gain in both frame and faculty, the turning 
points of these do not coincide. Nor do the different 
organs of the body coincide with each other. As the 
decline of the thymus begins in babyhood, and the 
decline of the eye in boyhood, and other organs at 
stated times before what we call maturity, we say that 
decline begins for an individual only when the general 
nutritive activities have diminished, until the output is 
greater than the income, the waste than the repair. 
From this time on, functional activities fail, decay and 
the special degenerations of old age (fatty and calca- 
neus) begin, and we soon see the cessation of all func- 
tions, i. e. death. Fxactly which function is the last 
to fail, varies with the cause of death. Usually it is 
the heart, but “death” occurs whenever either the 
brain, the heart or the lung, ceases to perform its func- 
tion. If we note with great care, we may get an 
approximate idea of when death occurs, in so far at 
least as the cessation of the chief objective functions is 
concerned. This cessation of mechanical function we 
call somatic death, but there is a slow progressive loss 
of functional activity on the part of the tissues which 
we call molecular death, and to which we can assign no PHYSIOLOGY 
25 26 
PHYSIOLOGY 
time limit. Somatic death, (practical death,) could we 
but see the internal working’s of the thoracic viscera, 
might be limited to a second ; but molecular death can 
not be so limited, for it is a gradual process, merging 
insensibly into that state, popularly known as decay. 
It is but the loss of functional activity by one tissue 
after another, till all cease and life truly ends. 
CHAPTER 11. 
The Tissues. 
In the study of Histology we learned the form, the 
size, the color, and other structural properties inherent 
to the cells, and their aggregations, the tissues. In 
the study of Anatomy we saw these cells and their re- 
sulting tissues grouped into symmetrical parts and 
organs, which were constant in their presence, and 
bore a definite relationship one to another. It is be- 
tween these two realms that the physiologist finds one 
of his most profitable fields of labor. This lies in the 
study of the functional relations of one tissue to an- 
other, and of the tissues to the organs. This study of 
the minute detail of the organs is called “microscopical 
anatomy,” because while still anatomy, the microscope 
is necessary to its elucidation. The physiologist 
however requires more than this, he must consider not 
only the relationship, but the development, the life 
history, the chemical composition, etc. Here we will 
take up first, the simpler relations of the tissues to 
each other—where they are found and where they are 
not; their physical, and later their chemical proper- 
ties ; and finally their functional activities in detail. PHYSIOLOGY 28 
PHYSIOLOGY 
While a knowledge of histology is presupposed the 
following simple classification is given for the advance 
light it throws on physiology and pathology. Fore- 
casts of function must from time to time be made, as 
the nature of the subject demands. 
EPITHELIAL TISSUES. 
Squamous epithelium.—Of two kinds. (1) Strati- 
fied, found covering the general body surface and lin- 
ing all open body-cavities. Preeminently protective. 
Our chief defense against sepsis either chemical or 
bacterial in character. (2) Pavement or Simple, found 
in the alveoli of the lung, in the capsule, neck and 
narrow loop (Henle’s) of the tubule of the kidney, and 
in pigmented form, as the inner-most layer of the cho- 
roid. Protective. 
Columnar epithelium.—Elongated vertically. Pound 
lining the alimentary canal, from the cardiac end of 
the stomach to the anus. Protective and secretory. 
Spheroidal, glandular or cuboidal epithelium.— 
Pound in all glands, forming their active secretory part 
or parenchyma. Secretory. A gland, whatever its kind, 
always consists of a basement membrane on the inner 
face of which we find the glandular epithelium with a 
free face next the central lumen. Outside of this base- 
ment membrane is a plexus of blood vessels supplied by 
nerves. The secreting epithelium is also supplied by 
nerves. 
Transitional epithelium.—Dissimilar multiple lay- 
ers. Pound lining the prostatic urethra, the bladder, 
the ureter and the pelvis of the kidney. The only 
tissue which can long withstand the irritating influence 
of urine. Protective. 
Ciliated epithelium.—Pound lining the respiratory 
tract, with its lachrymal canal and eustachian tube, the PHYSIOLOGY 
29 30 
PHYSIOLOGY 
tubes and tubules of the testicle, the fallopian tubes 
and upper part of the uterus, the cerebral ventricles 
and the canal of the cord during- foetal life. Locomo- 
tive and protective. 
ENDOTHELIAL TISSUES. 
Serous (synovial) endothelium.—Found lining- all 
closed body-cavities, both serous and synovial. Both 
secretory and protective in function. The pleural, 
mesenteric and sub-diaphragmatic endothelium, pre- 
sents stomata. This tissue when inflamed tends to 
adhere and form an organic union with any similar 
surface with which it is in contact, giving peritoneal 
and pleuritic “adhesions,” iritic synechiae, etc. This 
property is taken advantage of in abdominal surgery 
and in the treatment of varicocele. 
Vascular endothelium. Protective in function. 
Pound lining the heart and all blood vessels. The 
seat of late syphlitic deposits. It presents no stomata. 
SKELETAL TISSUES. 
Connective or fibrous tissues.—In the order of their 
relative abundance and importance. (1) Areqlar tissue. 
One of the most widespread of all tissues, but espe- 
cially abundant in the subcutaneous, submucous, and 
subserous planes. A modified form of it is adipose 
tissue. When this loose open tissue is distended with 
excess of transudate the condition is called “oedema" 
and where general it is called “anasarca.” (2) White- 
fibrous tissue. This may be arranged in bundles of 
parallel fibres, forming cords, as tendons, ligaments, 
etc., or in felted membranes, more or less open, 
that invest of all the organs of the body. The first 
form of this tissue (tendons, etc.) is the most fre- 
quent seat of rheumatic inflammation, (3) Yellow- 
fibrous, or elastic tissue. Pound in the inner layers PHYSIOLOGY PHYSIOLOGY 
of larger blood vessels, ligamentum nuchae, ligamen- 
tura subflava, the ligaments of the larynx, true vocal 
cords and certain layers of the trachea, the bronchi, 
and their prolongations. (4) Retiform or adenoid tis- 
sue, is found as the supporting framework of all 
adenoid bodies, lymph nodes, ductless glands, etc. 
Besides these, a special connective tissue (neuroglia) is 
found supporting the nerve cells, and another (mucous 
or gelatinous) the vitreous humor of the eye. The 
latter is also found as the jelly of the umbilical cord. 
Cartilaginous tissue.—All are covered by perichon- 
drium. (1) Hyaline cartilage, is the variety found en- 
crusting the articular faces of the bones, and forming 
the costal, laryngeal, nasal and tracheal cartilages. 
(2) White-fihro cartilage, forms the intervertebral 
discs, interarticular pads, and the circumferential 
rings around the glenoid fossa and acetabulum. (3) 
Telloxv - elastic cartilag'e, forms the epiglottis, the eusta- 
chian tube, the corniculae laryngis and the cartilages of 
the external ear. 
Bony tissue.—(1) Compact bone, found chiefly in the 
shafts of the long bones, the medullary cavity of which 
contains the fatty yellow marrow, (fat embolism). 
(2) Cancellated hone, forms the framework of the flat, 
cubical and irregular bones, and the extremities of the 
long bones. The cavities of this form of bone are 
filled with the albuminous red marrow. Both the 
above are enveloped in periosteum. (3) The teeth are 
but modified forms of bone, and are composed of enam- 
al, covering the crown, crusta petrosa (bone) covering 
the neck and fangs, and dentine (ivory) forming the 
internal body substance. 
CONTRACTILE TISSUES. 
Skeletal or striated muscle.—This tissue forms 
nearly half of the body weight and varies in mass from PHYSIOLOGY 34 
PHYSIOLOGY 
the “stapedius” to the “quadriceps extensor.” It is 
always enveloped in fascia and supported by internal 
septa of fibrous tissue. Supplied chiefly by cerebro- 
spinal nerves. Quick acting- and voluntary. 
Cardiac muscle.—This variety is found only in the 
heart. Imperfect striation, the arrangement of its 
nuclei, and absence of sarcolemma, differentiate it from 
the other two forms of muscle. It is supplied by both 
sympathetic and cerebro-spinal nerve fibres (digitalis). 
Quick acting but involuntary. 
Visceral smooth, or non-striated muscle.—This 
form of contractile tissue, while quite widespread, is no 
where in large mass, except in the uterus. It is found 
in the walls of the following organs; all the hollow 
visceraand their ducts, all blood vessels and lymphatics, 
the trachea and bronchi, and the cavities and ducts of 
the generative organs. It is also found in the skin, 
spleen and iris (ergot). It is supplied chiefly by sym- 
pathetic nerves. Slow acting and involuntary. 
CONDUCTIVE TISSUES. 
Nerve corpuscles.—These can not be classed histolo- 
gically, but functionally they may be grouped into three 
classes. (1) Those cortical cells which alone among 
cells have the power of initiating nerve impulses. They 
preside over all other cells and cell functions. (2) 
Those lower cerebral, medullary, spinal and ganglionic 
corpuscles, whose function is to transfer and distribute 
impulses received. They may be stimulated by per- 
ipheral (sensory) or central (motor) impulses ; but in 
either case they receive, transfer and distribute all 
impulses to their proper channels, augmenting or 
inhibiting them, as the case may require. In their 
order from above down they can handle any stimuli, 
from those calling for the most elaborate and complex 35 
PHYSIOLOGY 36 
PHYSIOLOGY 
movements, to those most simple. (3) Those corpus- 
cles which, having- no independent action, can only 
transform stimuli received, (a) Those peripheral termi- 
nal fibrils, end-bulbs, tactile corpuscles and special 
sense org-ans, which can transform physical stimuli 
into nerve (afferent) impulses, (b) Those deep seated 
muscle plates on skeletal muscle, or fibrillar terminals 
in visceral muscles or glands, which can transform 
nerve (efferent) impulses into other forms of functional 
activity, as contraction, secretion, etc. 
Nerve fibres.—(1) Non-medullated or “grey” fibres. 
These supply chiefly the viscera and blood vessels. 
They are usually connected with the sympathetic 
nervous system. (2) Medullated or “white” fibres. 
These form the fibres of the cord and other parts of 
the cerebro-spinal nervous system. They supply chiefly 
the muscles. 
THE FLUID TISSUES. 
THE BLOOD. 
In man, and in fact in all vertebrates, the blood is a 
fluid which when examined shows the following: 
Physical properties.—In color it is a scarlet red, 
when rich in oxygen (arterial), and a purplish red when 
poor in oxygen (venous). The color is not in the fluid 
portion of the blood, but is in the corpuscles or floating 
elements. The reaction of blood is faintly alkaline 
and the taste is saltish. The alkalinity of the blood, 
which varies in its intensity but is never absent, is 
due to the presence dfl di-sodium phosphate and to a less 
'extent try carbonate of soda. The temperature of the 
blood in the warmest part of its course, as in the liver, 
is about one degree above normal body temperature or, 
99.6° F.; but in the extremities it is often as low as 
body temperature (98.6°F), or lower. Its specific 
gravity is about 1060, an average between the specific PHYSIOLOGY 38 
PHYSIOLOGY 
gravity of the corpuscles (1075) and the fluid portion 
(1045). 
Histological characters.—When examined with a 
microscope, blood is seen to consist of an immense num- 
ber of disc-shaped cells or cor pits clcs floating in a clear 
fluid called the plasma, or liquor sanguinis. There 
are two principal forms of corpuscles, fthe red and the 
white, the former being several hundred times the 
more abundant. The Red blood corpuscle as found in 
man is a circular, bi-concave disc with rounded edges 
and a depressed center, about 1-3500 of an inch in 
diameter and-about one-fourth of this in thickness. 
When viewed by transmitted light, these corpuscles 
are a pale yellow, and are red only1 by reflected light. 
More closely examined, each shows a colorless, elastic, 
structureless frame-work or stroma, infiltrated with a 
red coloring matter, haemoglobin. In nearly all speci- 
mens of blood, we wall see some corpuscles smaller 
than the above, paler and of variable shape ; these are 
"ball or blood platelets. Various theories 
have been given to account for their presence. The 
influence of reagents on the red corpuscles is best 
noted in the case of the gases, as N. 0., which colors it 
violet red; C. 0., cherry red; and 0., wdiich in varying 
amounts, gives from scarlet to purple. Rouleaux may 
often be formed from the simple shedding of blood, 
and less often crenation or the formation of spines 
(Physostigmin.) Other agents as heat, static electric- 
ity, tannic acid, etc., also affect the corpuscle. The 
red blood corpuscles are formed during foetal life in 
the vessels, but in later infant life in the blood glands, 
as the liver, spleen, etc., and in adult life probably in 
the red marrow of the bones. 
The destruction of the red corpuscles probably takes 
place in the spleen and liver. The great variation in PHYSIOLOGY 40 
PHYSIOLOGY 
their ratio to the white corpuscles in the splenic vein 
and artery points to this organ, while the formation of 
bile pigments from haemoglobin points to the liver or 
a connected viscus. 
The White (blood) corpuscles, or leucocytes, differ 
from the red in that they are found, not only in the 
blood vessels, but in many other parts of the body also. 
As “wandering cells” we see them in the general 
interstitial lymph spaces, as “lymph corpuscles” in 
the spleen, lymph nodes, adenoid bodies, bone marrow, 
etc. ; and this for the simple reason that, as free mi- 
gratory bodies, they pass through vessel walls (diape- 
desis) and other tissues at will. Hence the immense 
variation in the ratio between red and white corpuscles 
in the various parts of the vascular system. Close!}7 
resembling the primitive unicellular organism found in 
our ponds, etc., the “amoeba,” and possessing the same 
free movements, we call these movements in the leuco- 
cyte, “amoeboid.” They are evident in all its forms, 
and alone enable it to perform its multifarious functions. 
These corpuscles, when at rest, are globular bodies 
variable in size, but usually about 1-2500 of an inch 
in diameter. They can throw out prolongations of 
the body substance (pseudopodia) at will, and follow 
after by their internal “streaming” movements. In 
this way they can either move from place to place, or 
flowing around a foreign body enclose it for food or 
otherwise. (Phagocytosis.) Reagents affect them 
variously, acetic acid clearing up the perinuclear 
protoplasm and showing clearly the nucleus, while 
magenta, and other stains, have apparently an affinity 
for the nucleus alone. The great variety in the size 
and other peculiarities of these white corpuscles has 
led to an attempt at classification by their affinity for 
certain stains. The term oxyphile (eosinophile) is PHYSIOLOGY 42 
PHYSIOLOGY 
applied to those staining- most readily by acid stains, 
while basophile is reserved for those staining- most 
readily with basic stains. The conditions 
to free amoeboid movement are a suitable media and 
proper temperature. Very many disappear as soon as 
the blood is shed, and their component parts are prob- 
ably concerned in the coag-ulation that follows. These 
white corpuscles are probably formed in the adenoid 
bodies and lymph gdands. 
Comparative Histology shows us that all mamma- 
lians, except the Camelidae, have circular, non-nucle- 
ated, red corpuscles ; while all birds, reptiles, 
amphibians, and fishes, except the Cyclostoraata, have 
the same corpuscles, oval and nucleated. The medico- 
legal value of this is most important. The more active 
the functional life of the animal, as the smaller deer, 
the smaller the colored corpuscle, to give superficial 
area for carrying oxygen, while for the same reason 
the corpuscles of the sloth is large. 
The fluid and coagulating elements of the blood are 
in the plasma, or liquor sanguinis, which forms 65 per 
cent of the blood weight. When the blood is shed, a 
part of the plasma previously fluid becomes solid bv 
coagulation. This newly formed solid is elastic and 
contracts, entangling in its open meshes the corpuscles, 
both red and white. The solid formed is called fibrin, 
and the entangled mass it makes, a clot. As the fibrin 
of the clot still further contracts, it squeezes out a 
straw colored fluid, the unaltered portion of the plasma, 
called serum. 
Upon further study of this substance we find that 
fibrin (Hamersten’s theory) is composed of two factors, 
one a globulin called fibrinogen, and an extractive 
substance called the fibrin ferment. The first of 
these, fibrinogen, is the chief factor and forms the PHYSIOLOGY 44 
PHYSIOLOGY 
great mass of the fibrin. It is readily gotten from 
such serous exudates as pleuritic, pericardial and 
hydrocele fluid. There is another gdobulin, paraglo- 
bulin, always found in blood serum, which was long 
thought to play an active part in this process but it is 
now known to be a passive agent entirely. The fibrin 
ferment, so called, is not really a ferment, but is prob- 
ably also a globulin ; a cell globulin, derived from the 
breaking up of the white corpuscle or other cells when 
the blood is shed. It is the exciting cause of coagula- 
tion, for regardless of other factors, if it be absent, 
coagulation cannot take place. It also seems proven 
that calcium salts are necessary to the coagulation of 
blood and that it can be prevented by their withdrawal. 
The especial characters of the globulins will be given 
later. 
Coagulation is influenced by the state of the white 
corpuscles, and of the tunica intima, or lining of the 
blood vessels, for when this is injured (cell globulin) 
coagulation begins. The presence in the blood of for- 
eign bodies, oxygen in quantity ; and heat, all favor 
coagulation, while cold, carbon dioxide, and above all 
venom globulin, check or prevent it. Haemophilia is an 
hereditary disease afflicting males, (but derived only 
through female lines,) in which a tendency to free 
bleeding from slight wounds exists. Persons so af- 
flicted are popularly called “bleeders,” and no doubt 
have blood of imperfect coagulating power (calcium 
chloride). A tendency to hemorrhage in purpura, 
scurvy and other diseases is also noted. 
The pigment of the colored corpuscle, called haemo- 
globin, is a complex chemical substance of red color, 
crystalizing (rhombic system) more or less readily in all 
vertebrates. These crystals are obtained with some 
difficulty from human blood, but are readily gotten PHYSIOLOGY 
45 46 
PHYSIOLOGY 
from that of a rat or guinea pig. The haemoglobin in 
the corpuscle can be dissolved out of the stroma, in 
time, by the serum alone, but more readily by water 
and still more freely by a solution of bile salts. This 
is aided by freezing the blood. Aqueous solutions 
coagulate at about 64° C. While crystalline, haemo- 
globin is hardly diffusible, and is therefore practical!}' 
colloidal. Thither in solution or in a dry state haemo- 
globin ultimately decomposes into an amorphous blue- 
black pigment, (haematir\, and a:-colorless proteid, 
probabl}T a globulin. The haeraatin carries the iron 
of the haemoglobin with it. A chloride of haematin, 
called haemin, is crystalline ; and these crystals (Teich- 
man’s), which can be obtained from old blood spots, 
are of medico-legal value. When, however, the blood 
decomposes in a blood vessel or in the tissues, as in 
extravasations, haematin is not formed, but a crystal- 
line, yellowish red body, haematoidiii, seemingly 
identical with the bilirubin of the bile. The “old 
gold” of a “black eye,” and the yellow of the corpus 
luteum, is due to this pigment. The most character- 
istic property of haemoglobin, however, is its power 
of uniting loosely with gases, notably with oxygen. 
In vacuo or away from O, it is haemoglobin, in arterial 
blood or wherever O is abundant, it is oxy-haemoglo- 
S:in, and when long exposed to the air as in old blood 
stains, or in the crusts and scabs of bloody wounds, it 
is meth-haemoglobin. This tendency of the haemoglo- 
bin of the red corpuscle to unite with gases is not 
exhibited for O alone, but it is also shown for CO, 
C02, etc. When C O is brought into contact with 
haemoglobin, a permanent union is made, so permanent 
in fact that the functional activities of the pigment are 
lost, while the haemoglobin union with COo is but 
temporary and loose. EAchofthe foregoing haemoglo- PHYSIOLOGY 
47 48 
PHYSIOLOGY 
bin compounds .has its own definite spectrum, which is 
of much medico-legal value. The gases of the blood, 
when measured at standard barometric pressure and 
temperature, are found to equal about 60 volumes per 
cent; that is, 100 cubic inches of blood, gives about 60 
cubic inches of gas. This is made up of varying 
quantities of the gases O and CO,, and a definite and 
almost unvarying quantity N. The quantities of the 
two former gases vary markedly, only when taken 
from what, we will learn, are different kinds of blood, 
as in the table, thus : 
100 Vol. of blood, Vol. O. Vol. CO,. Vol. N. To. Vol. 
Arterial blood, 20 39 1 60 
Venous blood, 10 49 1 60 
The O and CO, differ markedly, however, in the 
ways by which they are held. The O is chief!}7 in 
loose chemical combination with the haemoglobin of 
the corpuscles (oxyhaemoglobin), only the “absorp- 
tion” amount being in the fluids of the' blood. The 
CO-2, on the contrary, is in loose chemical combination 
with both the corpuscles and the plasma. In the 
plasma, the CO, is chiefly united in an imperfectly un- 
derstood chemical union with the basic phosphates and 
cajObuonates of soda, while a small amount is simply 
absorbed. In the corpuscles a quantity of CO, is in 
extremelv loose chemical union as above. When we 
place the blood in an air pump and exhaust, a vast 
difference in '‘'‘chemical combination" is shown. Only 
the absorption amount of O comes off in accordance 
with the laws of absorption, the bulk of it coming off 
suddenly when a low pressure is reached. In the case 
of the CO,, all comes off in accordance with the law of 
absorption,—the “combined” as well as the absorbed. 
Nitrogen is always simply absorbed. PHYSIOLOGY 
49 50 
PHYSIOLOGY 
The blood considered as a whole, is seen to be the 
great “common carrier” of the body ; the gases, the 
heat, the food, the waste products, are all carried by 
this medium. As the food and fluids of nutrition vary, 
not only in amount, but in the times when taken, the 
quantity of the blood must vary, and that irregularly ; 
for the loss of fluids from the body through the skin 
and other channels is just as irregular as their taking 
in. Still by experiment we have learned that the 
average weight of the blood in the body is about 1-13 
of the body weight. The method of obtaining this 
relative weight (Welkers) is as follows : From a can- 
ula in the carotid, draw, say 1 oz. of blood, wrhich we 
will dilute with 499 ounces of water and set aside. 
Draw all the remaining blood from the body, wash 
the blood-vessels till clear, and then macerate the 
finely chopped body, keeping note of all the’ water 
used in these washings. The first blood drawn is 
used as a color-test solution (1 in 500), and water is 
added to the body blood and washings, the amount be- 
ing noted, till the body blood solution, and test solu- 
tion, agree in color. Three factors being known, we 
compute the fourth. In practice CO is passed through 
both solutions, to fix the haemoglobin in an unchange- 
able form. The distribution of the blood at any given 
time is about as . follows : in the liver ; %. in the 
muscles ; % in the heart, lungs, and larger vessels ; 
and % in the skin and the remainder of the body. 
Abnormal conditions of the blood, exist (1) by reason 
of variations in the proportions of the blood, and (2) in 
the presence of unusual org-anic constituents, and (3) in 
the presence of living- org-anisms in the blood. Of the 
variations in relative proportion, an increase in the g-en- 
eral mass of the blood is called •plethora, while a de- 
crease in the amount is anaemia. In addition to this PHYSIOLOGY 
51 52 
PHYSIOLOGY 
variation in mass, there is a variation in the ratio of 
red and white corpuscles, the former decreasing-, the 
latter increasing, as in leukaemia. There is also a 
variation in the ratio of solids and fluids, an excess of 
the latter producing hydraemia. The conditions of 
unusual organic constituents are mellitaemia or sugar 
in the blood, lipaernia or fat in the blood, and uraemia, 
or urea in the blood. The living organisms which 
may be in the blood are, the bacteria in various forms, 
the bilharzia haematobia, the plasmodium malariae y 
etc. 
THE LYMPH. 
The lymph is that portion of the plasma which, 
having- been dealt out to the tissues for their nutrition 
in excess, is returned unused to the g-eneral circulation, 
throug-h the lymphatics. It is a colorless alkaline fluid 
containing- leucocytes or lymph corpuscles. The nor- 
mal org-anic constituents of lymph are much the same 
as those of plasma, but the proportions differ. The 
fibrin-factors are more feeble, and a lymph clot is soft 
and delicate. The lymphatics from the intestinal tract, 
during- the dig-estion of fatty foods, bear great quanti- 
ties of “fatty granules” in their lymph, giving them a 
milk-white color and their name, lacteals. This fat 
laden lymph is called chyle, A worm-like organism, 
the filaria sanguinus, is, in certain conditions, found 
in the lymph (elephantiasis). PHYSIOLOGY 
53 PHYSIOLOGY 
CHAPTER 111. 
CHLMISTRY OP THE BODY. 
In a general way we have already considered the 
chemical elements that make up the body, but rather 
as units, than aggregations. We must now approach 
the most complex and unstable of all known chemical 
substances, the higher organic compounds, sometimes 
called the 'plasmata. Some of these are so very un- 
stable, that their simple removal from the body, or 
even disturbance in the body, will bring about changes, 
not only of chemical relation, but of physical condition. 
Such bodies as these, viz.: protoplasm, blood-plasma, 
muscle-plasma, haemoglobin, etc., we will probably 
never know the true composition of, even if they have 
a definite chemical composition. But somewhat lower 
in the scale we have bodies formed from the above, 
which, while still unstable, have a definite composition, 
and certain fixed physical properties always present, 
which justify us in classifying them together. These 
form one of our chief sources of food, in fact our most 
essential food, and we group them under the name, of 
proteids. 
Proteids are divided into several classes, but all are 
colloidal, laevogyrous, nitrogenous bodies, coagulable 
by certain reagents. They are the anhydrides of the 
peptones, and may be divided into the true proteids or 
albumins, and the false proteids or albuminoids. 
(1) Under the head of the albumins are classed the 
true proteids having the general percentage composi- 
tion given on page 16, and possessing the following 
general characters. They are all amorphous, all are PHYSIOLOGY 56 
PHYSIOLOGY 
changed by heat, and all when heated with strong 
nitric acid turn yellow, which in turn is changed to 
orange, if ammonia, caustic soda, etc., be added. The 
first group in this class are the native albumins, viz. ; 
egg albumin, forming the white of egg, and serum 
albumin, found in blood serum, and forming the albumin 
of albuminuria, etc. The next group are the derived 
albumins (albuminates), viz. : acid albumin, alkali 
albumin, and perhaps casein. The two first are formed 
when acids or alkalies respectively are added to a 
native albumin. The latter is formed, when the pro- 
teid constituents of milk are coagulated under the in- 
fluence of rennet, etc. The third group includes the 
globulins, which, while bearing a general resemblance 
to the other albumins, are distinguished by being 
soluble in dilute saline solutions, and precipitated by 
strong saline solutions. They are :[ globulin, forming 
in an impure state the crystalline lens of the eye ; 
paraglobulin, one of the serum 
the chief of the fibrin factors $ myosin, the coagulat- 
ing factor of muscle plasma C vitellin, the proteid con- 
stituent of the yellow of egg ; a constituent 
of the complex body haemoglobin. The fourth group 
includes the complex body fibrin alone. The next 
group, coagulated albumin, alone, which is formed by 
the influence of heat, nitric acid, alcohol, etc. (The 
peptones, while the hydrides of the albumins, can 
the albumins, in varying manners, which we will con- 
sider under digestion.) 
hardly be classed with them. They are formed from 
(2) The albuminoids are nitrogenous, non-crystalline 
bodies, closely allied to the albumins in general chemical 
composition, but differing from them in many ways. 
While closely allied chemically to the true proteids, and 
givingthe proteid reaction with nitric acid and ammonia. PHYSIOLOGY 
57 58 
PHYSIOLOGY 
they are not available as food stuffs to any practical 
extent. They ar\mucin* the characteristic component 
of mucus f\chondrin, obtained by boiling- cartilaginous 
tissues “3gelatin, obtained in the same way from fibrous 
(white) tissues as tendons, ligaments, etc, ;i-fkeratin, a 
constituent (rich in sulphur) of hair, nails, horn, epi- 
dermal scales, etcJfelastin, obtained by boiling yellow 
elastic tissue ; and nuclein, a constituent of the nuclei 
of pus corpuscles, and of the yolk of egg. 
Carbohydrates are organic compounds containing C, 
H, and O ; but the ratio between the H and the O is like 
that in HaO, two atoms of H, to one of O. The mem- 
bers of this class which we will consider in the human 
body are but four. They are maltose (C12H220u) 
the end product of starch digestion and forming 
the largest part of our food ; milk sugar or lactose, 
(Cl2H22On+H2O) which occurs in milk, and is charac- 
teristic of this secretion ; and inosit, (C6H1206+2H20) 
or muscle sugar, a rare substance found but sparingly 
in the human body in health, and not in great abundance 
in disease (Bright’s disease). Lastly, we have the all 
important glycogen (C6H1005), formed in the liver bv 
the action of the liver ferment on maltose. When not 
so converted, the maltose enters at once into the 
circulation, to be eliminated in the urine, giving dia- 
betes mellitus. 
The neutral fats, improperly called hydrocarbons, 
also,contain only C, H, and O, but the ratio is not like 
that above, the C and H being vastly in excess of the 
O. This disproportion necessarily renders them read- 
ily combustible and great heat producers. They are 
neutral bodies (ethers), formed by the union of glycerin 
with the radicles of the acetic and oleic acid series. 
Olein, (C21H3806) a fluid fat or oil at almost all tempera- 
tures, is formed by the union of glycerin (C:>HsO;s), with PHYSIOLOGY 
59 60 
PHYSIOLOGY 
the oleic acid radicle (C18H30O2), giving the formula 
above. Palmatin (ClsH4oos) is a solid fat at ordinary 
temperatures, hence it forms suet, tallow, etc., rather 
than the oily fats. Stearin (C21H4006) is still more solid, 
and the very firm consistence of any tallow or suet 
depends upon its presence. The two latter fats are 
formed by the union of glycerin and the palmitic and 
stearic scid radicles respectively. Both these acids 
are of the acetic acid series. The alkalies readily 
displace the glycerin from its union with all of these 
acids, forming soaps, soft if potash be used and hard 
if soda. 
Temporary or intermediate products, of various 
kinds, will be seen in the course of our studies of 
digestion, etc., but while all essential to this and other 
functions, they are in no sense foods. They are 
formed for some useful purpose, but do not remain 
long in their original shape, being broken up into other 
compounds, changed, reabsorbed or eliminated. They 
are quite numerous, but we will only take up the chief 
members. United with the base soda, two acids exist 
in the bile forming bile salts. These are glycocholic 
(CaUUNO,;) and taurocholic (C25H45N075) acids. The 
former is the more abundant in the bile of man and the 
herbivora; while the latter, though found in human 
bile, is chiefly abundant among the carnivora. Both of 
these acids on boiling split up into cholic acid, and glycin 
and taurin respectively. The bile pigments are also 
two in number. Of these, an orange red pigment 
called bilirubin (C1(;H18N203) predominates in man and 
the carnivora, while biliverdin (C16H20N205) a dark-green 
oxidized form of the above, is found chiefly in the bile 
of the herbivora. It is believed that both of the above, 
as well as the pigments of the urine (urobilin) and of 
faeces (stercobilin), are derived from the pigment of PHYSIOLOGY 
61 62 
PHYSIOLOGY 
the blood, haemoglobin. Ckolesterin, (C26H440) a 
crystalline, monatomic alcohol, found sparingly in a 
free state in the body, is abundant only in pathological 
fluids, cysts, etc. It is eliminated through the bile. 
It forms the chief constituent of gall-stones, and also 
of the floating crystals which sometimes occur in the 
vitreous humor of the eye. Other less important 
bodies, as lecithin, neurin, protagon, etc., are found but 
can not be considered here. 
Effete or waste products. We will hereafter learn 
that the bulk of the foods used in the body (starches, 
sugars, and fats) are, after their combustion, eliminated 
as simple II20 from the lungs, skin, and urine, and as 
C02 from the lungs. The class of nitrogenous foods 
which we call proteids give us, however, waste 
products in the urine, which are primarily much more 
complex. Urea, CO(NH2)2, the most abundant, as 
well as the most important, of these representatives of 
the tissue waste, is found only in the urine of the 
mammalia. It is chemically a diamide of C02; and, if 
in solution, will, in the presence of certain septic 
agencies, become hydrated, and form carbonate of 
ammonia, thus : 
CO(NHj)2+2H20=(NH1)3C0s. 
It will be seen that this salt is readily decomposed 
into NH3, H2O and C02. Observe the chemical sim- 
plicity of our waste products as compared with our 
foodstuffs. 
Uric Acid (CsH4N4o3),found in large quantities in the 
excrement of birds and reptiles, is found only in a small 
and variable amount in the urine of man. In certain 
pathological processes, as in gout, it is deposited per- 
manently in the tissues ; and again, when in too great 
excess in the urine, it is precipitated, giving the so- 
called “gravel,” and even “calculi.” In a free state it PHYSIOLOGY 64 
PHYSIOLOGY 
is quite insoluble, especially in cold fluids ; its salts are 
more soluble, its lithium salts being' especially so. The 
cause of the deposits of “urates” in the fingers, toes 
and ears of gouty subjects is due to the fact that ab- 
sorbed to saturation in the warm blood of the liver 
these urates crystallize out of their solutions when the 
blood is by exposure cooled down in the superficial 
parts named. Hippuric Acid, (C9H9NO3) exists in 
man’s urine in about the same quantity as uric acid, 
but is abundant in the urine of herbivora. It appears 
to be formed from benzoic acid or allied substances. 
Benzoic acid administered by the mouth is eliminated 
in the urine as hippuric acid, thus rendering- the urine 
more acid. As all the benzoic acid is not so changed, 
some appearing as free acid or benzoates we find this 
agent of great value in cystitis, ammouiacal decompo- 
sition, etc. The extractives kreatin and kreatinin 
form the basis of most modern “meat extracts”. They 
have the unfortunate property of slowing the heart 
when given in quantity. PHYSIOLOGY 
65 66 
PHYSIOLOGY 
CHAPTER IV. 
CIRCULATION. 
By the term, the circulation of the blood, is meant 
the passage of this fluid from the heart to all parts of 
the body, through special vessels called arteries, and its 
return again to the heart by other vessels, called veins. 
Between the part we call an artery and the one we call 
a vein, we have a system of minute vessels, called 
capillaries, infinite in number and permeating every 
part of the tissues. The cause of the circulation is a 
difference in pressure on the blood in different parts of 
the vascular system, the heart producing the pressure. 
William Harvey demonstrated the complete circulation 
of the blood during the years 1616-1619, a curious 
mixture of truth and fallacy having existed previous to 
•this time. Harvey was the first to show that there 
was, in reality, a double circulation, and two pumps ; 
the right heart pumping blood to the lung, from 
whence it returned to the left heart, (-pulmonary circu- 
lation) ; and the left heart pumping it to all parts of 
the general system, (systemic circulation,) whence it 
now returned to the right heart, to begin its course 
anew. The so called “portal circulation” was de- 
monstrated much later. 
The circulatory apparatus, consists of a heart, having 
right and left auricles and ventricles, with their walls, 
septa and valves, investing membranes, etc., and a con- 
necting system of blood vessels, the anatomy of all of 
which the student is here expected to review. The 
study of the structure of the auricle in man, shows 
that its thin wall is made up of two sets of cardiac PHYSIOLOGY 
67 68 
PHYSIOLOGY 
muscle fibres, a longitudinal and a circular or trans- 
verse. The longitudinal fibres run irregularly from 
the openings of the veins above, down to the auriculo- 
ventricular septum, and some are prolonged on the 
auricular face of the valves of the septum. The 
circular or outer fibers run around each auricle sepa- 
rately, (through the septum,) and around both contin- 
uously, more or less parallel to the auriculo-ventricular 
groove. Prom this line they continue up to the base 
of the heart, and there these circular fibres of cardiac 
muscle are continued on upon the veins entering the 
auricles, for, in some cases, an inch or more. This 
is most marked on the pulmonary veins, is somewhat 
less on the superior vena-cava, and is least on the 
inferior. These partly extra-auricular cardiac fibres, 
on the right side, are the last to stop their rhythmical 
contractions on the death of the heart, (ultimum 
moriens,) and the normal contraction wave of the heart 
seems to begin here. (Remak’s ganglion.) 
The structure of the ventricle is more complex. 
Prom without in we have some seven layers of cardiac 
muscle fibres. The most external layer, leaving the 
fibrous auriculo-ventricular ring, runs downward to 
the apex, turns in, enters the heart and becomes the 
inner or let us say seventh layer. Some of these fibres 
form the papillary muscles. The second, or next most 
external, running more obliquely to the apex, turns in 
and forms the sixth. The third, still more oblique, 
forms say the fifth ; while the fourth is an almost cir- 
cular (or transverse) layer of fibres. 
The structure of the fibrous-framework of the heart 
shows first the dense fibrous auriculo-ventricular sep- 
tum, pierced by two large openings. Prom the mar- 
gins of these openings are continued inward the 
segmented fibrous sheets, which form the basis of the PHYSIOLOGY 
69 70 
PHYSIOLOGY 
valves. This septum, separates absolutely the muscu- 
lar fibres of the auricle and ventricle. It seems more- 
over to be unpierced by nerves or vessels. 
The -pericardium of the heart, covering- it from the 
apex to the large vessels at its base, is here reflected 
back from these vessels, to inclose it again. It con- 
sists of a layer of serous endothelium, upon a fibrous 
membrane, which is continuous with the connective 
tissue framework of the heart muscle ; for while 
cardiac muscle is without sarcolemma, it is divided 
into fasciculi by planes of perimysium. The pericar- 
dial endothelium is on the outer surface of the heart 
and the reflexion brings it to the inner surface of the 
sac, hence endothelial faces are in contact. The endo- 
cardium lines the cavity of the heart, and is prolonged 
as the so-called “intima” into the blood vessels. It is 
of vascular endothelium, on a membrane of mixed 
fibrous and elastic elements, the latter most abundant 
in the auricle, and the former continuous through the 
cardiac perimysium with the pericardium. The valves 
of the heart are but reflections of the endocardium on 
a fibrous membranous frame-work. Observe the ring- 
like bases from which the auriculo-ventricular valves 
spring ; and the semi-lunar valves with a similar set- 
ting, formed from the fibrous elements of the artery 
wall. Note that the auricular face of the mitral and 
tricuspid valves bears both muscular and elastic ele- 
ments, while the other face, less equipped, is the 
anchorage of the tendons of the papillary muscles. 
The lymphatics of the heart are found in two sets. 
One of these is subendothelial, being found under both 
peri- and endo-cardium. The other, a deeper set, is 
found between the layers of muscular fibres in the 
heart wall. The blood vessels of the heart are pecu- PHYSIOLOGY 72 
PHYSIOLOGY 
liar in their relative abundance, and correspond to its 
relative energy. The arteries of the heart are peculi- 
arly thick, being especially rich in elastic elements, 
while the veins are unusually well supplied with 
valves. The nerves of the heart consist of extrinsic 
and intrinsic ganglia, and the fibres that unite the 
various parts. The extrinsic ganglia of control are 
probably located in the floor of the fourth ventricle of 
the medulla, (cardio-motor centre) and in the three cer- 
vical sympathetic ganglia. The intrinsic cardiac 
ganglia, usually superficial, are quite widely scattered, 
but among them we may note three distinct ganglio- 
nic masses. The first of these, located in the upper 
back part of the right auricle (sinus venosus), is called 
Remak's ganglion. The second is located in the 
interauricular septum and is called Ludwig's (Bezold’s) 
ganglion. The third mass, located in the auriculo- 
ventricular groove, is called Bidder s ganglion. Ter- 
minal corpuscles (pressure sense) are found under the 
endo-cardium, and probably send afferent impulses. 
The nerve fibres supplying the heart, while quite 
complex, can be traced to at least two distinct sources, 
one to the cardiac branches of the vagus or tenth 
cranial nerve (inhibitor), and the other to the cardiac 
branches of the cervical sympathetics (accelerator) 
above mentioned. Other fibres, of unknown function, 
supply the heart. 
The structure of blood vessels varies with the vessel, 
or part of the vessel, we select. The artery, or stan- 
dard vessel, consists of three coats ; viz., the intima or 
internal coat, the media or middle coat, and the adven- 
titia or external coat. The intima in detail is seen to 
consist of an internal layer of vascular endothelium, a 
subendothelial layer of connective tissue, and last a PHYSIOLOGY 74 
PHYSIOLOGY 
layer of elastic fibres more or less open. This last 
layer is thickest in the larger arteries and thinner in the 
smaller ones, while it is practically absent in the veins 
and capillaries. The media or middle coat consists of 
a mixed layer of smooth muscular fibres and elastic 
tissue, which varies as follows. In the larger arteries 
we have chiefly elastic fibres, in the smaller arteries 
and “arterioles” chiefly muscular fibres circularly 
arranged. The veins are again relatively deficient in 
this coat, while as before it is wanting in the capilla- 
ries. The adventitia or outer layer consists of a 
felted network of white fibrous and areolar tissue, 
and in the smaller arteries a few elastic fibres are also 
found. This coat is best developed in the veins and is 
of course absent in the capillaries. In both the intima 
and adventitia scattered muscular fibres are often 
found, and these fibres often run in a longitudinal 
direction. The capillaries, we have seen consist 
merely of endothelium, with an areolar support behind 
it. The veins, strong in their outer coverings, are 
weak internally. They are usually provided with 
valves, which are mere folds of endothelium on a con- 
nective tissue flap, having elastic fibres on the inner or 
convex side. Nerve fibres supply the blood vessels, 
(vasomotor nerves) chiefly the smaller arteries, and end 
in the non-striated muscular fibres of the middle coat. 
The mechanism of the heart’s action consists in a 
contraction of its fibres in such order as to force the 
blood from the auricles into the ventricles, and then 
by a contraction of its ventricles to send it Into the 
aorta or pulmonary artery as the case may be. The 
movement of contraction begins in the circular cardiac 
fibres on the trunks of the large veins entering the 
heart, and the impulse imparted to their contained PHYSIOLOGY 
75 76 
PHYSIOLOGY 
blood, and the narrowing' of the opening's of these 
vessels, overcomes the necessity for valves here. The 
wave of contraction extending- on down the auricle 
reaches the fibrous auriculo-ventricular plate, and in a 
manner not understood is continued to the muscular 
fibres of the ventricle. As the fibres of the auricle 
complete their contraction (the blood being discharged 
into the ventricle), those longitudinal fibres that run 
out on the valves draw them back into the auriculo- 
ventricular opening, being aided in this by the elastic 
fibres. Now as the fibres of the ventricle act from 
above down, the back pressure of the blood completes 
the closure of these valves, which the tendinous cords 
of the papillary muscles limit. These muscles acting 
last, as we see they must, draw upon the valves and 
change a hitherto passive into an active source of com- 
pression. The contained blood of the ventricle is 
forced out into the artery, and as the ventricle relaxes 
its force, the backward rush of the blood closes against 
it the semilunar valves and prevents its return. The 
contraction of the auricles in their order, and of the 
ventricles, is synchronous, this synchronous action 
being intended not only to relieve the strain on a rel- 
atively weak septum, but to enable the heart to use all 
of its fibres. 
The writer believes that much of the functional 
cardiac trouble reported is ventricular-arythmia. Cases 
are often seen in which the heart beats greatly exceed 
the 'pulse beats, being sometimes double the number. 
This alone can explain this condition. It is most 
marked with the nocturnal palpitations, (cactus) 
The cardiac cycle, or time required in the heart’s 
movement, is in the adult about .8 of a second for each 
beat. If we analyze this we find that it may be 
divided as follows ; PHYSIOLOGY 
77 78 
PHYSIOLOGY 
Auricular contraction, (systole) .1 second 
Ventricular contraction, (systole) .3 “ 
A period of cardiac rest. (diastole) A “ 
Total .8 
This rate of action gives us, for man, about 70 or 75 
beats per minute. In the new born child it is about 
double this, while with other children the rate is in 
accordance with age. The change in rate may be made 
either by varying the time of systole, or of diastole, 
but usually it is the latter, (digitalis, etc.) 
The heart sounds may be divided into two parts, the 
first sound long and low, while the second is short and 
sharp. After the second sound is a pause nearly as 
long as the two sounds conjoined. (There is found 
upon analysis to be a short pause after the first sound, 
but it can not be differentiated by the ear.) The cause 
of the first sound is quite complex, but the chief ele- 
ments in its production are thejvibration of the auriculo- 
ventricular valves and teudinae, 
traction of the heart muscle, and thjeVrush of the blood. 
The second sound, short and sharp, is due to the vibra- 
tion produced by the sudden closure of the semilunar 
valves. 
The impulse of the heart against the chest wall 
varies with the force of the heart, and with the amount 
of intervening lung, fat, etc., between the heart and 
chest wall. It is greatest during the excitement of the 
heart, and greater in the hypertrophied than in the 
normal heart, is more pronounced in the thin than in 
the fleshy, and in a state of expiration than in inspira- 
tion. The cause of the impulse is the sudden tension 
of the heart muscle, (cardiograph.) 
The arterial pulse, due to the intermittent waves of 
the blood in the arteries, is our practical guage of the PHYSIOLOGY 
79 80 
PHYSIOLOGY 
heart’s action. When the ventricle discharges its 
blood forcibly into the aorta, for instance ; while the 
bulk of the energy is expended in dilating the vessel, 
some is used in producing a wave of vibration which 
travels along the surface of the column of blood in the 
vessel, just as a wave travels along the surface of the 
water in a stream. This vibratory wave travels infi- 
nitely more rapidly than the blood-current (20 to 1), 
and it is this impulse wave that we feel under our fin- 
gers as the “pulse.” The dilation of the aorta, men- 
tioned above, puts upon the stretch all of its elastic 
elements, and when the ventricle begins to dialate at 
the end of its systole, the rush of the blood back into 
the heart is eager. The sudden closure of the semi- 
lunar valves checks this rush ; and the blood striking 
their arterial faces, recoils and produces a second wave 
of vibration which travels after the first, at a distance 
from it proportionate to of the arterial wall, 
'quick action of the valves, etc. This wave is called 
the dicrotic wave. 
We may substitute for the finger on the pulse a 
mechanical device known as a sphyg’mograph, which 
will record on a moving surface the various phases of a 
pulse waive, and we will find these phases as follows. 
As the wave passes under the button, representing the 
finger, we have a quick, nearly vertical upstroke of the 
recording needle until it reaches the apex, then a grad- 
ual decline which is broken about the middle of the 
decline by a slight rise from the dicrotic wave, then a 
continued fall to the end and repeat. If many tracings 
are taken we will note the great variation in the location 
of the dicrotic notch ; and we will learn that when the 
vessels are full and intra-arterial pressure is high, then 
it is well up near the top, but when intra-arterial pres- 
sure is feeble it is lower down. This variation in the PHYSIOLOGY 82 
PHYSIOLOGY 
place of the dicrotic wave can be understood from what 
has gone before ; a full artery and high pressure causing 
a quick recoil wave from the valves and vice versa. 
Intra arterial pressure must always vary within quite 
narrow limits, if health is to be maintained, and yet the 
disturbing influences are so numerous that its regulation 
becomes one of the most complex of physiological prob- 
lems. When an artery subdivides, the area of the cross- 
section (capacity) of the resulting branches is greater 
than that of the parent stem, and as the vessel continues 
to divide, this increase in relative area also continues. 
The result is, that we find that the aggregate sectional 
area of the capillaries is several (5 -7) hundred times as 
great as that of the aorta. This is necessary in order 
that the capillaries may supply every part of the body, 
even the most remote, with blood. The outcome of this 
is, that the capillary system is as it were a lake in the 
blood stream ; and each single element of this system 
being in very elastic walls can dilate, and a dilation but 
little beyond the normal for each one will give a total 
increase in capillary volume that will drain the larger 
vessels dry. For its protection the arterial system 
must regulate the flow of blood into the capillaries and 
prevent any over-distention that will produce evil. The 
active factor in regulating this outflow is the small 
arterv called the “arteriole,” whose lumen is controlled 
by the large supply of muscular fibres in its wall ; 
these muscle fibres being in their turn under nervous 
control (vaso-motor). 
Thephysicalfactors necessary for the maintenance of 
the arterial blood-pressure, we can readily see, are but 
four, viz.: (1) the strength of the heart beat, (2) the per- 
fect working and coaptation of the cardiac valves, (3) 
the elastic resiliency of the arteries,and (4) the resistance 
offered to the outflow bv the contraction of the arteriole. PHYSIOLOGY 84 
PHYSIOLOGY 
The working- of the cardiac valves and the elasticity 
of the arteries being- in health fixed factors, we have left 
as factors for varying- blood pressure only the variations 
in the strength and rapidity of the heart beat, and the 
variations in the lumen of the arteriole. The varying 
combinations of harmonious action and intensity on the 
part of these factors g-ive us any degree of pressure, 
with also equal variations in speed of current. For 
instance, a slow weak heart and narrow lumen gives 
medium pressure and a slow current, while a strong 
rapid heart and open lumen gives the same pressure 
and a rapid current. Or, if we take pressure alone, a 
strong, rapid heart and a narrow outlet gives the 
highest possible pressure ; and a slow, weak heart and 
open vessel, the lowest. 
The heart and the arteriole being widely separated 
can not work in harmony without some means of com- 
munication or without, what is better, the regulation 
of a dominating centre which takes cognizance of blood 
pressure. Such a centre exists in the medulla and is 
called the vaso-motor centre. 
The vaso-motor centre lying just above the calamus 
scriptorius, in the floor of the fourth ventricle, is kept 
informed, through nerve fibres, of the state of the 
blood pressure in the heart, and through other com- 
municating nerves, called vaso-motor nerves, regulates 
the action of the muscular fibres in the arterial walls 
and thus the lumen. This centre may be influenced in 
three ways, centrally, directly and reflexly. 
(1) Central influences as shame, terror, etc., disturb 
it, giving as a result, blushing, pallor, etc. Shock, 
which is a profound disturbance of the central nervous 
system, through whatever cause, is chiefly manifested 
through disturbance of this vaso-motor centre : the 
intense lumen-constricting impulses sent out giving 
pallor, cold clammy skin, etc. 85 
PHYSIOLOGY 86 
PHYSIOLOGY 
(2) Directly, it may be influenced by the amount and 
quality of the gases in the blood, or by drugs in the 
blood, etc. The presence of COa in excess is a power- 
ful stimulent to the centre, while O in excess dimin- 
ishes its excitability. With drugs, strychnine stimu- 
lates, and opium, in a less degree, depresses. 
(3) Reflexly, it is influenced chiefly by impulses from 
the heart, where from terminals under the endocar- 
dium (pressure sense) fibres pass up, through the so 
called Cyon’s nerve, to join a (superior cardiac) branch 
of the vagus and thence to the centre. The impulses 
received in this manner are usually notifications that 
blood pressure is too high in the heart, but it may be 
the reverse. When uninfluenced from without, the 
vaso motor centre seems to be in a moderate state of 
tonic excitement, sending out vaso-constrictor impulses 
at all times. When so needed, these impulses may be 
diminished or even absolutely inhibited, such action al- 
lowing dilation of the vessels : and the impulses, (or 
lack of impulses), producing this are called vaso-dila- 
tor or better vaso-inhihitor. In the centres of the 
lower spinal cord and perhaps in the sympathetic gang- 
lia, some powers of local vaso-motor control seem to 
exist. The route of the vaso-motor nerves from the 
centre to the muscles of the blood vessels is as follows: 
Down the cervical cord to the level of the second dor- 
sal nerve, where they begin to leave the cord by the 
rami-communicantes of the anterior roots, and they 
continue to come off down to the second lumbar nerve 
inclusive. After leaving the spinal cord, they join 
their respective sympathetic ganglia and proceed from 
here to the arteries through the nerves of the sympa- 
thetic system, those for the upper extremities and 
head, up, through the cervical sympathetics, and those 
for the lower limbs, down. In addition to the im- PTIYSIOL.OQY 88 
PHYSIOLOGY 
pulses sent out through the vaso-motor nerves for 
controlling the tone of the arteries, the vaso-motor cen- 
tre sends out tonic impulses for the regulation of the 
heart. Those impulses for slowing and weakening 
the heart, called inhibitory impulses, go through the 
vagus, or tenth cranial ; while those for quickening 
and strengthening, called acceleratory impulses, go 
through the fibres of the cervical sympathetic, both 
these nerves joining the intrinsic cardiac ganglia. 
Thus we see that the controlling centre may quicken 
or slow the heart, may dilate or narrow the lumen of 
the vessel, or may use any combination of these. The 
need of a centre is seen, however, when we know that 
the heart’s action must need vary with the emotions, 
with variations in temperature, with muscular exer- 
cise, age, sex, posture, etc., etc. 
The normal pressure in the different vessels may be 
approximately determined, despite the variations in the 
tone of the vaso-motor centre and other disturbing- influ- 
ences. Trying’a canula in some largfe artery and con- 
necting- with a U tube, we see the blood rise to quite a 
heig’ht in the limb of the tube, and fluctuate with the 
heart beat. We can g-et the mean heig’ht of our blood 
column by averaging’ the extremes of fluctuation ; but 
the column of blood tends to coag-ulate, and is moreover 
unwieldy, so it is better to use a column of mercury. 
This mercury may moreover be made to carry a reg-- 
istering- float (manometer), and give us a graphic record 
of the arterial variation. We find a normal pressure in 
the aorta of about three pounds to the square inch, in 
the brachial artery of over two pounds, in the capil- 
laries of the fing’er three-quarters of a pound and so 
on, till we reach the larg’est veins, where we find a 
negative pressure of nearly one ounce to the square 
inch. This means that, if such a vein were punctured, PHYSIOLOGY 
89 90 
PHYSIOLOGY 
the air would tend to rush into the vessel with this 
degree of pressure. We can, of course, see the danger 
of operating on these vessels without proper precau- 
tions. 
The speed of the blood current varies in the different 
parts of the vascular system, being most rapid in the 
aorta, slower in the carotids, and slowest in the capil- 
laries, while in the large veins it rises to about the 
speed of the blood in the carotids. The use of an 
instrument (stromuhr) which allows the rapid reversal 
of the current, in a tube length of known volume, 
enables us to determine the speed with fair accuracy. 
The time required, in man, to complete the circuit of 
the average course of the blood vessels in about thirty 
seconds. 
The capacity of the heart’s cavities is found to be 
from four to six ounces for the ventricles, and about a 
third less for the auricles. It might at first seem 
strange that a six ounce ventricle could be filled from 
a four ounce auricle, but this is explained by the fact 
that the ventricle is partly filled before the auricle 
contracts. 
The innervation of the heart in detail. First, it 
must be known that the cardiac muscle fibre has the 
power of rhythmical contraction independent of ner- 
vous influences, and the same is perhaps true of the 
general muscular fibres of the bloodvessels. (Traube- 
Hering curves.) Various experiments show, however, 
that it is to the various masses of ganglionic nerve cells 
embedded in its substance, (see page 72), that we are 
indebted for its regular movements. The collection of 
nerve cells, to which the term Remak’s ganglion is 
applied, is found chiefly in the upper part of the right 
auricle ; and the fact that heart movements begin in 
this auricle and here cease last leads us to believe that PHYSIOLOGY 
91 92 
PHYSIOLOGY 
it is the true cardiac excito-motor centre. The experi- 
ments of Stannius on the frog’s heart indicate that 
this is the dominating centre for the heart at large, 
and that Bidder’s ganglion in the auriculo-ventricular 
groove is in a less degree the excito-motor centre for 
the lower heart ; while Ludwig’s or Bezold’s ganglion 
in the auricular septum is the intrinsic cardio-inhibitor, 
or depresso-motor centre. Outside the heart, as we 
have seen, impulses from the nucleus of the vagus 
depressor inhibit cardiac action, while impulses from 
the sympathetic excite it. 
The influence of the respiration on the ■ heart’s 
action is quite pronounced, especially in aiding- the 
diastolic dilation of the heart’s cavities. The effort of 
the distended elastic lung- to return to its condition of 
elastic equilibrium, as we shall see later, throug-h 
atmospheric pressure aids the filling of the auricles at 
least to the extent of its elasticity. It also aids in 
increasing the power of the lesser or pulmonary circu- 
lation. 
The usual pathological conditions influencing the 
heart are (1) functional depression (syncope on “faint- 
ing”) or excitement due to mechanical or nervous irrita- 
tion ; and (2) organic changes, which may be in the 
myocardium (degenerations), or in the valves. The 
openings of the valve may be narrowed (stenosis) or 
the valve may be warped and drawn until it does not 
close the opening (insufficiency). 
In the first case fear, on any profound nervous im- 
press, may produce either forceful palpitation or the 
reverse, extreme feebleness of heart, which being in- 
sufficient to supply the cerebral centers with blood, 
unconsciousness and loss of power (syncope) results. 
Lowering the head, will, by bringing gravity to the 
aid of a weak heart, restore consciousness. Some- PHYSIOLOGY 
93 PHYSIOLOGY 
times a gas distended stomach by pressing- on the heart 
from below will cause palpitation (carminatives.) For 
the organic condition stenosis we must add increased 
force to the muscular effort which is to force the blood 
through a contracted opening (digitalis) while in the so 
called insufficiency we must shorten the diastole or 
period during which the blood can leak back into the 
proximal cavity. 
The portal circulation, so-called, is but a part of the 
systemic circuit. As we saw, the blood from the 
right ventricle goes through the pulmonary artery to 
the capillaries of the lung to be returned by the pul- 
monary veins to the left auricle, giving the pulmonary 
circuit. The left ventricle now sends this out through 
the aorta to the general system to be returned to the 
right auricle, completing the systemic circuit. A part 
of this blood, however, follows a peculiar route. The 
blood, speaking in a general way, of the coeliac axis, 
superior and inferior mesenteric arteries and lesser 
branches, is gathered into a large vein called the portal 
vein. This does not as is usual join a larger vein and 
pass on to the right heart, but it passes on to the liver, 
there to ramify in a second set of capillaries, to be 
again gathered into veins which join others, and now 
enter the right auricle. Contrary to what we would 
suppose the branches of the portal vein have no valves. 
The term, lymph circulation, is scarcely an accurate 
one, for the reason that the lymph does not complete 
any circuit of its own, but is in reality only an aux- 
iliary part of the general vascular system. That part 
of the plasma which is not used, as well as all the 
tissue waste, is returned from the tissues by the 
lymphatics. The lymph vessels called “lymphatics” 
LYMPH CIRCULATION. PHYSIOLOGY 
95 PHYSIOLOGY 
and “absorbents” are, when small, much like cap- 
illaries, when larger, somewhat like the veins, in both 
cases having valves. The valves, in form and struct- 
ure, are much like the semi-lunar valves, but are 
usually only “two leaved.” The chief trunk of the 
lymph system, the thoracic duct, leads from the great 
lymph sac, the receptaculum chyli, to the junction of 
the left subclavian and jugular veins, where it opens 
by a valve-guarded orifice. The various faints of 
origin for the lymphatics are as follows. (1) The 
interstitial origin, or origin from the interstitial lymph 
spaces, is the most common, as well as the most im- 
portant. (hypodermic medication.) (2) The intestinal 
origin, from the lymph spaces of the intestinal villi. 
This differs from all other lymph systems in that it 
carries what we call chyle, a milk-white mixture of 
absorbed fats and lymph, the white color of which 
gives to the vessels the name of the “lacteals.” (3) 
The origin from stomata, which we have seen occur 
on many serous surfaces. These allow the absorption 
of excess of serous fluids. TheJvis-a-tergo of the blood 
in the capillaries is the chief cause of the movement of 
the lymph in its vessels, but the following other causes 
aid, viz.fythe contractile power of the villi of the 
lacteals, of the lymph vessels (valves) 
by muscular action, thoracic suction and the arterial 
pulse waves on the perivascular lymph spaces of bone, 
etc. The general course of all lymphatics is from the 
periphery toward the centre, by the most direct route, 
and there are usually two sets of vessels, a superficial 
and a deep. 
It will be observed that the lymph in greater part 
leaves the blood vessels where intra vascular pressure 
is still relatively high of a lb.) i. e. in the capillaries, 
that from these points the anatomical course of the PHYSIOLOGY 
97 .teHY^IQLQGY, 
is determined by but one thing, viz;, the 
reach that point of the circulatory route 
where blood pressure is negative, (see page 88). Here 
it can return to the blood circuit without resistance. 
CHAPTER V. 
THE BLOOD AND LYMPH GLANDS. 
The structures here taken up and called “glands” 
are not in reality glands, having no secretory epithe- 
lium, no basement membrane and no duct for the 
discharge of a secretion. At the same time their 
general appearance caused them to be called “glands” 
before these details were known, and we have since 
used the lack of a duct to distinguish them from the 
true glands. * 
The ductless, or blood glands, are the spleen, the 
/thymus, thc&hyroid, or ad-renals, the 
tonsils, the:pineal glands/vthe agminated 
glands (Peyer’s) of the intestine, and theftsolitary 
glands or adenoid bodies of the same and other regions. 
The details of function in these bodies is very imper- 
fectly known ; but that all are concerned in the 
production or elaboration of the blood and lymph, is 
now generally believed. The lymphatic “glands or 
•compound lymph nodes will be considered after the 
«ductless glands. 
The spleen is the most important, as well as the 
largest, of the so-called blood glands. Eying within 
the abdominal cavity and connected by large special 
trunks with the portal system of blood vessels, its PHYSIOLOGY 100 
PHYSIOLOGY 
position and general connections give evidence of the 
part it is to play. 
We find it covered superficially with its serous or 
peritoneal layer which forms its ligaments, and beneath 
this is a fibrous capsule which invests it, and sends in 
septa or trabeculae to furnish the framework or stroma 
of the gland. At the hilum, or point where the blood 
vessels enter the spleen, this capsule turns into the 
interior of the gland, and dividing in various planes 
joins the trabeculae from the periphery and divides 
the spleen up into small lacunar spaces called lobules. 
The branches of the splenic artery, entering at the 
hilum, follow without anastomosis the planes of con- 
nective tissue between the lobules, giving off as they 
go terminal branches to each one. This terminal 
artery in the lobule ends near its centre in a pear-shaped 
expansion, seemingly as if the walls of the vessel had 
become an open-meshed sac. This sac-like body or 
corpuscle is in reality composed of adenoid tissue, and 
its open meshes are filled in with lymph corpuscles. 
The space in the lobule around this corpuscle, often 
called a Malpighian corpuscle, is filled in loosely with 
a dark-red granular mass of cells called spleen-pulp. 
Veins with open or cribriform walls take origin in the 
spleen-pulp of the lobule, and pass out through the 
connective tissue septa to the hilum to form the splenic 
vein. In the capsule internal septa, and trabeculae, 
elastic and (visceral) muscle fibres are found, the latter 
by their rythmical contraction, probably giving the 
pulsating powers of the spleen. We see from the 
above that the route of the blood in the spleen is 
through the splenic artery to the terminal artery of 
the lobule, here it percolates through the lymphoid 
cells of the corpuscle, passes out into the open meshed 
tissues of the spleen-pulp, through this into the open- PHYSIOLOGY 102 
PHYSIOLOGY 
ings of the outgoing veins, and thence away through 
the splenic vein. The degree of dilatation for the 
lobules is regulated by the tension of the elastic and 
muscular fibres in their walls. The function of the 
spleen is doubtless manifold, and yet it is not seemingh7 
essential to any special function, for it may be removed 
entirely without ill result ; a slight compensatory 
enlargement of the other blood glands alone showing 
that they have assumed its function. The connection 
of the spleen with the digestive functions is shown by 
its enlargement during the later stages of digestion, 
being used probably as a temporary reservoir for 
digestion products. Its part in‘.fplood-elaboration is 
seemingly the destruction of imperfect red blood cells; 
for the blood coming from the spleen is peculiarly 
poor in red blood cells, as compared with white, (only 
100 to 1), while in the blood entering the spleen the 
proportion of reds is greater than usual (1200 to 1). 
This may in part be due to the formation of leucocytes, 
but the presence of free pigment, (which the liver 
seems to use,) proves that red cells are destroyed. 
The muscular fibres of the spleen being under nerve 
(probably vaso-motor) control, we see how it may be 
used also as a reservoir to relieve excessive blood - 
pressure, congestion, etc. 
The thymus, another of the ductless or blood glands 
located in the anterior mediastinum and neck, may be 
called a temporary organ. It reaches its full size and 
functional developement at a little over two years of 
age in the human subject, and later atrophies to a mere 
anatomical “relation.” Composed usually of two, 
sometimes three lobes, it is invested in a capsule of 
fibrous tissue. The lobes are made up of an immense 
number of small lobules, each having a cortical and a 
medullary part. The cortical portion is of loose ade- PHYSIOLOGY 104 
PHYSIOLOGY 
noid tissue filled in with lymph corpuscles, while in 
the medulla the same tissue, still more open, contains 
granular cells and a peculiar flask-shaped corpuscle. 
The function of this gland is not known, other than that 
it appears from structure, etc., to be a bipod-elaborat- 
ing organ. As found in the calf, and other young 
domestic animals, the thymus furnishes the “sweet- 
bread” of our tables. 
The thyroid, unlike the thymus, persists in functional 
activity until late in life. It is somewhat larger in 
females than males, this being especially true of those 
who have borne children. In many of the lower 
animals it enlarges during the rutting period, most 
notably among the deer. Located on the trachea, it 
consists of two lobes and an isthmus which unites the 
lobes. The internal structure is shown to consist of a 
series of closed vesicles or sacs containing a glairy 
yellow fluid. The vesicles, of varying size, are sep- 
arated from each other by connective tissue septa con- 
tinuous with the capsule of the gland. E}ach vesicle 
is lined by a single layer of peculiar epithelial cells 
supported by a delicate adenoid reticulum. The ar- 
teries of the thyroid anastomose freely around the 
vesicles, and lymphatics are said to originate in their 
cavities. The yellow color of the vesicular fluid seems 
due to haemoglobin. The enlargement or hypertrophv 
of this gland gives rise to the disease called “goitre,” 
so common in Switzerland and other high altitudes, 
where it usually is associated with cretinism. The 
entire degeneration or removal of this gland will in 
man, and in most animals, give rise to a series of 
neurotic and trophic changes, which may result in 
cretinism or death, as the case may be. The symptoms 
are usually tetanoid, mucoidal and then cerebral in 
order. Myxoedema is a general mucoid degeneration PHYSIOLOGY 
105 106 
PHYSIOLOGY 
which in man follows pathological changes in the 
thyroid. The subcutaneous transplantation of the 
thyroid of a sheep, or other lower animal, into the 
human body has produced pronounced improvement in 
this disease, but not so pronounced as seems to follow 
the continued administration of a glycerin extract of the 
gland itself. (.Exophthalmic goitre, a disease char- 
acterized by intense rapidity of the heart’s action and 
a temporary congestion of the vessels of the thyroid 
and orbit, is not yet proven to be due to disease of this 
gland.) The function of the thyroid seems to be evi- 
denced in the following acts : I Blood elaboration, 
probably acting as a place of breaking up for degenerate 
corpuscles Regulating the formation of mucin in the 
of influencing in some way the sexual func- 
tions 
The ad-renals, or supra-renal capsules, lying one 
upon either kidney, are found to have the following 
structure form without in :—a thin, fibrous capsule, a 
cortical layer, and next a small medullary portion. 
The cortical layer is composed of a granular sub- 
capsular zone and cells, arranged in radial cylinders, 
containing more or less fatty matter and yellow 
granules. The medullary part contains, in an ade- 
noid framework, muscular elements, blood vessels, 
protoplasmic granules, and nervous elements. The 
latter are so abundant that many think that at least 
this part of the gland has ganglionic functions. The 
other parts have probably the general function of the 
blood glands. Addison s disease, evidenced by a 
peculiar bronzing of the skin, is usually found 
associated with disease of these structures. 
The tonsils, located between the pillars of the fauces, 
are composed of a mixture of lymphoid and epithelial 
tissue. A number of depressions or crypts sink in PHYSIOLOGY 
107 108 
PHYSIOLOGY 
from their mucous surface, and into the bottoms of 
these quite a number of mucous glands open by their 
ducts. Around these crypts adenoid tissue., filled with 
leucocytes, is found and large numbers of closed or 
solitary follicles. A thin capsule of fibrous tissue 
covers all but the free side. Inspisated masses of 
mucus mixed with dead leucocytes, etc., are often 
found filling these crypts and protruding from their 
orifices. During the early years of life the tonsils hy- 
pertrophy quite readily, but usually shrink before 
adolescence. The pharyngeal tonsil (Dushka’s), 
located on the pharyngeal vault, is of the same structure 
and it also hypertrophies. Only the lymphoid parts of 
these structures have the function of blood glands. 
The pituitary and pineal glands. The first of these, 
the pituitary body or hypophysis cerebri, consists of 
two distinct parts or lobes, the anterior or larger em- 
bracing the posterior or smaller. The posterior lobe 
is part of the brain, to which it is united by the in- 
fundibulum. The anterior lobe is somewhat like an 
ad-renal in structure, being composed of adenoid 
tissue, lymph corpuscles, etc. Its function is un- 
known. 
The pineal gland also consists of two lobes. The 
outer or cortical part is seemingly analogous in 
structure to the anterior lobe of the pituitary body. 
The inner part belongs to the brain, as above, and, con- 
tains a cavity (ventricle) lined in early life with ciliated 
epithelium. It was at one time supposed to be the 
seat of the soul—notwithstanding its size ! This 
cerebral off-shoot, obsolete in man, has in some of the 
lizards, (Hatteria, etc.), developed into a median eye, 
fashioned on the invertebrate plan. (The coccygeal 
and carotid glands are not well enough understood to 
describe.) PHYSIOLOGY 
109 PHYSIOLOGY 
The agminated and solitary glands are essentially 
the same in structure. The solitary glands, or lymph 
follicles, are found in the mucosa, and sub-mucosa of 
the alimentary tract, trachea, bronchi, bladder, ureter, 
etc. However much they differ in size, etc., they con- 
sist of small masses of adenoid tissue loaded with lymph 
corpuscles or leucocytes. Blood vessels enter them, 
but return in loops without distribution, lymphatics 
ramify around them but never communicate. In the 
centre of each is usually seen a “germ centre” with 
leucocytes undergoing- karyo-kinetic changes. If the 
phagocytic theory of Metznikoff is true, these follicles 
may be considered as barracks for the soldiers of de- 
fence, and they are placed where needed. The a§77ii- 
natedglands of the intestinal tract, Fever’s glands, 
are but groupings of a dozen or more of the above 
lymph follicles together in a peculiar manner. These 
“patches” are found chiefly in the lower part of the 
ileum, arranged under the mucosa in a linear manner, 
opposite the insertion of the mesentery of the gut. 
They ulcerate readily in cases of typhoid, fever and 
gradually disappear with age. Their location in the 
gut wall, at the point most remote from the supplying 
mesenteric vessels, alone explains the relative rarity of 
severe hemmorhage in euteric on typhoid fever. 
The lymphatic glands, or compound lymph nodes, 
differ from all the foregoing in that they are located on 
the line of the lymph vessels and form a part of them. 
They are found in great numbers on the lines of the 
lacteals in the mesentery, along the lymph lines of the 
abdomen and thorax, especially at the root of the lung. 
More superficially, they are found at the back of the 
neck, its sides and base, and under the jaw, in the 
axilla and arm as far down as the elbow, in the groin 
and sometimes in the popliteal space. (Some few lymph PHYSIOLOGY 
111 112 
PHYSIOLOGY 
vessels, however, undoubtedly join the thoracic duct 
without passing- through lymphatic glands.) They 
vary in size from a bird-shot to an almond, and may be 
enormously enlarged. 
The structure of the lymph gland shows first a cap- 
sule of connective tissue mixed with visceral muscle, 
and this capsule is turned in at the hilum to form the 
internal framework of the gland, and is united with 
trabeculae sent in from the periphery. These fibrous 
planes divide the gland into small spaces or alveoli 
which are large and distinct in the outer or cortical 
part, and become blended in the indefinite subdivisions 
of the medulla. These alveoli show an internal struct- 
ure which somewhat resembles the spleen, viz.—a 
central mass of adenoid tissue closely packed with 
lymph corpuscles, around this, next to the connective 
tissue of the capsule and trabeculae, is a. very open 
reticulum of adenoid tissue containing few lymph cor- 
puscles and forming a lymph channel around the central 
mass. The afferent vessels of the gland (lymhpatics) 
enter on the convex side, their various branches piercing 
the capsule and their intima becoming continuous with 
the endothelium of the lymph channel in the alveolus 
which they enter. The internal mass of adenoid tissue in 
each alveolus does not touch its walls, being separated 
by the lymph path, but at its inner extremity (next the 
medulla) it breaks up into several prolongations which, 
joining similar extensions from other alveoli, and also 
fibrous off-shoots from the trabeculae of the capsule, 
form the composite medullary structure. This medul- 
lary tissue of the gland is not so open as that of the 
lymph channel, nor so filled in with lymph corpuscles 
as the central adenoid mass of the alveolus. The 
lymph, having entered from the afferent vessels and 
traversed the lymph channel, percolates through this PHYSIOLOGY PHYSIOLOGY 
open medullary substance to enter the afferent vessels 
and go out at the hi]urn. Blood vessels enter the gland 
at various points, run in its fibrous septa and ramify in 
the closely packed adenoid masses of the alveolus and 
medulla, the veins of these vessels emerging at the 
hilum. The muscular fibres of the gland seem to have 
an influence on the flow of the lymph, bearing some 
analogy perhaps to the lymph hearts of the frog and 
other animals. Bearing on the function of these 
glands; we see how septic products, etc., when 
absorbed, are delayed in these glands, exposed to the 
phagocytic and other influences of the leucocytes here 
abounding, and perhaps further influenced by theoxidiz- 
ing power of the blood, brought into close relation with 
the lymph in the medulla and adenoid masses of the 
alveoli. PHYSIOLOGY 
115 116 
PHYSIOLOGY 
CHAPTER VI. 
RESPIRATION. 
Respiration, meaning* literally “to breath again,” is 
here used to describe the gaseous interchanges that 
take place in the blood. These interchanges take 
place at two points in the blood’s circuit; one in the 
capillaries in the lung, called pulmonary respiration, 
and the other in the capillaries in the tissues at large, 
called interstitial respiration; In pulmonary respira- 
tion the blood in the capillaries of the lung is, by the 
mechanical act of respiration, exposed to the influence 
of the O of the air ; and it takes up O, and gives off 
C02, which it contains in large excess. In interstitial 
respiration the blood flowing through the general 
capillary system of the body is brought into intimate 
relation with the tissues of every part, and it gives off 
to the tissues for their sustenance O, which we saw it 
take from the air, and now takes in exchange CO,, 
which, as we saw, it eliminates in the lungs. The 
latter form of respiration requires no apparatus aside 
from the general circulatory system, but for pulmonary 
respiration an elaborate, special apparatus is required, 
which we will now consider. 
The pulmonary respiratory apparatus consists of 
the following parts: (1) The accessory respiratory 
tract, including the nostrils, regio respiratoria of the 
nasal fossa, posterior nares, pharynx, and upper larynx ; 
(2) the true respiratory tract, including the lower 
larynx, trachea, extra- and intra-pulmonary bronchi 
and bronchioles ; (3) the lungs, made up of alveoli or 
air cells, blood vessels, interlobular septa, investing PHYSIOLOGY 
117 118 
PHYSIOLOGY 
pleura, etc.; and (4) the thorax, consisting- of a conical 
bony framework closed in by soft tissues, and capable 
of change of volume by the action of muscles. 
(1) The accessory parts of the respiratory tract. Con- 
sidered in detail, the nostrils are found to be capable of 
dilatation or of compression by the action of the muscles, 
dilator naris, ant’ and posterior, compressor narium, 
etc. These movements are seldom seen on the human 
subject, except in forced breathing, as in the asphyxia- 
tion stage of croup, etc.; but in the lower animals, as 
the horse, etc., their movement is pronounced. Note 
the stiff hairs or vibrissaeat the margins of the nostrils, 
to catch floating particles, etc. The “regio respira- 
toria” of the nasal fossa is all that part of the fossa 
lying below the level of the middle turbinated bone. 
The function of this part of the tract is to warm and 
make moist the air taken in, which is done by the 
passage of the air over the large vascular surfaces of 
the turbinated bones. Observe the fact that the excess 
of tears are discharged into the inferior meatus of this 
fossa, and aid in keeping moist the passing air. The 
posterior nares have no special function as regards 
respiration, their closure by the soft palate being a part 
of the acts of deglutition and phonation rather than 
of respiration. The mouth cavity is in no sense a part 
of the respiratory tract, persons only breathing 
through the mouth when the regio respiratoria, (polypi) 
or pharyngeal vault (adenoids) is obstructed. The 
pharynx is a cavity of double function, being a part 
both of the digestive and respiratory tracts. For the 
exercise of the function of deglutition it can be cut off 
from all respiratory connection above by the soft palate, 
and below by the epiglottis, The upper larynx is in 
reality a part of the pharynx, and may be here so con- 
sidered. PHYSIOLOGY 
119 120 
PHYSIOLOGY 
(2) The true respiratory tract may be said to begin 
at the vocal cords. The opening- of the glottis, or 
rim ag to ttidis, may be divided into two parts; that 
between the cords or anterior part, called the glottis 
vocalis, and that between the arytenoid cartilages or 
posterior part, called the glottis respiratoria. Not- 
withstanding the fact that both cords and cartilages 
may be widely separated, this is the most dangerous 
part of the respirator} - tract, in so far as ease of ob- 
struction is concerned. Foreign bodies of all kinds, 
from safety pins to lumbricoid worms, are found 
obstructing this opening ; inflammations simple (oe- 
dema glottidis) and croupous rapidly close it, while 
ulcerations leave cicatricial bands that narrow, and 
ultimately even close it. bower down in the trachea 
and larger bronchi we find the C shaped rings of car- 
tilage and their complemental trachialis muscle, giving 
an air tube firm yet flexible, open yet compressible. 
A section of the duct here shows [a) ciliated epithe- 
lium with its germinating layer at its base ; [b) a base- 
ment membrane which overlies the submucous areolar 
layer, in which we find small blood vessels, lymph 
vessels, nodes, etc.; (c) a longitudinal layer of elastic 
fibres overlying the true submucous areolar layer 
which contains large blood vessels, lymph vessels, 
nerves, mucous glands, etc.; (rtf) the cartilages and 
muscle, fibrous envelope, etc. As we descend toward 
the lung, layer after layer is lost, as follows : the car- 
tilaginous rings become irregular plates and disappear, 
the muscular fibres increase and become circular, and 
the areolar layers disappear step by step till we find in 
the smallest bronchi or bronchiole the following : 
internally, ciliated epithelium now almost cubical and 
bare of cilia, next the longitudinal elastic layer un- 
changed, then circular muscular fibres (asthma), a thin PHYSIOLOGY 
121 122 
PHYSIOLOGY 
submucous layer containing vessels, nerves, etc., and a 
thin fibrous layer continuous with the interlobular 
septa. It may be stated here that the cilia move up- 
ward towards the larynx and carry mucous and foreign 
particles of all kinds to the rima glottidis, whence they 
are removed by coughing. This action of the cilia, as 
well as the sensibility of the nerves of the larynx, etc., 
is depressed by the action of opium and anaesthetics. 
(3) The lung' structure in detail. When the bron- 
chial tubes become very minute (1-25 of an inch), they 
become beset all around with air cells called “alveoli,” 
and from this point they are called alveolar passages. 
As they continue outward they are surrounded by 
larger cavities, the inner walls of which are also beset 
with alveoli, these larger cavities being called “infund- 
ibula.” Fach terminal bronchiole with its alveolar 
passages, infundibula and their alveoli forms a “lob- 
ule,” and is separated from its fellows by interlobu- 
lar-septa derived from the fibrous trabeculae of the 
pleura. A pulmonary air cell or alveolus is a small 
cavity (1-100 of an inch in diameter), found on the per- 
iphery of a terminal bronchiole, or on the inner surface 
of the infundibula, lined by flat squamous cells, with 
swollen granular cells at intervals. These flat cells 
rest on an open membrane composed of fibrous and 
elastic tissue, with scattered non-striated muscular 
fibres. Between the squamous cells and the basement 
membrane wind the capillaries of the pulmonary art- 
ery. The surface offered by the aggregate area of 
capillary wall exposed to the air in the alveoli is enor- 
mous ; being estimated 
capillaries contain over JL..pints of blood which is 
renewed every Bor 9 seconds. Covering over the en- 
tire lung and investing all its lobes is a thin fibrous 
membrane called the pleura. From the general sur- PHYSIOLOGY 
123 124 
PHYSIOLOGY 
face it extends over the “root” of the lung-, on to the 
bronchi and large vessels that enter here, and from 
these trunks it is reflected back over the lung again as 
an investing sac. The inner layer of the visceral or 
pulmonary pleura is of fibrous tissue, and it sends in 
trabeculae to unite with the fibrous extentions of the 
smaller bronchioles. The outer layer of the visceral 
pleura is endothelial, but of course the reflection at the 
root of the lung brings a change in the relationship of 
these layers on the parietal pleura, and makes the 
outer layer the inner. 
The lung substance in the foetus, never having had 
its air cells or alveoli distended by respiration, is com- 
pact and heavy and will sink in water. The lungs 
after distention will not only float, but as a rule, will 
sustain the attached heart. After decomposition sets 
in, the lungs may from the retained gases of decompo- 
sition float temporarily. 
The blood supply of the lung is from two distinct 
sources, viz :—the pulmonary artery and the bronchial 
arteries. The blood from the pulmonary artery, fol- 
lowing the bronchi, courses ultimately in the capillaries 
in the walls of the alveoli to be aerated, and takes no 
part in the nutrition of the lung. The blood from the 
bronchial arteries following also the bronchi, and their 
connective tissue prolongations, supplies nutrition for 
the general lung tissues. These arteries do not anas- 
tomose in any part of their course, although following 
the same routes. Their respective veins do anastomose, 
however, to a slight extent. This is sometimes a 
serious matter ; for it must be remembered that the 
pulmonary vein carries arterial blood, and if there be 
any obstruction to the flow in the bronchial vein the 
impure blood of this vessel is thrown into the arterial 
blood of the general system. It is said that the collect- PHYSIOLOGY 126 
PHYSIOLOGY 
ive area of the pulmonary veins is smaller than that of 
the pulmonary arteries. If this be true, it is accounted 
for by the great loss of fluid from the blood by evapo- 
ration in the pulmonary capillaries. 
Ihe lymphatics of the lung are a deep and superficial 
set ; the deep having* an interstitial origin and follow- 
ing* peri-vascular and peri-bronchial channels, while 
the superficial set arise from pleural stomata and run 
in sub-pleural channels. The lymphatic gdands on 
these vessels, called bronchial gdands, are a dozen or 
more in number and located at the root of the lung*. 
In the ag*ed they are almost black in color. 
The nerves of the lung. Small ganglia are located 
along* the lines of the nerve trunks which follow the 
bronchi and in the mucosa. The nerve fibres are from 
the sympathetic and pneumogastric, the latter furnish- 
ing* motor (efferent) fibres for the tracheal and bronchial 
muscle anl sensory (afferent) fibres from the lung* to 
respiratory and other centres. 
(4) The structure of the thorax shows it to be de- 
signed for mobility with strength, the ligamentous 
union of spinal column, ribs, sternum and cartilages, 
pointing to this intent. In detail it consists of a strong 
but light conical bony framework having all its open- 
ings filled in. The diaphragm closes the lower 
opening, the parietal fascia, muscles, pleura, etc., the 
spaces between the ribs, and the numerous structures 
passing through the upper opening, with the thoracic 
fascia, close it also. 
Expansive power of the thorax. Laying aside the 
action of the diaphragm in directly increasing the 
capacity of the chest, the thorax can be increased in 
diameter both antero-posteriorly and transversely. Its 
antero-postcrior diameter can be increased by raising 
the sternum and attached ribs, as by the action of the PHYSIOLOGY 
127 128 
PHYSIOLOGY 
scaleni muscles, etc. This increase in diameter is 
due to the fact that the points of spinal attachment of 
the ribs lie on a higher level than their points of ster- 
nal attachment, so that the elevation of their anterior 
extremities increases the diameter to the full length 
of the rib, from point to point. The increase in trans- 
verse diameter is made in a much similar manner. 
The “droop” of a rib is such that the mid-point of its 
shaft lies below a line drawn through its spinal and 
sternal points of attachment; and this brings the mid- 
point near to the median line of the body, just as a 
wooden roller on the handle of a bucket is nearer to 
the vertical axis of the bucket when lying against its 
side, than it is wdien the handle is level. When all 
the ribs are raised till the “droop” becomes horizontal, 
the lateral transverse they all make from the median 
line increases the transverse diameter of the chest. 
The muscles of the thorax whose action influences 
thoracic capacity may be divided into three groups. (1) 
Those elevating• the sternum and ribs and increasing 
thoracic capacity (inspiration), as theleyatores costarum, 
serratus posticus superior and external-intercostals, for 
ordinary breathing, with the scaleni, sterno-mastoid, 
serratus maguus, pectorales, trapezius, etc., etc., when 
extraordinary breathing efforts are made. (2) Those 
depressing the ribs, sternum, &c., and decreasing tho- 
racic capacity (expiration) as the abdominal muscles, 
internal intercostals, triangularis sterni, serratus pos- 
ticus inferior, &c., which muscles act only, however, 
. 
when extraordinary breathing efforts are being made. 
Ordinarily thejflepression of the ribs, &c.,after elevation, 
is produced without muscular action, thd_ weight of the 
chest,arms, &c.2the elasticity of the stretched abdominal 
muscles, costal cartilages, &c., and tlibelasticity of the 
lungs, being sufficient to cause the faH. (3) The dia- PHYSIOLOGY 130 
PHYSIOLOGY 
phragm does not materially change the external shape 
of the thorax by its action, but being arched upward 
from its points of attachment, its contraction depresses 
it, and hence increases to that extent the length and 
capacity of the thorax. The central tendon being 
blended with the fibrous pericardium moves but little, 
and the chief change takes place in the lateral segments. 
The lower ribs would be drawn inward and upward by 
the contraction of this muscle, were it not for the action 
1 of theA quadratus lumborum, etc., in fixing them fast, 
in'other words an inspiration is made by dilating the 
thorax, the inspiratory muscles for ordinary tidal 
breathing being the levafbres costarura, serratus pos- 
ticus superioris, external intercostals and diaphragm. 
An ordinary expiration is made simply by the action 
of gravity and tissue elasticity. The muscles of forced 
expiration are the abdominal muscles and others 
named above. 
The mechanism of respiration. In the process of 
ordinary (tidal) respiration, the movements of the chest 
which cause the air to rush into, and then out, of its 
cavity must overcome some force, and we will take these 
movements and forces in detail. 
In ordinary inspiration the muscles before mentioned 
raise the ribs and sternum, and the antero-posterior and 
transverse diameters of the thorax are increased ; at the 
same time the diaphragm contracts and increases the 
capacity of the chest longitudinally also. The capacity 
of the chest being increased,atmospheric pressure within 
the thorax falls ; i. e,, the air in the chest which entered 
at a pressure of one atmosphere (15 lbs. to the sq. in.) 
is now at less pressure. But through the respiratory 
tract the atmospheric air communicates with the 
interior of the chest, and air rushes in through the 
nostrils and tract, and into the lungs until pressure in PHYSIOLOGY 132 
PHYSIOLOGY 
the lung- and external air is the same. This completes 
the inspiratory act. The forces which are overcome in 
this movement are, as we have seen, the weig-ht of the 
chest, the elastic tension of the abdominal muscles, 
costal cartilag-es and lung structure. If now we relax 
the muscular action which distended the thorax, the 
forces above named act, the ribs and sternum fall and 
the diaphrag-m rises. This decreases the thoracic 
capacity, and its contained air is subjected to a pressure 
greater than that of the atmosphere, and rushes out by 
the same channels through which it entered. This is 
an ordinary expiration, and these two acts repeated 
rhythmically give tidal respiration. If respiration is 
rapid, i. e., so rapid that the thorax dilates more rapidly 
than air can enter through the respiratory tract to 
equalize pressure, the force of atmospheric resistence 
must be added to the above. This in tidal breathing is 
nominal, but in laryngeal or similar obstruction it is 
most marked and is shown by the sinking in of the 
intercostal spaces during inspiration. 
Beginning of Respiration. Unlike the heart, 
which beats for months in utero, the lungs first get 
their fill at birth. A child in utero lies with arched 
spine and compressed abdomen and chest. The legs 
being folded on the abdomen press upon the abdominal 
viscera forcing the abdominal contents up into the 
concavity of the diaphragm and causing it almost to 
fill the thorax. When after expulsion from the womb 
the child is allowed as it were, to unfold, the abdomi- 
nal contents first assume their normal position and the 
diaphragm descending with them leaves the thorax 
almost empty. This would tend to create a vacuum in 
the chest but for the fact that the lungs which have 
hitherto lain in the upper part of the chest unexpanded, 
are now filled by the force of the atmospheric air PHYSIOLOGY 
133 134 
PHYSIOLOGY 
which rushes in through the trachea, etc., and by the 
force of its pressure distends the lung as the diaphragm 
recedes. At this time by a combined series of reflexes 
which we will later appreciate an inspiration is initi- 
ated, and breathing begins. This reflex is in all 
probability due primarily to the stimulus of cold, the 
relative difference in temperature between the uterine 
cavity and the average bed room being immense. We 
all know the deep inspiratory effort induced by the 
shower bath or the pranks of the rural swimming pool. 
At all events there is no method of producing lively 
respiratory movements in the new born child compared 
with that of the sudden sprinkling with cold water 
(atelectasis). 
The elastic traction of the lung can be best under- 
stood by an illustration. Let us take for example a 
large open glass bell jar, which will represent the 
thorax, pass through the cork in the neck of this a 
forked glass tube which will represent the trachea. 
Over the mouth of each arm of this tube tie a collapsed 
rubber toy balloon and then tie a sheet of thin rubber 
over the mouth of the glass jar, with a string fastened 
to its centre on the outside. Now, from a stop-cock 
exhaust the air in the bell-jar, and we will see the dia- 
phragm rise and will also see the balloons gradually 
become distended until they fill the entire space in the 
bell-jar. If now we pull on the string and depress the 
diaphragm, we see the balloons follow the diaphragm 
in its movements, while air rushes in and out of the 
open end of the forked tube as the diaphragm rises and 
falls. The balloons represent the lungs in their 
normal position, and whatsoever of space exists be- 
tween them and the walls of the glass jar, repre- 
sents the so-called pleural “cavity”. Now open 
the stop-cock and we will see the air rush in PHYSIOLOGY 
135 136 
PHYSIOLOGY 
here, and the balloons will gradually collapse to their 
original size, while air will, in equal ratio, rush out at 
the open end of the forked tube. This the balloons 
will do when the stop-cock is open, whether the dia- 
phragrn be high or low, but more powerfully when 
low. The deductions from this are simple—the lungs 
are distended and held against the parietal wall by 
atmospheric pressure, and in this state their elastic 
elements are put upon the stretch, less at expiration 
than at inspiration, but great at all times. If the chest 
be opened and atmospheric pressure be the same on 
both sides of the visceral pleura, the lung will collapse 
owing to its desire to return to a state of elastic equi- 
librium. The constant force which it exerts to leave 
the inside of the thorax and its contained organs, 
against atmospheric pressure, is its elastic traction. 
The influence of the traction of the lungs in the dila- 
tion of the heart may be studied with the same appa- 
ratus. Let us take a soft compressible rubber bulb 
provided wdth a rubber tube which passes out through 
the diaphragm and ends in a fluid in a glass. Now, 
as before, exhaust the air in the glass bell-jar through 
the cock and we will see the balloons expand and fit 
around the rubber bulb which also dilates from the 
rising of the fluid into it through the tube. Now pull 
down the diaphragm and note the result. As the dia- 
phragm descends more fluid rises in the bulb ; for 
when the internal capacity of the bell-jar is increased, 
atmospheric pressure in it falls (temporarily) and the 
normal pressure on the fluid in the glass forces the 
fluid up through the tube into the bulb. Conversely, 
when the diaphragm is pushed up and the pressure con- 
sequently rises, the fluid will fall to a slight extent, but 
only to a slight extent, for the elastic traction of the bal- 
loons keeps the bulb and its tube dilated and full at all PHYSIOLOGY 
137 138 
PHYSIOLOGY 
times. If a puncture could be made in the bulb, the 
fluid would pass through it into the bell-jar till the 
glass was drained, while the balloons would recede 
as the fluid came in. We can see from the anal- 
ogy how the traction of the lung on the heart keeps 
up a tendency to dilation, and how the blood is forced 
in from the large veins which come from without the 
thorax, and how this aids the right auricle and in turn 
the right ventricle. We can see, in addition to this, 
how the same influences on the pulmonary vessels 
would produce a fullness of these vessels during inspi- 
ration, and pressure on them during expiration, which 
pressure, as the pulmonary valves will allow the blood 
to flow but one way, drives the blood into the pulmo- 
nary veins and left auricle. 
The nerve mechanism of respiration. Any one who 
will experiment on himself will see that respiration is 
a voluntary function, whenever he so wills to use it. 
At the same time he cannot fail to see that at the 
moment he takes his mind off of its direction it lapses 
into an automatic movement which is equal to his 
needs, and gives him no concern. Upon further trial 
he will, however, learn that while his voluntary 
control extends to the point of stopping respiration, he 
cannot stop it long ; a time soon comes when in spite 
of the will it must start again. It is in fact involun- 
tary function, although the muscles that produce it are 
voluntary muscles. Its control, like that of all great 
functions, is presided over by a special nerve centre. 
The respiratory centre lies on the floor of the fourth 
ventricle, in close proximity to and perhaps involving 
the nucleus of the vagus. In ordinary or tidal 
breathing it is stimulated to action b\r afferent im- 
pulses received from the lung through the vagus. 
These impulses come from nerve terminals in the PHYSIOLOGY 
139 PHYSIOLOGY 
substance of the lung- which respond to pressure 
stimuli. When an expiration is made, and intra-pul- 
monary pressure rises, a terminal which will respond 
to this degree of pressure is stimulated, and sends an 
impulse to the centre. This impulse calls for a reflex 
movement, which is answered as follows :-Impulses 
go down the cord to the roots that make up the phrenic 
nerve, calling for the action of the diaphragm, others 
to those intercostal nerves that stimulate to action the 
external intercostal muscles, and still others to the 
posterior dorsal nerves that call into play the levatores 
costarum, &c. This produces, as we know, an inspi- 
ration ; and as intra-pulmonary pressure falls, a ter- 
minal in the lung which will respond to this degree of 
pressure is excited to action, and sends an impulse to 
the center which is answered by a cessation of the 
above muscular acts, and the influence of gravity on 
the elevated chest, &c., aided by the elasticity of the 
lungs, cartilages and abdominal muscles causes an expi- 
ration. This, as we saw, produces an inspiration, and 
thus automatic reflex respiration is maintained. When 
more than ordinary respiratory effort is .needed, the 
centre by other impulses down the cord calls the 
abdominal anl other expiratory muscles into action. 
It also, if needed, calls the accessory inspiratory muscles 
to the aid of those ordinarily used. As we know, we 
can inhibit the response to these impulses by the will, 
but whenever we relieve the centre of this inhibition 
it will act. If the action of the will in checking respi- 
ration continues too long, another influence on the 
centre comes into play—the centre can be stimulated 
directly. As we will learn, when respiration is checked 
COo accumulates in the blood. This is the great 
excitant of the respiratory centre (as well as of the 141 
PHYSIOLOGY 142 
PHYSIOLOGY 
vaso-motor) and when a sufficient amount of it has 
accumulated in the blood the centre is so strongly 
influenced that, in spite of the inhibition of the will, it 
sends out its call to the muscles and respiration begins. 
This is called central or “chemical” respiration. 
Experiments in proof of the foregoing may be made 
as follows : (1) Cut one vagus and little or no effect 
on respiration is produced ; (2) cut both vagi and for a 
time respiration ceases, and then begins, by a series of 
deep gasping efforts that fill the lungs to their utmost, 
but the rate of respiration is only half the normal ; (3) 
stimulate the central end of the cut vagus and respiration 
is increased. The following proof of the susceptibility 
of the centre to C02 exists. Tie two dogs on a table 
side by side back down, and call them A and B. An- 
aesthetize them, and cut the common carotid of each, 
next the other, and insert into these cut vessels tubes 
so that the blood from the central end of each vessel 
will flow into the distal end of its fellow. Now ligate 
the other carotid of each dog. Now the brain of each 
dog is supplied by the blood of its fellow ; and if we 
ligate the trachea of B we will find that he continues 
to rest easily, while his fellow A, who gets his C02, 
struggles violently and makes forced respiratory 
efforts. 
Subordinate centres for respiratory efforts seem to 
exist in the ganglionic cells of the spinal cord at the 
level of the distribution of the various nerves that 
supply the respiratory muscles. Cut the cord in a 
frog just below the medulla and respiration ceases ; 
but if the cord be cut at the same level in a frog 
whose centres have been rendered very irritable by the 
injection of strychnine, feeble respiratory efforts will 
be made for some time. PHYSIOLOGY 
143 144 
PHYSIOLOGY 
Modified respiratory movements. A cough is an 
expiratory blast or series of blasts discharged reflexly 
from the centre by impulses received through the 
vagus. While usually from the terminals of the vagus 
in the larynx, trachea, bronchi or lungs, other branches 
may produce it, as “ear-cough” from the auricular 
branch, “stomach-cough” from the gastric, and ‘.‘palate- 
cough” from the pharyngeal branches. Hawking is 
but a modified voluntary cough, to remove mucus, &c., 
from the tract. Sneezing is produced by an expiratory 
blast through the nose, preceded by a slow involuntary 
inspiratory spasm and opening of the post-nasal pas- 
sages. The impulse usually comes from the nasal or 
other neighboring branches of the fifth cranial. 
Snoring is the result of a relaxed pendulous soft 
palate, which vibrates with each expiratory blast. 
Hiccough is the result of an inspiratory spasm of the 
diaphragm, with closure of the glottis. It is the 
result of gastric irritation of the vagus terminals, or of 
irritation of the centre by toxic matters, urea, bile, &c., 
in the blood. 
Among the reflex influences on the respiratory 
centre, other than those just cited, may be mentioned : 
(1) The spasmodic inspiratory effort produced by the 
sudden application of surface cold, which is of such 
value in starting respiration in the new-born; (2) The 
reflex inhibition of respiration, through the glosso- 
pharyngeal, that occurs during deglutition; (3) The 
emotional inhibitory reflex that occurs in a crying 
child, “holding its breath;” and (4) The inspiratory 
inhibition and expiratory spasm that occurs from 
stimulation of the superior laryngeal by a foreign 
body at the rima glottidis. 
Capacity of the human thorax. The sum total of PHYSIOLOGY 
145 146 
PHYSIOLOGY 
the air capable of being- taken into the thoracic cavity 
may be divided as follows: 
Tidal Air—That going in and out during ordinary res- 
piration 20 
Complemental Air—That which can be taken in after an 
ordinary inspiration 100 
Reserve Air—That which can be expelled after an ordi- 
nary expiration 100 
Residual Air—That remaining in the lung after the most 
complete expiration 100 
320 
Cubic Inches. 
This is, of course, simply an average capacity, some 
are below it and some largely above it. The estimate 
of 20 c. i. for tidal air is rather low. 
The vital capacity is the measure of the greatest 
amount of air that can be taken into the lungs and 
expelled at a forced expiration. It is the sum of the 
tidal, complemental and reserve air or about 220 cubic 
inches. (Spirometer.) 
As residual air cannot be expelled during life, but 
only after opening the plural cavities, it does not figure 
in the vital capacity. 
The circumstances which chiefly affect the vital 
capacity are: (1) The height, each inch above the 
normal (5 ft. 8 in.) giving an increase of about 6 cu. in.; 
(2) The body weight, when above normal, is accompa- 
nied by a deposit of fat in the thorax which decreases 
vital capacity; (3) The age, in youth from deficient 
size and muscular power, after 35 from increasing 
stiffness of the thorax, &c.; (4) Sex, which both by 
influencing size and deficiency of muscular develop- 
ment, reduces it. Among pathological conditions 
disease of the thoracic and abdominal organs disturb 
it most. 
Diffusion of gases. The law of diffusion is a 
necessary factor in the performance of the respiratory PHYSIOLOGY 148 
PHYSIOLOGY 
function. The air that is habitually found in the lung 
(the sum of the residual, reserve and tidal air) is 
changed only to the extent of 1-8 or 1-10 at each res- 
piratory effort. We have seen that the tidal air is but 
from 20-25 c. i. and as this will not fill the trachea 
and larger bronchi it is apparent that none could ever 
reach the lung were other agencies not at work. In 
short without diffusion as an aid, forced respiration 
would be constantly demanded. 
The number of respirations is influenced by age and 
many other causes. At birth it is about 40 per minute 
and at maturity 20 ; from which time to middle life it 
is 18, and thence on it is slightly increased. Influenc- 
ing conditions, other than age are, (1) an active or 
passive condition, as being in motion, asleep or awake; 
(2) position of the body, whether recumbent sitting or 
standing ; (3) disease, &c. Temperature makes but 
slight change so long as we can regulate body heat, 
but beyond this point it increases very rapidly, although 
not proportionately. 
Relation of respiration to pulse-beat. Ordinarily 
the ratio existing between these functions is 4 to 1, or 
sto 1, in favor of the heart. Emotional excitement 
increases both pulse and respiration, but does not ma- 
terially alter the ratio. Upon exertion, however, the 
increased production of C02 gives rise to more irrita- 
bility of the respiratory centre than of the cardiac, and 
breathing is increased in greater ratio. On the con- 
trary, in fever the hot blood as well as the increased 
C02 influences the centres, and as a rule, in simple fever 
the pulse is relatively more rapid. Some diseases, like 
rheumatism, give a very rapid pulse in proportion to 
the respiration ; others, like pneumonia, an excessive 
respiratory ratio ; but the general rule holds that at 
least in the early stages of disease a serious discrepancy PHYSIOLOGY 
149 150 
PHYSIOLOGY 
in the above ratio indicates some trouble in the nerve 
centres, i. e., some cerebral disorder. 
The modes of breathing differ in the sexes, being 
chiefly abdominal or diaphragmatic in men, and costal 
or thoracic in women. The cause of this variation is 
not altogether understood, but it probably arises from 
the following combination of influences, viz., the in- 
fluences of maternity, which requires thoracic breath- 
ing, the influence of corset or dress compression 
requiring the same, and the relative rigidity of the 
thorax in man, which also points to the divergence we 
see existing. 
Difference in inspired and expired air. (1) Chem- 
ical changes. Everywhere on the earth’s surface at- 
mospheric (inspired) air gives the following analysis 
(volume), under which we have placed that of expired 
air for comparison. ' 
Oxygen (O) Nitrogen (N) Carbon Dioxide (COa) 
Inspired Air 21 79 .04 per cent. 
Expired Air 16.S 79 4.5 (?)percent. 
The analysis of expired air under the atmospheric or 
inspired air shows a marked loss of O and a decided 
gain in C02, the exact ratio between the oxygen re- 
tained and the C02 given out being 4.78 to 4.39. 
Observe that C02 is in atmospheric air at the rate of 
only 4 parts in 10,000. An increase to 7 parts is dele- 
terious, 10 parts very injurious, and much above this 
rapidly toxic. This is not due so much to the C02 
per se, as to certain organic compounds with which it 
is associated, and of which it is our best measure. 
These organic compounds probably belong to the class 
leucomaines. In addition to these, we have in expired 
air broken down epithelium, fatty matters, etc., with 
sometimes H2S and other mephitic gases absorbed from 
the intestine by the blood. PHYSIOLOGY 
151 152 
PHYSIOLOGY 
(2) Changes in temperature. Expired air is in 
temperature always very close to body beat. Whether 
inspired at a temperature below the freezing- point, or 
at a temperature far above the body heat, it will be ex- 
pired but little above, or below, as the case may be. 
If the air be warmed, as it usually is, the amount by 
volume is seeming-ly increased, althoug-h owing- to more 
O being- absorbed than C02 given off, it is really by 
volume 1-50 less. 
(3) Changes in moisture. During- ordinary respira- 
tion expired air is saturated with moisture. The per- 
centage falls during- rapid respiration, especially if the 
inspired air be warm and dry. 
The gaseous interchange in the lungs. The ex- 
change between the gases of the blood and those of the 
air in the pulmonary alveoli is not perfectly under- 
stood, but enough is known to render it certain that it 
is primarily dependent upon the chemical affinity of the 
haemoglobin for O. The C02 on the contrary is given 
up to the air of the alveoli by a process of simple dif- 
fusion, and at a rate dependent upon the difference in 
tension between the CO2 in the air of the lung and in 
the blood of the capillaries. The belief of some (Bohr) 
that the glandular cells of the alveoli play a part in 
the dissociation of these gases is not altogether devoid 
of support. 
The gaseous interchange in the tissues. Internal 
respiration is carried on under very different conditions 
from those we see existing in the lung. There is no 
varying pressure as in the respiratory act. The avid- 
ity with which O is seized upon by the protoplasm of 
the tissues and enters into their molecular structure 
leaves little or no oxygen pressure in the tissues. On 
the contrary the C02 formed, having no great affinity 
for any of the compounds of the tissues, accumulates, PHYSIOLOGY 154 
PHYSIOLOGY 
and as a result C02 tension in the tissues is high till 
relieved by the passing blood. The most active 
sources of C02 are the muscles and the observation 
that C02 will still be given off in a muscle if a simple 
saline solution be substituted for the blood-stream 
leads us to the belief that the O in the protoplasmic 
molecule is not used for immediate oxidation purposes, 
but is added to the general reserve fund of the body, 
to be used as needed. 
Apnoea, Dyspnoea, Asphyxia, &c. When a person 
by will power makes for some moments deep but rapid 
respiratory efforts, such a saturation of the haemoglobin 
with O occurs that the respiratory centre is depressed 
(satisfied) to the point that it will not for a time send 
out impulses to breathe, and we call this condition 
apnoea. Whenever the condition of ordinary easy tidal 
breathing, called eupncea, is passed, and many of the 
accessory muscles of respiration have to be called into 
play, we call this state dyspnoea. If this condition 
progresses till, in spite of the intense stimulation of 
the respiratory centre by the accumulation of C02, and 
in spite of the discharge of the most intense respiratory 
impulses to all muscles that can aid in relief, sufficient 
O to maintain the vitality of the nerve centres and 
other tissues is not obtainable, the subject dies, and we 
call such a death asphyxia. Note that the conditions 
here are such that if after apparent death we relieve 
the cause of the asphyxia and supply the centres with 
O before molecular death has taken place, we can 
restore life. As, however, the respiratory centres can 
make no effort to supply O, and will soon lose their 
remaining vitality without it, artificial respiration or 
some other method of giving O at once is the only hope 
in cases of strangulation, drowning, &c. The stages 
of death by asphyxia are, (1) labored inspiratory move- PHYSIOLOGY 
155 156 
PHYSIOLOGY 
merits, then (2) labored expiratory efforts, ending- in 
(3) general muscular spasm which is succeeded by the 
(4) relaxation of exhaustion, and (5) a final weak in- 
spiratory spasm. A full right heart and an almost 
empty arterial system are evidences of this form of 
death, these conditions being produced by vaso-motor 
spasm, the result of C02 poisoning. 
The respiration of foreign gases. The indifferent 
gases are CH4, H, and N, for they will not unite with 
the corpuscles. The 'poisonous gases CO and CNH 
form permanent compounds with haemoglobin. This 
is itself the cause of death with the former, but the 
latter kills directly. Of the narcotic gases, C02, in a 
pure state, is not fatal up to a large per cent.; NaO, 
“laughing gas,” forms temporary union with haemo- 
globin with the production of temporary anaesthesia, 
and if continued it kills. Of the reducing' gases ELS 
disturbs the oxygen of the corpuscles, forming ELO 
and S ; while PEL, AsEL, and SbEL, absorb O and 
form acids, and CJSL decomposes the blood. The 
irrespirable gases NH;i, Cl, Br, I and many various 
acid vapors cause spasmodic closure of the glottis, by 
irritation of the mucous membrane of the respiratory 
tract. 
Cutaneous respiration. With the water of perspira- 
tion given off by the skin will be found from one to 
two, drachms per day of C02. The amount of O taken in 
by the skin is still less. The water given off by the 
skin is usually one-third more than that given off by 
the lungs, while the C02 is only about 1-200 of that 
by the lungs. These ratios vary infinitely, depending 
upon exercise, temperature, etc. 
The contamination of air by a person varies with the 
conditions of sleep, rest, exertion, sex, age, etc. As 
engaged in the usual duties of life an adult man pro- PHYSIOLOGY 
157 158 
PHYSIOLOGY 
duces hourly.Ja-of a cu. ft. of CCb. This is gotten by 
multiplying the tidal capacity (20) by the number of 
respirations (20 X 60), reducing to feet and finding 
what proportion (4.38) of this is C02. The amount of 
vitiation allowed is .06 per cent, of expired C02,’ or 6 
parts only in 10000. 
CHAPTER VII. 
FOOD AND DIGESTION. 
FOOD. 
The food of all animals including man can be divided 
into but four kinds, three of which correspond to the 
chemical bases of the body, studied as ■proteids carbo- 
hydrates and fats ; to which we may add the inorganic 
foods, water and the various essential salts. 
The proteid foods include all flesh, other than fat, 
milk and its derivatives, eg-gs, and the reproductive 
parts of grains, fruits and vegetables. The general 
percentage composition of the proteids is, as we have 
seen before, CsoH7N18023S2. Flesh may be obtained 
from the ox, sheep, pig, wild animals, domestic fowls, 
fish, etc. It is nearly 75 per cent water, and contains 
as its nutritious elements myosin and other globulins, 
serum albumen and albumeuoid principles. Milk is 
intended chiefly for the use of the young, and contains 
all the elements of a typical food. Its various casein 
derivatives, curd, clabber and cheese are much more 
rich in proteid constituents than milk itself. Eggs, 
as foods, represent to the embryo of the oviparous ani- 
mals what milk does to the mammalia. Its food value 
lies in the egg albumen and vitellin it contains. The 
proteid elements of the cereals lies in the gluten, but PHYSIOLOGY 
159 160 
PHYSIOLOGY 
the leguminous seeds contain, in the form of legumin,, 
twice as much nitrogenous matter. 
The carbohydrate foods include, as we saw, the 
starches and sugars, with their various modifications. 
Starch is found as the chief constituent of the cereals, 
maize, potatoes, etc., while sugar (saccharose) is abund- 
ant in the cane and beet. The amount of sugar in 
even the sweetest fruits is relatively small, and sugar 
from this source plays no practical part in the diet, 
but the very essential vegetable acids these fruits con- 
tain make them useful foods. 
The fats and oils, as foods, are found in butter, 
bacon, lard, suet, and the fixed vegetable oils, as cot- 
ton-seed oil, olive oil, etc. The animal products con- 
tain olein, palmitiu and stearin, but the vegetable oils, 
as a rule, contain no stearin. 
The inorganic foods. With the exception of water, 
the members of this class, while imperatively needed, 
are needed in extremely small amounts, so small that 
in eating the general food allowance they are incident- 
ally obtained. Sodium chloride is perhaps an excep- 
tion, so much being required that it is also taken as a 
condiment. Calcium and potassium salts are found in 
both meats and vegetable foods. 
The artificial preparation of foods, to aid their diges- 
tibility, is limited with most foods to cooking. Heat 
applied to meats, either as dry heat or hot water, coagu- 
lates the surface albumen and causes the retention of 
the more volatile essences. The further heating coagu- 
lates all the albumen, etc., and gelatinizes the connect- 
ive tissue, in both cases rendering them more digest- 
ible. If the essences are to be extracted for food, 
obviously a temperature below boiling must be applied, 
while salt should be added to dissolve out the globu- 
lins, etc. Starches are rendered much more digestible PHYSIOLOGY 
161 162 
PHYSIOLOGY 
by boiling, the starch granules swelling- and bursting 
their cellulose envelopes. Bread is made more open 
and porous by the expansion of the g-ases in its doug-by 
substance under the influence of heat. The contained 
g-ases may be air worked in mechanically, but it is 
usually C02 evolved from bicarbonate of soda or gen- 
erated by the action of the yeast plant (torula cerevi- 
siae) on the sugar of the doug-h. The coagulation of 
the gluten sets the rise. 
Variations in diet. The conditions of diet for health 
require that the total quantity of food be not only suffi- 
cient, but in the proper proportion and digestible. The 
amount of water free food needed for a man at ordinary 
work, is about 24 oz. per day, in about the following- 
proportions : proteid food 1 part, fatty foods .6 of a 
part, and carbohydrates 3.5 parts. As we will see in the 
study of metabolism, the proteids subserve a function 
that cannot be assumed by the others, while the 
carbohydrates and fats, in proper proportion, are more 
or less interchangeable. 
DIGESTION. 
With the exception of water, the salts, and various 
forms of fruit sugars, the foods previously mentioned 
have to be modified in constitution before they can be 
taken into the system and made a part of its substance. 
The chief function of the digestive organs is to render 
capable of absorption the materials otherwise not avail- 
able, and all the mechanical aids, as mastication, 
deglutition, insalivation, &c., are subservient to this 
chief end. As this end is practically obtained by con- 
verting colloidal bodies into crystalloidal bodies, this 
may be said to be the aim of chemical digestion. These 
processes differ in the various parts of the alimentary 
tract, and we accordingly divide the tract into parts as 
indicated by functional differences existing. Taking 163 
PHYSIOLOGY 164 
PHYSIOLOGY 
the reaction of the digestive medium as a basis of 
division, we get mouth, stomach, and intestinal diges- 
tion. 
I. Mouth digestion, as it is called, includes that 
series of digestive phenomena which take place between 
the lips and the cardiac end of the stomach. It there- 
fore anatomically includes the mechanical grinding of 
the food, called mastication, and that elaborate reflex 
act of swallowing, called deglutition, as well as the 
special digestive act, insalivation, peculiar to this part 
of the tract. 
Mastication is performed by crushing and grind- 
ing the food between the teeth of the upper and lower 
jaw. Civilized habits have, in man, rendered the 
prehensile incisors and tearing canines almost function- 
less, the premolars and molars doing the bulk of the 
work. The vertical motion of the lower jaw, which 
crushes, is made by the action of the temporal, mas- 
seter and internal pterygoid, while the grinding action 
is produced by the alternate (single and conjoined) 
action of the external pterygoid. All muscles of this 
group are supplied by motor branches of the sth cranial. 
The depressors of the lower jaw are the mylo-hyoid* 
(5), genio-hyoid (12), and anterior (5), and posterior (7), 
bellies of the digastric. As the food is crushed and 
ground it is driven from between the teeth and requires 
to be replaced. The internal muscle of replacement is 
the tongue or lingualis (12), while external replacement 
is done by the orbicularis-oris (7) and buccinater (7). 
Insalivation includes the proper secretion of saliva 
and its admixture with the food. Saliva is the essen- 
tial digestive secretion of the mouth, and contains the 
hydrolytic ferment 'ptyalin. It is produced by the 
following glands in decreasing amounts ; parotid. 
*These numbers refer to the cranial nerve supply. PHYSIOLOGY 166 
PHYSIOLOGY 
subtnaxillary, sub-lingual and the scattered mucous 
glands. 
The parotid gland, located around the glenoid fossa, 
discharges its secretion by Stenson’s duct, which opens 
on the mucous surface of the mouth, opposite the 
second molar tooth of the upper jaw. It is a “serous" 
or true salivary gland and is the chief source of the 
ferment ptyalin. Its secretion contains also small 
quantities of carbonate of lime (calculi) in solution, and 
a variable amount of sulpho-cyanide of potash. 
The submaxillary gland lies in the subtnaxillary fossa 
and its secretion is discharged by Wharton’s duct, which 
opens on the apex of the papilla under the tongue. This 
gland is a mixed one, part of its elements being mucous 
and part serous. This muco-salivary secretion contains 
ptyalin, but not in the same proportion as the secretion 
of the parotid. 
The sublingual gland is located, as its name implies, 
under the tongue, and opens by a number of small ducts 
(Rivini)on the floor of the mouth, one larger duct called 
the duct of Bartholini joining the sub-maxillary duct. 
This is strictly a mucous gland and furnishes a strongly 
alkaline fluid rich in mucin, but containing no ptyalin. 
The mucous glands are scattered over the entire 
buccal surface, tongue and lips, and vary from the size 
of a pins-head to that of a pea. Bike the larger sublin- 
gual gland, they secrete a product called mucinogen 
which is converted into mucin, the chief constituent of 
mucus, but they secrete no ptyalin. 
The saliva, as we find it, is the mixed product of all 
of these glands. It is a_yiscid alkaline fluid containing 
about .s_per cent, of solid matter and having a specific 
gravity of about 1008. The chief organic constituents 
of saliva ar^mucin and ptyalin, while as 
morphological elements it bears^salivary corpuscles. PHYSIOLOGY 
167 168 
PHYSIOLOGY 
epithelial debris and of many kinds. The 
amount secreted daily varies exceedingly, ranging from 
a half to three or more pints. 
Nerve supply of the salivary glands. The usual 
impulses that excite these glands to action are sent from 
the nerve terminals located in the raucous membrane of 
the tongue, buccal wall and pharynx. The afferent 
fibres that call for this reflex run in the glosso-pharyn- 
geal (chorda-tympani ?) and the lingual and buccal 
branches of the fifth cranial ; the centre for salivary 
secretion probably lying in the nucleus of the former. 
The efferent impulses to these glands follow separate 
routes, one being through the sympathetic and the other 
through acranial nerve. The sympathetic gives to the 
gland secretory and vaso-constrictor fibres, while the 
cranial furnishes secretory and vaso-inhibitory fibres. 
The parotid gland receives fibres from the glosso- 
pharyngeal through the otic g'anglion and (probably) 
from the carotid plexus of the sympathetic. The siih- 
maxillary and sub lingual each receive fibres from the 
chordatympani(thirteenth cranial)and from the internal 
maxillary plexus of the sympathetic. As the stimula- 
tion of the sympathetic calls for secretion with a poor 
blood supply, the resulting saliva, called “sympathetic 
saliva,” is thick and scanty, being overloaded with 
solids ; while the stimulation of the chorda_-tympani, 
producing dilation with secretion, gives as “chorda 
saliva,” a thin and watery, but abundant output. 
Central influences as well as gastric irritation will 
produce a reflex flow of saliva, as evidenced by the “wat- 
ering of the mouth” when agreeable viands are smelled, 
and the flow of saliva that precedes vomiting. The 
various nerve connections of these glands seem to exert 
an inhibitory influence on them, for when cut off from 
all nerve control they begin and secrete continuously a PHYSIOLOGY 
169 170 
PHYSIOLOGY 
“paralytic saliva,” till atrophic changes set in from 
exhaustion. Atropia paralyzes the secretory terminals 
in the glands but does not influence the vaso-motor 
terminals, so that we may get, on stimulating the 
chorda a vaso-dilation of the vessels in the gland, but 
no saliva. 
The changes in the gland cells during rest and during 
secretion are most marked. These changes to a certain 
extent occur in all glands, salivary and otherwise, but 
the process differs with the gland. In the serous or 
true salivary glands the granular protoplasm accumu- 
lates in cells during the period of rest, and the cells 
swell until they almost obliterate the lumen. After a 
period of activity the cells are smaller and the small 
amount of granular matter left is found next the lumen, 
the remainder being clear. In the mucous glands the 
cells during the period of rest become filled with clear 
mucigen, which presses the protoplasmic elements and 
nucleus aside. During activity the mucigen is con- 
verted into mucin and discharged, and the cell becomes 
smaller. 
The chemistry of insalivation. The amylolytic or 
diastasic ferment fityalin, in an alkaline medium such 
as the mouth, changes starch into sugar. It does this 
by causing the starch to take up water and hence this 
action is also called a hydro-lytic action. The starch 
grains to be acted upon have an external envelope of 
cellulose and internal to this is the granulose or true 
starch. Unless this envelope be broken by either 
crushing or boiling, the ferment can not act on the 
starch. The resulting product of this diastasic action 
is the sugar maltose and dextrin, a starch which is 
converted into maltose later. 
This power of converting’ starch into sugar is not 
limited to the animal ferments, as we find that the PHYSIOLOGY 
171 172 
PHYSIOLOGY 
vegetable ferment “diastase,” as found in germinat- 
ing barley and other cereals, possess the same powers. 
Being equally efficacious and much cheaper commercial 
diastase and malts entirely displace ptyalin in therapy. 
Deglutition. After the fluid saliva has been mixed 
in with the food, softening it and otherwise acting 
upon it, there arises, from experience, a sense of being 
“ready,” and we voluntarily “swallow.” We must 
not suppose from this seeming control of the act that 
deglutition is voluntary ; only the first step is volun- 
tary, and that only so long as we have some food, saliva, 
or other substance in the mouth wherewith to excite 
the reflex. 
The voluntary part of the process is performed by 
the lingualis muscle or tongue, and is as follows : 
The tongue is formed into a scoop, and taking the food 
upon its upper surface it forces it against the roof of 
the mouth where it is moulded into an oval bolus. The 
tip of the tongue is now turned up in front of the bolus, 
and its upper longitudinal fibres contracting, it is 
drawn back, bringing the food against the pillars of 
the fauces, and the reflex to complete the act is thereby 
excited. 
The involuntary or reflex part of the act is an elab- 
orate effort, and is produced as follows : The sub- 
stance carried back by the tongue is brought in contact 
with the sensory terminals of the palatine nerves in 
the pillars of the fauces and soft palate. These are 
stimulated and send an afferent impulse up through 
the spheno-palatine ganglia and middle root of the fifth, 
to the centre in the medulla. The reflex efferent 
impulses are sent out through the pharyngeal branches 
of the vagus to the palato-glossus and palato-pharyn- 
geus, and through the facial by way of the (vidian) 
spheno-palatine ganglia to the muscles of the soft PHYSIOLOGY 
173 PHYSIOLOGY 
palate. The above group of muscles now contract and 
narrow the ithmus of the fauces (sphincter) from before 
backward. As the bolus of food touches the post- 
pharyngeal wall it excites a reflex (entirely through 
the vagus) for the contraction of the pharyngeal con- 
strictors, and these respond in order from above down, 
the pressure of the food in the lower causing the action 
of the upper, etc. In precisely the same way it tra- 
verses the oesophagus, till at the cardiac orifice of the 
stomach the contraction wave of the oesophagus merges 
into the movements of the stomach. 
At the instant at which the faucial reflex was excited, 
elevators of the larvnx were stimulated to draw that 
organ upward under the base of tongue, thus turning 
the epiglottis down and over the rima glottidis. The 
glosso-pharyngeal terminals also stimulated at the 
same instant inhibit the respiratory function till 
swallowing is completed. 
The oesophagus is the part of the alimentary canal 
that lies between the pharynx and stomach. It 
consists of four coats ; a thin external fibrous coat ; a 
muscular coat, containing an outer longitudinal and an 
inner circular layer; a submucous and a mucous layer. 
The muscular fibres are striated above, and gradually 
become non-striated below, where they continue on as 
the muscular fibres of the stomach. Squamous epi- 
thelium lines this tube and mucous glands open freely 
on its surface. 
11. Stomach digestion. This includes all digestive 
processes taking place between the cardiac and pyloric 
orifices of the stomach. 
The stomach, the principal organ of digestion, is a 
fusiform sac, curved on itself, and holding when 
reasonably full a]jout-twQ .quarts. 
It consists of four coats, arranged as follows : an PHYSIOLOGY 
175 176 
PHYSIOLOGY 
internal or mucous coat, a submucous coat, a muscular 
coat, and a serous or endothelial coat. 
(1) The mucous coat consists of a delicate connective 
tissue reticulum thrown into folds and pits, covered 
throughout with columnar epithelium (goblet cells) on 
a basement membrane, and supporting glands of 
several kinds, blood vessels, lymphatics and muscularis 
mucosae. 
These glands are of two kinds, one found chiefly in 
the cardiac end of the stomach or fundus, and called 
“fundus glands,” and the other in the pyloric end of 
the stomach, called “pyloric glands.” 
The fundus or peptic glands are multiple tubular 
glands, and, within the basement membrane below the 
short duct, we have two kinds of cells, central and 
parietal. 
The central cells are believed to be the source of the 
special ferment of the stomach, pepsin, which is here 
secreted as pepsinogen and afterwards converted into 
the above. The function of the parietal cells, often 
improperly called peptic cells, will be considered later. 
The pyloric or mucous gknids, not so abundant as 
the foregoing, are confined to the pyloric end of the 
stomach, and are continuous through the pyloric orifice 
with Brunner’s glands in the duodenum. The lumen 
of the ducts and tubes is quite large, and lined with a 
cubical epithelium that corresponds to the central cells 
of the fundus glands. They secrete mucus and 
possibly some ferment. 
The muscularis mucosae encircles by circular and 
longitudinal fibres the deeper parts of these glands, 
and by periodic contractions empties them of their con- 
tents. 
Blood vessels run into the honey-comb like processes 
of raucous membrane between the glands, and lym- 177 
PHYSIOLOGY 178 
PHYSIOLOGY 
phatics encircle the tubes of the glands and their 
necks. 
(2) The sub-mucous coat. An areolar reticulum 
lying below the mucous coat and containing the larger 
vessels which supply the glands and interglandular 
folds with capillaries, lymphatics, &c. Adenoid bodies 
are found especially in the pyloric region. Meisner’s 
plexus of nerves is found here, whose function is the 
control of the glandular secretions of the stomach. 
(3) The muscular coat consists of longitudinal fibres, 
continuous with those of the oesophagus and intestine, 
and circular fibres, found within the former. On the 
fundus the inner circular fibres are irregularly dis- 
posed in figure 8 loops, hence termed oblique. Between 
the outer and inner muscular layers we have Auer- 
bach’s plexus of nerves, whose function is the control 
of the peristaltic movements of the stomach. 
(4) The serous coat. A serous endothelium covering 
the surface at nearly all points. Under it lie the 
superficial lymphatics. 
The nerves of the stomach. The right vagus sup- 
plies the post. surface and the left the anterior. The 
splanchnics of the sympathetic also give it a free 
supply. The function of these nerves seems to be 
■one of regulation only, for while the ganglia of the 
stomach (Auerbach’s and Meisner’s) seem able to carry 
!on its movements and secretions properly, the stimula- 
tion of the vagus intensifies both these acts, and the 
stimulation of the sympathetic inhibits both. The 
vagus is probably the bearer of vaso-dilator, and the 
sympathetic of vaso-constrictor impulses. The emo- 
tions seem capable of influencing digestion through 
either channel. 
Mechanism of stomach digestion. When a bolus of 
food is received into the stomach at the cardiac orifice. PHYSIOLOGY 
179 PHYSIOLOGY 
the mechanical impact stimulates Auerbach’s plexus 
of nerves and excites the muscular coat to action. By 
progressive peristaltic movements the bolus is carried 
along' the greater curvature to the pylorus, and thence 
along- the lesser curvature back to the cardiac opening-. 
This grinding-, churning- movement of the org-an is 
repeated until the food is disintegrated into a grumous 
mass of broken down material called '‘'‘chyme. ” During 
all this period the pyloric orifice is closed, and it does 
not open till the more solid parts of the food are broken 
down and softened. 
The gastric secretion. The gastric juice is an al- 
most clear, colorless fluid, of acid reaction and a spe- 
cific gravity of 1002-8. It is secreted at the rate of from 
12 to 15 pints daily in man. It contains the ferment 
fief)sin as its chief organic constituent, a peculiar milk- 
curdling ferment calleSyrenni?i, and HCI to the 
amount of .2 per cent. In addition, we usuallvjind 
lactic an<Vbuty.ricacids, with salfip of lime, styla/ppot- 
ash, etc. No satisfactory explanation of the presence 
of this HCI has yet been given. It is undoubtedly 
formed from the Na Cl of the blood for the blood be- 
comes more alkaline after its secretion but further than 
this we know little. It is thought by some to be 
formed, through the dissociating influence of the parie- 
tal cells of the fundus glands but this is very doubt- 
ful. It seems to disappear in carcinoma of the stomach, 
(tropeolin test.) 
Chemistry of stomach digestion. The function of 
the gastric juice in digestion is to convert the colloidal 
proteid foods into crystalloidal, and consequently ab- 
sorbable, peptones. This is done after the following 
manner. When a proteid food is exposed under the 
proper conditions of temperature, etc., to the action of 
H Cl it is gradually changed into a substance called PHYSIOLOGY 
181 182 
PHYSIOLOGY 
acid albumin/ This acid albumin is acted upon by the 
ferment pepsin, and after a series of intermediate 
changes is converted into peptone. This elaborate 
process is but one of hydration, the peptones as we saw 
(page 56) being- the hydrides of the albumins, and 
their action is really a hydrolytic action. The essen- 
tials to this action are a proper temperature, (98.6—100 
F.) an acid medium, the mechanical disintegration of 
the tissues by the teeth and stomach movements, and 
the removal of the products of dig-estion as formed. 
Absorption in the stomach. The numerous capil- 
laries that ramify in the interg-landular folds of the 
mucous membrane of the stomach rapidly absorb the 
water, salts, sug-ar, &c., Introduced, and also the 
sug-ar and peptones formed in the stomach. The 
lymphatics aid to a certain extent in absorption. 
111. Intestinal digestion. The processes here In- 
volved extend from the pyloric end of the stomach to 
the rectum inclusive. The anatomical parts broug-ht 
into play are the duodenum and (jejunum) ileum of the 
small intestines, and the colon with its various parts, 
and the rectum, of the larg-e. We consider here also 
the glandular appendag-es of the intestines, both 
intrinsic and extrinsic. The intrinsic glands are 
those in the intestine, as Brunner’s glands, crypts of 
Ivieberkuhn, &c., while the extrinsic glands are the 
pancreas and liver. 
The small intestine consists of the same four coats 
we had in the stomach, and Meisner’s and Auerbach’s 
plexus of nerves continue as above. The muscular 
coat here has no “oblique” layer, simple circular 
fibres being internal to the longitudinal. In the duo- 
denum, just beyond the pylorus, the mucous la}7er of 
the gut is thrown into high ridges or folds, called 
valvulae conniventes, which extend around the inner PHYSIOLOGY 184 
PHYSIOLOGY 
face of the gut throughout the small intestine. They 
are most pronounced at the openings of the ducts of 
the extrinsic glands, and disappear near the ileo-coecal 
valve. We also find throughout the small intestine 
minute tit-like projections upon the mucous membrane, 
called villi. These villi are found on the valvulae con- 
niventes and other parts of the surface, down to the 
iliocoecal valve, and are covered like all parts of the 
intestine with columnar epithelium. This epithelium 
has a peculiar “rodded” appearance, and rests upon a 
basement membrane. Within this membrane ramif}T 
loops of capillaries, and within these is an open lymph 
space, from which a lymph radicle leads to the lacteals 
of the mesentery. Circular and longitudinal fibres of 
visceral muscle (muscularis muucosae) surround the 
lymph space and force its contents out at intervals. 
Brunner s glands, near the pylorus, are structurally 
and functionally much like the pyloric glands of the 
stomach. The other intrinsic glands of the intestine 
are the glands or crypts, of Lieberkuhn. These are 
-small tubular follicles located on the mucous surface 
between the villi, and sinking down into the sub- 
mucosa. They are lined with (secretory) columnar 
■cells, resting on a basement membrane around which 
is a plexus of blood vessels. These follicles, unlike 
the villi, are found not only in the small intestine but 
also in the large, almost down to the anus. As we 
saw (page 110) the solitary lymph nodes are found 
throughout the intestines, while Peyer’s “glands” are 
found in the ileum only. 
The pancreas discharges its secretion into the 
intestine a few inches below the pylorus by a duct 
which is fed by other ducts in its substance. Struct- 
urally it is somewhat like the true salivary glands, but 
softer in texture, its capsule being extremely delicate. PHYSIOLOGY 
185 PHYSIOJ.pGY 
It is fully supplied with blood vessels, lymphatics 
and nerves, pacinnian corpuscles also being- often found 
in its substance. 
Pancreatic juice may be obtained from a pancreatic 
fistula. It is a colorless, transparent, slig-htly viscid 
‘fluid of alkaline reaction, ancj, a specific gravity of 
about 10121 It contains thtrfe digestive ferments, 
trypsin, and'/steapsin, a[|rfiilk-curdling 
ferment, some proteid matters and traces of the aroma- 
tic acids leucin and tyrosin. The ferment trypsin has 
in an alkaline medium an action analogous to pepsin, 
converting- proteids into peptones. This ferment is 
formed in the pancreas as trypsinog-en or zymog-en. 
Amy lop sin is a ferment very closely resembling- ptyalin 
in its action on starches, &c. The other ferment, 
strap sin, has no analog-ue among- the enzymes, being- 
in some animals a fat-splitting- “ferment,” which 
causes the fatty acids to separate from their gdycerin 
base. In man, as in all animals, its aids in the emul- 
sification of fats, and in this assists the alkaline fluids 
of the intestine. 
The automatic secretion of the pancreas, and, as we 
shall also see, of the liver, is probably due to intrinsic 
ganglionic nerve cells. These local centres receive 
impulses from terminals in the intestine (Meisner’s) 
wdien digestion is excited by the presence of food. 
The “regulation” of these extrinsic glands is probabUT 
under the care of the vagus and sympathetic as above. 
The liver is the largest gland in the body. It con- 
sists of an external serous layer, and underneath this 
is a fibrous capsule, called the “capsule of Glisson." 
On the under side of the liver, where the great vessels 
enter, the capsule turns into the substance of the gland 
and dividing into various planes forms the framework. 
The various fibrous planes of these internal septa.. PHYSIOLOGY 188 
PHYSIOLOGY 
joining with the trabeculae from the peripheral capsule, 
divide the liver into small spaces called lobules. The 
nutrient artery of the liver is the hepatic artery, which 
entering at the fissure follows the capsule in its various 
divisions and nourishes all its parts. The blood of the 
portal vein, rich in the products of absorption, enters 
the liver and also follows the planes of internal septa, 
giving off small veinlets which run in the capsule be- 
tween the lobules, and are called interlobular veins. 
From these veins capillaries pass in toward the centre 
of the lobule to join a system of veins which run more 
or less at right angles to the interlobular veins, and 
these are called intralobular veins. Their blood is 
gathered into larger veins, often called sublobular, and 
uniting, as the hepatic veins, joins the inferior vena cava. 
The hepatic veins also carry the blood of the hepatic 
artery. In each lobule of the liver, and lying around 
the capillaries that lead from the inter- to the intra- 
lobular veins, are found the glandular cells of the 
liver. They are packed so closely around the cap- 
illaries that the border of each cell is grooved by the 
vessel. The sides of the cells that lie in contact with 
each other also contain grooves which, fitting into each 
other, form tubular channels between the cells. Into 
these “inter-cellular channels” the bile secreted by the 
cells is discharged, and being gathered into larger 
ducts leaves the liver by the hepatic duct. This hep- 
atic duct, after giving off a diverticulum to the gall 
bladder, the cystic duct, is continued on to the intestine 
as the common bile duct. 
The bile in man is an orange-colored fluid, of sweetish 
1 fitter taste, having an alkaline reaction and a specific 
"gravity of 1025 to 1030. It contains : the bile salts be- 
fore considered, glyco-cholate and tauro-cholate of 
soda ; the bile pigment bilirubin, isomeric with PHYSIOLOGY 
189 190 
PHYSIOLOGY 
haematoidin and probably derived in this form from the 
haemoglobin liberated in the spleen ; mucus derived 
from the mucous glands in the gall bladder ; a mild 
diastasic ferment ; cholesterin, &c., &c. Human bile 
on being exposed to the air or an oxidizing agent turns 
green from the oxidation of the bilirubin into biliverdin. 
The secretion of bile is constantly taking place, but 
is increased after the ingestion of food. The bile 
secreted during the interval between meals is stored 
up in the gall bladder, to be emptied by reflex mus- 
cular contraction of the bladder walls, excited by food 
in the intestine. This reflex may be intensified by 
duodenal irritants, and most of the so-called “cho- 
logogues” act simply by emptying the gall bladder 
(calomel). It is a curious fact that the secretion of 
bile is carried on with a “secretory force” that is 
greater than the force of the blood pressure in the 
capillaries of the liver. If, therefore, any obstruction 
occurs in the bile duct which prevents the outflow of 
the secreted bile, the force of secretion will cause it to 
pass into the contiguous blood vessels producing “jaun- 
dice” or icterus. 
The function of the bile is that both of a secretion 
and an excretion. As a secretion it acts: (1) on the 
mucous coat of the gut as a stimulus to peristalsis ; (2) 
both by reason of its alkalinity, and by its special 
properties it aids in emulsifying the fats; (3) it influences 
the absorptive power of the columnar cells of the villi, 
and (4) it is a mild antiseptic. As an excretion, it 
carries off with it the products of katabolic metabolism 
in the blood, &c. This is most marked in foetal life, 
where in spite of an empty intestinal tract, the bile is 
formed as regularly as after digestion begins. 
The glycogenic function of the liver is the terra 
applied to the power it has of forming- glycogen, or PHYSIOLOGY 
191 192 
PHYSIOLOGY 
animal starch, from the maltose absorbed from the 
intestines. The sugar absorbed is carried to the liver 
by the portal vein, and as it passes through the capil- 
laries it is brought under the influence of the liver 
cells and converted into glycogen, which is largely 
stored up in the liver. That the liver can, under certain 
conditions, reconvert this starch into maltose is shown 
by the experiment of Bernard as follows : Some time 
after a full meal remove the livers from two animals. 
By injecting water into the portal vein wash all the 
blood out of each. Cut into small pieces and dip the 
pieces of one into boiling water to kill all ferments, but 
leave the other unboiled. If tested some hours later the 
boiled liver will contain no sugar, but glycogen, while 
the liver in which the diastasic ferment was not killed 
will contain much sugar but no glycogen. How or 
where this glycogen is used is uncertain. 
Glycosuria or diabetes mellitus is due to free sugar in 
the systemic vessels and its elimination by the kidney. 
While a much disputed point, it seems caused by some 
vaso-raotor disturbance of the vessels of the liver, which 
so interferes with the proper conversion of maltose that 
it passes on unchanged into the general circuit. Injury 
of the vaso-motor centre, of the greater splanchnic or of 
the sympathetic ganglia in or near the pancreas will 
produce it. 
The large intestine. This gut shows the same four 
coats that we have in the small intestine and stomach, 
but in several of them changes of importance occur. 
The longitudinal fibres of the muscular coat are here 
gathered into bands whose length is less than that of the 
other coats, and this produces in the gut the sacculated 
folds peculiar to this intestine. This puckered appear- 
ance of the gut extends from the appendix to the lower 
part of the sigmoid flexure, where the fibres of the three PHYSIOLOGY 
193 194 
PHYSIOLOGY 
longitudinal bands spread out to surround the gut as in 
the small intestine. No valvulae conniventes, no villi, and 
but few lymph nodes are found in this gut, and no gdands 
except the follicles of Lieberkuhn, which are abundant. 
The rectum, while larger, has the same general struct- 
ure as the small intestine. In its upper part several 
valve-like folds of mucous membrane are found, (sphinc- 
ter of Hyrtle) and in its lower the circular fibres are de- 
veloped into a thick internal band, forming the sphincter 
ani. The fibres of the muscularis mucosae inordinately 
developed here give the appearance of an internal longi- 
tudinal layer. Striated muscular fibres radiating from 
the margin of the anus form the corrug'ator ani, or so- 
called “external sphincter.’’ 
The snccus entericus. This term applies to the 
secretion of the intrinsic intestinal glands, but as the 
secretion of the glands of Brunner is relatively insig- 
nificant, in practice it applies to the secretion from the 
crypts of Ldeberkuhn, mixed in with mucus from the 
goblet cells. Its secretion seems to result from 
the same nerve stimuli as the glands above. No spe- 
cial ferments have been found in it but it has several 
important functions, seemingly as follows : (1) it has a 
■slight diastasic action on starch, forming maltose ; (2) 
it can convert or “invert’’ cane sugar (saccharose) into 
•dextrose, and (3) it has a feeble peptonising power. 
This latter action it is well to note, as it suggests arti- 
ficial digestion for the proteids of nutrient enemata. 
Chemistry of intestinal digestion. The starchy 
,forms of carbohydrate food which escape the action of 
the ptyalin in mouth digestion undergo but slight 
change in the acid medium of the stomach, but when 
the alkaline region beyond the pyloric orifice is reached 
the ptyalin seems again to begin its diastasic action. 
At the same time these starchy food stuffs are brought PHYSIOLOGY 
195 PHYSIOLOGY 
under the action of the more powerful diastasic fer- 
ment amylopsin, which in this medium rapidly con- 
verts the remaining- starch into sugar. How this is 
done is not well understood. Amylopsin and the dia- 
stasic ferment of the succus probably convert dextrin 
into maltose, while the sugar, (saccharose) is reverted 
by the ferments of the succus entericus alone. The 
proteidforms of food which have escaped the action of 
the pepsin in the stomach, or at least have been but 
partly acted upon, are here again subjected to the 
action of a proteid ferment, trypsin. This ferment in 
an alkaline medium converts proteids into peptones, 
under the following- conditions : The proteids which 
had been converted in the stomach into acid albumen,, 
are now precipitated by the alkaline media in which 
they find themselves. These precipitated albumens 
and other (untouched) proteids are converted into alkali 
albumens, and these being acted upon by the trypsin 
are converted into peptones. The continued action of 
trypsin upon the peptones it has formed (hemi-pep- 
tones) produces a variety of nitrogenous compounds, 
chief among which are leucin, tyrosin, and various 
acids. The fatty foodstuffs which in the stomach 
were unaffected by its juices, other than to have their 
proteid support dissolved, are now modified in various 
ways. In the presence of the alkaline fluids, especi- 
ally the bile, these liberated fat globules break up 
into a fine emulsion, in which form, as we shall see, 
they are capable of being absorbed. Some of the fats, 
in the presence of the fat-splitting ferment steapsin, 
probably break up into glycerin and their correspond- 
ing fatty acids. These acids, in turn, become saponi- 
fied by the alkalies of the intestine. Both soaps and 
emulsion are capable of absorption, but in different 
ways. PHYSIOLOGY 
197 198 
PHYSIOLOGY 
Putrefactive phenomena in the intestines. Swal- 
lowed with the food, fluids and air are many bacteria, 
as we saw in the saliva. Many of these are the peculiar 
bacteria that produce fermentation and putrefaction, 
and in the lower intestine their action upon the products 
of proteid digestion yields a variety of putrefaction 
products, among- which are the foul-smelling- material 
that gives to human faeces its characteristic odor, 
tog-ether with indol or indican (CSH7N), skatol (C9H9N), 
phenol (C(jH,;O), &c. These processes, tog-ether with the 
fermentation of carbohydrates, are accompanied by the 
evolution of g-as. , Among- the g-ases found as the 
result of these decompositions are H, C02, CH4, and 
BLS in small quantities. These g-ases in quantity 
produce distension and colic, especially in infants. In 
hysteria and other neuroses g-as may be formed in the 
stomach at a rate that seems to preclude the idea of 
fermentation alone, and sug-gests dissociation. The 
putrefactive processes, especially with proteid foods, 
may give rise to highly toxic products, suggesting- in 
their action the ptomaines, (auto-intoxication.) 
Absorption in the intestines. The water and 
mineral food stuffs are absorbed as easily as in the 
stomach. The starchy parts of the carbohydrate food 
are after conversion into sugar (maltose) readily 
absorbed by the blood vessels of the villi and mucous 
membrane. The peptones, the results of proteid diges- 
tion, are absorbed as in the stomach by the capillaries, 
but wherever absorbed they seem to be reconverted 
into proteids (serum albumen) in the process of absorp- 
tion. The fats, when emulsified (not saponified,) are 
absorbed by the peculiar columnar epithelium covering 
the villi. The globules seem to be taken into the 
bodies of these cells and discharged into the lymph 
space of the villus, whence, by the periodic contractions PHYSIOLOGY 
199 200 
PHYSIOLOGY 
of the muscular fibres, they are forced into the lacteals 
(chyle). Most of the gastric and intestinal juices of 
secretion are reabsorbed, and bile is in large measure 
reabsorbed to return to the liver. Whenever, owing 
to obstruction or imperfect muscular action, the decom- 
position products are retained for a long time in the 
canal, they are in a large measure also absorbed. Some 
of these produce the faecal odor observed in such 
cases, and indican may appear in the urine at such 
times in appreciable amounts. 
Mechanism of intestinal movements. The normal 
movements of the intestine are dependent upon the 
stimulation of Auerbach’s plexus. This stimulation 
produces contraction waves (peristalsis) from the upper 
toward the lower parts. The presence of the intesti- 
nal contents, bile, etc., furnishes the normal stimulus, 
but it may be modified by many conditions. The 
amount of fluid in the gut influences peristalsis, (saline 
purgatives) excitement of its local ganglia aids it 
(strj'chnin), irritation of the mucous membrane also 
powerfully excites it (croton oil, etc.) paralysis of the 
inhibiting terminals of the sympathetic allows it freer 
action (atropiu), while stimulation of the inhibiting 
centres check it (opium). 
Muscular and nerve mechanism of defaecation. 
Peristaltic movements carry the faecal masses along 
the large intestine until they reach the lower part of 
the sigmoid flexure. Here it seems as if their pres- 
ence ceases to act as a stimulus to the gut, and that 
the folds of the mucous membrane in this region 
mechanically prevents their descent. When, however, 
this region becomes full and distended with faeces, the 
pressure induces a desire to go to stool. This desire 
is brought about by nerve terminals in the gut wall, 
which send impulses to the centre of control. This PHYSIOLOGY 
201 202 
PHYSIOLOGY 
centre, called the ano-s-pinal centre, lies in the lumbar 
cord. It is in a tonic state of activity, keeping the 
sphincter ani tightly closed, but such impulses as 
those above increase its tone and the intensity of its 
impulses to the sphincter. There is a portion of the 
gut, however, in the lower rectum called the “sensi- 
tive rectum,” the stimulation of which by fascal mat- 
ter not only causes relaxation of the sphincter, but 
increases powerfully peristalsis above. When an 
action is desired, man seeks his accustomed place and 
making forced (voluntary) abdominal pressure aids the 
peristaltic movements in forcing the faecal matter down 
until it touches the sensitive rectum. Here the sensi- 
tive portion of the gut is stimulated and an impulse is 
sent to the ano-spinal centre causing a reflex inhibition 
of the sphincters below. These sphincters may also 
be voluntarily inhibited when desired. Peristaltic 
and voluntary muscular forces then press the mass 
onward through the patulous opening below. As it 
tends to drag the gut onward with it in its descent, 
this is overcome by the muscularis rauscosae and leva- 
tor ani drawing the gut and perineum upward over 
the mass, and the sphincter closes behind it. The 
corrugator ani by alternate contraction and relaxation 
then frees the anus of adherent faecal matter. We 
may by the will “silence” these calls to the defaecation 
centre until the terminals in the gut become function- 
ally almost inactive, and constipation and dilation, 
with all attendant evils, result. 
Time occupied in digestion. Peristalsis begins in 
a few minutes after food has been introduced into the 
stomach, and continues there for a period of about five 
hours. The chyme remains in the small intestine 
about three hours, and the excretory matter in the large 
intestine usually about twelve hours. PHYSIOLOGY 
203 204 
PHYSIOLOGY 
Vomiting and its mechanism. The vomiting centre 
lies upon the floor of the fourth ventricle, near the nu- 
cleus of the tenth nerve. It maybe stimulated reflexly 
by afferent impulses from : the stomach (10th); the soft 
palate, circumvellate papillae, pharynx, &c., (9th) ; the 
uterine nerves (pregnancy); the intestinal tract, hernia, 
invagination, &c., (mesenteric nerves) ; the ureter and 
kidney, (least splanchnic); the gall duct and liver 
(splanchnic); the lungs in phthisis (10th). The cen- 
tre may act under impulses from the sensorium, stimu- 
lated through the nerves of sight, hearing, taste and 
smell. It may be stimulated directly by drugs, or the 
terminals in the stomach may be stimulated. The act 
is ushered in by an undefinable feeling of nausea, per- 
spiration may occur, and a rush of saliva to the mouth 
(chorda). Then a deep inspiration, to lower the dia- 
phragm, is taken and the glottis closed. In this 
condition the abdominal muscles make a powerful 
expiratory movement, compressing the stomach and its 
contents against the lowered diaphragm. At the same 
time the pyloric orifice being closed and the cardiac 
aperture opened the contents of the stomach are forced 
out through the oesophagus and mouth. The young 
infant vomits chiefly by the contraction efforts of the 
stomach itself, and hence they bring up no bile. With 
adults the first effort empties the gall bladder into the 
duodenum, and continued efforts bring some of it into 
the stomach and thence up (“biliousness”?). The ap- 
plication of ice over the larynx (sup. laryngeal of 
vagus) will often inhibit vomiting. 
The administration of ferments, prepared from the 
digestive appendages of lower animals, is of much 
value in various forms of atonic dyspepsia. The 
artificial diastase obtained from “malt” supplements 
the action of ptyalin and amylopsin. Pepsin, pre- PHYSIOLOGY 
205 206 
PHYSIOLOGY 
pared chiefly from the stomach of the hog-, is of much 
service. The administration of dilute HCI is also of 
decided benefit in certain cases. 
Post-mortem digestion of the stomach wall, and 
even of contig-uous organs, sometimes occurs. Why 
this is not done during life is not understood, but is 
probably due to the protective influence of the alkaline 
blood circulating in its walls. 
CHAPTER VIII. 
THE SKIN AND ITS FUNCTIONS. 
The skin of the human body shows a surface of from 
14 to 18 square feet. It is histologically an extremely 
complex structure, its varied elements giving evidence 
of its manifold functions. It varies in thickness not 
only on the different parts of the body, but in the 
different races—climate, attention and environment 
producing marked changes in this respect. The skin 
may be divided into two layers, which separate readily 
on blistering, maceration or decomposition. The 
superficial layer is called the epidermis or cuticle, 
while the internal or true skin is called the derma or 
cor i urn 
The epidermis is a relatively thin layer overlying the 
true skin, but which becomes much thickened in 
the parts exposed to habitual pressure, as the heel, soles 
of the feet and palms of the hands. In the various 
flexures it is thinner than on the general body surface 
(inunction'), but on the eyelids, lips, glans penis, female 
genitals and external auditory canal it is extremely thin PHYSIOLOGY 
207 208 
PHYSIOLOGY 
(infection atria). It consists of four layers from without 
in, as follows : (1) The stratum corneum, a thin layer 
of flat, horny scales, which have lost their nuclear 
constituents and other resemblance to cells, and are 
now chiefly keratin. (2) The stratum luciduni, more 
or less flat squamous cells, the superficial layers of 
which are keratinous. (3) The stratum granule sum, 
much similar in shape to the layer above, but containing 
granules of eleidin. (4) The stratum malpighi, or rete 
mucosum. This layer is as thick as all the preceding- 
layers combined, and while its external face is parallel 
with the layers above, its inner face follows the contour 
line of the papillae of the coriura, alternately rising over 
and dipping between them. The malpighian layer 
consists of first an external layer of “prickle cells” 
whose ridges do not interlock but simply touch, and 
secondly a layer of very long columnar-like cells which 
lie parallel but have no cement substance between them. 
This layer is pigmented (melanin) in the darker-skinned 
white races and in the negro ; all the layers in the latter 
race are more or less dark. The open spaces of this 
layer allows the percolation of lymph to the stratum 
granulosum unchecked. Nerve fibres also run in the 
stratum malpighi almost up to the granular layer. The 
superficial horny scales are being cast off from the 
surface at all times, and are renewed by the prolifera- 
tion of cells in the rete mucosum which are moved up 
to take their place, degenerating as they go. 
The cerium, derma or cutis vera is the thick dense 
layer of the skin lying below the epidermis. Its upper 
surface is raised into tit-like processes ov papilla?, made 
up of dense fibrous tissue intermingled with elastic 
fibres. Below this is a more open reticulum of much 
similar tissue, and this in turn is continuous below 
with the subcutaneous areolar tissue. The space PHYSIOLOGY 210 
PHYSIOLOGY 
between the skin and the muscles, &c., is filled in, even 
in the lean, with adipose tissue or fat. This is 
especially true of women, and gives the rounded 
contour peculiar to this sex. There is no fat beneath 
the skin of the genitals, eyelids or upper parts of the 
ear. The fafillcc are of variable size, some of the 
larger having smaller papillae springing from their 
apices. These are called compound papillae. On the 
palms of hands and soles of the feet these papillae are 
arranged in rows, forming lines and fissures of great 
complexity, but usually symmetrical on the two halves 
of the body. In many of the papillae, especiallv of the 
fingers, may be found the complex nerve terminals 
called touch corpuscles. Throughout the derma, but 
particularly near the hairs, may be found scattered 
non-striated muscle fibres whose contraction puckers 
the skin, giving the so-called “cutis anserina.” The 
blood vessels of the skin are derived from branches of 
the deeper vessels which make toward the surface. 
As they pass up they give off branches to the masses 
of fat cells that lie in the areolar layer, then to the 
sweat and sebaceous glands, and finally end in minute 
capillary loops in the papillae of the corium. From 
these exudes the lymph that supplies the epidermal 
tissues. 
The epidermal appendages are the hair and the 
nails. These are composed of the same modified 
keratinous cells that form the horny layer on the 
.general surface of the skin. 
The hair is an elongated column of keratinous tissue 
(debased cells) which grows from a papilla sunk deep 
in the true skin. It is composed of an imbricated 
external envelope, then the cortex or hair substance, 
and in this a core or medulla of more or less pigmented 
polyhedral cells. The hair follicle is composed of PHYSIOLOGY 212 
PHYSIOLOGY 
many layers, of which we will only say that all inter- 
nal to the hyaline membrane are epidermal, and all 
external are from the corium, the membrane itself 
being- derived from the thin but dense portion of the 
connective tissue that forms the surface of the papillae. 
The presence of this epidermal tissue deep in the sub- 
stance of the skin is of great importance in the 
regeneration and repair of superficial injuries (epider- 
mization). From the base of each hair follicle there 
passes obliquely upward a bundle of non-striated mus- 
cle fibres, the erector pili muscle. These in times of 
fear or emotion make “each particular hair to stand on 
end” and by post-mortem contraction give rise to the 
tales of growth of hair after death. The hairs are of 
three varieties : (1) The long hairs, found on the scalp, 
genitals, and armpits of both sexes, and on the face 
and to a variable extent the breast and general body- 
surface of males. (2) The stiff hairs, as the vibrissse 
of the nostrils, the eyelashes of the lids and the eye- 
brows. (3) The downy hairs found on the general 
body surface, and sometimes in the caruncula lachry- 
malis. Hairs are found on all parts of the body except 
the palms of the hand and the soles of the feet, the 
exposed mucous membranes, eyelids, and last phalanx 
of the extremities. Straight hair is usually round on 
cross section, curly hair oval and wooll}" hair flat. 
Gray hair is usually produced by imperfect formation 
of the internal pigment, but sudden blanching is pro- 
duced by the vacuolation of the shaft by gas. The 
lanugo or downy hair of foetal life is shed entirely by 
the time the child is six months old. Diseases of 
general malnutrition produce falling of the hair, termed 
alopecia (fever, syphilis, etc.). 
The nails are, as it were, compound hairs. They 
grow from the matrix rapidly, but as a very thin layer. PHYSIOLOGY 
213 214 
PHYSIOLOGY 
which thickens as it progresses by growth from the 
long- rows of proliferating papillae over which it moves. 
The spots often seen on the nails are due to vacuolation, 
but parasitic diseases may alter the structure (onycho- 
mycosis) and general diseases, as syphilis, may cause 
shedding of the nails as of the hairs (onychia). An in- 
growing nail is always produced by the pressure of 
the adjacent toe raising the flesh up over the nail-groove. 
The glands of the skin are both secretory and excre- 
tory in function. The secretory glands, those that 
produce something needed by the body (or its offspring), 
are the sweat glands, mammary glands and the seba- 
ceous glands with their modifications. The excretory 
glands, those which remove something not formed in 
the gland and detrimental to the body, are the upper 
parts of the sudoriparous or sweat glands. 
The mammary glands are two large hemispherical 
eminences or mammce located upon the lateral aspect 
of the pectoralis major muscle. Undeveloped accessor}" 
mammae are sometimes found located in aline down the 
breast below the others, in the axilla or even on the 
shoulder. The mamma presents at the centre of its 
convexity a smaller conical eminence, the nipple or 
mammilla. This tit or nipple is composed of areolar 
tissue, surrounded with circular and radiating plain 
muscular fibres (erection) pierced by fifteen or twenty 
milk-bearing or lactiferous ducts. These ducts ex- 
pand at the base of the nipple into larger cavities or 
amfullcc. The skin of the nipple is, in the virgin, of 
a pinkish brown, and surrounded by a zone or areola 
of rosy tint. In pregnancy this areola begins to darken 
about the second month, and continues to darken and 
widen till at the full term it is in brunettes almost 
black, and twice the previous diameter. The base and 
sides of the nipple are set with sebaceous glands, and 
often misplaced lactiferous ducts open on its sides or PHYSIOLOGY 
215 216 
PHYSIOLOGY 
base. If we follow the lactiferous ducts we will see 
that they radiate from the nipple into the substance 
of the mamma, that they receive ducts as we follow 
them, and the ultimate ducts come from lobules of 
glandular elements that secrete the milk. The acini 
of these glands contain short columnar secretory cells. 
During the periods between pregnancy the ends of 
these cells next the lumen undergo fatty degeneration 
and break off into the cavity forming colostrum cor- 
puscles. It is this rich unctious matter that the child 
gets when first nursing, and it acts as a very desirable 
purgative to empty its bowels of meconium, &c. The 
third or fourth day after labor the secretion of true 
milk begins, but oil globules still form in the cells 
and are extruded, forming the cream. The interstices 
between the lobules are filled in with fat, and the 
whole structure supported by fibrous tissue inter- 
mingled with plain muscular elements which aid in 
the expulsion of the milk. The blood supply of this 
gland is abundantand varied, coming from the axillary, 
intercostal and internal mammary arteries. The lymph 
ducts are numerous, and follow the lower border of 
the pectoralis major to the axilla, being beset with 
manv lymphatic glands (carcinoma). The nerves are, 
strange to say, all from the cerebro-spinal system. 
Human milk is a thin bluish white fluid of quite 
sweet taste and sp. gr. of 1030. When first drawn 
milk is faintl}" alkaline, soon becomes neutral and then 
slightly acid. A “good mother” secretes daily from 
two and a half to three pints. The comparative 
analysis with cow’s milk below gives its general 
chemical peculiarities : 
(Percent.) Pats. Casein. Lactose. Salts. Water. 
Human milk, 2.5 2 5 .5 90 
Cow’s milk, 4 4 4 1 87 
We can see from the above why water should be PHYSIOLOGY 
217 218 
PHYSIOLOGY 
added to cow’s milk. The proteids of milk are casein 
and lact-albumen. 
The casein exists in milk as caseinogen, seemingly 
an alkali albumen, which is (precipitated) coagulated 
by acids or special ferments, and converted into casein. 
The ordinary “souring” of milk is due to the forma- 
tion of lactic acid from lactose, (lime water), under the 
influence of the wide spread ferment, bacterium lactis. 
The fats are in the form of an emulsion, cream. The 
chief salts are basic phosphate of calcium, chlorides of 
soda and potash, traces of iron, etc. 
The sebaceous glands are either single or multiple 
racemose glands, whose saculi are filled wdth columnar 
cells do not really secrete, but, like the mam- 
mary cells during the inactive stage, undergo fatt}- 
degeneration. These fatty cells are discharged into 
the large ducts of the glands forming an oily unctious 
mass, the sebum which keeps the skin soft. Some- 
times these glands have ducts of their own, but usually 
one or more of them open into the necks of the hair 
follicles. These glands are only absent from the 
plantar surfaces of the feet, and palmar surfaces of the 
hands, being most abundant on the hairy parts and the 
regions around the various openings of the body. 
This sebum appears at the open orifices of the ducts, 
being pushed out by the proliferation of the fat cells 
behind. As these orifices are darkened by dirt, the\r 
receive the common name of “black heads” and are 
properly called comedones. There is a parasite 
(demodex folliculorum) found in them at times, but 
not always. When these duct mouths become closed 
we have the large sebaceous retention-cysts found on 
the back, behind the ears, &c. On the female genitals 
and under the prepuce in man we have a modified form 
of sebaceous gland which gives the secretion peculiar 
to these parts. PHYSIOLOGY 
219 220 
PHYSIOLOGY 
The sudoriparous or sweat glands. These have 
two distinct functions, the one secretion of sweat, and 
the other the excretion of C02 and other deleterious 
matter. The structure of a sweat gland shows this 
variation in function. These glands are scattered over 
almost the entire body. They are absent only from 
the glans penis and prepuce, are scanty on the back, 
while abundant on the face, hands, feet and flexures. 
They consist of long tubular glands, of two distinct 
parts, having separate functions. The deeper is the 
glandular portion, and the superficial the respiratory 
portion. The coiled or glandular portion of the tube 
(“glomerulus”) is deep in the subcutaneous areolar 
tissue. It consists of a basement membrane and single 
layer of long spheroidal epithelium. A plexus of cap- 
illaries surrounds the coil, with lymphatics, nerves, 
&c. The upper or respiratory part of the tube makes 
its way in a spiral or corkscrew-like manner through 
the epidermis to open by a mouth on the surface. It 
is lined by several layers of small cubical cells whose 
lumen surface is covered by a delicate membrane. 
Sweat and its secretion. The sweat is an almost 
colorless fluid, containing about one per cent, of solid 
matter, and is usually alkaline. It contains, besides a 
volatile oil, C02 and a little urea. The relative pro- 
portion of solids and gases varies greatly in exercise, 
disease, &c. The amount secreted per diem varies 
with the climate, race, individual, state of health and 
muscular activity. Broadly stated it varies from one to 
three pints of fluid daily, with traces of the volatile fatty 
acids, that give the peculiar racial odors, and the amount 
of CO, given on page 156. A reciprocal action exists 
between the function of the skin and the kidneys, In 
the moist, cool climate of England the amount of 
perspiration is small and the urinary secretion is large, PHYSIOLOGY 
221 222 
PHYSIOLOGY 
while on the dry plains of the southwestern United 
States the urinary secretion is small and the action of 
the skin very great. The secretion is under the con- 
trol of a centre and special set of nerves. The domi- 
nating centre is in the medulla, and like all medullary 
centres is bilateral. Subordinate centres are in the 
cord. Impulses from this centre seem to follow the 
routes pursued by the vaso-raotor impulses. Central 
stimulation may be produced by emotion, super-heated 
blood, venous blood, or by drugs (nicotin). Some drugs 
act both centrally and on the peripheral secretory nerves 
(pilocarpine). Reflex stimulation is usually produced 
by increase of temperature, in the air and surround- 
ings (hot-air bath). The secretion of sweat may be 
checked by paralyzing the terminals of the secretory 
nerves (atropine) or by the application of moist surface 
cold. 
The functions of the skin as based upon the fore- 
going- studies lead us to note: (1) It is a -protective 
covering for the body, impermeable to ordinary chemical 
poisons, bacteria and other forms of virus, when its 
horny layers are unbroken ; (2) It is a -poor radiator of 
body heat when dry. Any interference with its 
natural surface, as a burn of large superficial area, or 
varnishing the skin, produces serious depression of 
temperature. The subcutaneous layer of fat is a most 
valuable non-conductor of heat; and when by the con- 
traction of the muscles of the skin and vaso-motor 
constriction of its vessels the blood is gotten behind 
this barrier, man is in his best state of protec- 
tion against cold ; (3) Its power of lowering body heat 
by the action of its glandular elements, the sweat 
glands, and the subsequent evaporation of the sweat 
from the surface of the body. The full influence of 
this lowering is gotten by dilating the superficial PHYSIOLOGY 
223 224 
PHYSIOLOGY 
capillaries and thus exposing- the blood to be cooled as- 
it passes ; (4) It aids in the excretion of the deleterious 
products of metabolism, and while this is relatively 
small it may be made use of to aid vicariously other 
organs (uremia) ; (5) It contains the terminals for most 
of the somatic senses. The end org-ans of touch, 
temperature, &c., are all in the skin. The presence 
of the temperature terminals in the skin causes them to 
play a peculiar part in what we call a “ chill. ” When 
from any internal congestion, as pneumonia, pleurisy 
or the essential fevers, the vaso-motor centre to main- 
tain pressure cuts off the supply of blood to the skin, 
and the muscles of the skin contract, we have the 
cold, ‘‘creeping-” sensations of a chill and probably 
a rig-or. This is due to the fact that the tem- 
perature terminals in the skin, which are usually 
kept warm by the hot blood circulating- around them, 
are now deprived of this warmth, and although the 
rectal temperature may be several degrees above 
normal, the patient shivers ; (6) (Notwithstanding its 
powers of resistance, the skin possesses some small 
capacity for absorption. This is especially true of the 
oils and fats, which are more readily absorbed than 
other substances. This power is of use in the adminis- 
tration of drugs in the form of ointments, by rubbing 
them into the soft skin of the flexures (inunction). 
Pathological lesions of the skin dependent on its in- 
ternal structure are many, among which we will note 
the following : A blister is produced by any agency 
that will cause a pronounced and continued congestion 
of the capillaries of the skin, to the extent that the 
effusion or exudate poured out from the vessels lifts the 
epidermis or scarf skin from the corium. The effect 
of this on the system is first the one derived from the 
extraction of this amount of fluid (blood) from adjacent PHYSIOLOGY 
225 226 
PHYSIOLOGY 
parts, and secondly the effect produced by it on the 
large number of nerve terminals which it necessarily 
affects. A blister may be produced by heat ; by the 
vesicants, as cantharides, &c., and by the so-called 
rubefacients if their action is prolonged, in fact by any- 
thing that fulfills the conditions above given. As 
intra-capillary pressure is essential to the formation of 
a blister, this lesion is of medico-legal value in proving 
the existence of life. A vesicle is essentially but a 
small blister, and all the “vesicular” diseases from 
eczema to pemphigus are produced by the same condi- 
tions. To go further whenever the local congestion of 
the capillaries is only sufficient to produce a change of 
color in the skin it produces a macule, but when suffi- 
ciently pronounced to cause a local infiltration of the 
tissues, and an elevation above the normal skin level 
we call it a papule. It is only when the congestion is 
both pronounced and continued that it produces an 
outpouring sufficient to create a local cyst or vesicle. 
If chemical or bacterial agencies add their action and 
pus forms in the vesicle we have a pustule. This 
epitome of local action gives as we see a brief outline of 
the usual “types” of skin disease. The exciting cause 
in these cases is probably local (eruptions), although 
central vaso-motor disturbance may cause dilation of 
the vessels and exudation. Parasites, as the female 
acarus scabiei, may produce vesicles and hatch young 
in them. Warts of the skin and mucous membrane are 
but hypertophied papillae, “moles” being pigmented 
forms of the same. Freckles are caused by the group- 
ing of pigment cells in the superficial layers of the 
stratum malpighi under the influence of the sun’s rays. PHYSIOLOGY 
227 228 
PHYSIOLOGY 
CHAPTER IX. 
THE KIDNEY AND ITS EUNCTIONS. 
The two organs that bear the above name are placed 
on the posterior wall of the abdomen, and are purely 
excretory in their functions. It is their province to 
remove from the blood the waste products of tissue 
metabolism and also those products of absorption which 
play no part in the constructive processes of the body. 
The kidney, while covered by the peritoneum in 
front, has no serous covering except in one of the forms 
of the rare condition called “floating kidney. ” The ex- 
ternal coat of the kidney is a fibrous capsule joined 
loosely to the tissues below by connective tissue fibres. 
This capsule covers the entire surface and dips down 
into and lines the cavity (sinus) on the concave side of 
the organ. A longitudinal section of the kidney shows 
it to consist of two parts ; An external or cortical part 
lying next to the capsule on the convex side, and an 
internal or medullary part lying within the former and 
opening by a series of pyramidal projections into the 
sinus. These pyramids of malpighi, as they are called, 
have their basis next the cortex, and where these join 
we have a distinct boundary line called the cortico- 
medullary line. The supporting framezvork of the 
kidney is most dense in the capsule, next in the apices 
of the pyramids, and after this in the boundary layer, 
or zone of the medulla next the cortico-medullary line. 
In the cortex the framework is loose and open, a re- 
ticulum of fibrillar elements filled in with the par- 
enchyma of the gland. The muscular elements of the PHYSIOLOGY 
229 230 
PHYSIOLOGY 
kidney (visceral) are found as a thin investing- layer 
under the capsule, as a ring of fibres around the apex 
of each of the malpighian pyramids, and in the walls 
of the blood vessels, except the vasa recta. 
Vessels of the kidneys. The arteries. The renal 
artery, usually single, breaks up into from four to six 
branches called the arteriae firofiriae renales, which 
pass up between the pyramids to the cortico-medullary 
line, where they divide and follow this line as the 
cortico-medullary or arcuate arteries. They give off 
(1) cortical branches called the interlobular arteries 
which furnish the vasa-ajferentia and glomerulus (and 
vasa efferentia) and also the terminal arteries of the 
subcapsular plexus. The vessels which leave the 
glomerulus, called the vasa-afferentia, and ramify 
around the uriniferous tubule, especially the convoluted 
parts, help to form the interlobular plexus. (2) The 
medullary branches which running straight down into 
the pyramids, are called the arteriolae rectae, all end 
in the pyramidal plexus. The veins. The blood from 
the sub-capsular plexus and from the plexus around the 
convoluted tubule (interlobular plexus) unite to form 
the interlobular veins. These join vessels lying in 
the cortico-medullary plane called cortico-medullary 
veins. These cortico-medullary veins also receive the 
blood of the venae rectae coming from the medullary 
side and emptying the pyramidal plexus. There is an 
anastomosis between the plexus of the convoluted 
tubule and the pyramidal plexus. The blood of the 
vasae efferentiae nearest the cortico-medullary line is 
divided, part going as above to form the interlobular 
plexus and the remainder going straight down in a set 
of vessels called the vasae rectae which, crossing the 
cortico-medullary line, pour their blood into the pyra- 
midal plexus. Observe the fact that should there be PHYSIOLOGY 
231 PHYSIOLOGY 
an obstruction to the flow of the blood in the inter- 
lobular veins, the blood of the lower vasa efferentia, at 
least, can take a “short cut” through the vasa rectae 
to join the pyramidal plexus. Also observe the fact 
that the dilation of the terminal vessels of the inter- 
lobular arteries and the contraction of the vasa 
afferentia will allow the blood to pass through the 
subcapsular plexus and interlobular plexus to join the 
interlobular veins without passing through the glom- 
erulus. The lymphatics are of two kinds, the superficial 
set running on the surface of the gland under the 
capsule, and the deeper or interlobular lymphatics in 
the substance of the cortex. 
The uriniferous tubule. When the vasae aff ereutiae 
leave the interlobular arteries they curve upward as 
very small vessels which are twisted and coiled on 
themselves, forming ball-like plexuses, the glomeruli, 
from which the blood is carried by the outgoing ves- 
sels or vasae efferentiae. Around each glomerulus we 
have a delicate membrane of squamous cells which is 
reflected on itself to form the capsule (Bowman’s) of 
the glomerulus, and from which leads the neck of the 
uriniferous tubule. This leads into the proximal con- 
voluted tubule, having the same lumen but thick walls 
made of rod-beset epithelium. Becoming spiral the 
tube now dips down into the substance of the boundary 
layer and returns {Henle'1 s loop) to about the same 
level. The epithelium of this part of the tube is thin, 
being composed of squamous plates set in a peculiar 
alternate manner. Becoming again spiral the tube as- 
cends in the cortex to about the level from which it 
started, and turning in an irregular manner at a sharp 
angle it forms the distal convoluted tubule. This has 
a rod-beset epithelium almost identical with the proxi- 
mal tube, and differs only from the irregular tube in PHYSIOLOGY 
233 234 
PHYSIOLOGY 
having- the nucleus of its cells central. From this* 
point the “glandular” functions cease, and the collect- 
ing tubule joins a straight tube which runs down in 
the pyramids and unites with a discharging tube 
which opens at the apex of the papilla in the calyx. 
Nerves of the kidney. A dozen or more filaments 
supply the kidney. They are derived from the renal 
plexus, which receives branches from the great, and 
especially the lesser splanchnic divisions of the sym- 
pathetic. Kach kidney is supplied bv fibres from both 
sides of the sympathetic cord. These nerves supply 
the non-striated muscular fibres of the vessels, and 
sensation. No evidences of secretory nerves exist, the 
vaso motor impulses controlling the output. Ganglio- 
nic cells are found in the substance of the gland, and 
seem to have some control over the vaso-motor condi- 
tions independent of the vaso-motor centre. 
The secretion of urine. There are two distinct 
stages in the formation of urine, from the blood enter- 
ing the vasa-afferentia. As the blood flows rapidly 
from the more or less straight vessels into the closely 
coiled glomerulus, friction and peripheral resistance 
cause a rise in intragloraerular blood-pressure. This 
results in the filtration of water through the glomeru- 
lar walls into its investing capsule. As the blood, 
now in concentrated form, leaves the glomerulus by 
the vasa efferentia, it is carried through the plexus of 
capillaries surrounding, and in intimate relationship 
with, the rod-beset epithelium of the convoluted tu- 
bules. Here the salts and specific urinarv constituents 
are extracted from the blood by the special action of 
the epithelium cells of the tubules, and are removed by 
the water flowing within them. When we consider 
that in the lumen of the uriniferous tubule we have 
nearly pure water, and in the capillaries surrounding; PHYSIOLOGY 
235 236 
PHYSIOLOGY 
the tube a more or less concentrated saline solution, 
we might call this latter exchange osmosis. It is not, 
however, a purely physical process, but the vital 
action of the tubular epithelium is involved in this 
elimination, and that of the glomerular epithelium in 
the “filtration.” If partly or purely an osmosis, a 
proportionate amount of water must be absorbed from 
the tubule for salts, etc., going in. Heidenhain dem- 
onstrated the above as follows : He injected into the 
blood of a dog a solution of sulph-indigotate of soda, a 
blue pigment, and waiting till it began to appear in 
the urine, killed the dog. An examination showed the 
cells of the convoluted tubules filled with the pigment 
granules and stained blue, while the epithelium of the 
glomerulus was not stained. If the above theory be 
true, a rise of blood pressure in the renal artery should 
give an increase in the amount of urine, and we find 
that the urine does increase pari passu with the blood 
pressure. 
Physical characters of urine. It is a mobile, amber- 
colored fluid, normally of slight acid reaction, with a 
specific gravity varying from 1010 to 1025. The 
average adult made secretes about 35 or 40 ounces in 
24 hours in this climate. It has a characteristic odor 
and taste. As modifying its physical character we may 
note : Increased quantities of salt, even the patholo- 
gical constituents, sugar and albumen, ma}T make it less 
mobile and give it a tendency to froth when shaken. 
The urinary pigments which give color to urine vary 
but little in health, hence the marked color variations 
found depend chiefly upon the amount of water with 
which they are diluted. Ordinarily varying from 
light to dark amber, in disease and toxaemia it may 
range from the water white of diabetes and h}Tsteria to 
the yellow of santonin, red of senna, red-brown of bile, PHYSIOLOGY 
237 238 
PHYSIOLOGY 
brown of rhubarb up to the black of phenol poisoning-. 
The acid reaction of fresh urine becomes alkaline on 
standing-, especially if in a warm place. The adminis- 
tration of alkaline or earthy bases or their carbonates, 
etc., renders the urine less acid or alkaline, while the 
administration of acids, especially benzoic acid, makes 
it pronouncedly acid (page 64), The variation in the 
amount secreted (as seen under variations in color) gives 
the normal variations in specific gravity ; but only dis- 
ease gives the extreme limits of range, as hysteria and 
diabetes insipidus 1001-4, and diabetes millitus 1030-40. 
The variations in quantity range from absolute sup- 
pression to 8 and even 12 quarts daily in diabetes. 
The odor varies from the characteristic odor of fresh 
urine to the putrescent ammoniacal smell of the old 
article. The administration of various essential oils 
and balsams make it highly aromatic, other drugs, as 
valerian, asafoetida, etc., also give their characteristic 
odor. Old diabetic (mellitus) urine is sour, while 
fresh has a sweet odor. 
Constituents of urine. Normal urine contains about 
96 per cent, of water and 4 per cent, of solid matter. 
About two-thirds of the solid matter is organic, the 
remaining one-third inorganic. The chief organic 
constituent is urea, and the chief inorganic sodium 
chloride. 
Urea, (CO (NH2)3) the dlamide of C02, is the chief 
end product of the oxidation of the nitrogenous constit- 
uents of the body. It represents about one-half of 
the solid constituents of the urine, being about 2 per 
cent. About one ounce is excreted daily by an adult. 
It is isomeric wdth cyanate of ammonia, and may be 
formed artificially. The amount of urea is increased 
by an increase of proteid food, by hastening nitroge- 
nous tissue-metabolism, and also to a less extent by PHYSIOLOGY 
239 PHYSIOLOGY 
increasing- the g-eneral urinary output. When we 
consider the necessity of O in maintaining- the stability 
of the complex proteid constituents of the body, we 
will see why in dyspnoea and other conditions of 
imperfect oxidation it is increased. Starvation diminishes 
it to about one-fifth, where it remains fixed till death. 
In fever the amount is increased till the crisis, and then 
falls. While we know that it is not formed in the 
kidne\T, we arc not absolutely assured of the point of 
formation, unless it be the liver. The decomposition 
of urea and water into carbonate of ammonia takes 
place on standing-, and may take place in the bladder 
in the presence of certain micro-org-anisms, as the 
micrococcus ureae (pag-e 62). 
Uric Acid (C5H4N403,) is, next to urea, the substance 
that represents the N eliminated. The amount elim- 
inated is about 10 grains daily, making the ratio of 
urea to utic acid about 48 to 1. It is seldom or never 
eliminated as free acid, but combined with soda (or 
potash) as a salt. To obtain it free add HCI to urine, 
or keep in a cool place till acid fermentation begins. It 
appears in brick-red rhombic crystals of various forms. 
In birds, reptiles and insects it represents almost the 
total output of N eliminated. In the urine of herbiv- 
ora it is small in amount or absent, and a vegetable 
diet decreases the amount formed in man. The amount 
is increased in man by severe physical exercise, rheu- 
matism, leukaemia, and digestive troubles. In gout 
there is reduced elimination rather than increased 
formation. The salts of uric acid vary greatly in 
solubility, lithium salts being most soluble, potash 
salts next, soda next, and ammonia least. 
Urinary pigments, &c. There is much doubt as to 
which special pigment can be called the pigment of 
normal urine. Urobilin is present in the urine of PHYSIOLOGY 
241 242 
PHYSIOLOGY 
fevers and to a certain extent in normal urine. Uro- 
chrome, uroerythrin and uromelanin all occur in 
varying- quantities and conditions, but all are derivatives 
of the bile pigment bilirubin, in its turn a derivative 
of the coloring matter of the blood. Kreatinin, formed 
by the dehydration of the kreatin of muscle, is a 
nitrogenous body occurring in about the same quantity 
in urine as uric acid. Oxalic acid combined with a 
calcium base is of variable occurrence in human urine, 
(calculi). 
Inorganic constituents of urine. The quantity of 
inorganic salts is usually not great, seldom exceeding 
one-half oz. daily. They may be taken in in the same 
form in which they are eliminated, but you must 
remember that the phosphates and sulphates, &c., may 
be formed by oxidation of the P and S of the food. 
Sodium chloride is the most abundant, varying with 
the amount eaten, &c. In certain diseases it is markedly 
diminished, as in pneumonia and various effusions. 
Two kinds of phosphatic salts occur. (1) The phos- 
phates of the alkalies. These may be acid sodic 
phosphate or acid potassic phosphate. It is to these 
acid salts, especially the former, that we owe the 
acidity of the urine. (2) The earthy phosphates. 
These are the acid phosphates of lime and magnesia. 
They have the peculiar property of being precipitated 
by heat, which the alkaline phosphates have not. 
Sulphuric acid occurs in the urine in two forms. The 
most usual is that in which it is united with alkalies 
to form salts. The other is the union of sulphuric 
acid with certain aromatic ether bases, indol, skatol, 
etc., to form definite compounds. 
Conditions influencing output of urine, salts, etc. 
Increase of the total contents of the vascular system 
increases blood pressure and consequently the output PHYSIOLOGY 
243 244 
PHYSIOLOGY 
of urine, as copious drinking-, intravenous injection, 
etc., while decrease of vascular contents diminishes it, 
as profuse sweating-, bleeding-, etc. Increase in the 
capacity of the vascular system, as by dilation of 
superficial vessels from warmth, etc., diminishes 
blood-pressure and the output of urine ; while decrease 
of vascular capacity, as by the influence of cold, con- 
stricting- vessels of skin, etc., increases pressure and 
urine. Variations in blood pressure brought about by 
the vaso-motor centre directly act in the same way. 
Increased action of the heart, with increased force, 
produces greater output of urine, and conversely 
feebleness of heart or valvular disease gives the 
reverse. 
Effects of retention of excretory products. The 
retention of urea in the blood gives rise to a special 
form of toxoemia known as uraemia, and the retention 
of uric acid produces a condition known as lithaemia. 
Uremia is rapidly fatal when pronounced, but if the 
suppression of the activities of the kidney is temporary, 
or onlv partial, stimulation of the vicarious action of 
the skin and bowels often checks the convulsions and 
tides the patient over. Lithaemia is due to a deficient 
alkalinity of the blood, and not to the excessive forma- 
tion of uric acid. Uric acid is very insoluble, but as 
we saw, its salts are more readily held in solution. 
The excessive and improper use of the starches, sugars, 
malt and spirituous liquors, is apt to produce acid 
dyspepsia, the lactic, butyric and other products of 
which, being- absorbed, negative the normal alkalinity 
of the blood, and produce retention of uric acid and 
often deposit in the tissues. Gout, rheumatism, cystic, 
and nephritic calculi, or the peculiar general nervous 
symptoms of retention are apt to occur. PHYSIOLOGY 
245 246 
PHYSIOLOGY 
Diuretics and their influence. Some diuretics, as 
digitalis and its class, produce diuresis by increasing 
the force of the heart’s action and general rise of pres- 
sure. The nitrite class of diuretics, where they act at 
all, act by causing a dilation of the vessels of the kid- 
ney. Still others, as the alkaline type of diuretics, 
while not well understood, seem to produce their result 
by their endosmotic influence on the filtering and 
secretory tissues of the kidney. The class of stimulat- 
ing diuretics, which are usually essential oils, (as 
juniper,) stimulate the secretory and possibly the 
filtration elements. 
Abnormal constituents of urine. Albumen. The 
most important clinically of the abnormal constituents 
of urine is albumen. It is derived from the serum al- 
bumen of the blood and may be more or less mixed with 
serum globulin. The appearance of albumen in per- 
ceptible quantities in the urine is indicative of disease. 
The presence of albumen may indicate either organic 
disease of the glomerular or tubular epithelium 
(nephritis) or marked increase of intra-glomerular blood 
pressure. If the latter condition be the cause and it be 
transient, no organic disease may result. (Physiolog- 
ical albuminuria?) Other temporary causes of albu- 
minuria are proteid plethora, the exenthemata (scarla- 
tina), renal irritation by drugs, pregnancy, etc. 
Tests for albumen. Heller’s test. Pour one-half 
inch of urine into a test-tube, and then holding the 
tube obliquely pour in about an equal quantity of H 
N 03) which by reason of its density will settle down 
under the urine. If albumen be p resent, where the 
two zones meet will be formed a white ring of pre- 
cipitated albumen. Care is necessary not to mistake 
copaiba, acid urates, etc., for albumen. Heat test ; 
Place an inch or more of clear urine in a test-tube and PHYSIOLOGY 
247 248 
PHYSIOLOGY 
apply beat to the upper part slowly. If albumen be 
present it will be indicated by a whitish coagulum 
forming- in the urine. This may vary from only a 
cloud to a dense mass, according- to quantity. Earthy 
phosphates, if present in quantity, will be precipitated 
in a similar manner, but require more heat. If ten or 
twelve drops of H N Os be added to the urine contain- 
ing the precipitate, and it be albumen, no change will 
take place, but if the precipitate be earthy phosphates, 
it will disappear. This test is not-as good as the pre- 
ceding. 
Sugar is next to albumen the most important abnor- 
mal constituent of urine. When large quantities of 
grape sugar are taken into the body we find a tempo- 
rary glycosuria, but it is only when the output of sugar 
is habitual, as from disturbance of the vaso-motor 
supply of the liver, that we have true diabetes mellitus. 
In this disease the output of urine is largely increased 
as well as the sugar. This seems to be due to a stim- 
ulation of the secretory elements of the kidney by the 
sugar in the blood, as lactose administered in large 
quantity will produce the same result. In mellituria 
or diabetes mellitus the sugar may run as high as 12 
to 15 per cent. 
Tests for sugar. Indigo-carmine test : A solution of 
indigo-carmine made alkaline with sodic carbonate, 
when boiled with diabetic urine changes from blue to 
violet, then red, and finally to a straw color. As the 
solution cools it will, if shaken, give these colors in 
the reverse order. The urine should be added, drop 
by drop, as the test is delicate. Fehling’s or Pavy’s 
test; To 20 drops of Pehling’s solution add four times 
its bulk of water, and boil for a few seconds. Add 
urine drop by drop, and if any great amount of sugar 
ibe present we will get the orange-yellow precipitate of PHYSIOLOGY 
249 250 
PHYSIOLOGY 
cupric oxide. If we get no precipitate from the first 
few drops, continue to add urine, heating occasionally,, 
till a volume is added equal to the original solution. If 
we get no precipitate, sugar is absent. This test may 
be applied to determine the amount of sugar quantita- 
tively. Blood may be found in the urine (haematuria) 
coming either from the kidney, as in malarial fevers, 
or from the urinary tract. Urine containing blood is, of 
course, always albuminous. Bile may be found in the 
urine (choluria), being eliminated from the blood by 
this channel, but evidence of its presence is presented 
in other ways, as jaundice. 
Deposits in urine. These may be either organized 
or unorganized, pathological or normal. Organized 
deposits. (1) Mucus. This is found to a slight extent 
in nearly all urine, as a flocculent cloud at the bottom 
of the vessel. (2) Pus cells. In urine they closely 
resemble white blood corpuscles and indicate inflam- 
mation of the kidney or tract. Acetic acid will resolve 
their nuclei. Caustic potash added to pus sediment 
makes it viscid and ropy. (3) Spermatozoa may some- 
times be found, usually after intercourse. (Sperma- 
torrhoea ? ) (4) Bacteria of various kinds, but not in 
normal urine. (5) Tube casts. These are of vast 
diagnosic value. They are formed by the plasma, 
which by reason of pathological conditions has come 
through the walls of the glomerulus. It coagulates in 
the uriniferous tubule, and may be forced onward pre- 
senting simply the mould of the tube (hyaline casts). 
The pathological condition may be accompanied by 
exfoliation of the epithelium of the tubule (epithelial 
casts) or by the outpouring of blood (bloody casts) or 
by the formation of pus (purulent casts). The forced 
passage of these casts often breaks them into small 
granular masses, held in place by continued coagula- PHYSIOLOGY 
251 252 
PHYSIOLOGY 
tion around them (granular casts). (It should however 
be noted that epithelium shed by the tubes in catarrhal 
states may at times be pressed into form and moulded 
into casts without fibrin; and that the same is true of 
amorphous urates.) (6) The various forms of epithe- 
lium from the urinary tract, with dirt, cotton and wool 
fibres, etc. 
Unorganized deposits. These may be amorphous, 
as urates, calcium phosphate, etc., or crystalline, as 
uric acid, calcium oxalate, triple phosphate, ammon- 
ium urate, etc. 
The urinary tract. The ureter. Beginning- with 
the calices, which open into the pelvis, it narrows into 
a small tube which extends to the bladder and pierces 
the wall of that viscus obliquely, forming a perfect 
valve. On section it shows three coats, an external 
fibrous, a middle muscular (non-striated) which is in 
its turn formed of three layers, and an internal mucous 
coat. The muscular coats consist of a thick external 
longitudinal, a middle circular and internal longitudi- 
nal, best developed in the last inch that pierces the 
bladder wall. The mucous coat (transitional) contains 
in its sub-mucosa some adenoid and mucous glands. 
The nerves of the ureter are derived from the mesen- 
teric and spermatic plexus. (This anatomical relation 
explains why in cases of nephritic colic we so fre- 
quently have the pain reflexly referred to the testicle 
or to the glans penis.) While gravity no doubt aids, 
the movement of the urine is due, primarily, to the 
action of the muscular coat of the ureter. Beginning 
in the sphincter of the papillae it is excited reflexly 
downward (nephritic calculi). This action of the 
ureters is claimed to be alternate. The nerve supply 
of the ureter is associated with that of the sphincter PHYSIOLOGY 
253 254 
PHYSIOLOGY 
urethrae as the writer has often seen the passage of a 
sound relieve a paroxysm of nephritic colic. 
The bladder is a hollow viscus, the reservoir for the 
urine, normally holding’ about a pint, but capable of 
infinite distension. The walls are composed of three 
complete coats, the mucous (transitional), sub-mucous 
and muscular. The latter is very irregular in its 
arrangement (detrusor urinae). The interior of the 
empty bladder is thrown into numerous folds or ruga?. 
The mucous coat is freely movable on the muscular 
except at the trigonum vesicas. The prostate gland 
which encircles the neck of the bladder is a very pecu- 
liar body, composed of mixed muscular (sphincter) and 
glandular elements. It is pierced by the urethra and 
ejaculatory ducts, and contains the sinus pocularis 
(uterus masculinus). The nerves of the bladder are 
from the fourth sacral and sympathetic, and numerous 
ganglia are located in the mucous and muscular coats. 
The lymphatic and vascular supply are abundant, the 
latter being from the three vesical arteries (urachus) 
in the male, and the uterine and vaginal, in addition, in 
the female. 
The urethra in the female has a purely urinary 
function, in the male it is more complex, serving 
genito-urinary purposes. In the female it is made up 
of muscular, erectile and mucous coats from without 
in, and is lined with squamous and transitional epithe- 
lium. It is capable of great dilation. The male 
urethra is divided into a prostatic, membranous and 
spongy portion. The first is lined like the bladder, 
of which it is a part, with transitional epithelium. It 
is quite dilatable, and of horse-shoe shape on section. 
The membranous urethra is surrounded by the com- 
pressor urethrae (striated) muscle, and is lined with a 
columnar-like epithelium. In the spongy portion we PHYSIOLOGY 
255 256 
PHYSIOLOGY 
find it as before of nearly uniform size except just 
behind the meatus, where it expands into the fossa 
navicularis. The meatus is lined with squamous 
epithelium. At the fossa navicularis there is a change 
in the axis of the urethra, its long axis passing from a 
horizontal to a vertical position as at the meatus. The 
prostatic glands discharge their thin milky acid secre- 
tion into this canal, as do also- Cowper’s glands, and 
the numerous mucous glands (Lfittre) along the tract 
(gleet). The secretion of the first is chiefly at the time 
of coitus, forming no small part of the seminal fluid. 
It is also a peculiar fact that while the spermatozoa 
are virile while in the seminal vesicles their power of 
active motion is not attained till in the act of ejeculation 
they are mixed with prostatic or other urethral fluids. 
Mechanical and nerve mechanism of micturition. 
As the bladder becomes distended by the increase of 
urine, no nervous impulses are generated until the 
bladder becomes almost full. (Adult, 16-18 oz.) As 
this condition is reached, impulses originating in the 
sensory terminals of the bladder wall are sent out. 
Some of these go to the sensorium, and the indescribable 
sensation of a full bladder is experienced. Others go 
to the urino-spinal centre of the cord, and there excite 
reflexly periodic motor impulses to the muscles of the 
bladder and to the sphincter urethrae. These offset 
each other for a time, but in the end the power of the 
bladder will overcome, and a few drops of urine will 
be forced past the sphincter into the sensitive part of 
the urethra. Sensory impulses starting here reflexly 
excite in the lumbar centre inhibitory impulses to the 
sphincter and it relaxes, while the bladder is still 
stimulated and the urine flows freely. This is the 
process in the child or infant. With experience man 
learns to voluntarily inhibit the tonic impulses to the PHYSIOLOGY 
257 258 
PHYSIOLOGY 
sphincter and to initiate the act by the use of the 
abdominal muscles. The influences of fear, &c., 
markedly affect this centre through the cerebrum. So 
also does suggestion, as seeing another urinate, the 
sound of falling water, etc. The emotion of modesty 
or shame is a powerful inhibitor. While the normal 
healthy bladder is uninfluenced by the presence of 
urine, unless in large amount, any excess of acidity is 
quickly irritating (alkalies) & when markedly irritated 
normal urine will excite the bladder to action even 
when in small amount (hyoscymus). 
Changes in urine after expulsion. When fresh urine 
is set away in a cool place, with time it becomes more 
and more acid. This is called the acid fermentation of 
urine. It seems to depend upon a special fungus of 
little known character, and partly, perhaps, upon the 
influence of mucus in normal urine. It results in the 
formation of free uric acid, and an increase of acid 
sodium urate, calcium oxalate, etc. This freeing of 
the uric acid is probably due to the formation of lactic 
and acetic acids, by the decomposition of certain organic 
constituents (mucus) of urine. When urine is kept 
still longer, especially in a warm place, alkaline fer- 
mentation takes place. This is evidenced by its 
reaction and ammoniacal odor. The agent is the 
micro-organism (micrococcus urae) which causes the 
urea to take up water and form carbonate of ammonia. 
'The same & kindred organisms when introduced into 
the bladder, as by a dirty catheter, will cause there the 
same ammoniacal decomposition. This is particularly 
true of the bladders of elderly men in whom changes 
in the prostate prevent the complete emptying of this 
viscus (henzoic acid). PHYSIOLOGY 
259 260 
PHYSIOLOGY 
CHAPTER X. 
METABOLIC PHENOMENA. 
The term metabolism includes that series of phe- 
nomena by which all living- org-anisms incorporate the 
substances obtained from their foodstuffs into their 
tissues, and make them into integral parts of their own 
bodies. Thus a store of potential energy is formed, 
which can, in accordance with the needs of the organism, 
be converted into kinetic energy, as muscular force, 
heat, etc. These changes in the constituents of the 
tissues result in the formation of excretory products, 
which is but another part of the process of metabolism. 
The normal process of metabolism then requires : a 
supply of food qualitatively and quantitatively suitable, 
the assimilation and incorporation of this food in the 
body, a regular transformation of tissue constituents 
in the body, the formation of waste products and their 
elimination from the body by their proper channels. 
The constructive part of this process is called ana- 
bolic metabolism, the destructive part katabolic 
metabolism. Of the functions, that of digestion is 
distinctly anabolic, while that of urinary excretion is 
preeminently katabolic, and respiration divides its 
honors. 
An analysis of metabolic processes. There is in 
each human organism, in a state of health, a daily gain 
and a daily loss of body weight. The gain is obtained 
the lungs, from the O of the atmosphere 
(insignificant); (2) the digestive tract from food, i. e. 
proteids, carbo-hydrates, fats, salts and water. The PHYSIOLOGY 262 
PHYSIOLOGY 
loss is through (1) the lungs, C02 and water ; (2) the 
kidneys, water, urea, uric acid, salts, etc.; (3) the skin, 
water, a very small amount of C02, and body emana- 
tions ; (4) the bowel, water, insoluble salts, and 
residues of foods, etc. When the income exactly 
equals the expenditure (quantitatively) we have the 
state called metabolic equilibrium. 
Chemical comparison of foods and excretory pro- 
ducts. Leaving out of consideration water and salts, 
which are excreted almost unchanged, man’s food 
consists of complex organic and yet but slightly 
oxidized bodies. (See formulae.) The excretory pro- 
ducts on the other hand are such simple bodies as C02, 
H2O, and Urea, which in its turn readily becomes 
NH;! and C02, etc. It will be seen from this, and 
what we know of interstitial respiration, that the 
excretory products are the indirect result of oxidation 
processes in the tissues. The oxidation of proteids gives 
as a result H2O, C02, LTrea, etc.; the oxidation of fats, 
C02 and H2O; while the oxidation of carbohydrates 
gives C02 alone, the H being already-satisfied. The 
prime function of the 'proteids (albumins, etc.) taken in 
is to supply the materials for reconstructing• the cells 
and protoplasmic elements which have undergone 
degeneration and death. We saw an example of this 
loss in the study of the epidermis. The body, as we 
saw, being incapable of forming albumen, no other 
food can take its place. The function of the fats and 
carbohydrates is by their oxidation to furnish the 
energy for maintaining the mechanical functions of 
circulation, respiration, etc., and also the heat neces- 
sary to maintain body temperature. It must be remem- 
bered that proteids contain all the constituents of the 
carbohydrates and fats, and can therefore take their 
place in the production of energy. This can only be PHYSIOLOGY 
263 264 
PHYSIOLOGY 
done at the cost of an enormous waste of proteid food 
and of serious injury to the digestive organs. 
The effects of starvation, partial or complete, 
demonstrate these facts clearly. Any warm-blooded 
animal deprived of all food, but water, must in order 
to maintain body temperature, and the necessary 
amount of mechanical work, utilize the potential con- 
stituents of its own body, losing weight, day by day, 
until death occurs. Adults die when they lose four- 
tenths of body weight, young individuals die sooner. 
If water be not given, of course the time is greatly 
lessened. On a purely flesh diet man cannot subsist 
long. As we have seen, the normal proportion be- 
tween the nitrogenous and non-nitrogenous foods is 1 
to 3.5. In a flesh diet (lean beef) the proportion of 
nitrogenous material or proteids, to the carbohydrates 
and fats, is vastly in favor of the former as compared 
with the above. A healthy person excretes as CO-2 
through various channels 8 to 10 oz. of C daily and 
to obtain this from such a flesh diet he must eat slbs. 
of meat a day. The digestive organs are unequal to 
this task for any great length of time. On a purely 
carbohydrate or fat diet man will live but little longer 
than when on water alone. Fats, sugar, etc., cannot 
replace the protoplasmic elements of the tissues lost. 
Still it is seen that on a diet of fat, etc., individuals 
eliminate less urea than when starving absolutely. In 
this case it is seen that the carbodrates, etc., are used 
for energy, and the draft is made on the body tissues 
only for the repair of the protoplasmic elements used. 
This albumen-sparing action of fats and carbohydrates 
is important, as a small quantity of either will greatly 
limit proteid metabolism. Carbohydrates will take 
the place of fats in food, but the amount must be larger, 
as 17 to 10; the former however are the more readily PHYSIOLOGY 
265 266 
PHYSIOLOGY 
oxidized. Fats may be formed from a proteid diet 
alone, but practically they are not so formed. In the 
wasting- process of starvation, the tissues are not used 
equally. The fats are the first to go, and ultimately 
disappear absolutely. The muscles suffer the greatest 
actual loss, but not the greatest relative loss, except 
in the very corpulent. The nervous system loses al- 
most nothing, the muscles, etc., being- used to repair 
waste here. Note the relative prominence of the ner- 
vous structures in a cadaver where death has occurred 
from tuberculosis or other wasting- disease. 
Corpulence and its prevention. Corpulence is a 
disturbance of the metabolic processes evidenced by a 
pronounced tendency to the formation of adipose tis- 
sue. It is usually the result of an inherited tendency, 
begotten of free living with little physical exercise. 
This tendency in man is a misfortune, but among our 
domestic animals it is cultivated as a virtue. The inges- 
tion of fat is not necessary to its production, as it is 
equally apt to result from carbohydrate food. This 
condition is not to be confused with fatty degenera- 
tions ; the latter may occur among the lean and thin as 
well as among the fleshy. 
Growth and its limitations. Growth is the result 
of a metabolic condition in which an amount of nutri- 
tive material is received by the organism sufficient 
not only for all its needs in the development of heat 
and mechanical work, but beyond this giving an excess 
to be used in the construction of body substance. The 
increment of gain (both in weight and stature) in the 
progress from childhood to adolescence is quite rapid 
at first, but declines year by year till it practically 
ceases at thirty and even before. The increase in the 
total weight of the average human organism from birth 
to full development is measured by the ratio 1 : 20* PHYSIOLOGY 
267 268 
PHYSIOLOGY 
while the increase of the abdominal viscera in the same 
period is in the ratio of 1 : 13. Thus we see that 
while the general mass of the tissues requiring- nutri- 
tion has been increased twenty fold, the abdominal or- 
gans, which supply this nutritive material by absorp- 
tion, have been increased but thirteen fold. In other 
words, if the needs of the organization in the way of 
expenditure had remained proportionately the same in 
infant and adult, the adult would be a loser in nutri- 
tive power by reason of a relative decrease in the 
capacity of his abdominal viscera. But in the way of 
expenditure the adult demands infinitely more, as will 
be seen by the following example : Take a child one 
meter high and let him grow to two meters. His 
height has doubled. If the general proportions of his 
figure remain the same, his strength, which is mea- 
sured by the area of the cross section of his body and 
limbs (the square), will have quadrupled, but his 
weight will be eight times as great, as it increases 
with the cube. In other words, while his stature has 
doubled and his strength has increased four fold, his 
weight, to be sustained and moved, is eight times as 
great, and on a relative decrease in nutrition he has to 
exert eight times the energy previously required to 
overcome inertia and momentum. Constructed upon 
plans essentially similar, this shows why the child in 
early life has such an excess of nutritive material over 
what is required for his needs in energy, and why in 
man the limit is reached in which all is needed for 
energy and none can be spared for growth. There 
are other factors of limitation, as the increased work 
of the heart required in the larger body, etc., while 
still other factors are in favor of the growth of the 
child, as the immensely greater relative capacity of 
the lungs. The only point in which the child calls PHYSIOLOGY 
269 270 
PHYSIOLOGY 
for a relatively greater expenditure is in supplying’ 
heat for a relatively greater radiating- surface of body. 
Heat, its sources, elimination, etc. The maintenance 
of the body-temperature requires the almost uninter- 
rupted evolution of kinetic energy in the form of heat. 
When the temperature of the surrounding- media is 
greater than man’s body temperature (93.6 F. or 37 
C.), of course the evolution of heat is not required, but 
this state of affairs is relatively rare. In certain re- 
spects warm-blooded or homoiothermal animals differ 
greatly from the cold-blooded or poikilothermal forms. 
The former maintain their fixed temperature regardless 
of changes in the media around them, while the latter 
follow quite closely the changes in temperature of their 
surroundings. This difference in relation to body-heat 
produces marked variations in functional activities in 
warm and cold-blooded creatures under the same con- 
ditions of temperature. Cold in man and all warm- 
blooded. animals increases not only heat production but 
a desire for bodily activity ; while with the cold-blooded 
forms it not only decreases heat production but makes 
them torpid and sluggish. Conversely warmth makes 
sluggish all warm-blooded creatures, and excites to 
full activity the cold-blooded. 
An analysis of heat production in the body. Heat is 
produced in the body by the transformition of the chem- 
ical constituents of the food that are endowed with 
great potential energy, into such substances as have 
little or none. The combustion of the Cof the food 
into CCb, the H into H2O, etc., whereby heat is pro- 
duced, forms the chief source. As Ois the agent of 
combustion in all cases, there is the relation of cause 
and effect between the amount of O consumed and heat 
produced. As the I muscles form the greater part of 
the tissues in which metabolism is active, they are the W^iMob'Y 272 
PHYSIOLOGY 
great centres of thermogenesis, and probably four-fifths. 
of the body heat is produced by them. The larger 
secreting- glands, as the liver, pancreas, etc., are also 
centres of marked heat production. Any chemical 
change in the constituents of the body, whereby the 
atoms pass into more stable positions and the available 
potential energy of the tissue is diminished, leads to 
heat formation. Certain physical processes are a 
source of heat, as the muscular action of the heart, it 
being confined with its resistance to the body. A cer- 
tain part of such work as is transferred to external ob- 
jects produces heat in the body, as friction, shock, etc. 
The chemical changes in the food above mentioned, 
if carried to the point of forming CCb etc., will give 
exactly the same number of heat units that the same 
food would give if burned in a furnace. The appara- 
tus for measuring the heating power of foods is called 
a calorimeter. Water is usually placed around the 
central combustion chamber or animal chamber to ab- 
sorb the heat, and the elevation in temperature of a 
known volume of water by a given amount of food can 
be accurately determined. Taken in as foods, 52 parts 
of fat, 100 parts of albumen, 114 of starch or X2Q- of 
sugar (maltose) will give the same amount of heat, i. 
e., they are isodynamic. 
Conditions influencing temperature of the body. 
The greater the metabolism in a part the greater its 
heat. It is thus that the act of secretion produces 
heat, proved by the venous blood from a gland being 
warmer than its arterial blood, and the contraction of a 
muscle produces heat. As metabolism is decreased 
during hunger (starvation), we find the temperature 
lowered during this state, while the temperature rises, 
during digestion. 
The so-called daily variations are probably results of PHYSIOLOGY 
273 274 
PHYSIOLOGY 
the accumulating- influence of meals and modifying- in- 
fluences of habit. Ag-e and feeble constitution have a 
lowering- tendency, and the loss of blood has a pro- 
nounced influence in lowering-. Certain drugs, as 
alcohol and quinine, seem to render the tissues less 
free to undergo metabolic changes, and thus lower the 
temperature. Strychnin acts in a manner just the 
reverse, and thus tends to raise the temperature. 
The regulation of temperature. To maintain the 
body temperature constant as we find it in health there 
must be some agencies in the body that contribute to 
its regulation. These agencies are the heat-producing 
(thermogenic), the heat discharging (thermolytic), and 
the heat balancing (thermotaxic). The last, function- 
ally the highest, is onl}r found in homoiothermal animals, 
and is easily disturbed. Having considered the ther- 
mogenic agencies in the previous sections, and the 
thermolytic under the functions of the skin, we will 
•only consider thermotaxic phenomena here. From 
what we learned of the skin we can see how the 
temporary application of moderate cold can excite the 
functions that raise the body-heat, and the application 
of heat excite, in a similar way, those that lower it. 
Cold in any great degree produces involuntary muscu- 
lar movement (rigors, etc.) as well as a desire for 
-voluntary muscular movements, both of which produce 
heat. Cold sends much of the blood to the deeper 
:parts, oxidation is increased, and we breathe more 
rrapidly to eliminate the C02 formed, but the same 
movements supply the increased amount of O needed 
■for combustion, and at the same time reduce the general 
temperature by evaporation from the lungs and the 
warming of the large amount of cold air used. The 
presence of heat produces the reverse of these processes. 
Cold, al ways increases one’s appetite for food, especially PHYSIOLOGY 
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PHYSIOLOGY 
fats ; in hot weather the reverse holds true, and if 
food is wanted it is not fat. 
Storage of heat, clothing, etc. Warm clothing- is 
the equivalent of food in that it saves the heat of the 
body, by preventing- its radiation, and thus less food is 
burned to maintain the normal temperature. As small 
bodies have greater radiating surface in proportion to 
their bulk (measure of heat production), they must be 
more warmly clad than larger bodies for the same 
temperature. Thus we see why children need rela- 
tively warmer clothing than adults, and why they are 
dwarfed by exposure, being required to use for heat 
what should have gone for body-construction. Observe 
the influence of these laws on the workings of 
nature. E)ven in the tropics no small bird or animal is 
naked although the elephant, hippopotamus, rhinocerus 
and tapir are so found. In northern latitudes such an 
amount of food is needed for heat production that but 
little can be used for growth, giving such dwarfing as 
is found in the Shetland and Iceland ponies. In the 
selection of materials, their capacity for conduction 
(fur, wool, cotton, flax, silk,) for radiation (rough, 
smooth,) for absorption (black, dark, light), for per- 
meability of air, etc., must be considered. 
Fever. Fever (;pyrexia) consists in a “disorder of 
the body-heat.’’ The mechanism for the regulation of 
the balance of income and expenditure is disturbed. 
Ivittle of the potential energy is transformed into 
mechanical work in this state, almost all being trans- 
formed into heat. Combustion in the body is vastly 
increased, giving rise to the wasting or “consumption” 
long observed. The excretion of COa is therefore 
vastly increased (60-80 per cent.); the elimination of urea 
also (30-60 per cent.), and the urinary pigments, potash 
salts, etc., likewise. But we must never forget the PHYSIOLOGY 
277 278 
PHYSIOLOGY 
difference between calorimetry and thermometry. For 
instance, fever may result from deficient heat elimina- 
tion, with very slight increase in production and no 
serious injury to tissue, and yet the thermometer show 
pyrexia. On the contrary, if heat formation and 
elimination be both increased, with serious injury to 
the patient, the thermometer may show little or no 
rise. High temperature (hyper-pyrexia) shows such a 
marked thermotaxic disturbance as would lead us to 
believe that not only are the heat producing processes 
increased, but heat eliminating processes are diminished. 
High temperatures long continued will produce fatty 
atrophy of the tissues, as heart muscle, etc. (typhoid 
fever). Quinine, and perhaps alcohol, are almost the 
only drugs that act as antipyretics by alone preventing 
heat formation, most antipyretics, as antifebrin, anti- 
pyrin, phenacetin, etc., acting largely by increasing 
heat elimination, as well as by preventing heat- 
formation. PHYSIOLOGY PHYSIOLOGY 
CHAPTER XI. 
THE CONTRACTILE TISSUES. 
The simplest form of that shortening-, which when 
exerted by masses of cells in a definite direction we 
call the contraction of muscles, is seen in the amoeba. 
It is also seen in white blood cells, salivary corpuscles, 
etc. It is however indefinite in direction in all of these. 
The first evidence of a tendency to definite movement 
is seen in the cilia, the vibrating- hair-like processes 
seen on certain cells. They are more or less flattened 
appendages attached to the free ends of the cells, often 
as many as a score to each cell. They do not vibrate 
in unison, but a wave of movement travels from cilia, 
and across from cell to cell, at regmlar periods, many 
times a second. The amplitude of this vibration is 
20°-30°, and the return is only one-half the speed of 
movement in the direction of its impulse. Under the 
influence of g-entle heat they are stimulated to increased 
movement, while cold retards them. Anaesthetics, 
like ether and chloroform, produce a temporary pa- 
ralysis of their action, and opiates produce the same 
effect in less degree. Caution as to the use of opium 
in cougdi mixtures is necessary, especially with children. 
Much hig-her in the scale than these simple hair-like 
bodies we find the muscular tissues. 
Muscular tissues, their chemistry, etc. The three 
forms of muscle fibre, striated, cardiac, and non- 
striated, all consist alike of protoplasmic contractile 
elements. The variations in structure seen histologic- 
ally and the difference in time of action, nerve supply^ PHYSIOLOGY 282 
PHYSIOLOGY 
etc., are acquirements of late date, the internal sub- 
stance being- essentially the same. Striated muscle is 
the highest type, and it is of this form that most is 
known ; being not only the most important and 
abundant, but being also voluntary, it is better suited 
for experiment. Of this form of muscle, as of the 
others, it may be said that the protoplasmic sarcous 
substance is as much a fluid as a solid. Taken in mass,, 
muscle contains 75 per cent, water, and of the 25 per 
cent, of solids, 12 are proteids, while salts, extractives 
and fats form the remainder. From fresh disintegrated 
muscle we can express a faintly alkaline or neutral 
fluid, the muscle plasma, which spontaneously coagu- 
lates, forming myosin and an acid muscle serum (rigor 
mortis). Traces of a myosin ferment have been found. 
Striated muscle is very elastic, and recovers, if not 
overstretched, its original length almost completely. 
The increment of lengthening with an increasing load 
is a receding one ; i. e., if the load of a muscle be 
repeatedly doubled it will not stretch to double the 
amount previously stretched, but less and less till it 
will no longer stretch at all. This elasticity is of 
service in giving quickness of action, as no time is lost 
in taking in slack when a muscle is stimulated to action. 
In excised muscle electrical currents may be detected 
with the galvanometer, having a definite direction and 
constancy. They are called the natural muscle currents 
in passive muscle. In such they are from the pole to 
the equator in the muscle and hence the reverse in 
direction in the conductors outside the muscle. Not 
only do they pass from pole to equator, but the point of 
lowest potential being at the centre of the polar section, 
and the highest at the periphery of the equatorial plane* 
intermediate currents can be seen of varying intensity. 
These currents are lessened by fatigue, and gradually PHYSIOLOGY 
283 284 
PHYSIOLOGY 
disappear with loss of vitality. To prevent the 
influence of polarization in these experiments, what 
are called non-polarizable electrodes must be used. 
These electrodes are usually made of glass tubing 
filled with a good conducting fluid and ending in a tip 
of porous clay that absorbs the fluid. Wires inserted 
into the fluid of the tubes connect with a delicate 
galvanometer. 
The active state of muscle. A muscle has the 
power when properly stimulated, of passing from the 
passive elongated condition into one of contraction or 
activity. The degree of this capability is called its 
irritability, and the influences bringing it about are 
called stimuli. The various stimuli may be enu- 
merated as follows : (1) The normal stimulation, such 
as we see in healthy muscles acting under the impulse 
of the will through the centres and nerves. (2) Elec- 
trical stimulation, produced by any variation in the 
intensity of an electric current when passing through a 
muscle. (3) Chemical stimuli are produced by the 
application of certain drugs to the cut end of a muscle, 
viz : mineral acids, many mineral salts, dilute glyce- 
rine, etc. (4) Mechanical stimulation may result from 
a pinch or blow, etc. (5) Thermic stimulation. If the 
temperature of a muscle bs reduced, it will shorten 
before freezing ; and if raised, it will begin to contract 
below body temperature and pass into a state of spasm 
(heat rigor) about 121° P. In experimenting the sec- 
ond method chiefly is used, the induced (Paradic) cur- 
rent being the most convenient. 
Changes in muscle on entering the active state. 
The metabolic changes always taking place in passive 
muscle are markedly intensified in active muscle, and 
new chemical decompositions occur. The blood vessels 
are all dilated, the amount of O absorbed is increased, PHYSIOLOGY 
285 286 
PHYSIOLOGY 
and the C02 excreted markedly raised. There is less 
glycogen and maltose in an active muscle than in a 
passive one, but muscles devoid of all these compounds 
will still respond to stimuli. At the same time these 
carbohydrates are habitually the chief source of mus- 
cular energy. An active muscle becomes acid in reac- 
tion, and its temperature is increased. It becomes less 
elastic during the active state, that is, a given weight 
will extend it more. The most marked change is in 
its electrical current. When a stimulus to action is 
applied through the muscle nerve, the natural current 
at once ceases. This is called the negative variation 
of the muscle current. It is shown with difficulty by 
the galvanometer, but if the nerve supplying another 
muscle be laid so that one point touches the pole and 
another the equator of the muscle stimulated, its nega- 
tive variation acts (by induction) as a stimulus to the 
applied nerve, and excites a contraction in the muscle 
it supplies. (Rheoscoplc frog.) 
Rigor Mortis. Both striated and non-striated mus- 
cles at a variable time after death pass into a state of 
cadaveric rigidity or rigor mortis. The cause is the 
spontaneous coagulation of the m}7osiu factors within 
the sarcolemma of the muscle fibre. During the process 
heat is formed and acid set free, as in active muscle. 
The onset varies from a few moments to seven hours, 
and lasts longer the later it begins. Violent muscular 
action before death hastens it. Its duration is usually 
from one to six days. It begins in the muscles of the 
jaw and extends downward, ceasing first where it 
began. 
Recording muscular contractions. The apparatus 
used in recording graphically the periods and phases of 
muscle contraction is called a myograph, of which we 
have several forms. When a muscle is coupled to this PHYSIOLOGY 
287 288 
PHYSIOLOGY 
apparatus and stimulated, the resulting- muscle curve 
that is traced gives us an accurate knowledge of its 
contraction. The abscissa gives us the duration of 
the contraction, and the ordinates give us the degree of 
contraction at any particular time in its cycle. By a 
parallel chronographic tracing accurate periods of time 
can be read off on the abscissa. 
A simple muscular contraction. When a single in- 
duction shock or momentary stimulus is applied to 
human striated muscle, the myograph records : (1) A 
so-called latent period, which elapses after the muscle 
is stimulated, before we get a reaction. It lasts usually 
.01 of a second, often less, and its relation to the neg- 
ative variation is such as to lead us to believe it is the 
time taken in the production of this change. (2) A period 
of increasing- energy or contraction, in which the ordi- 
nates show a slow, then a rapid and then again a slow 
rise, lasting .03 to .04 of a second. (3) A period of 
decreasing energy or elongation, in which the fall is 
first slow, rapid and slow, lasting about .04 of a second. 
The total cycle is thus from .08 to .09 of a second. 
There is a period of after vibration that varies with 
the weight and elasticity of the muscle. The breaking 
shock produces in muscle stronger contraction than 
a making shock. In the long muscles, as the sartorius, 
the progress of the wave of contraction can be meas- 
ured, and is found to be 12 or 15 feet per second. 
Muscle fatigue lowers the curve of contraction and 
lengthens the latent period. A contraction from a 
single stimulus shortens the muscle to nearly one-half 
of its original length. 
A summation of contractions, or tetanus. EAch time 
a muscle receives a strong induction shock it responds 
with a full contraction, but this is not the maximum 
amount the muscle can contract under repeated stimuli. PHYSIOLOGY 
289 290 
PHYSIOLOGY 
If a muscle receive a second impulse of proper strength 
when at the apex of its curve, it will respond with a 
second contraction, and the sum of the effect produced 
will equal the height of the two contractions. This 
may be continued by repeating the stimuli until the 
muscle reaches its maximum amount of contraction, 
something like one-forth of its original length. When 
these stimuli are repeated at intervals of less than the 
■duration of a single contraction, a summation of con- 
tractions occurs and the results accumulate until the 
muscle remains fixedly contracted during the period 
of stimulation, and we call this condition tetanus from 
the similarity in result to that induced in the disease of 
this name. It cannot long be maintained with a weak 
stimulus, without increasing the strength of the stim- 
ulus. The number of stimuli necessary to maintain 
this state in human muscle is not less than_2o per sec- 
ond. If kept up for some time the muscle does not at 
once return to its normal length, but remains tempo- 
rarily partially contracted (cramp). 
Muscle irritability and fatigue. The activity of 
muscle tissue depends upon a proper supply of nutri- 
tion, and if long cut off from this supply it loses its 
irritability. We also know that muscles, perfectly 
supplied with blood, after prolonged activity become 
fatigued and are incapable of further action. This is 
the result of the accumulation of the decomposition 
products, often called “fatigue stuffs’’in the tissues, 
as we would expect from past studies. Time (rest) 
suffices for the removal of these accumulative products, 
but it can be hastened b}T stimulating the action of the 
skin, etc., or by massage. (Turkish bath.) These 
products are peculiarly apt to accumulate in muscles 
that are put to unaccustomed exercise, while habitual 
exercise of a proper character (training) greatly in- PHYSIOLOGY 
291 292 
PHYSIOLOGY 
creases the eliminative power of these organs. That it 
is the presence of these fatigue stuffs alone that is often 
the cause of muscular incapacity, is proven by the fact 
that if a prepared muscle be stimulated until it will no 
longer respond, and we then wash out its vessels with 
a simple saline solution, its vigor is renewed. 
Muscle tone. While the tracing of a tetanized 
muscle is a straight line, the contraction is produced by 
a series of variations in tension that cause the muscle to 
give forth a distinct tone or note. This muscle tone 
can often be heard, sometimes in the disease called 
tetanus. It corresponds to a note produced by vibra- 
tions of 20 or more to the second. 
Non-striated muscle. For the histology, nerve 
supply and peculiar distribution of this tissue you will 
refer to previous lectures. Its response to stimulation 
is not rapid like that of its kindred tissue, but is slow 
and steady, the contraction wave passing from cell to 
cell. There are two points in the body, however, in 
which it is possessed of reasonably rapid -movement, 
viz., in the iris and in the intestinal coats. It is 
slowest in the blood vessels and next perhaps in the 
uterus and its latent period in the uterus is about one 
second. Cardiac muscle responds poorly to electrical 
stimulation but is singularly sensitive to mechanical 
stimulation, as evidenced in the palpitations produced 
by the upward pressure of an overdistended stomach, 
(carminatives). Rigor mortis invades all muscular 
tissues, even the uterus responding to the extent of a 
post mortem expulsion of its contents. 
Application of the skeletal muscles. With few excep- 
tions skeletal muscles are attached at both origin and 
insertion to bones, which they move as levers. The 
bones of the body represent all of the three classes of 
levers. One bone may be made to illustrate all of the PHYSIOLOGY 
293 294 
PHYSIOLOGY 
three. The ulna (and radius) represents the first in 
striking- a blow, the second in raising- the body on the 
extended arm, and the third in lifting- a weig-ht in the 
hand, in the semiflexed position. 
CHAPTER XII. 
THE NERVOUS SYSTEM. 
The nervous system includes the various mechanisms 
by which the distant parts of the body are kept in 
functional relationship with one another. The brain 
and spinal centres are kept informed of the condition of 
various parts of the body and its surrounding’s, and in 
turn reg-ulate the activities of the various org-ans. In 
other words it is the telegraphic system of the organism. 
A sketch of the system and methods of study. We 
have seen simple protoplasm (amoeba) receive and trans- 
mit impulses, and on a higher scale we saw the same 
power possessed by muscle fibre, but the transmitter of 
nervous impulses in the body is a highly differentiated 
and delicate protoplasmic cell process specialized for 
this purpose. As in the telegraphic world some of these 
nerve cell processes are insulated (medullary sheath), 
and some are not, but all have on their line of conduction 
a relaying battery or cell body to energize the impulse 
they have received. When we see that the fibrils that 
conduct and the cell bodies—that relay and receive are 
all microscopic in size and complex in arrangement, we 
will understand the difficulties of their dissection. 
When the fibres are in small groups or isolated cords 
the problem is easy, but when the fibres run in large PHYSIOLOGY 
295 296 
PHYSIOLOGY 
complex cords (as in the spinal axis) or traverse masses 
of other nervous tissue, dissection is impossible. The 
following- methods have been used to trace the fibres 
in such cases. (1) Turck's method. Discovering- that 
nerve fibres deg-enerate when severed from their 
controlling- cells, he studied the degeneration that 
resulted from the destruction of certain limited areas of 
the brain, etc., in man and the lower animals. (2) 
Gudden s method. As we saw, Turck destroyed or at 
least studied the results of the destruction of the central 
endings of the nerve fibres. The author of this method, 
on the contrary, applied the principles of degeneration 
by destruction of the peripheral endings. He removed 
in very young animals an eye or an extremity, etc., and 
then noted at a later period the central degenerations 
that ensued. (3) Flechsig's method. At a later date 
the author of this method observed that in the embryo 
certain bundles of nerve fibres in the brain and spinal 
cord become completely developed before others. By 
means of sections of embryonic brains he was able to 
confirm the result obtained by Turck’s method. (4) 
Following upon these experiments come those of Ferrier 
(and Munck), who, exposing the cortex of the brain, 
stimulated the centres learned from degenerative 
methods, and noted the muscular reaction that followed. 
(5) Finally the study of the comparative anatomy of the 
nervous system, by and others, showed that in 
some animals environment and habits of life had pro- 
duced degeneration of certain organs, and consequently 
of their nerve supply, and from this source much was 
learned. So far from the standpoint of history. 
(6) In the early part of this decade Weigert devised 
a process of staining by which nerve fibres, whether 
degenerated or not, could be the better traced, and 
Golgi soon after began the improved methods of staining PHYSIOLOGY 
297 298 
PHYSIOLOGY 
by which the true histological structure of the nervous 
system was first clearly brought out. The work of 
these men, with that of Ramon y Cajal and His, has 
absolutely changed our ideas of nervous structure. 
First, the old idea of a nerve “fibre” connecting two 
remotely located nerve “cells” has been shown to be 
false. The structural frame work of the nervous 
s}’stem, the neurolgia, is now known to contain but 
one functional unit, the true nerve cell or neuron. 
Prom this neuron, and usually from opposite poles, 
grow out processes. 
The first type of these, a long slender and but 
slightly branched cell process, is called the axon and 
as it is often in the major part of its course covered 
with a medullated sheath, it is recognized as our old 
friend, the “medullated nerve fibre.” The few 
branches coming off from an axon, called “paraxons,” 
come off at right angdes to the main process, and end 
in fibrillated tufts by simple free terminals. The 
other type of process, far less highly specialized, seems 
but a protoplasmic outgrowth of the cell. In most 
cases, however, it rapidly subdivides and forms an 
aborescent expansion of terminals called dendrites. 
The cell body from which these nerve processes or 
“fibres” extend is of various sizes and shapes, but seems 
always to show a cell wall and an intercellular stroma 
with which the axonic process seems to be continuous. 
The cell processes, while always slender, vary greatly 
in length, some being but the fraction of an inch while 
others are a yard or more long ; for example, the axons 
and dendrites which form the nerve “fibres” of the 
nerve trunks of the lower extremity have their neurons 
in the cord and on its posterior root. The route, there- 
fore, of the nerve impulses from, let us say, the foot 
to the brain and the brain to the foot, is made up, as. PHYSIOLOGY 
299 300 
PHYSIOLOGY 
far as conduction is concerned, of a series of nerve 
cells or neurons with their long- conductive nerve 
processes on axons and their more arborescent ter- 
minals, the dendrites. The most singular thing- in 
connection with this chain of conductile units is that 
the terminal processes of one neuron never fully touch 
those of another. The axons, come quite near to the 
dendrites and it may be that in the active state the}7 
extend their terminals and touch, as a part of the act 
of conduction, but in the cell as seen in the dead bodv 
axonic and dendritic terminals are always free. As 
far as the body of the neuron is itself concerned, the 
dendrites are functionally afferent (cellulipetal), while 
the axons are the bearers from the cell of efferent im- 
pulses (cellulifug-al). In short, in nerve conduction we 
now have, in the place of the old hypothetical conjoined 
nerve cells and fibres, a chain of anatomically isolated 
units. In figurative terms the dendrite of a neuron re- 
ceives a stimulus which it conducts to the cell body, 
from this point it is relayed, so to speak, to the axon and 
proceeds to the axonic terminal. Here, in a manner 
not yet understood, it is conveyed by means of another 
neuron, on toward the higher centres and brain. In 
the cortex of the brain it must, as we can see, reach a 
final neuron where conduction ceases and perception, 
or a voluntary or even a reflex efferent return, begins. 
In corroboration of the last there are monaxonic, dk 
axonic and polyaxonic neurons both in the cortex and 
in the cord. 
From the above we see that we should, in the strict 
sense, no longer speak of nerve “cells” and nerve 
“fibres,” and yet, not only is it impossible to overcome 
the usage of years in a day, but if we use the terms 
cell and fibre, with a due appreciation of what they are 
known to be, we cannot improve on them. PHYSIOLOGY 
301 302 
PHYSIOLOGY 
Functional classification of nerves. Cell processes 
on “nerve fibres” may, still as previously agreed, be 
classified according to tlieir function. In modified 
form, then, as compared with page 34, we may 
classify them as follows :—(1) Afferent nerves, which 
bear impulses from the periphery to the centres. They 
are called sensory when they convey an impulse which 
will give rise to a percept regardless of whether this 
perception come through the nerves of special sense 
(sight, taste, smell or hearing) or through the nerves 
of general sensation. The term general sensation 
includes the sense of touch, of temperature, of muscle 
sense, etc., or th q exaggeration of these, pain. Certain 
afferent impulses which arise from the viscera, etc,, 
may induce reflexes of motion, secretion, or inhibition, 
without giving rise to a mental perception, and such 
afferent impulses are called excito-reflex. These may, 
however, bear vague impulses of general sensation, as 
impressions of hunger, fatigue, etc. (2) Efferent 
nerves, which carry impulses from the centres to the 
various organs throughout the body. Those which go 
to the muscles, either striated or non-striated, are called 
motor impulses. Those which call forth the activity 
of a gland, secretory impulses. Those which check or 
prevent some activity by the impulse which they carry, 
inhibitory. Those which seem to control the nutritive 
processes or metabolism of the various tissues, trophic, 
etc. (Electric impulses in electrical fishes belong to 
the efferent class.) Intercentral nerves act as bonds 
of union between the several ganglionic cell masses or 
centres of the nervous system. The two sides of the 
brain, medulla, etc., are intimately united by such 
fibres. They are often called associating fibres. 
Nerve stimuli. L/ike muscle, nerves may be 
regarded as having a state of rest and a state of activity, PHYSIOLOGY 
303 304 
PHYSIOLOGY 
but the two states are not obvious in the same striking- 
way as in muscle. As in muscle, the state of activity 
is brought about as the result of stimuli. With but 
few exceptions, the same stimuli that produce the 
active state in muscle will produce it in nerves. The 
various forms of stimulus .for nerves are, (Ij The 
normal or physiological stimulus. Of this we know 
but little as it is not as yet explainable by any phys- 
iological law. We only know that so long as a 
certain force or “spirit” abides in a healthy body that 
body will obey its behests in opposition to the phys- 
ical laws of inertia, momentum, gravity, etc. (2) 
Electrical stimulation. For both experimental and the- 
rapeutical purposes this is the most important of them 
all for the physiologist. As in the case of muscle, 
any sufficiently rapid variation in the intensity of an 
electrical current passing through a nerve will bring 
about the molecular change which we call excitation, 
and the nerve will initiate an impulse. (3) Chemical 
stimulation is produced as in muscle, by the application 
of various drugs, especially those that abstract water. 
Ammonia will excite a muscle, but has no effect upon a 
nerve. (4) Mechanical stimulation will give the same 
result in nerve as in muscle, while (5) Thermic stimu- 
lation is far less intense than in muscle. The poison 
curari, or as it is also called woorari, will, if injected 
into an animal in proper dose, paralyze the last neuron,, 
next the muscle, and prevent all muscular action. Its 
influence on afferent nerves is uncertain. 
Electrical properties of nerves. In a nerve, as for 
example a section cut from the sciatic, we find the 
same natural electric current that we find in muscle 
similarly excised, and we get much the same negative 
variation when the nerve is similarly stimulated. We 
also find that if an excised nerve be tested either at the PHYSIOLOGY 
305 306 
PHYSIOLOGY 
two poles or at any two points equidistant from the 
equator, a constant current flows in it called the axial 
icurrent, in a direction contrary to the normal direction 
of its impulse. We can therefore see that the so-called 
negative variation is here a more complex change than 
in muscle. Using the electric current in experimenta- 
tion on nerves, we find it best to stimulate by placing 
the wires from a battery at different points on the 
nerve. In view of the fact that it is the variation in 
the intensity of a current that initiates the impulse in a 
nerve, the question arises, at which pole does the 
impulse start ? As the current enters the nerve at the 
positive pole or anode in a making shock, and leaves it 
at the negative pole or cathode in a breaking shock, we 
would expect the impulse to begin at these points 
respectively. The facts are found to be just the con- 
tram7. In a making shock the stimulation takes place 
at the cathode, and with a breaking shock, at the anode. 
If a strong constant current pass through a section of 
nerve for some moments, we get on breaking in place 
of a simple contraction a temporary tetanus (Ritter’s 
tetanus). The impulse is always stronger with a given 
current the more distant from the muscle the stimula- 
tion be applied to the nerve (avalanche theory ?). The 
impulse wave travels in nerve at about 35-40 yards per 
second, a little more than ten times the speed of the 
-contraction wave in muscle. 
Electrotonus and its results. When a constant 
-current is passed through a section of nerve the natural 
currents disappear, and in their place is a current 
running throughout the length of the nerve, and in the 
-direction of the exciting (polarizing) current. It is 
most marked near the polarizing current. The passage 
to this condition, the state of electrotonus, is evidenced 
by pronounced changes in the irritability and con- PHYSIOLOGY 
307 308 
PHYSIOLOGY 
ductivity of certain parts of the nerve. Great increase 
of irritability is seen in the region of the cathode 
(catelectrotonus,) and marked decrease of irritability in 
the region of the anode (anelectrotonus). Between the 
electrodes in the intra-polar region lies a point in which 
the irritability and conductivity is normal, called the 
indifferent point. With a strong current this point 
moves toward the cathode, and reduction and exaltation 
of excitability are respectively intensified. The result 
is that almost the whole intra-polar segment becomes 
anelectro-tonic and incapable of conducting an impulse. 
There is a variation in the results of this polarizing 
current, dependent upon whether it flows with the 
course of the nerve’s impulse, a “ descending ” current, 
or against it, an “ ascending ” current, and also in the 
results that follow the opening or closing of the 
circuit. 
Degeneration of nerves. Nerve fibres remain in a 
condition of normal nutrition only so long as they are 
connected with their “centre” that presides over the 
nutritive or trophic processes in the nerve. Late 
studies seem to indicate that the body of the neuron is 
the centre which presides over the nutrition of its 
axons and dendrites. The trophic centres, or cell 
bodies for the motor spinal nerves are in the anterior 
horn of the cord at their origin, while the trophic cen- 
tres for the sensory spinal nerves are in the ganglion 
on the posterior root. When any part of a nerve 
(spinal) is separated from its trophic centre, in from 
four to six days it will begin to degenerate, and so 
continue till in two weeks or more the peripheral or 
cut-off portion is functionless. The fibres of the 
stump the next cord, or brain, degenerate very slowly, 
and then only from functional inactivity. This is called 
retrograde degeneration. PHYSIOLOGY 
309 310 
PHYSIOLOGY 
The cut or injured fibres of the spinal cord itself 
always degenerate in the direction of their impulse. 
Lesions of the sensory columns degenerate upward 
from the point of section (ascending) and the motor 
columns downward (descending). 
Reaction of degeneration. Muscles which have 
been, for some time, cut off from their spinal centres of 
control present a peculiar response to electrical stim- 
ulation. The motor nerves which supplied them being 
“dead,” and irresponsive, we would expect no response 
from the muscle, but we find as follows ;—To the 
induced or faradic current, to which a muscle is 
usually most susceptible, no response, or at most a 
feeble one ; while to the constant or galvanic current 
the contraction, while not so strong, is more prolonged 
than usual. We also get C. A. C. =C. K. C. which 
is against the rule, but the first is the more practical 
test. When we learn that a muscle paralyzed by 
injury of the motor cortex or cord above the level of 
its spinal segment does not present the reaction of 
degeneration ; while injury to its (motor) spinal nerve 
or the cord at its segment does give this reaction, we 
can see the practical uses. In short it sometimes 
enables us to differentiate central and peripheral palsies. 
The other practical applications of electricity in diag- 
nosis are, in addition to the above, to unmask malinger- 
ers, to prove the existence of death, to detect metallic 
bodies in the tissues, etc. 
Functions of nerve cells or neurons. The nerve 
cells or neurons are the real actors in nervous opera- 
tions, the fibres as we have seen being but their agents. 
Terminal cells (neurons) of various kinds are placed 
in all the superficial parts of the body, and receive 
through their dendrites impulses of the most varied 
kinds. Some of the more highly specialized types PHYSIOLOGY 
311 PHYSIOLOGY 
(special sense terminals) receive only luminous, sono- 
rous, odorous or gustatory impulses. Others, by far 
the greater number, (touch and temperature corpuscles) 
are generally distributed over the entire body, where 
they will be brought into contact with the mechanical 
and thermal conditions surrounding the body, and 
make known to us our environment. Still other cells 
are more deeply placed in the tissues to act as local 
distributing agents of impulses, as the visceral ganglia, 
etc. Still others, deep in the tissues, report upon the 
conditions of functional activity, as pressure and 
muscle-sense, etc. In addition to and above all these 
are the aggregated masses of central neurons which 
we term centres. These have not only the power of 
receiving through their dependent neurons impulses 
to be co-ordinated and recorded, but some have a still 
higher power, that of initiating impulses which appear 
as movements, etc., in the organism. Taking no note 
of the psychological and spiritual questions here in- 
volved, we may say that the nerve centres possess the 
powers of reflexion, augmentation, inhibition, co-ordi- 
nation and automatism, while in them we also find the 
powers of higher mental activity, including perception, 
volition, memory and thought. PHYSIOLOGY 
313 314 
PHYSIOLOGY 
CHAPTER XIII. 
THE SPINAL CORD AND ITS CENTRES. 
The spinal cord includes not only the anatomical cord, 
but the medulla, with its nuclei and cranial branches, 
the pons varolii and its peduncles, and the diverging 
crura cerebri above. In the study of these parts we will 
pass from the simple to the complex, and hence we will 
take up the cord from below up, in order, leaving- the 
complex nerves of the medulla and their nuclei for 
further study. 
The spinal nerves. The thirty-one pairs of nerves 
which leave the spinal canal by the intervertebral 
openings are called spinal nerves to distinguish them 
from the cranial nerves above. They are all attached 
to the spinal cord by two roots, an anterior or motor 
root, and a -posterior or sensory root which has on it a 
rounded ganglionic enlargement, the trophic ganglion. 
These roots unite in the intervertebral canal, and from 
this point the nerve is a mixed nerve, that is capable of 
carrying both sensory and motor impulses. In short a 
spinal nerve trunk consists of the axons (motor) and 
dendrites (sensory) of neurons which are found in the 
gray matter of the cord and in the ganglion on its 
posterior root. Studied as a whole, a typical segmental 
spinal nerve, formed as above, consists of three branches 
on each side. These are (I) The posterior primary 
division, small in size and supplying the muscles of the 
back and dorsal integument with motion, sensation, etc. 
(2) The anterior primary division (somatic), the largest 
and most important, supplying the body wall and the PHYSIOLOGY 
315 316 
PHYSIOLOGY 
limbs, where they exist, with motion, sensation, etc. 
(3) The visceral or splanchnic division (ramus commu- 
nicans) unites the spinal axis with the sympathetic 
gangliated cord, and supplies the viscera, blood vessels, 
etc., with vaso-motor, excito-reflex, sensory and motor 
filaments. 
The spinal cord, its structure, etc. The cerebro- 
spinal axis consists of neurons and their processes held 
together by neuroglia. Where the neuron body is found 
the color is dark or gray, where only axons and dendrites 
are grouped it is white. Hence the cord will show us 
two distinct kinds of substance, the white matter and 
the gray. In the brain the gray matter is chiefly on 
the surface (cortex), while a smaller portion is in the 
central part, with the white fibres between. In the cord 
the gray matter is all in the centre, and the white fibres 
surround it. This gray matter is arranged roughly in 
the shape of a letter H. The parts corresponding to 
the two verticals are called respectively the right and 
left cornua. The horizontal portion is the gray com- 
missure, anterior or posterior as it lies before or behind 
the central canal. The periphery of the cord is marked 
by the following points. In the central front part is 
the anterior median fissure, outward from this on either 
side the funiculi of the anterior roots, while the post, 
median fissicre (?) is in the centre behind, and lying 
externally to this the posterior funiculi. The white 
tracts (communicating fibres ) within the limits 
marked above are, (1) The direct pyramidal tract 
(Turck’s) lying on either side of and contiguous 
to the anterior median fissure (motor). (2) The pos- 
tero median tract (Golls) lying on either side of and 
diverging from the posterior median fissure, (sensory). 
(3) The poste.ro external tract (Burdachs) lying external 
to the above and extending outward on either side to PHYSIOLOGY 
317 318 
PHYSIOLOGY 
the posterior roots (sensory). (4) The direct cerebellar 
tract, a thin superficial plane of fibres extending' for- 
ward on either side almost to the funiculi of the ante- 
rior roots (excito-reflex). (5) The crossed or lateral 
■pyramidal tract, a large column that came originally 
from the opposite side, and here lies between the 
above and the gray cornua of either side (motor). (6) 
The anterior root zone is the region lying- around the 
funiculi of anterior roots and extending- from the direct 
pyramidal tract on either side, outward and backward 
to the direct cerebellar tracts before mentioned (mixed 
impulses). The gray matter is subdivided into the 
following parts—anterior (motor) and posterior (sen- 
sory) gray column, applied to the anterior and posterior 
extremeties of the gray cornua respectively, and the 
vesicular column (Clarke’s) found in certain parts of 
the cord, in the angle between the post-gray column 
and the gray commissure. The white tracts viewed 
collectively give th q anterior and posterior white col- 
umns, each pair united by the anterior and posterior 
white commissure, and on the lateral aspect of the 
cord the lateral zvhite columns. 
The medulla oblongata. This is the expanded 
portion of the cord at the base of the brain. It consists 
of the representative parts of the cord above given, 
with some additional gray matter. To picture the true 
changes taking place here in the pirts of the cord, 
imagine the posterior median fissure spread wide open, 
down to the central canal, as by the thumb nails. The 
open space disclosed is the floor of the fourth ventricle. 
Observe that this would bring the anterior gray col- 
umns nearer the median line, and the posterior gray 
columns nearer to the lateral parts of the floor. The 
important changes in the relationship of the white 
columns in the medulla are the following ; The white PHYSIOLOGY 
319 320 
PHYSIOLOGY 
lateral column almost disappears in the medulla, as 
its direct cerebellar tract becomes the restiform body, 
and forms the inferior peduncle of the cerebellum, 
while the large crossed pyramidal tract goes forward 
and across to the other side to enjoin the direct pyra- 
midal tract on its inner side. The fibres of the posterior 
median tract are continued into the medulla as the 
fasciculus gracilis, which here expands by reason of 
the formation of a gray nucleus, the gracile nucleus or 
clava, within its walls. The fibres of the postero-lat- 
eral tract, which seem intimately related to those of 
the above tract, continue upward to form the fasciculus 
cuneatus of the medulla, and here also expand from the 
formation of a gray nucleus, the cuneate nucleus. 
Some of the fibres of these two columns do not termi- 
nate in their respective nuclei, but pass on to join that 
intermingling of transverse and longitudinal fibres 
with gray matter, which gives us the so-called for- 
maiio reticularis in the body of the medulla. 
The superadded gray matter of the medulla is 
found chiefly in the olivary body, with its nucleus the 
corpus dentatum, and the other smaller masses are the 
gracile nucleus of the fasciculus cuneatus. The pre- 
existing gray matter of the cord is spread out on the 
floor of the fourth ventricle, its lower and outer 
portions entering into the formations of the formatio 
recticularis as described, its chief central portion 
forming the centres of the medulla which will be given 
later. 
The pons varolii. The white fibres that we have 
followed from the cord through the medulla here have 
a very simple arrangement. The conjoined pyramidal 
tracts, now in a more or less rounded trunk, lie deep 
in the lower aspect (anterior) of the pons, having below 
it the superficial and above it the deep transverse PHYSIOLOGY 
321 322 
PHYSIOLOGY 
bonds that form the middle -peduncle of the cerebellum. 
Just under the prolongation of the floor of the fourth 
ventricle, on the upper (posterior) side of the pons, lies 
the continuation of the formatio recticularis which we 
saw carried most of the fibres of the posterior (sensory) 
columns of the cord below. Just outside of this is the 
fillet tract, which connects the spinal nuclei of the 
medulla with their centres in the cortex. Remember 
that about the middle of the pons the 7th nerve fibres 
decussate. (Gubler’s line.) 
The crura cerebri. Just below the anterior (upper) 
border of the pons the fibres that we have been fol- 
lowing are collected on either side into two trunks 
called the crura cerebri, and each diverges to its 
respective lobe of the cerebrum. The pyramidal tracts 
lie on the inferior face of their respective crura, called 
the crusta, about the middle line. Above this tract is 
quite a large mass of gray matter, the substantia nigqer, 
while above this, rather on the lateral aspect of the 
crura, is the tegmentum, which carries the fibres 
(sensory) from the formatio reticularis of the pons and 
medulla, and in which we also find the fillet tract 
above-mentioned. Above the inner border of the sub- 
stantia niger is the red nucleus of Stilling. On the 
upper surface of the posterior part of the crura, before 
they diverge, are the corpora quadrigre?nina (which 
will be studied later) and under them, in the median 
line, lies the prolongation of the central canal of the 
■cord, the aqueduct of Sylvius (iter a tertio, etc.). This 
canal, as in the cord, is surrounded with gray matter 
'which is most abundant below, the part corresponding 
Jo the prolongation of the floor of the fourth ventricle. 
Above the crura the tracts we have been considering 
pass chiefly into the internal capsule, a broad band of 
white fibres lying between the basal ganglia, and to be PHYSIOLOGY 
323 324 
PHYSIOLOGY 
studied later. From thence our tracts pass through 
the coronarachata to the c centres of the brain. 
Functions of the spinal tracts. While in the pre- 
vious histological study of the cord, etc., we did not 
consider with care their course, we will now take the 
fibres in the direction of their impulses. The volun- 
tary motor nerves of spinal distribution leave the cor- 
kCu' Tl°r f "treS’ PaSS throu^h the internal capsule 
behind the knee, through the pyramidal tract of the 
crusta in the crura, between the deep and superficial 
transverse fibres in the pons until they reach the 
medulla. In the upper part of the medulla the motor 
fibres decussate. The bulk of them cross over to the 
other side, and go down in the crossed pyramidal tract, 
w ere they pass into the anterior gray column (trophic 
centre) when they reach their level of distribution, 
and from thence out through the anterior roots to their 
distribution. The remaining motor fibres, few in 
number, continue on down on the same side, forming 
the direct pyramidal tract of the cord. When they 
reach their level of distribution they pass across 
Trough the anterior white commissure to the ant 
S ray column of the opposite side, where they join' the 
fibres from the crossed pyramidal tract and go out 
through the ant. roots with them. As regards the in- 
voluntary motor impulses, as the vaso-motor, etc., we 
ave reason to believe that they descend from the 
vaso-motor centre of the medulla, through the post 
part of the anterior root zone to their level of distribu- 
tion, and then they go out through the anterior roots 
to join the rami-communicantes. The sensory and 
other afferent routes in the cold are but imperfectly 
understood. We can only give reasonable conjecture 
as regards many of them. We know that coming 
from their peripheral terminals they enter the cord at PHYSIOLOGY 
325 326 
PHYSIOLOGY 
its posterior or gangliated root. This root enters the 
cord seemingly as a single trunk, but it is in reality 
three, an internal, middle and external division. The 
internal fasciculus, believed to carry the impressions 
from the tendons (muscle sense) and those of touch and 
locality, as it enters sweeps around through the post- 
ero-external tract, and some fibres curve sharply up- 
ward before joining the gray matter. The external 
fasciculus, carrying impressions for the cutaneous re- 
flexes and temperature, also curves upward to join the 
posterior gray columns. The middle fasciculus, as 
well as the most internal fibres of the other fasciculi, 
run straight in to the gray horn and seem to carr}r 
impressions of pain. Within the cord the routes are 
still more varied. The fibres carrying the impres- 
sions of pain possibly travel through the gray matter, 
although observations made by Gowers and others 
point to the mixed tracts, behind the anterior root 
zone, as the place of pain conduction. Those of touch, 
temperature, and muscle sense travel in the posterior 
column, the impulses from the lower extremities 
chiefly in the postero-median tract, and those for the 
trunk and upper extremity chiefly in the postero-exter- 
nal. (locomotor ataxia). All of the fibres of the pos- 
terior root are processes of the small neuron cells of 
the post, root ganglion, which act as relays to the im- 
pulse, before a second distribution on its route. One 
set of these fibres are processes of the cells of Clarke’s 
column, and from this point they run horizontally out- 
ward through the crossed pyramidal tract to join and 
ascend in the direct cerebellar tract. This vesicular 
column of Clarke is only found in certain parts of the 
cord, being most pronounced in the dorsal region, and 
it would seem to transfer to the direct cerebellar tract 
those afferent (excito-motor) impulses which come from PHYSIOLOGY PHYSIOLOGY 
the viscera. The fibres for the direct cerebellar tract 
do not decussate, but ascend on the same side in which 
they entered the cord. All the other fibres carrying- 
impulses of touch, temperature, pain, and perhaps 
muscle sense, soon decussate or cross over to the pos- 
terior median, the postero-lateral or gray tracts of the 
opposite side (sensory decussation.) None of these 
decussate on entering-, but all of them cross shortly 
after, touch first, pain, etc., next, and temperature 
last. This decussation of all nerves carrying- cutaneous 
and other reflexes applies also to the cranial nerves. 
((Experimental section of the cord.) Above, in the 
medulla, the impulses coming up through the postero- 
median column break joint in the gracile nucleus, the 
postero external in the cuneate nucleus, etc. Above 
this some pass to the cerebellum through its posterior 
peduncle, and some through the fibres of the formatio 
reticularis to the tegmentum and thence to the sensory 
basal ganglia (optic-thalamus) and cortex. 
Reflexes of the cord. Having considered the tracts 
and conducting powers of the cord, we come now to 
study its powers of reflexion. By a reflex movement 
or action is meant one caused by the stimulation of an 
afferent nerve. The impulse is carried centripetally in 
the afferent nerve, and then by central transfer to an 
efferent nerve is carried centrifugally to the muscle, 
etc., of action. A simple reflex is one in which a 
single muscle, or at least a single group of muscles, is 
called into play by the stimulation, as, for example, 
reflex closure of the lid from conjunctival stimulation. 
A radiating or incoordinate reflex is one in which, 
either by reason of the intensity of the stimulus or by 
reason of the excitability of the centre, other groups of 
muscles or even of all the muscles of the body (spasm) 
-are thrown into action. Various poisons or drugs, as PHYSIOLOGY 
329 330 
PHYSIOLOGY 
strychnin, etc., will produce this condition of exalted 
excitability. Complicated coordinate reflexes may be 
excited where the movements are “purposive” in char- 
acter, but they are the result usually of experience 
(habit), for example, the guarding- of the head from a 
quick blow, the peculiar balancing and other com- 
plicated feats of a decapitated frog, etc. The inhibition 
of reflexes may be voluntary, as by the will, for exam- 
ple, keeping the eye open while the conjunctiva is 
touched, etc. Inhibition may also be produced by the 
strong stimulation of a sensory nerve, as for example,, 
preventing sneezing by pinching the lip, etc. Certain 
drugs, as chloroform, chloral, morphin, etc., lower 
reflex excitability by depressing the action of the 
centres. The reflexes are of much service in diagnosis. 
They are divided into the superficial and the deep or 
tendon reflexes. The superficial reflexes are the 
plantar, cremasteric, gluteal, abdominal, etc. The 
deep reflexes are the patella reflex, ankle clonus, etc. 
They test the condition of the cord at the “point of re- 
flection.” 
The centres of the spinal cord. Within the cord lie 
several centres, some of them seeming-lv independent, 
while others are more or less under the” control of the 
hig-her centres. They are (1) the cilio-spinal centre, 
in the upper dorsal cord ; (2) the ano-spinal centre ; 
(3) the vesico-spinal centre ; (4) the copulation centre, 
and (5) the parturition centre. The last four all lie in 
the lumbar cord. The spinal vaso-motor and sweat, 
centres are subservient to the medulla. PHYSIOLOGY 
331 332 
PHYSIOLOGY 
CHAPTER XIV. 
the cranial nerves and their Functions ; 
In addition to the thirty-one pairs of spinal nerves 
taking- origin from the cord, we have twelve or more 
pans that arise from the medulla and brain, and are 
hence called the ctcltiiul nerves. Two of these, the 
most highly specialized, run more or less directly from 
the cortex of the brain, but all the others arise from 
special nuclei in that mass of gray matter forming the 
floor of the fourth ventricle, and its prolongation, the 
aqueduct of Sylvius. As before shown, the most 
central parts of this gray matter are formed from the 
antenoi or motor cornua, while the lateral Darts are 
foi med from the posterior or sensory cornua, and as a 
result the nerves arising from nuclei near the median 
line are usually motor, and those from lateral nuclei 
more or less sensory. Always remember that both 
spinal and cranial nerves are constructed on the same 
geneial plan. The old classification of Willis, while 
fixed in anatomical nomenclature, is absurd for 
physiological purposes, and we will use the classifica- 
tion of Soemmering. The histological and physio- 
logical bearings of the nerves onlv will be given here ; 
for further details of anatomy, etc., see “Scheme of 
Nerves,” at the end of the book. 
The floor of the fourth ventricle. As all the cranial 
nerves exept the first two take their origin from nuclei 
in this floor and its upward prolongation, we will 
consider this area in minute detail. The diverging 
columns of the fasciculus gracilis bound, its posterior PHYSIOLOGY 
333 334 
PHYSIOLOGY 
triangle, the calamus scriptorius. The inner border 
ot the superior peduncles of the cerebellum {valve of 
Vieussens) limit its superficial area above, while the 
lateral limits extend to the middle cerebellar peduncle. 
In the median line is a fissure, which divides the floor 
into equal parts, and ends below in the central canal of 
the cord, while above, it extends onward as the aqueduct 
o y vms. Under the surface so bounded are masses 
of gray matter in varying quantities, and the same 
nerve tissue is prolonged forward as a tube around the 
aqueduct of Sylvius. The macroscopic appearances on 
mther half of this floor, from before backwards, are as 
o ows dhe locus coeruleus, a spot of bluish tint on 
the anterior part of the floor partly under the edge of the 
valve. Just below this is the eminentia teres, a pro- 
jection caused by the nucleus of the 6th nerve, while 
extending backward and forward from the inner side of 
this eminence is a ridge, the fasciculus teretes, caused 
by the cerebral fibres of the posterior column passing 
upward to the tegmentum. In the lower part of the 
calamus scriptorius, and next the median line, is an 
eminence marking the nucleus of the 12th nerve, and 
just above this is a triangular area of ashy color the 
alci cinerea. On section and histological study we 
find the various nuclei of the floor to be located as 
follows : On the floor of the aqueduct of Sylvius, just 
under the anterior corpora quadrigemina, and above 
he red nucleus, is the nucleus of the 3d nerve. Just 
behind it, and conjoined with it, under the posterior 
corpora quadrigemina, is the nucleus of the 4th, both 
being dose to the median line. Just under the 
eminentia teres is the nucleus of the 6th. Slio-htlv 
behind and to the outer side of the above nucleus" and 
much deeper in the floor, is the nucleus of the 7th nerve, 
he nucleus of the sth is a very complex one. There PHYSIOLOGY 
335 336 
PHYSIOLOGY 
is a small (motor) nucleus lying- externally and anteriorly 
to the eminentia teres, but external to this and extending 
from about the level of this nucleus down in the poste- 
rior cornua of the cord to the level of the second cervical 
vertebra is the long- (sensory) nucleus. A part is cut 
off from the rest. Both sensory and motor nuclei are 
deep in the floor, the latter being the deeper. The 
nucleus of the Bth nerve is likewise a double one, or 
more truly there are two nuclei, each of which is 
double. There is an internal pair located just behind 
the eminentia teres, and an external pair at the very 
lateral limit of the floor and at about the same level as 
the other. The nucleus of the 9th nerve is partly in 
front of and partly under the ala cinerea (the so-called 
13th nerve of Wrisberg has a common nucleus with it). 
Part of its nucleus is quite near the median line and 
part at some distance. The 10th nerve nucleus lies 
under the ala cinerea abutting the nucleus just given, 
and it is the more superficial of the two. The nucleus 
of the 11th nerve is below the preceding, and but to a 
slight extent under the floor, being mainly a spinal 
nerve. Its nucleus at the point mentioned is separate 
and distinct from the spinal nucleus, which is in the 
outer side of the anterior cornua of the cord, extending 
as low down as the fifth cervical vertebra. The nu- 
cleus of the 12th nerve lies internal to the medullary 
nuclei of the three preceding, and is very superficial. 
First cranial or olfactory nerve. The cortical centre 
for this primitive sense is probably the gray matter 
covering the anterior superior aspect of the temporo- 
sphenoidal lobe, and called the uncinate gyrus. From 
this point a long band of fibres runs backward and 
upward, decussates (olfactory chiasm), passes forward 
to groove the head of the caudate nucleus, and emerging 
from the fissure of Sylvius is joined by an internal and PHYSIOLOGY 
337 PHYSIOLOGY 
external root, forming- the triangular olfactory tract 
which joins the olfactory bulb. These two short roots 
are from the side of the brain on which they join the 
tract, but their orig-in is uncertain. From the inferior 
surface of the bulb, which lies on the cribriform plate, 
run from 15 to 20 filaments, downward throug-h the 
foramina. The filaments at first run under the 
mucous membrane, grooving- both the vertical plate 
and lateral mass, but ultimately pierce the membrane 
and appear superficially, over the regio olfactoria. 
This nerve is excited only by gaseous odorous bodies, 
but any form of stimulation of the trunk gives a sen- 
sation of smell. 
centre is found in the cuneus of the occipital lobe. 
From this centre a broad band of fibres (optic radiation 
of Gratiolet) converge to join the pulvinar and the 
external geniculate body. Receiving fibres from these 
bodies, and through them from the cerebellum, the 
of tic tract is formed, and sweeping around the crura 
the two tracts meet in the of tic chiasm. In the chiasm 
there is a decussation, in which about half of the fibres 
of each tract cross, the right tract sending fibres to 
the right half of the left eye, and the left tract fibres 
to the left half of the right eye. The outer half of 
each retina is supplied by the fibres of the tract on its 
own side. After leaving the chiasm each nerve pro- 
ceeds through the optic foramen to its respective eye 
and ends in the retina. The optic nerve is the special 
sense nerve of sight, and can be excited only by the 
influence of the vibrations of the luminous ether on the 
rods and cones of the retina. Other forms of stimulus 
produce only the sensation of light. Hemianopia is 
usually caused by injury to one of the tracts (homony- 
mous) but injury of the anterior part of the chiasm 
Second cranial or optic nerve. The cortical visual PHYSIOLOGY 
339 PHYSIOLOGY 
will produce double nasal hemianopia, and the outer 
half of each tract double temporal. Communicating- 
fibres pass from the ant. corpora quadrigemina to the 
nucleus of the oculomotorius. The converging fibres 
of the radiation pass through the lower posterior part 
of the internal capsule. 
The third cranial nerve or motor oculi. From its 
nucleus, this nerve without apparent decussation sinks 
down through the crura to the post, perforated spot. 
Its nucleus is united by fibres with the corpora quad- 
ragemina above and with the nuclei of the 4th and 6th 
nerves on the floor. The nerve in the orbit is con- 
nected with the ophthalmic (ciliary) ganglion by a 
short root. It carries (1) motor fibres for all the ex- 
ternal muscles of the eyeball, except the external 
rectus and superior oblique, and also fibres for the 
levator palpebrae; (2) motor fibres for the sphincter 
pupillae ; and (3) motor fibres for the ciliary muscle. 
Impulses for the two latter pass through the ganglion 
(atropia). 
The fourth cranial nerve or trochlearis. Prom its 
nucleus this nerve passes backward and upward, de- 
cussates, pierces the valve of Vieussens, and turning- 
outward runs around the crura cerebri to their outer 
side and makes its way to the orbit. Its nucleus 
receives fibres from the nuclei of the 3d and 6th. It 
supplies motor fibres to the superior oblique or troch- 
learis muscle. 
The fifth cranial nerve or trigeminus. In the 
cranial nerves so far considered the departure from the 
spinal nerve type has been pronounced, but here we 
meet a nerve bearing strong analogy to the spinal 
nerves considered. From the long sensory nucleus 
and its anterior isolated extremity a large band of 
fibres starts. This is joined by a band of fibres from PHYSIOLOGY 
341 PHYSIOLOGY 
the motor nucleus, and together they pass outward and 
downward to emerge about the middle of the pons on 
either side, the motor fasciculus being, as it started, on 
the Inner side. It should be noted here that these 
roots have no direct decussation, but that their nuclei, 
especially the sensory nuclei, have intimate bonds of 
union, not only with their fellows of the opposite side, 
but with all the other nuclei on the floor. In addition 
to this, fibres of communication unite their nuclei with 
the cerebellum and also the corpora quadrigemina. 
Hence the vast number of reflex relations of the sth 
nerve. From its apparent origin from the pons it runs 
forward, where its sensory root develops a large 
ganglion, the Gasserian ganglion (trophic). From 
this point the sensory trunk divides into three branches, 
as follows : 
(1) The Ophthalmic Division. It gives first a 
recurrent branch to the tentorium cerebelli, etc., then 
the lachrymal, which gives sensation to the conjunctiva, 
upper lid and contiguous parts, and secretory fibres to 
the lachrymal gland. The frontal of this division 
gives off branches of sensation to the upper lid, brow 
and forehead as far as the vertex. The branches of 
the naso-ciliary after devious routes supply sensation 
to the lachrymal canals and sacs, the bridge, tip and 
alae of the nose and the mucous membrane of the nasal 
fossa that covers the cartilages, septum and turbinated 
bones (sneezing). The naso-ciliary also gives the long 
root for the ciliary or ophthalmic ganglion, and the 
long ciliary nerves of the eye, carrying sensory and 
trophic impulses. [ The ophthalmic or ciliary gang'lion 
will be considered with this (ophthalmic) division of the 
sth. It receives, by its short, root motor fibres from 
the 3rd, by its long root, as stated above, sensory and 
trophic fibres from the sth, and by means of the PHYSIOLOGY 
343 344 
PHYSIOLOGY 
sympathetic root, from the carotid plexus, motor and 
vaso-motor fibres. It gives, by the ciliary nerves, 
sensation to the cornea, iris, choroid and sclerotic, 
vaso-motor fibres for the iris, choroid, etc., motor 
fibres to the sphincter papillae (dilator papillae) and 
tensor choroidae muscles and trophic impulses for the 
entire eye.] 
(2) The superior maxillary division. This division 
also has a recurrent branch, which supplies the dura 
mater in the region of distribution of the middle 
meningeal artery. The orbital branch supplies sensa- 
tion to the check and temple. The dentals supply 
sensation to the upper teeth and the cavities of the jaw, 
by means of their various branches. The infra-orbital 
branch gives sensation to the skin of the face, from the 
lower lid to the angle of the mouth inclusive. The 
spheno-palatine branches go to the ganglion of the same 
name. [The sfheno-falatinegang lion, (Meckel’s) will 
be considered with this (Sup. Max. Division) branch of 
the fifth nerve. It receives motor fibres from the 7th, 
via the great superficial petrosal, (vidian), sensory and 
perhaps secretory fibres from the sympathetic (vidian). 
It gives sensation to the post, portion of the mucous 
membrane of the nasal cavity, and the hard and soft 
palate, etc., through its nasal, naso-palatine and post, 
palatine branches. Motor fibres are also supplied to 
the azygos uvulae and levator palati through the post, 
palatine nerves. Secretory impulses to the mucous 
glands of this area are also sent out.] 
(3) The Inferior maxillary division. While the 
branches of the fifth originating from the Gasserian 
ganglion are all sensory, the motor root follows this 
division, hence it is really a mixed trunk. The sensory 
branches are a recurrent, as in the other branches, the 
buccinator, supplying the mucous membrane of the PHYSIOLOGY 
345 346 
PHYSIOLOGY 
cheek and angle of the mouth, the lingual, supplying 
sensation and tactile acuity to the tip and ant. half of 
the tongue (taste?), the inferior dental which supplies 
sensation to the teeth and the chin, and the auricula- 
temporal, which gives sensation to the tympanic mem- 
brane, ant. wall of the canal, ant. part of the ear and 
maxillary articulation. The motor branches are those 
to the muscles of mastication, the temporal, masseter 
and two pterygoids ; and those which supply the mylo- 
hyoid and anterior belly of the digastric. [The otic 
granghon, as well as the other given below, will be here 
considered. The otic receives motor fibres from the 
motor branch of the sth, a secretory branch from the 
glosso-pharyngeal through the tympanic plexus, 
vaso-motor fibres from the meningeal plexus of the 
sympathetic, and a branch of communication from the 
chorda tympani. It gives motor twigs for the tensor 
tyrapani and tensor palati muscles, and secretory fibres 
foi the parotid gland as described. [The submaxillary 
ganglion. This ganglion receives secretory and vaso- 
inhibitory fibres from the chorda tympani, secretory 
and vase-constrictor fibres from the sympathetic, ami 
sensory fibres from the lingual of the sth. It gives 
secretory fibres to the sub-maxillary and sub-lingual 
salivary glands, as well as sensation to the same parts.] 
The fifth nerve presides over all the trophic processes 
in the region it supplies (hemiatrophy). 
The sixth cranial nerve or abducens. From its 
nucleus on the floor of the fourth ventricle, a fine band 
of fibres drops down through the substance of the me- 
dulla to appear just below the pons and internal to the 
olivary body. Its nucleus is connected with the nucleus 
of the third nerve of the opposite side. The function 
of this nerve is to supply motion to the external rectum 
of the eye. Its long route and small size makes it PHYSIOLOGY 
347 PHYSIOLOGY 
quite subject to injury. Its nucleus seems to be the 
centre for the coordinate control of eye movements. 
The seventh cranial nerve or facial. The nucleus 
of this nerve lies deep in the medullary floor, but the 
nerve trunk runs from this origan upward to turn down 
again under the eminentia teres and go out at the lower 
border of the pons. Passing1 out through the meatus 
auditorius internus and aqueductus fallopii, in company 
with the roots of the Bth and the 13th, the first branch 
to be given off is the great superficial petrosal. This 
runs from that expansion of the 7th nerve, (called the 
“geniculate ganglion,” but which is not in reality a 
ganglion) out through the hiatus fallopii, where joined 
by twig’s from the carotid plexus and the 9th, it 
passes through the foramen lacerum and vidian canal 
to give motor impulses to Meckel’s gang-lion, as we 
previously learned. The next is the branch (small 
superficial petrosal) from the geniculate swelling to 
the second tympanic twig of the glosso-pharyngeal, 
as it goes to join the otic ganglion. Then we have the 
motor branch to the stapedius muscle, and after this 
the chorda tympani or 13th, which has thus far fol- 
lowed the 7th, and now leaves it like a branch. After 
leaving the stylo-mastoid foramen we have a communi- 
cating branch to the petrous ganglion of the 9th, and 
the peripheral branches which supply motion to all 
the muscles of expression, the buccinator, platysma, 
occipitalis, stylo-hyoid and post, belly of the diagastric 
as well as the external ear muscles. The facial nucleus 
is but a subservient centre to the cortical face centre. 
The cortical area of control for facial movements 
lies in the lower end of the ascending frontal 
convolution. Prom this point fibres pass through 
the corona radiata to the knee of the internal 
capsule and down through the crura cerebri to PHYSIOLOGY 
349 350 
PHYSIOLOGY 
the pons, where on a level with a line (Gubler’s) 
joining- the roots of the fifth nerve, they decussate and 
join the nuclei of the opposite side. (Crossed paralysis 
versus normal hemiplegia.) Central and peripheral 
lesions of the facial are both quite common. 
The eighth cranial nerve or auditory. As we saw, 
this nerve arises from two separate pairs of nuclei, 
therefoi e we are not surprised to find that it is a nerve 
of double function, or, more truly, two distinct nerves 
conjoined, as we saw with the 7th and 13th. One is 
the nerve of hearing-, the stimulation of whose periph- 
eral teiminals gives rise to the sensation of sound, 
tne other is the nerve of equilibration, being- connected 
with the semi-circular canals. The cochlear branch 
(auditory). This arises from the two posterior nuclei 
by a median and lateral root which unite to form the 
nerve, which accompanies the other branch out through 
the int, auditory meatus and ends in the terminals in 
the organ of Corti. The vestibular branch (equilib- 
rium). This, like the other, arises by a median and a 
lateral root, from the anterior pair of the nuclei of the 
Bth. These roots uniting form the vestibular nerve, 
which passes with the cochlear nerve outward and 
ends in the special terminals of the membranous sacs 
and canals of the vestibule. The nuclei of this branch 
are in intimate relationship with the cerebellum, while 
the nuclei of the auditory branch are united with the 
cortex of the lateral aspect of the temporo-sphenoidal 
lobe of the opposite side of the cerebrum. This union 
with the cortex is accomplished as follows : When the 
fibres from the cochlea reach their nuclei, they are 
transferred across to the opposite side, up to the post, 
corpora quadrigemina and internal geniculate body, 
thence through the most posterior part of (the lower 
levels of) the internal capsule to the first and second 
gyri of the temporo-sphenoidal lobe. PHYSIOLOGY 
351 352 
PHYSIOLOGY 
The ninth cranial nerve or glosso-pharyngeal. This- 
nerve arises from its nucleus, the anterior part of which 
is likewise the nucleus of the 13th nerve or chorda 
tympani. Emerging below, internal to the olivary body, 
it goes out through the jugular foramen, and at this 
point its root presents a ganglion, sometimes double, 
thz petrous ganglion. At this ganglionic enlargement 
it receives fibres from the 7th, 10th, and from the 
sympathetic. It here gives off its tympanic branch 
(Jacobson’s nerve). This nerve pierces the base of the 
temporal bone, enters the tympanic cavity and divides 
to form the tympanic plexus, which supplies the inner 
wall of the cavity and sends out a branch to join the 
great superficial, and one to form the small superficial 
petrosal, and go to the otic ganglia (parotid secretion) 
and also one to join the carotid plexus of the sympa- 
thetic. The 9th then sends fibres to the posterior one- 
third of the tongue, and to the arches of the soft palate. 
These fibres end, some in the taste-buds of the circum- 
vallate papillae and some on the general surface, and 
they supply thisarea with the special sense 
with general sensation. It is also the inhibitory nerve 
of respiration during the act of deglutition, and if over 
stimulated may reflexly excite vomiting. This nerve 
also supplies motor fibres to the stylo-pharyngeus and 
the middle constrictor of the pharynx, etc. At the same 
time the glosso-pharyngeal is not truly a motor nerve, 
being purely sensory at its nucleus, and the motor fibres 
with which it is later endowed come from the 7th. The 
glosso-pharyngeal nucleus is believed to be joined with 
the cortical area presiding over the sense of taste. This 
centre is believed to be in the inner side of the uncinate 
gyrus and from this point fibres run down through the 
tegmentum, pons, etc., to join the glosso-pharyngeal - 
nucleus of the opposite side. PHYSIOLOGY 
353 354 
PHYSIOLOGY 
The tenth carnial nerve or vagus. The nucleus of 
this nerve, lying under the ala cinerea, is in part a 
representative of the cells of the vesicular column of 
Clark, but other fibres especially those concerned in 
respiration, take their origin from the grav matter 
lower down in the cord. From this nucleus, and con- 
tiguous parts of the cord, the fibres come out external 
to the olivary body, and form the root of the nerve, 
which passes downward through the jugular foramen. 
In this foramen it expands into a ganglion, the jugular, 
which is continued onward to its exit, seemingly making 
two ganglia. The nerve in the region of this ganglion 
gives or receives the • following communicating 
branches. A branch from the petrous ganglion of the 
9th, the entire inner half of the 11th, and a branch 
from the sympathetic. The first branch given off is 
the recurrent, which supplies sensation to the posterior 
part of the dura matter of the brain (cerebral vomiting). 
The auricular branch of the 10th (Arnold’s nerve) is 
joined by a small twig from the 9th, and conjoined 
they make their way to the external auditory canal, 
where they supply its floor, post, wall and post, part of 
the outer ear with sensation, (ear cough.) The pharyn- 
geal plexus consists of two or more branches from the 
vagus, joined by branches from the 9th and sympa- 
thetic. The function of this plexus is to supply 
motion to the three pharyngeal constrictors and sen- 
sation to the mucous membrane of the pharynx from- 
the soft palate downwards. The laryngeal branches 
are two. The superior laryngeal goes direct to the 
larynx, and it divides into an external and internal 
branch, the former supplying motion to the crico- 
thyroid muscle, while the internal branch supplies 
sensation to the rima glottidis and the raucous mem- 
brane of the larynx and base of the tongue. The PHYSIOLOGY 
355 356 
PHYSIOLOGY 
stimulation of this nerve produces reflexly a cough, 
and an arrest of respiration. There also joins this 
nerve trunk a branch coming- from the heart (sup. 
cardiac), which carries afferent fibres, for the cardio- 
motor centre (Cyon’s nerve). The inferior laryngeal 
supplies motor fibres to the oesophagus and lower end 
of the pharynx and to all the muscles of the larynx 
except the crico-thyroid. (aphonia.) The cardiac 
branches are two, the inferior or thoracic cardiac and 
the superior or cervical cardiac. The extreme irreg- 
ularity of anatomical arrangement in these nerves 
makes their physiological description imperfect and 
unsatisfactory. However, the inhibitory fibres of the 
heart come from the trunk of the vagus (low down) 
while the impulses indicating too great (depressor) or 
too little (pressor) intra-cardiac pressure pass up, in 
the superior laryngeal and trunk of the vagus. The 
pulmonary branches of the vagus have the following 
functions : To supply motor impulses to the non- 
striated fibres of the whole tracheal and bronchial 
system, (asthma.) To supply sensory cough exciting 
(excito-reflex) fibres to the bronchial system and 
lungs, and to supply sensory fibres whose reflex 
stimulation shall alternately excite inspiration and 
expiration, etc. The oesophageal plexus is made up 
of branches from the vagus, at various levels, and sup- 
plies motor fibres to the non-striated muscular coat of 
the oesophagus for its entire length, and sensation 
(excito-reflex) to the upper part. The gastric plexus 
consists of the right and left branches of the vagus, 
united with the sympathetics. To the stomach, intes- 
tines, etc., the vagus gives motor and vaso-motor fibres 
and also secretory fibres. The exact influence of the 
vagus on the other abdominal organs is very largely a 
matter of conjecture, and will not be given here. It PHYSIOLOGY 
357 358 
PHYSIOLOGY 
would seem that the motor fibres of the vagus do not 
originate from its nucleus, but are derived from the 
branch it receives from the 11th. 
The eleventh cranial nerve or accessorius. This 
nerve arises by two distinct roots from its two nuclei. 
The root from the medullary nucleus joins the root 
from the spinal nucleus, but does not unite with it. 
Together they pass through the jugular foramen, 
where they divide, the trunk from the medullary nu- 
cleus turns inward to join the 10th nerve at its gang- 
lion, while the spinal branch turns outward to furnish 
the trapezius and sterno-mastoid muscles with motion, 
just as the internal branch endowed the vagus, (torti- 
collis.) 
The twelfth cranial nerve or hypoglossal. From 
the nucleus of the same name this nerve arises and is 
distributed to the muscles of the tongue, including the 
genio-hyoid and thyro-hyoid. It endows these with 
motion only. There is a centre of control for the 
tongue in the cortex, just below the centre for the face, 
in the extreme lower end of the ascending frontal (ant. 
central,) convolution. Prom this point the hypo-glos- 
sal tract runs through the knee of the internal capsule, 
with the face tract, and down through the pons to 
decussate at the level of the nuclei above given. 
Remember that while the hypo-glossal tract supplies 
the nucleus from the cortex, it is entirely distinct from 
the speech tract which we will consider later. 
The chorda tympani or thirteenth cranial nerve. 
(Wrisberg.) This nerve is usually considered a branch 
of the 7th, but is distinctly a different nerve. It 
arises from the anterior part of the nucleus of the 9th 
nerve. From this point, between the 7th and Bth 
nerve trunks, as the pars media of Wrisberg, it enters 
the internal auditory canal. It follows the 7th through PHYSIOLOGY 
359 360 
PHYSIOLOGY 
the aqueductus fallopii, and about a quarter of an inch 
before the 7th reaches the stylo-mastoid foramen, it 
leaves this trunk and runs forward through the tym- 
panic cavity to emerge from the glasserian fissure and 
join the lingual at an acute angle and follow it on to 
the sub-maxillary ganglion. Here a few of its fibres 
join the ganglion, while most of them continue on- 
ward, to supply the tips and anterior two-third of the 
tongue with the special sense of taste. It is also prob- 
ably united, as is its fellow the 9th, with the cortex of 
the internal border of the uncinate gyrus of the tem- 
poro-sphenoidal lobe of the opposite side. 
CHAPTER XV. 
THE BRAIN AND ITS FUNCTIONS. 
The cerebrum. The cerebrum consists of neuroglia 
supporting numberless neurons with their axons and 
dendrites. As a rule the neurons of the brain have 
relatively short processes as compared with those of 
the cord. The neuron bodies en masse give the “gray 
matter” while the grouping of the axons and dendrites 
into tracts or bundles gives the white matter. The 
gray matter is arranged in a different manoer in the 
brain from that which we saw in the cord. There 
the gray matter was only in the interior, but here we 
have it both inside and out, with the white matter or 
fibres chiefly between. The superficial gray matter is 
called cortical matter, and follows the sulci and gyri 
in their folds over the entire surface, without much 
variation in thickness. The internal gray matter is PHYSIOLOGY 
361 362 
PHYSIOLOGY 
collected into masses of various forms and sizes, ta 
which we apply the names basal ganglia or nuclei► 
Under this head are included the corpus striatum, with 
its two nuclei, the optic thalamus, corpora quadri- 
gemina, etc. The functions of these basal ganglia are 
variable, some are undoubtedly sensory, and others 
less certainly motor. The functions of the cortex 
vary with the area, some parts being- sensory and some 
motor, etc. 
The cortical areas and their functions. We will 
first consider the motor area. The general shape of 
the area having this function is triangular. Taking 
the angle between the ascending and horizontal limbs 
of the fissure of Sylvius as the apex, one side is ex- 
tended to join the median fissure where it is cut by the 
parieto-occipital sulcus, and the other is extended verti- 
cally upward to join the median fissure at a right 
angle. This gives a triangle, roughly enclosing all the 
cortex that we at present know to be motor in function. 
The general details of this area can best be remem- 
bered by imagining the human body in minature laid 
along the median border of the triangle, feet to the 
rear. Then we can say in a general way that the 
cortical area below each part of our model in the tri- 
angle will preside over that part of the body. In the 
wide head zone the upper part of the face, etc., is 
above, while the lower part of the face, the lips, 
tongue, etc., are below. The same is true of the 
shoulder, arm and hand centres as well as those of the 
leg and foot. The sensory area is made up of centres 
widely separated. Por the special senses we saw that 
the cuneus of the occipital lobe was the cortical centre 
for vision, that the superior temporo-sphenoidal convo- 
lutions were the cortical areas for auditory impressions, 
the upper central part of the uncinate gyrus, for olfap- PHYSIOLOGY 
363 364 
PHYSIOLOGY 
Tory impressions and the inner part of the same proba- 
bly J;pr_taste. The part of the cortex stimulated by 
the reception of impressions of general sensation is not 
certainly known. General cutaneous sensibility, it is 
claimed, and fairly well proven, is presided over by 
the gray matter of the Whether all 
the sensory fibres run here or not, is not proven. It 
is believed also by some that the sensory cortex lies 
just behind themotor triangle, while th ere are manv 
things that point to the fact that the reception of such 
impressions as muscle sense, etc., is by means of cells 
lying in the area described as motor, in other words, 
that the centres of the triangle are of double function. 
We can only say that cutaneous sensibility is under 
the control of the gyrus fornicatus, and that the rest 
is uncertain. The frontal lobes are as yet an unknown 
region to us, but the little evidence that we have points 
to these centres as the seat of the higher mental activi- 
ties, such as volition, thought, etc. (tamping-iron 
case.) The speech centre will be considered later. 
The corpora striata. These are two large masses of 
gray matter located on either side near the centre of 
the cerebrum, and they have received this name from 
the fact that on section their gray substance is marked 
with white striae (fibres). A part of each corpus 
striatum lies on the floor of the lateral ventricle, and 
this part we call the intra-ventricular portion or cau- 
date nucleus. It is pear-shaped, with the neck 
extending backward. The other part, called the 
extra-ventricular portion or lenticular nucleus, is 
imbedded in the white substance of the hemisphere, 
and consists of three segments. Internal to the 
lenticular nucleus, and separating it from the caudate 
nucleus in front, and the optic thalamus behind, is the 
internal cafisule, while external to it and separating it PHYSIOLOGY 
365 PHYSIOLOGY 
from the claustrum, is the external capsule. The 
fibres of the internal capsule seem to have little or no 
communication with the cells of these ganglia. Still 
it is claimed that the gray matter of these ganglia, 
when stimulated, excite active movements of all the 
muscles of the opposite side of the body. In man a 
lesion involving the greater part of one of these gray 
masses has been followed by temporary paralysis of 
the opposite side, and this in turn, followed by con- 
tracture. While these facts lead us to believe that 
these ganglia are probably concerned in the regulation 
of motor impulses, perhaps even in their augmentation 
or inhibition, it is not claimed that the function of these 
bodies is in any sense proven. More recently it seems 
that the corpora striata are concerned in some way 
with heat formation.. Whether irritation of these 
ganglia increases heat production through the muscles 
or in other ways is not yet certain but experimental 
injury in the lower animals and traumatism in man is 
often followed by greatly increased heat production. 
The optic thalami. These are likewise two masses 
of gray matter, each lying upon one of the crura 
cerebri, and seemingly united with its tegmentum. 
They are placed, one on either side, between the 
diverging portions of the corpora striata. Bach one 
forms the outer wall of the 3d ventricle, and the inner 
boundary of the posterior limb of the internal capsule. 
A part of this ganglion lies on the floor of the lateral 
ventricle, and the remainder sinks down in the white 
substance of the cerebrum to form the roof of the 
descending horn of the lateral ventricle. Behind on 
its extreme inferior aspect are the two geniculate 
bodies, internal and external, which join the anterior 
and posterior tubercula quadrigemina respectively to 
the optic thalamus. The posterior part of this gan- PHYSIOLOGY 
367 368 
PHYSIOLOGY 
g-hon is called the pulvinar, and the anterior part is- 
divided into several nuclei. The function of this 
ganglion is undoubtedly sensory. The posterior part 
of it, we have already seen, is united with the cortical 
centre for vision, and very probably with the auditory 
cortical centre also. The tegmentum joins it below, 
and direct simulation of its substance at various points 
g-ives no motor response. Clinical observation in man 
has shown that disease of this ganglion gives rise to 
disturbance of sensation on the opposite side, some- 
times almost equal to hemianaesthesia. Irritation of 
this centre will sometimes produce hallucinations, as 
has been often shown by pathological growths, etc. 
The corpora quadrigemina. The corpora or tubercula 
quadrigemina consist of two eminences on either side of 
the median line (the nates and testes) just above the 
aqueduct of Sylvius. We have already traced bonds of 
communication between them and the cerebellum, the 
occipital cortex, the temporal cortex, etc. The function 
of each pair of these twin bodies differ. Dither of the 
anterior corpora quadrigemina when destroyed give as 
a result loss of sight in their respective half of each eye. 
There is also apt to be interference with the action of 
the ocular muscles, especially those giving the pupillary 
reflexes. The posterior corpora quadrigemina when 
destroyed or injured give as a result disturbance of 
equilibrium and inco-ordination of movement. Unilateral 
injury of the corpora produces what we call forced 
movements. In such cases movements, while executed 
on both sides, are not harmonious, and the victim will 
run in a circle, run around the fixed posterior limb, etc. 
It would also seem that the route of communication 
between the nucleus of the auditory nerve and the 
cortical auditory centres was by way of the posterior 
pair of these nuclei. The functional lines of demar- 
cation in these bodies are not very sharply drawn. PHYSIOLOGY 370 
PHYSIOLOGY 
The other nuclei of the brain. The central gray tube 
is the name applied to that continuation of the graj7 mat- 
ter of the 4th ventricle upward around the aqueduct of 
Sylvius. Except for the nuclei of the 3d and 4th nerve 
that lie in it, we know nothing- of its function. The 
same is true of the claustrum, that thin streak of gray 
matter lying external to the external capsule, and also 
of the other masses of cells below, the substantia niger, 
red nucleus, etc., found low down in the brain. 
The white matter of the cerebrum. In the cord we 
saw that the white fibres run up and down in the con- 
ducting systems, and that in the gray matter they ran 
from the cells of the posterior columns to those of the 
anterior columns, and from the cells of one side to those 
of the other, etc. In the brain we have the analogues 
of all these fibres. The afferent and efferent fibres 
join their respective conducting systems below, and an 
infinite variety of inter-central or associating fibres 
join the component parts of the brain. The first group 
of these to be considered are the fibres that cross in the 
corpus callosum. They join all the cortical centres of 
one side with their fellows of the other. In each 
hemisphere all fibres leaving or coming to the lateral re- 
gions of the cerebrum passthrough that radiating mass 
of white matter which we call the corona radiata, which 
leads to or from the internal capsule or through the 
corpus callosum. The anterior limb of the internal 
capside lies between the caudate and lenticular nuclei, 
in front of the knee, while the posterior limb extends 
backwards from the knee between the optic tha- 
lamus and lenticular nucleus. The function of 
the ant. limb is not known, but the posterior limb 
bears from before backward the following tracts : 
(1) Motor fibres for the face, lips and tongue ; (2) arm 
and hand ; (3) leg, and perhaps the trunk ; (4) sensory PHYSIOLOGY 
371 372 
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fibres for all the regions mentioned above, (likewise 
for the opposite side) (5) the speech tract ; and (6) the 
crossing of the optic radiation, etc. The fibres of the 
anterior limb are not capable of electrical stimulation, 
but they degenerate when the frontal lobes are removed. 
The fibres that join the nucleus of the auditory division 
of the Bth with its cortex cannot be traced anatomically 
much above the corpora quadrigemina, but they are 
believed to run, at least in the lower parts of the 
internal capsule, in the sensory tract (4) described 
above. We know almost nothing of the function of 
the external capsule. 
The cerebellum and its connections. The cerebel- 
lum, or little brain, ftjth the size of the cerebrum, lies 
underneath and at the posterior extremity of its ana- 
logue. As we have seen, it is connected with almost 
every column and tract in the cord through its inferior 
±peduncle. Through its middle peduncles its two lobes 
are kept in intimate relationship, and through the right- 
angled decussation of its deeper layer it is probably 
connected with the nuclei of the medulla, especially the 
olivary body. Its superior 'peduncle brings it in inti- 
mate relationship with every part of the cerebrum. 
From a'knowledge of these facts and from experimen- 
tation, we find that the function of the cerebellum is 
probably that of a general co-ordinating centre. This 
applies to the movements of locomotion and those of 
manual co-ordination especially. Experimental re- 
moval of the cerebellum in animals proves the above. 
Such animals are not deprived of any of the “senses,” 
nor is muscular power impaired ; they are only inca- 
pable of making co-ordinate movements, being unable to 
stand, walk, fly, or execute any accustomed movement 
requiring harmony of action. Clinically, almost the 
same thing is observed in man, cerebellar disease gives 373 
PHYSIOLOGY 374 
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the staggering gait, and general evidence of a disturb- 
ance of the centers where “impressions of touch and 
position are associated with those of time and space.” 
Forced movements are even more pronounced after 
injury of the cerebellum than after injury of the cor- 
pora quadrigemina. 
The membranes of the brain (and cord). The most 
external is the dura mater, of densely matted fibrous 
tissue. It is the periostium of the flat bones of the 
skull, to which bones it is intimately adherent. Its 
inner surface is lined with serous endothelium, and it 
forms a closed cavity, being prolonged as an investing 
sheath on all nerves leaving the cranium and spinal 
canal. The space between this membrane and the 
next contains some serous fluid, but not very much. 
The next membrane, the arachnoid, is an open meshed 
mixture of yellow and white fibrous tissue, and is cov- 
ered externally with serous endothelium, making the 
subdural space, as it is called, a true serous cavity. 
On its internal face the open reticular structure is con- 
tinued to the pia and is filled with the so called cere- 
bro-spinal fluid. The cavities containing this fluid 
are largest at the base of the mid. and hind brain, and 
act as cushions to break the force of all the mechanical 
shocks received in jumping, falling, etc. The pia 
mater, an open fibrous membrane, carrying the blood 
vessels for the cortex and following every fold of the 
convolutions, is the most internal layer, and insinuates 
itself into all the ventricles and cavities of the brain. 
The blood vessels of the brain, etc. The circle of 
Willis is formed by a cross branch from one ant. cere- 
bral vessel to the other, and by antero-posterior 
branches joining the post, and 7niddle cerebrals. The 
terminal vessels of the above-named cerebrals supply 
the cortex of the brain, while perforating branches PHYSIOLOGY 
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PHYSIOLOGY 
from them near their origan, and from their communi- 
cating- trunks, supply the region of the basal ganglia. 
The ganglionic branches areof four sets ; (1) Those 
perforating branches from the ant. communicating that 
enter the area of the lamina cinerea, and supply the 
caudate nucleus ; (2) those that enter at the post, per- 
forated space, from the roots of the post, cerebrals, 
and supply the optic thalamus; (3) those from the 
middle cerebral (Sylvian), which entering at the ant. 
perforated space supply the lenticular nucleus and in- 
ternal capsule (lenticulo-striate or “artery of hemor- 
rhage”) ; (4) those which leave the posterior cerebrals 
and pass around the crura-cerebri to supply the corpora 
quadrigemina and pulvinar. The cortical branches, 
which have not the slightest communication with those 
just given, are from the terminals of the three cerebral 
arteries given : (1) The ant. cerebral supplies chiefly 
the frontal lobes and extends back along the median 
line to the pre-cuneus ; (2) the middle cerebral follows 
the fissure of Sylvius until opposite the island of Reil, 
where it divides into four branches, one for the inferior 
frontal convolution, one for the ascending frontal, one 
for the ascending parietal, and one for the superior 
temporal and angular convolutions ; (3) the post, cere- 
bral winds backward, giving branches to the uncinate 
gyrus, second temporal convolution and cuneus. The 
medulla and spinal cord are supplied anteriorly by the 
anterior spinal artery, formed by the union of two 
trunks which gives a vessel descending in the ant. 
median fissure and reinforced as it descends by branches 
from the vertebral, intercostal, lumbar, etc. The me- 
dulla and cord are supplied posteriorly by the two 
small posterior spinals, one on either side, descending 
and reinforced as in the previous case. The lenticulo- 
striate artery, referred to above and called the artery PHYSIOLOGY 
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PHYSIOLOGY 
of cerebral hemorrhage, is the largest of the Sylvian- 
group of perforating branches, and usually ruptures 
near the knee of the internal capsule, (“paralysis”.) 
The pressure here produced by the clot of rupture en- 
croaches upon the functions of the fibres as the clot 
grows. This will explain the orderly onset of the 
symptoms so often observed in ruptures of this kind, 
and the inverse order of recovery as the clot is absorbed. 
The very small size of the posterior spinal arteries of 
the cord, for their length, renders them peculiarly liable 
at some place in their course to the endo-arteritis of 
late syphilis. This explains perhaps the relation be- 
tween this disease and locomotor ataxia, the latter 
being produced by degeneration of the posterior white 
columns, chiefly the median column. Note the analo- 
gous seat of the lesion producing the ‘ ‘Argyll Robertson 
pupil,” in both the lesion is squarely behind the cen- 
tral canal of the cord, i. e. posterior columns. PHYSIOLOGY 
379 380 
PHYSIOLOGY 
CHAPTER XVI. 
ABNORMAL CONDITIONS OP THE CORD AND BRAIN. 
Perverted reflexes. For the reaction of a simple 
normal reflex it is necessary (1) that the neuron of 
posterior root with its processes bearing- the impulse 
(afferent) shall be intact ; (2) that the large neuron 
cells of the anterior gray horn shall be functionally 
active ; and that the connecting- processes—shall be 
uninjured. The functional activity of the sending 
nerve “corpuscle” and terminal “motor plate,” etc., 
is taken for granted. A radiating reflex will occur 
whenever (1) the afferent impulse is sufficiently intense, 
or whenever the (2) excitability of the cells of the cord 
is unduly exaggerated. In either case, whenever the 
neuron of the posterior root is stimulated, impulses 
will pass from it not only to the anterior horn of its 
own, but to the horn of the opposite side as well. If 
both of the abnormal conditions above-mentioned exist, 
the radiation may extend not only as stated, but to 
other segmients of the cord as well, and may even 
become general (convulsion). The cause of the excita- 
tion of the cells of the cornua may be (1) that thev 
are cut off from cerebral or higher ganglionic (inhibit- 
ing) control, (2) local congestive or inflammatory 
irritation, (3) the influence of certain toxic agents 
(tetanus) or of certain drugs (strychnia). The afferent 
impulse in the cutaneous reflexes starts from a touch 
corpuscle or other terminal in the skin, and the same 
for the deep reflexes conies from the tendon corpuscles 
(muscle sense) in the tendons. The complete destruc- PHYSIOLOGY 
381 382 
PHYSIOLOGY 
tion of any of the cells or any of the fibres in the above 
reflex loop, abolishes the reflex on that line. Spasm is 
a symptom of excessive action of the neurons of the 
reflex arc. The spasm here referred to, is not that 
temporary discharge of nervous energy from the 
cortical motor areas, that we have in epilepsy, etc., 
but is a tonic nervous influence existing in the cord 
itself. Continued it gives permanent contracture of 
the muscles supplied from the affected spinal seg- 
ments. As seen before it is usually caused by a 
separation of the cells of the ant’ cornua from the 
control of the cortical motor areas above. Whether or 
no the peculiar views of Setschenow, that the corpora 
quadrigeminia are the centres for the tonic inhibition 
of the reflexes of the cord, will be proven, is of little 
import. Either that theory, or the well-proven old 
one, that a centre released from the control of a 
dominating higher centre, is in a state of increased 
irritability, will suffice. 
Hemiplegia, etc. From what we have seen of the 
origin and course of the motor impulses we can under- 
stand how a lesion of any of the motor centres of the 
cortex, will give a paralysis in its corresponding body 
part.of the opposite side, (monoplegia.) The same is 
true of a lesion of the fibres in the corona radiata, the 
internal capsule and in the crus cerebrum, If the 
lesion referred to take place at any point above Gubler s 
hue, as in the capsule, we will have limbs and face 
paralyzed on the same side, (normal hemiplegia), but if 
below this line, down to the nucleus of the 7th, we 
have the face paralyzed on one side and the limbs on the 
opposite side. (crossed hemiplegia.) Below this 
nucleus we have the pyramidal decussation and there 
will be paralysis on the same side as the lesion, the 
face not being affected at all. (spinal hemiplegia.) PHYSIOLOGY 
383 384 
PHYSIOLOGY 
Here motion is lost on the side of the lesion and sensa- 
tion on the other side. We can readily understand this 
by remembering- that although connected with the 
same side of the brain, the fibres that carry sensory 
and motor impulses pursue different routes in the cord. 
If both be considered as coming down, the motor fibres 
may be said to cross in the lower part of the medulla, 
and the sensory to cross (obliquely) at the level of dis- 
tribution, lower down. The oblique direction taken 
by the sensory fibres as they pass over, allows quite a 
number of them to be cut in even a narrow unilateral 
section of the cord. This gives a narrow zone of 
anaesthesia a little below the section on the same side 
of the body. Paraplegia is the term applied to the 
results of a complete or bilateral section of the cord, it 
g'ives a loss of all motor and sensory conduction below 
the level of the section. The function of the spinal 
centres, below the section, are disturbed for a time, 
but the reflexes of defsecation and micturation ultimately 
return. They are, of course, unconscious acts hence- 
forth. 
Disturbance of language, speech, etc. To appreciate 
the lesions that produce these disturbances we must 
remember that what we call language may be conveyed 
either by word, symbol or gesture. Presiding over all 
of these motor manifestations is a cortical area, located 
near the face area, in the posterior part of the left 
inferior frontal (Broca’s) convolution of the brain. Any 
disturbance of this area or its connections, in right- 
handed men, is evidenced by some deficiency in the 
proper formation, or arrangement of the words, by 
which we convey ideas. The idea of language implies 
that an individual has a concept, which he wishes in 
some manner to convey to others. He must first have 
his ideas, he must wish to convey them, and he must PHYSIOLOGY 
385 386 
PHYSIOLOGY 
be able to put his ideas into a sound, a sign, or a 
symbol, which expresses his conception to others. 
The inability to properly form the word or sentence, 
is due to some derangement of this motor language 
centre itself. This abnormal state is called motor or 
ataxic aphasia. Let us first consider the influence of 
ataxic aphasia on articulate language. We must be 
careful to avoid confusing the conditions here involved 
with aphonia or loss of voice. Aphonia is due to an 
entirely different cause, viz.; some defect in the work- 
ings of the larynx and vocal cords, usually a congestion 
of the substance of the cord itself, or a paralysis of the 
inferior laryngeal nerve that regulates laryngeal ten- 
sion and control. There is no disturbance of the idea 
of language, for as we know, we may often read from 
the movements of the auxiliary lips, whatever is said. 
In ataxic aphasia on the contrary, there is a defect in 
the cerebral apparatus by which we transfer the word 
image which represents our idea, into such harmonious 
action of the muscles (of our organs of speech) as will 
reproduce the sound or movement we desire. To see 
what needs to be done here, let us first see how speech 
is produced. There goes out from the word-forming 
■centre (Broca’s convolution) a band of fibres called the 
speech tract which passes through the corona radiata, 
the posterior limb of the internal capsule behind the 
sensory fibres, and whose impulses are distributed as 
follows : Through the nuclei of the medulla, to the 
10th cranial nerve for the vocal cords, larynx and 
pharynx, to the 12th for the tongue-, to the sth and 7th 
for the jaws, lips and soft palate. In addition to these, 
impulses go down the cord and through the phrenic, 
intercostal, dorsal and other nerves below, for the 
muscles of respiration. The centre that presides over 
the organization, distribution and regulation of these PHYSIOLOGY 
387 388 
PHYSIOLOGY 
varied impulses must be liable to derangement from its 
very complexity. The simplest lesion that can take 
place here is “ blocking ” of the speech-tract routes. 
This may be produced by capillary congestion or rup- 
ture along the line of fibres of the so called speech- 
tract. In this lesion there is no paralysis of the vocal 
cords, or tongue, or lips, or any part of the muscular 
system. The patient can perform the acts of mastica- 
tion, deglutition, coughing, etc., which involve the 
muscles of this region, but he cannot properly associate 
his impulses to produce speech. He wishes to speak, 
he knows what he wishes to say, and the relation 
between the word representing his idea and the sound 
to express it is clear, and he formulates his impulses, 
but without avail. He can, however, as we readily 
see, speak by gesture or by writing, (Luke I, 20-22, 
and 59-64.) 
The next form of lesion in ataxic aphasia is derange- 
ment of the word-forming centre itself. This may be 
partial or complete, i. e., may be due to diminished 
excitability in some parts of the centre, or increased 
excitability, or both, or there may be complete func- 
tional loss of parts of the centre. Some patients can 
repeat only the vowels ; in others the sounds are mis- 
placed, as placing the last syllable of a word in the 
middle (inco-ordination), and in still others, the substi- 
tution of one word for another occurs (paraphasia). 
Some patients can repeat only a single word or phrase, 
often meaningless. Their vocabulary, of its kind, is 
more extended during anger or excitement than during 
quietude, the irritability of the center being then more 
exalted. Strangely some cases can repeat only the 
phrase of expression ‘ ‘on the mind” at the time the lesion 
occured, as the expression, “I want protection,” which 
was being pronounced as the injury was received. This PHYSIOLOGY 
389 390 
PHYSIOLOGY 
looks as if the molecular arrangement for the impulses, 
existing at the time, still persisted. [ln some rare 
cases which present undoubted evidence of disease of 
the motor speech centre, there exists more or less in- 
ability to write, or even to gesticulate with meaning, 
which seems to indicate that the motor center, so-called, 
presides over more than simple vocal word formation, 
but the coordination necessary to sentence-forming of 
every kind as well.] There is still another form of apha- 
sia, which we call sensory or amnesic amphasia. In this 
case the patient is devoid of language because he has 
lost or “forgotten” the word, character, or even move- 
ment that represents his idea. To appreciate the 
lesions that produce this state, we must understand 
that the memor}1' of a percept is retained by the centre 
that receives it. The memory of things seen, charac- 
ters, symbols, etc., is retained in the cells of the cor- 
tex of the cuneus, of sounds heard, words, etc., in the 
cortex of the first temporo-sphenoidal convolution, of 
movements made, as by the arm, in the cortex of control 
for the arm, etc. As we have seen, associating 
(intercentral) fibres join these centres and therefore 
the trouble may lie in the associating tract as well as 
in the centre. When the lesion lies in the first tem- 
poro-sphenoidal convolution, (left?) or its associating 
tract that unites it to the motor speech centre, we have 
what is called “word deafness The patient can not 
speak for he does not remember the sound that repre- 
sents his idea, nor can he understand spoken language, 
for he does not remember ever to have heard language 
before, his memory of words heard is lost, and all lan- 
guage sounds to him as foreign. He is not deaf for 
he will turn when called to, or for any noise. If the 
angular gyrus of the occipital lobe or its associating 
tracts is involved we have “word blindness.''1 Here PHYSIOLOGY 
391 392 
PHYSIOLOGY 
the patient can talk and can see (cuneus) but as the 
memory of written words once seen is gone, he can 
not read. He may even write correctly from dictation 
but he can not read what he has written. His writing 
in this case is done by reason of memory of movements 
made, just as we write with the eyes shut. Any of 
the sensory forms of amnesic aphasia may be combined 
with more or less ataxic aphasia and give us mixed 
symptoms, very difficult to determine. Related to the 
above are a series of disturbances of the language cen- 
tres, in which the patient is incapable of writing, 
(agraphia), incapable of making appropriate gestures, 
(amimia) or even incapable of recognizing the common 
objects of every day use (apraxia). The latter condi- 
tion may reach such a state that he can not even recog- 
nize the usual articles of clothing worn, putting his 
gloves on for shoes, etc. In a case of “word blind- 
ness” in which a patient could not read by sight, 
(alexia), he was able to read by tracing the letters with 
a pen and recognizing the movements made. (The 
student is referred to special works on disease of the 
general nervous system, for the details of symptoms, 
and for the systematic examination necessary to differ- 
entiate these varieties of cerebral lesion.) In addition 
to the lesions previously described which are due to 
cerebral hemmorhage, embolism, trauma, etc., we 
have functional troubles of a kindred nature affecting 
the same centres. We all know that some men are 
fluent, and others slow talkers, but the difference in 
two such men is not as great as is the variation in the 
capacity of either of them, at varying times. A tem- 
porary amnesic aphasia attacks every speaker at times 
and in spite of every effort he is below his standard. 
This variation in the natural capacity of “speakers” 
is not nearly so pronounced as is their variability in the PHYSIOLOGY 
393 394 
PHYSIOLOGY 
use of gesture language. The sign language of some 
orators is the very embodiment of graceful expression, 
while others are dumb along this line. As we would 
expect, men are rarely equally good as writers and as- 
speakers. Stuttering is not a disease of the speech 
centre, but is due to irritability of the nuclei of the 
cranial and other nerves used in phonatiou, especially 
those of the sth and 7th. From these nulcei reflexes are 
radiated to the inhibitors of respiration, or to the mus- 
cles of mastication, giving the tremulous spasm of the 
jaw, and in severe cases to the entire distribution of 
the 7th, giving the facial contortions so often seen. Its 
relative intensity depends upon the degree of excite- 
ment of the subject, being increased by emotion, rage, 
embarrassment, etc. Where the impulses are sent in 
rythmical order, as in singing, etc., they are never 
mixed. Writers cramp, and similar manipulative dis- 
eases, are due to essentially the same cause, the irrita- 
bility and radiate spasm being due to excessive excita- 
tion of the gray matter of the anterior horn of the 
upper cord. PHYSIOLOGY 
395 396 
PHYSIOLOGY 
CHAPTER XVII. 
THE SENSES. 
Mental physiologists divide the senses into two 
primary groups or classes. These are (1) the vague 
senses (sensus vagus) whose impressions cannot be 
referred to any special end organs or nerve terminals, 
and cannot therefore be localized ; as the senses of 
weariness, hunger, anxiety, etc. ; (2) the fixed senses 
(sensus fixus) whose impressions are referable to certain 
special terminals or sense organs, and are thus fixed. 
Por anatomical reasons, the latter are divided into the 
somatic senses, including the senses of touch, tempera- 
ture and muscle tension ; and the cephalic senses of 
taste, smell, hearing and sight. A sense of pain 
largely subjective, may result from overstimulation of 
any sensory nerve or terminal. In the excitation of 
the sensory terminals, a specific stimulus is required ; 
i. e., a touch corpuscle will not be stimulated by heat, 
nor a temperature terminal by pressure, nor a visual 
terminal by sound, etc. A nerve trunk will however 
respond to electrical or mechanical stimulation applied 
at any point on its route, and not only will it respond 
in kind, auditory nerves giving sensations of sound, 
gustatory nerves sensation of taste, etc., but the 
response is referred to the distal (sense) terminal of 
the nerve stimulated. This “ law of peripheral refer- 
ence ” is well demonstrated in cases of amputation, 
where the ensuing irritation of the cut nerve trunks is 
referred to the terminals of the lost member. In some 
cases of nerve lesion (locomotor ataxia) the sensation of PHYSIOLOGY 
397 398 
PHYSIOLOGY 
pain and to a less extent of touch, may be delayed 
(several seconds) between the receiving- terminal and 
the perceptive centres. This is due to no disease on 
the part of the terminal or centre, but presumably to 
the impulse having to take a new route and make many 
“ relays.” Of the somatic senses, touch is largely an 
objective sense and temperature and pressure sense are 
predominantly subjective. Of the cephalic senses, 
taste and smell are (in man) subjective senses and sight 
and hearing objective. It should be borne in mind that 
even touch is an objective sense only when functionally 
pure. Thus an iron wire held against the hand gives 
the idea of a foreign body and a definite idea of locality, 
but if the wire as held be heated sufficiently to produce 
piin, the sensation at once becomes one of body state, 
and the sense of locality is largely lost. While we 
say in a general way that we see with the eye and hear 
with the ear, it must be understood that the impression 
is received only by the sensorium. When a sensation 
is felt it simply means that the sensorium is stimulated. 
The habit of peripheral reference makes us refer all 
sensations to external causes. Under certain con- 
ditions of abnormal excitability, the sensation may 
originate in the brain itself, but being from habit 
referred to an external cause, we have the hallucina- 
tions so common in cerebral disease, delirium, etc. It 
is a curious fact that the illusions of delirium tremens 
should always be of a frighful, horror-inspiring 
character, as of snakes, demons, etc., while the 
primary sensations of alcohol, opium and other stimu- 
lants that produce such mania are just the reverse, 
pleasant and agreeable. 
The sense of touch or tactile sensibility is limited to 
no part of the body, for while varying in degree in 
different localities, it is present everywhere. Its PHYSIOLOGY 
399 400 
PHYSIOLOGY 
excitation is dependent upon the stimulation of the 
terminals in the papillae, etc., of the skin, and the rela- 
tive acuity of touch in a part is dependent upon the 
relative supply of terminals it receives. The theory of 
Weber is that the mind estimates the distance between 
two points touching- the skin by the number of unexcited 
nerve ending-s between the points touched. The varia- 
tions in tactile sensibility in the different parts of the 
body are made manifest by the following figures, which 
represent the distance in millimeters at which the points 
of a pair of compasses can be disting-uished as separate 
points. Tip of tong-ue 1, tip of third fing-er 2, lower 
lip 4, tip of nose 6, palm of hand 10, back of hand 25, 
dorsum of foot 37, back of neck 50, and inter-scapular 
reg-ion of .the back 65. The sense of locality and space 
comes purely as a matter of experience (Aristotle’s 
experiment). This, with the marked increase in tactile 
sensibility, developed with practice, g-ives the wonderful 
manipulative power of the blind. The sense of pressure 
is a modification of that of touch. This should not be 
confused with muscle sense, althoug-h used conjointly 
with it. Thus, in an effort to estimate the weig-ht of a 
bar of lead, we judg-e almost as much by the necessary 
amount of pressure of the fingers against it, to hold it, 
as we do by the degree of muscular effort put forth. 
The relative value of these senses can be compared as 
follows : Place the hand, palm up, upon a table and 
putin the palm of the hand a weight, now lift the hand 
from the table and compare the weight as appreciated 
by simple pressure, with the weight now appreciated 
by muscle sense and pressure. 
The sense of temperature is distinct from tactile 
sensibility, but is like it in being general over the entire 
body. There are two sets of terminals in the nerve 
distribution of this sense, one for impressions of w7hat PHYSIOLOGY 
401 402 
PHYSIOLOGY 
we call cold and the other for impressions of heat. The 
distribution of each set of terminals is punctiform,gi ving 
hot and cold “spots” of quite uniform distribution, at 
least as compared with the variations found in tactile 
The perception of cold seems to be more 
intense than that of heat. To appreciate why this is 
true we must remember that the bulk of the human 
race live and die without often experiencing- the influence 
of a medium as warm as body heat, but none have ever 
lived without experiencing- for long periods of time a 
temperature lower than that of the human body, i. e. 
cold. If we took the temperature of the body as a 
standard we would be always cold, but in reality the 
temperature of the skin is taken as a standard, and as 
this varies with the medium around, we have no abso- 
lute standard. For this reason we can get accustomed 
to almost any temperature and in time live in comfort in 
any climate. This skin standard makes all estimates 
of heat (fever, etc.) by mental comparison fallacious. 
This is well seen in the following ; If we place one 
hand in ice water (32°) and the other in hot water (110°) 
we appreciate fully the sensations, but if we now place 
both hands in warm water (75°) the previously cold 
hand will feel warm and the warm hand cold. 
The sense of muscle tension, or as it is usually 
■called muscle sense, is not well understood. It origi- 
nates in certain nerve terminals found in the tendons 
of various muscles. These nerve corpuscles are sub- 
jected to pressure when their tendons are put upon the 
stretch (tendon reflexes). As we have previously seen, 
a part of the perceptive power referred to this sense 
is due to the sense of touch or cutaneous pressure. 
To what extent we are further indebted to a knowledge 
of the amount of nerve energy sent out, in executing 
any discriminating muscular effort, is not known. PHYSIOLOGY 
403 404 
PHYSIOLOGY 
That the amount of nerve impulse is conditionally known 
and regulated for each act is proven by the serious 
wrench to the muscles when we err in judging the 
weight of an object to be picked up, moved or thrown. 
We see the same thing illustrated in the clumsiness 
with w?hich one first handles a new weapon or tool of 
different weight from that to which he is accustomed, 
or makes an unaccustomed effort with a weight or tool 
previously familiar for other work. So far it would 
seem that there was no muscle sense, but that we 
make use of two other functions to determine the 
intensity and amplitude of muscular exertion. How- 
ever, if we will allow some one to take, say the hand, 
while the eyes are closed, and make certain passive 
movements with it, as tracing figures, letters, etc., we 
will be astounded to learn how accurately we can 
recognize the scope and relation of the movements 
made, the form and size of figures traced, etc. This 
is purely muscle sense, as no nervous energy was 
expended, nor was tractile sensibility materially in- 
volved. As stated the small pacinian-like bodies found 
in the tendons seem to be the terminals taking cog- 
nizance of these movements, and it is no doubt to these 
end organs that we are indebted for the impulses that 
record what we call the memory of movements made, 
as writing, etc. The combined sum of these “senses,” 
is capable of wonderful achievements. All that we call 
higher automatic dexterity, all that comes of long and 
continued manual training is due chiefly to the culti- 
vation of this group of senses, as seen in the complex 
movements of the violinist, etc., etc. The most inter- 
esting illustration of the use of this sense memory is 
in cases of late acquired deafness. If loss of hearing 
occur before adolescence, the patient will ultimately 
lose the power of speech ; but if it occur later the long PHYSIOLOGY 
405 406 
PHYSIOLOGY 
practice of speech makes such an impress upon the 
cortex, that by simple memory of muscular movements 
made the patient will be enabled to continue to speak* 
in a disagreeable but still intelligible voice. 
The use of after sensations, or memory of movements 
made, is the means by which the blind, in whom these 
senses are cultivated to their highest degree, recognize 
by form and size, faces and other objects once known. 
Pain is not a special sense but is in a measure the 
intensification of any of the senses. We use the term 
“in a measure,” because while we say that “a loud 
noise hurts the ear,” or “a bright light is painful to 
eye,” the impressions produced here are not sensations 
of pure pain as we know them, say with the somatic 
senses, but are simply feeling’s akin. With the 
two most subjective of all the senses, taste and smell, 
the feeling- is still less one of true pain. It is hard to 
conceive of a true g-ustatory or odorous impulse intense 
enoug-h to produce a state of genuine pain. Hence 
what we know specifically as pain may be considered 
as due only to the intensification of the impulses of the 
somatic senses, tactile sensation, temperature, etc. 
The sense of smell, if we may judge from compar- 
ative development, is perhaps the primitive sense. It 
is also the most delicate of the senses, particles of mat- 
ter being easily detected by this sense, that are invisible 
by the microscope or even incapable of demonstration 
by the spectroscope. Camphor vapor in the proportion 
of one part in three billions of atmospheric air is capa- 
ble of detection by this sense, while musk in the pro- 
portion of one in three hundred millions is readily 
discernible. To be smelled a substance must be 
brought in contact with, and dissolved in, the natural 
fluids covering the nerve terminals. This being true, 
only such substances as can be volatilized or suspended PHYSIOLOGY 
407 408 
PHYSIOLOGY 
in a finely divided state in the air can be perceived as 
odors. To bring- the odorous gases or particles into 
abundant contact with the moist olfactory membrane, 
we sniff, or draw the air up into this part of the cavity. 
This sudden inspiration produces something of a vac- 
uum in the nasal fossa and hence the incoming air is 
forced to find its way into the more remote regio-olfac- 
toria as well as into the well travelled regio-respira- 
toria. The odorous substance must be freshl}T dissolved 
in the fluids of the membrane to be appreciated ; to be 
simply a soluble substance in solution will not suffice, 
for the nasal fossa may be poured full of an aromatic 
fluid (eau de cologne) without exciting the sense of 
smell. 
The end organs of this sense lie in the mucous 
membrane of that part of the nasal fossa which lies 
above the middle turbinated bone, and called the regio- 
olfactoria. This membrane, often called the Schneide- 
rian membrane, is of a light yellowish brown tint, and 
is not covered with true ciliated epithelium as is the 
lower part of the fossa, the regio-respiratoria. On 
section it shows (1) the supporting cells, most numer- 
ous but least important, quite long columnar cells, with 
an oval nucleus ; (2) between these are very long and 
slender cells with a large nucleus and having several 
cilia-like rods extending from their free surface, while 
a delicate nerve fibre extends from the other end and 
joins the olfactory nerves. These long slender nucle- 
ated cells are the end organs of the sense of smell. 
They are quite small as compared with the supporting 
cells between them. Their free rodded ends are prob- 
ably the real sense terminals. Under the mucous 
membrane we have a number of muco-serous glands 
(Bowman’s) which secrete continuously the fluid nec- 
essary for the membrane’s functional activity. In cer- PHYSIOLOGY 
409 410 
PHYSIOLOGY 
tain cases, usually of hysteria, there is marked increase 
in the sensitiveness of these terminals (hyperosmia). 
Morphine locally applied will paralyse the sense ter- 
minals, wThile the administration of strychnine in a less 
marked manner intensifies their activity. We must 
remember that disturbances of this sense are quite 
often subjective. The mutual relations between this 
sense and the sense of taste will be considered under 
the head of the latter. 
The sense of taste. To be appreciated by this sense 
a substance must be in a state of solution, or at least 
soluble in the fluids of the mouth. The sense terminals 
are in the various forms of papillae on the tongue, etc., 
hence for taste to be appreciated the epithelium cover- 
ing- the tong-ue and its papillae must not be too thick, 
and the mucous membrane and terminals must be 
moist. In fevers, etc., the accumulation of exfoliated 
epithelium, dried mucus, etc., (sordes) on the mucous 
surfaces of the mouth almost inhibits taste. This, 
sense is also markedly interfered with by the local 
influence of heat and cold, especially the former. The 
salts of cocaine, locally applied, also blunt it, most 
markedly for bitters. The principal seat of this sense 
is the posterior third of the tongue, the region of the 
circum-vallate papillae, the area of distribution of the 
glosso-pharyngeal nerve. Besides this, the anterior 
two-thirds of the tongue, the soft palate and its arches, 
and to a less extent the posterior pharyngeal wall are 
all endowed with this sense. The anterior part of the 
tongue seems to be supplied by the chorda tympani, 
while the other areas above mentioned are supplied by 
the glosso-pharyngeal nerve. The papillae of the 
tongue are of three kinds, filiform, fungiform, and 
circum-vallate. Filiform papillae are found over the 
entire surface of the tongue. They are compound PHYSIOLOGY 
411 412 
PHYSIOLOGY 
papillae in which the epithelial covering- of the second- 
ary divisions is prolonged into conical processes, often 
hair-like in form and structure. The capillary loops 
and nerve terminals are not prolonged into the second- 
ary papillae. 'Fungiform -papillae, so called from their 
general toadstool appearance, are larger compound 
papillae in which each secondary papillae receives its 
own plexus of vessels and nerves. They are more 
readily seen in children (“strawberry tongue”) than in 
adults, and are most abundant on the sides and tip of 
the tongue, but are nowhere as abundant as the filiform 
type. The circum-vallate papillae, some twelve in 
number, are arranged in the form of a V on the poste- 
rior part of the tongue. They each consist of a large 
central compound papilla surrounded by a deep circu- 
lar depression or fossa. On both the central and pe- 
ripheral faces of this fossa open many of the peculiar 
gustatory terminals called “taste bulbs.” These 
consist of a number of protective or “barrel stave” 
cells arranged around the half a dozen or more central 
gustatory cells, which are united with the terminals 
of the glosso-pharyngeal nerve. These gustatory cells 
have their free ends projecting from an opening in the 
cylinder of protective cells, and these free ends are 
equipped with delicate, hair-like processes (dendrites) 
which extend into the gustatory fossa around the cir- 
curavallate papillae. In a modified form these taste 
bulbs are also found on many of the lower fungiform 
papillae, the soft palate, epiglottis, etc. 
Gustatory sensations take but four forms, viz., im- 
pressions of bitter, szueet, acid and saline. It would seem 
as if the four forms of this sense have each separate 
end organs. The acuity of taste varies with the form 
of sense tested, bitters being most easily detected, 
acids next, etc. The time required for a percept varies PHYSIOLOGY 
413 414 
PHYSIOLOGY 
also, salines here being- first and bitters last, but the 
latter impressions are very persistent. The combined 
synchronous action of the senses of smell and taste 
gives us what is call flavor, and the various com- 
binations of the four forms of taste with tactile im- 
pressions give us the distinctive tastes of our foods, 
etc. We do not appreciate to what an extent tactile 
and other sensory impressions are confounded with and 
modify taste sensations, giving the so-called cooling, 
astringent, gritty, oily and soothing tastes. The nerve 
terminals by which we receive ideas of this kind are 
those of the lingual branch of the sth, sometimes, from 
its associated powers of taste, called the “gustatory” 
branch of the above. When one wishes to appreciate 
fully a taste he takes enough of the substance into 
the mouth to cover the surface of the tongue, lets it 
run back to the circumvallate area, and pressing the 
tongue against the roof squeezes the sapid substance 
into the gustatory fossae and brings it into direct con- 
tact with the processes of the gustatory cells. The 
galvanic current passed through the tongue gives a 
sensation of taste, which is acid at the anode and saline 
at the cathode. Subjective sensations of taste often 
give great annoyance, especially to the insane. Before 
pronouncing a taste sensation subjective, we must 
exclude elimination of sapid substances through the 
saliva, as iodides, santonin, mercury, etc. The two 
other special senses, those of sight and hearing, will 
be considered more fully. PHYSIOLOGY 
415 416 
PHYSIOLOGY 
CHAPTER XVIII. 
THE SENSE OF HEARING. 
The sense of hearing, may, like the sense of vision.' 
be called a physical sense, in contra-distinction to the 
chemical senses of smell and taste. The registration 
of atmospheric vibrations for analysis and comparison 
demands an extremely complex apparatus and one so 
delicate in parts as to require absolute protection against 
mechanical injury. The apparatus consists of the 
external ear and auditory canal, the middle ear or 
tympanic cavity and the internal ear or labarynth, with 
its canals, cochlea, etc. 
The external ear or pinna consists of a plate of yellow 
elastic cartilage folded and bent on itself, with attached 
muscles, adipose tissue, etc., and covered with thin 
integument. The cartilage of the external ear is pro- 
longed inward as a tube to form the outer two-fifths of 
the external auditory canal. This canal is about If 
inches long and smallest (fm.) at its centre, and the 
floor sloping downwards both ways from the center 
makes this also the highest point. The canal expands 
a little in its vertical diameter at its outer end and 
expands horizontally at its inner end (speculum). Its 
inner extremity is closed by the tympanic membrane, 
which extends obliquely across it, making the front 
wall and floor of the canal longer than the roof and 
post. wall. The nerve supply of the external auditory 
canal is from Arnold’s branch of the 10th, and the- 
auriculo-temporal of the sth, and inspissated wax or 
foreign bodies in the deeper sensitive parts of this PHYSIOLOGY 
417 418 
PHYSIOLOGY 
canal often gives unsuspected but distressing reflexes, 
the former nerves causing cough or even vomiting (9th), 
and the latter various facial neuralgias. The inner 
face of the canal presents the orifice of numerous 
ceruminiferous glands. These glands are structurally 
like the lower part of the sweat glands, but they 
secrete wax, often in considerable quantities. The 
muscles that move the ear are, in man, almost function- 
less. 
The middle ear or tympanum is an irregular cavity 
excavated in the bone, just within the tympanic mem- 
brane. It is about the size and general shape of a 
grain of Indian corn placed on edge with the point 
forward. It presents six bounding walls or surfaces. 
(1) The external zuall presents the tympanic mem- 
brane set in a bony ring (annulus tympanicus). The 
tympanic membrane consists of three layers, an external 
cuticular, a middle fibrillar and an internal raucous. 
The middle layer consists of white and yellow elastic 
fibres woven like the bottom of a basket, i. e., with 
interlacing circular and radial fibres. The bony ring 
in which this membrane is stretched is incomplete at 
the top, and the membrane here is slack and receives 
the namzmembrana flaccida. In the upper half of this 
membrane is hung the handle of the malleus, one of 
the bones of the middle ear. The chorda tympani nerve 
passes like a chord across the upper segment of the inner 
face of the tympanic membrane, hence its name. It 
comes through an opening at the posterior border of 
the external wall, the iter chordae posterius, passes 
across the tympanum, over the handle of the malleus, 
and goes out through a similar opening on the front 
part of the outer wall, just above the opening of the 
tympanic plexus, called the iter chordae anterius, 
which leads into Hugier’s canal, etc. PHYSIOLOGY 
419 420 
PHYSIOLOGY 
(2) The internal zuall of the tympanum or middle ear 
presents about its centre a rounded eminence called the 
-promontory, which is grooved by the branches of 
tympanic plexus of the 9th. This nerve supplies 
the inner and anterior wall and sends branches as fol- 
lows : One to join the first branch from the geniculate 
enlargement of the 7th and thus form the great super- 
ficial petrosal, which joining- the deep petrosal forms 
the vidian ; another to join a smaller branch from the 
7th, thus forming the lesser superficial petrosal, which 
joins the otic ganglia (parotid gland); and a third 
join the carotid plexus of the sympathetic. At the up- 
per back part of the promentory is a kidney-shaped 
opening, hilum down, called the fenestra ovalis, while 
at the lower back part is a round opening the fenestra 
rotunda. To locate these openings and get a general 
conception of the relations of the internal parts of the 
tympanum, it is well to remember that a plane which 
cuts in half the carotid foramen on the base of the 
petrous portion, and also cuts the internal and external 
auditory canals, will pass between the fenestra ovalis 
and rotunda. Just behind the openings here consid- 
ered is the pyramid, which bears at its apex the open- 
ing for the tendon of the stapedius, and arching from 
the roof of the inner wall, down behind the pyramid, 
is the curved osseous canal, the aqueductus fallopii. 
(3) The anterior zuall presents, low down, the open- 
ing of the eustachian tube and the osseous canal of the 
tensor tympani muscle above it. The tube is osseous 
next the tympanum and cartilaginous next the pharynx 
(catheter). Its trumpet-shaped pharyngeal opening is 
dilated only during the act of deglutition (inflation). 
(4) The posterior zuall presents the openings of the 
mastoid cells, both large and small, but both lined by 
the continuation of the mucous membrane of the tym- 
panum (mastoid disease). PHYSIOLOGY 
421 422 
PHYSIOLOGY 
(5) The inferior wall, or floor, presents only the 
opening- of entrance for Jacobson’s nerve, giving the 
tympanic plexus above described. 
(6) The superior wall or roof presents nothing of 
interest, only a thin plate of bone separating it from 
the cranial cavity above. 
The auditory ossicles, three in number, are called 
respectively the malleus, incus and stapes. The mal- 
leus, the most external, as we saw before, has its long 
process or handle woven into the middle layer of the 
tympanic membrane, and this imparts a motion to the 
malleus which, by an interlocking union, is transmitted 
to the incus, thence to the stapes, and by the “foot 
piece” to the perilymph of the internal ear. From the 
neck of the malleus there runs forward a ligament 
(“laxator tympani” ?) which passes into the glasserian 
fissure. A part of this ligament is always ossified, 
forming the processus gracilis of the malleus. 
From the neck of the malleus there runs backward 
in the membrana tympani a thickened fold of this 
membrane, forming a functional analog-ue to the an- 
terior ligament. Around these ligaments as an axis 
the malleus rotates, so that when the manubrium goes 
in the head of the bone moves out and vice versa. 
The incus lies next the malleus and between it and 
the stapes. It is fastened by an interlocking union, 
and a uniting ligament, to the malleus, and by a short 
thick ligament, extending back from its short process, 
to the posterior wall. The union with the malleus is 
a peculiar one, a sloping cog fitting into a socket, so 
that to move the handle of the malleus inward causes 
a simular movement of the incus, but an outward 
movement of the malleus causes no change in the other 
bone. This allows distention of the middle ear with- 
out damage to the attachment of the stapes (effusion). PHYSIOLOGY 
423 424 
PHYSIOLOGY 
The stapes, shaped like a stirrup, is the most internal 
of the auditory ossicles. It is united by a capsular 
ligament to the long process of the incus and its base 
is fitted into the fenestra ovalis, to the margins of 
which it is attached all around by an annular ligament, 
but most strongly at the front end. 
The mitscles of the ossicles are two, the tensor tym- 
pani and stapedius. The first, supplied by the sth 
through the otic ganglion, draws the handle of the 
malleus, and with it the tympanic membrane, inward. 
This couples the interlocking action of the malleus 
and incus, and also by a variation in tension gives a 
varying fundamental tone to the membrane, etc., etc. 
The second muscle the stapedius, supplied by the 7th, 
draws the neck of the stapes backward, and this in 
turn moves the base. As, however, from its relative 
fixity the anterior part of the base cannot move, 
when the neck comes back the posterior part of the 
base necessarily moves in and compresses the fluid of 
the internal ear, in a degree proportionate to the tension 
.of the muscle. 
The internal ear or labyrinth lies just internal to 
the tympanic cavity. It consists of a central portion 
or vestibule, a posterior portion formed of the three 
■semi-circular canals and an anterior portion or cochlea. 
The cochlea is primarily the auditory part of the ear, 
the canals the part chiefly concerned in equilibration, 
and the vestibule is curiously concerned in both. The 
■osseous labyrinth has within it a more or less exact 
membranous imitation of its external form. This 
■enclosed membranous labyrinth is filled with a muco- 
serous fluid called endolymph, while around the mem- 
branous labyrinth, and between it and the osseous 
wall, is the perilymph. 
The vestibule is an excavated cavity in the bone PHYSIOLOGY 
425 426 
PHYSIOLOGY 
having- the same g-eneral shape as the tympanum, but 
smaller, and having- the following- limiting- walls. (1) 
The outer wall which presents the fenestra ovalis, 
filled in by the base of the stapes, its annular lig-aments, 
etc. ; (2) the internal wall presents a rounded depression 
(fovea hemispherica) with numerous perforating- fora- 
minia (macula cribrosa), and the opening- of the aque- 
ductus vestibuli; (3) the posterior wall presents the five 
opening's of the three semi-circular canals ; (4) the 
anterior face presents the larg-e opening of the scala 
vestibuli ; (5) the roof bears another perforated 
depression (fovea hemieliptica) ; and (6) the floor shows 
in front the posterior extremity of the lamina spiralis. 
The semi-circular canals, three in number, are 
located above and behind the vestibule. They are of 
very unequal length, but each describes a little more 
than half of a circle. One end of this semi-circle is 
dilated to about twice the diameter of the rest of the 
tube, and called the ampulla. The canals lie in such 
relation to each other that each one is at right angles 
to the other two and yet at the same time a canal on 
one side of the body is always in a plane parallel to 
that of some canal on the opposite side. The six canals 
in other words lie in but three planes and these planes 
represent the three dimensions of space. The superior 
canal, roughly parallel to the sagittal plane of the body,, 
has its ampullated end opening free in the upper part 
of the vestibule, but its other end is common with the 
posterior canal next mentioned. The posterior canalT 
with a general direction in the transverse plane of the 
body, has its ampullated end opening into the lower 
part of the posterior wall of the vestibule, the other 
joining the superior canal. The horizontal canal is the 
smallest of the tubes, and has two distinct openings. 
The ampullated end is just external to the upper open- PHYSIOLOGY 
427 428 
PHYSIOLOGY 
ing of the superior canal and the other just external to 
the common orifice. 
The membranous labyrinth of the canal consists of a 
membranous tube loosely filling- each canal, but dilated 
(ampullated) and closely adherent to the bone at the 
ampulla. At each end these membranous canals are 
joined to a membranous sac, called the utricle, which 
lies in the posterior end of the vestibule. This utricle 
is joined by a Y-shaped tube to a smaller membranous 
sac, in the vestibule, called the saccule, the third end 
of the Y-tube passing through the aqueductus vestibuli. 
A small tube, the canalis reuniens, now unites the 
saccule with the scala media of the cochlea. Histolog- 
ically the membranous labyrinth consists of three 
dissimilar layers, the external having fibrous processes 
on its outer surface by which the canals, utricle, etc., 
are anchored to the bony walls around them and sup- 
plied with nutrition ; and the inner layer consisting of 
secretory cells, which secrete the endolymph. The 
middle layer, called the tunica propria, forms the chief 
element of the membranous walls of the canals and sacs. 
The vestibular branch of the Bth sends divisions to 
each ampulla of the semi-circular canals, and through 
the macula cribrosa to the saccule and utricle, which 
end as follows : In each ampulla there projects from 
one side of the membranous canal an elevation from 
which a series of fine hair-like rays extend into the 
cavity of the ampulla. This elevation is called the 
crista acustica, and each hair-like ray is united with a 
terminal fibre of the vestibular nerve. In the utricle 
and saccule we have a nerve terminal equally elaborate, 
here called the macula acustica. It is less elevated 
than the other, and has entangled in its hair-like pro- 
cesses amorphous and crystalline particles of carbonate 
of lime to which the term otoliths is applied. The func- PHYSIOLOGY 
429 430 
PHYSIOLOGY 
tion of these beautiful terminals seems to be as follows : 
The endolymph by reason of its mobility is free to 
move in the canals, so that when any movement of the 
head is made in the plane of any canal, the endolymph 
(of that canal) by reason of its inertia seems to flow 
against the movement. This causes a streaming of the 
endolymph through the hair cells, [which cells, of 
course, move with the head,] and a stimulus is thereby 
imparted to the nerve endings in the hair. When a 
movement in a given plane is long continued, the endo- 
lymph of the canal in that plane is finally set in motion 
and this motion continues after that of the body ceases, 
giving a sense of vertigo as seen in children who turn 
around till they “get drunk.” By the movement 
imparted to this fluid and its influence on the vestibular 
terminals, we are enabled to judge of our relative posi- 
tion and plane of movement in any act, as compared 
with a previous position and course. The loss of this 
function produces marked disturbance of locomotion, 
as seen in the condition called Meniere’s disease. 
The cochlea consists of a cavity in the bone, of very 
peculiar shape and formation. It is formed as if a 
conical tube were coiled, like a snail shell, two and 
half times around a central axis. It is placed in front 
of the vestibule and its central axis or modiolus is in 
the line of prolongation of the internal auditory canal. 
This tube, as it winds around, is divided into two 
parts by a septum partly osseous and partly membra- 
nous that extends along its lumen from the base 
almost to the apex of the coil. This septum is called 
the lamina spiralis. Its inner half, or half next the 
central axis, is composed of a spiral ridge of bone the 
lamina spiralis ossea, which projects out from the in- 
ner wall of the canal, as if to divide it in half. The 
external portion of this septum is a thin fibrous mem- PHYSIOLOGY 
431 432 
PHYSIOLOGY 
brane, called the membrana hasilaris, and it extends 
from the osseous lamina to the outer wall of the canal, 
to which it is attached by the ligamentum spirale. 
This septum, as stated, extends from the base of the 
coil almost to the top, and divides the tube into two 
canals, an upper or scala vestibuli, and a lower or 
scala tympani, which are in communication through 
the undivided part of the tube, at its apex, called the 
helicotrema. The lower end of the scala vestibuli 
opens directly into the vestibule (observe the names), 
and the lower end of the scala tympani abuts 
against the (internal) tympanic membrane, that closes 
the fenestra rotundum, and thus separates this canal 
from the middle ear. Both of these canals are filled 
with perilymph continuous with that of the vestibule. 
There lies upon the outer part of the osseous lamina 
spiralis a cartilage-like mass, the crista spiralis, from 
the upper surface of which there springs a membrane 
(Reisner’s) which extends upward and outward to join 
the external osseous wall of the canal and cut off a 
portion of the scala vestibuli as a separate canal, the 
scala media or ductus cochlearis. This latter canal, 
extending from the inferior origin of the lamina 
spiralis to the helicotrema, becomes larger as it 
ascends, is filled with endolymph through the canalis 
reunions, and contains the organ of corti. This organ 
lies upon the membrana basilaris and includes as a 
central feature the so-called tunnel of corti. This 
tunnel is formed of inner and outer rod-shaped cells 
wrhich rest upon the basilar membrane and lean against 
each other at the top, like the rafters of a house, leaving 
the triangular tunnel below. On either side of this 
column of rod-shaped cells, w’hich form the tunnel, we 
have a line of hair cells, the inner row being single, 
and the outer row triple, while both have the slant of PHYSIOLOGY 
433 434 
PHYSIOLOGY 
corti’s rods, inner and outer respectively. These hair 
cells have hair-like processes extending- from their 
upper surface, and these project throug-h suitable 
openings in a fenestrated membrane, the membrana 
reticularis, which overlies the hair cells. Above this, 
extending outward from the crista spiralis, is a heavy 
dense membrane the membrana tectoria which touches 
the tips of the hair-like processes of the hair cells, and 
seems to act as a damper to excessive vibration. 
The cochlear nerve comes with the vestibular branch 
through the foramina at the extremity of the internal 
auditory canal. Here the nerve passes through a tubu- 
lar opening in the modiolus, in the osseous central 
axis of the cochlea, to give off fibres to the organ of 
corti as follows : As the nerve ascends in the central 
canal of the modiolus branches pass out through radi- 
ating perforations in the osseous lamina spiralis, to 
■emerge under the crista spiralis and supply with ter- 
minal fibres the inner hair cells, while others passing 
between these cells and across the tunnel supply also 
the outer hair cells. In cavities excavated for them in 
the substance of the osseous lamina, these nerve fibres 
present a ganglionic enlargement, the so-called gan- 
glion spirale. 
The function of the various parts of the auditory 
■apparatus here given may be briefly summarized as 
tfollows ; Sound waves coming through the external 
auditory canal, etc., produce sympathetic vibrations in 
the tympanic membrane. All sound waves cause 
-vibration of the tympanic membrane, but naturally it 
is most affected by those tones which correspond with 
its own fundamental tone or its octaves. But as we 
have seen the action of the tensor tympani gives it a 
variable fundamental tone, and in addition the ossicles 
act as a damper preventing excessive sympathetic 
vibration. The vibrations are conducted through the physiology 436 
PHYSIOLOGY 
chain of ossicles, and the tympanic membrane being' 
many times (30 to 1) larger than the base of the stapes, 
these vibrations are intensified in power and are thus 
transmitted to the perilymph. If enclosed solely in 
the rigid osseous walls of the labyrinth, noncom- 
pressible fluids like the peri- and endo-lymph when 
subjected to pressure and vibratory forces, would do 
great damage to the delicate structures of the organ 
of corti, ampulla terminals, etc. The secondary tym- 
panic membrane closing in the fenestra rotunda, by its 
elasticity obviates this difficulty, and vibration waves 
transmitted from the base of the stapes are conducted 
through the perilymph of the scala vestibuli to the 
helicotrema and around through the scala tympani to 
the terminal tympanic membrane. By these waves 
the membrana basilaris, etc., is thrown into sympa- 
thetic vibration which is greatest at the point whose 
fundamental tone accords with the wave. This vibra- 
tion is thus analysed and registered by the terminal 
hair cells of the organ of corti, and the impulses gen- 
erated pass through the cochlea branch of the Bth to 
the posterior nuclei of the same. It is probable that 
they then pass over to the opposite side and up through 
the tegmentum to the (inferior levels of) the posterior 
limb of the internal capsule and hence through the 
corona radiata to the cortex of the superior temporo- 
sphenoidal convolution. Here the impulse is “per- 
ceived” and the memory of the percept is stored in the 
some centre that received it. Irritation of this cerebral 
auditory centre will produce subjective impressions of 
sound which are referred to an external source, and 
in some cases give rise to dangerous hallucinations. 
The power of the internal ear to analyze and differ- 
entiate sounds makes its possessor sensible not only 
to the beauties of harmony, but in equal measure to the 
agonies of discord. PHYSIOLOGY 
437 438 
PHYSIOLOGY 
CHAPTER XIX. 
THE SENSE OE SIGHT. 
This is the sense that never rests while man is 
awake. A man may practically rid himself of disturb- 
ing- sounds, smells and tastes, and still pursue his reg- 
ular vocation, but so long as he is engaged in anything 
requiring the use of the eye at a focal distance of less 
than 20 feet, the eye is engaged in muscular effort. 
This “eternal vigilance ” explains the frequency 
with which neuroses result when the eye is so diseased 
or so constructed as to require more than ordinary 
muscular effort in the performance of its functions. 
We will take up first the appendages of the eye, and 
then the organ of vision itself. 
The appendages ofthe eye. These are the lids, the 
lachrymal glands, the lachrymal sac, with its various 
canals, etc., the external eye muscles, etc. The func- 
tions of these accessories are so intimately related to 
the function of the eye itself and so necessary to its 
perfect working, that it will profit us to go into detail. 
The lids. A vertical section of the lid shows us 
from before backward (1) the integument, thin, almost 
hairless and devoid of subcutaneous fat ; (2) the trans- 
verse section of the fibres of the orbicularis 'palpebra- 
rum, differentiated near the margin into the muscle of 
Riolanus (entropion) ; (3) the tarsal plate, a thick dense 
fibrous membrane curved to fit the eye ball, containing 
in the substance of its posterior layer the meibomian 
glands and covered internally with a vascular membrane 
the conjunctiva. The meibomian glands consist of PHYSIOLOGY 440 
PHYSIOLOGY 
long- tortuous central tubes, joined by lateral ducts 
ending- in sacculated glands, sebaceous in character 
(chalazion). The oil here secreted prevents the over- 
flow of the tears. Mohls' gdands, modified sweat 
glands, open between the cilia or eye lashes and the 
mouths of the meibomian gflands (hordeolum). 
The lachrymal gland lies in the upper outer part of 
the orbit, suspended from the periostium above and 
resting- upon the eye ball below. It resembles a 
serous salivary gland in structure, and its half-a-dozen 
or more ducts open in the upper conjunctival cul-de-sac. 
The saline fluid (tears) secreted by this gland passes 
down over the front of the ball and keeps moist and 
healthful its delicate surface. The excess of tears are 
removed by the drainage apparatus below given. 
The lachrymal canals begin as two minute openings, 
the puncta lachrymalia, seen at the junction of each lid 
with the lacus lachrymalis. Prom each of these 
orifices two small canals or canaliculi run outward to 
join the lachrymal sac. This sac, lodged in the 
osseous lachrymal groove, is continuous with the 
lachrymal duct below, which opens into the inferior 
meatus of the nose, where its mucous membrane forms 
a valve-like fold (Hasner’s). The sac and duct are 
composed of a fibrous elastic coat, with an internal 
mucous membrane, continuous with the mucous mem- 
brane of the nose. This sac is compressed periodically 
by the action of the orbicularis palpebrarum and tensor 
tarsi (Horner’s) muscle, but the outflow of the tears 
seems chiefly due to siphonage. 
The external muscles of the eye. We will first con- 
sider the orbicularis palpebrarum (7) which performs 
the periodic act called “ winking.” This act, as we 
saw, not only aids in emptying the lachrymal sac and 
favors aspiration of the tears through the puncta, but PHYSIOLOGY 
441 442 
PHYSIOLOGY 
it also passes the margins of the lids over the cornea,, 
moistening it and removing any dust or adherent 
particles. This periodic act is a reflex one, excited 
through the ciliary and other nerves. It is also a 
voluntary act, but if the above nerves, or the optic 
nerves, be intensely stimulated it is involuntary and 
beyond control (blepharospasm). The elevation of the 
upper lid is by means of the levator palpebrae (3), while 
the lower lid falls by gravity. In looking downward 
the action of gravity is here supplemented by the action 
of the inferior rectus, whose tendon of insertion is 
conected by a few fibres with the tarsus of the lower 
lid. 
The true ocular muscles are the four recti and the 
two obliques. When the eyes are at rest the muscles 
are in a state of elastic equilibrum. When the eyes 
move in any direction from this state of rest they move 
under the guidance of the above mentioned muscles,, 
the external rectus (6) producing outward rotation and 
the internal rectus (3) inward, etc. As the axis of the 
orbit in which the eye ball rests, does not coincide with 
the visual axis of the eye, any movements, other than 
the two given, must be made by the conjoined action 
of two or more muscles ; as upward by the sup’ rectus 
(3) and inf’ oblique (3), downwards by the inf’ rectus 
(3) and sup’ oblique (4), etc. 
The eye, or as it is called the “eye ball,” consists of 
several layers or tunics. The most external of these 
includes the sclerotic and its transparent prolongation 
the cornea. The second layer, or tunica uvea, includes 
the choroid, the ciliary bodies and the iris. The 
internal layer embraces the retina and its anterior 
prolongation the -pars retinae ciliaris. Within the 
latter, and in front of it, we have the refracting media 
or humors of the eye ; the virtreous humor, the lens PHYSIOLOGY 
443 444 
PHYSIOLOGY 
and its capsule and the aqueous humor. These, with 
the vessels of nutrition, and the nerves of the control, 
make up the eye. 
The Cornea, whose diameter represents about one- 
sixth of the periphery of the globe of the eye, is com- 
posed of five layers, from before backward, as follows : 
(1) An epithelial layer, the continuation of the stratified 
squamous epithelium of the conjunctiva, supported on 
a more or less columnar layer below. (2) The anterior 
elastic layer (Bowman’s), a thin structureless basement 
membrane. (3) The substantia propria ot the cornea, 
which layer comprises nine-tenths of its thickness. 
This layer consists of a series of open connective 
tissue membranes superimposed upon each other with 
inter-communicating lymph spaces between them. 
These lymphspaces are filled from the lymphatics of the 
conjunctiva, and in each of the spaces lies a branched 
corneal corpuscle. Nerve fibrils ramify in the sub- 
stantia propria, some perforating the anterior elastic 
lamina. (4) The posterior elastic (Descemet’s) layer 
bears a verv close resemblance to the anterior elastic, 
but is more dense and resistant. At its periphery this 
lamina breaks up into a series of radial fibres, some of 
which are prolonged backward to form the tendon of 
origin for the tensor choroidae muscle, and others 
turn inward to form the connective tissue support of 
the iris or ligamentum pectinatum iridis. (5) The 
last or most internal la}7er is the endothiloid layer of 
single cells lining the inner face of the above. At the 
junction of the cornea and sclerotic, and just external 
to the peripheral sub-division of Descemet’s membrane, 
is the circular peripheral lymph canal of the cornea 
(Schlemm’s), and just external to it in the sclerotic is 
a venous plexus. Openings through the radiating 
fibres of the posterior elastic lamina, called the fora- PHYSIOLOGY 
445 446 
PHYSIOLOGY 
mina of Fontana, connect the canal of Schleram with 
the anterior chamber of the eye. (drainage angle.) 
The Sclerotic forms the outer envelope of the eye and 
is a dense white fibrous tunic, thickest at the corneo- 
scleral junction. Behind, its outer layers are continu- 
ous with the sheath of the optic nerve while the 
internal fibres are continued as an open net work across 
the opening- of the optic nerve forming- the lamina 
cribrosa. The sclerotic (and cornea) is normally al- 
most spherical, but is long in its antero-posterior diam- 
eter in myopic or “near-sighted” eyes, and is rela- 
tively short in hyperopic or “far-sighted” eyes. It 
receives the insertion of the recti and other eye mus- 
cles and is poorly supplied with blood vessels and 
nerves. Having considered the outer tunic we take up 
the middle coat or tunica uvea. This as before stated 
includes the choroid, the ciliary bodies, with their con- 
tained muscles, and the iris. 
The Choroid. This layer lies inside the sclerotic 
and extends forward as far as the ciliary bodies, with 
which it becomes continuous. It is not continuous over 
the opening of the optic nerve behind and it is this cir- 
cular opening in the choroid, which produces the so- 
called optic disk. The choroid is composed of the 
following layers : 1. The thin external layer or 
lamina supra-choroidea perforated by lymph channels 
and having large lymph spaces on both its external 
and internal face. 2. The substantia propria, a layer of 
large blood vessels and elastic fibres. In this, the thick- 
est layer of the choroid, runs the long posterior cili- 
ary arteries forward to their point of distribution, and 
here also are the larger branches of the short post’ 
ciliary arteries and the ciliary or vorticose veins. Pig- 
ment cells are scattered throughout its substance and 
externally we find large lymph spaces lined with cndo- PHYSIOLOGY 
447 448 
PHYSIOLOGY 
theliura. (3) The dense limiting membrane that sepa- 
rates the above from the following-. (4) The chorio-cafil- 
iaris a layer containing- the plexus of small capillaries 
from the short posterior ciliary arteries which pierce 
the above limiting- membrane for the nutrition of the 
internal parts of the eye. It is more or less pig-mented 
and is separated from the retina by (5) the hvaline layer 
or lamina vitrea. The lymphatics of the choroid are 
in the outer layers, where they nourish also the sclero- 
tic. They pass out around the vorticose veins and are 
continuous with channels which lie in the optic sheath. 
The aqueous from the vessels of the chorio-capillaris 
passes inward and than forward to the anterior cham- 
bers of the eye, etc. 
The Ciliary bodies, which contain the ciliary or ten- 
sor choroidea muscle, are the anterior continuations of 
the choroid. This ciliary muscle arises at the corneo- 
scleral junction from the tendonous processes of the 
posterior elastic lamina of the cornea, and in inter- 
rupted bundles extends radially backward to end in 
the elastic fibers of the substantia propria of the choroid. 
When it contracts it stretches and draws forward the 
anterior portion of the choroid and all attached parts, 
hence its name. Besides these muscular fibres a few 
others, especially marked in hypermetropic eyes, run 
around the inner face of the eye at rig-ht angdes to the 
course of the other fibres. This gives a somewhat 
sphincter-like muscle called Muller’s muscle. The 
remainder of the ciliary bodies that exist are continua- 
tions of the choroid, but the substantia propria is thinner 
and more pigmented, the internal limiting layer and 
chorio-capillaris have largely disappeared and the 
lamina vitrea is thicker and more dense. Internal to 
this is the tapetum nigrum of the retina and the pars 
ciliaris retinae to be considered later. PHYSIOLOGY 
449 450 
PHYSIOLOGY 
The Iris, also a part of the uveal tract shows on 
section from before backward the following- parts : 
(1) An endothelial layer, flat polyhedral cells which in 
dark eyes contain some pigment. (2) An open base- 
ment membrane the continuation of the ligamentum 
pectinatum iridis. (3) The substantia propria iridis, 
continuous with that of the ciliary bodies and choroid. 
This contains the peripheral and the marginal plexus 
of capillaries and the muscles of the iris. One of these 
consists of circular muscular fibres disposed on the 
posterior surface of the pupillary border of the sub- 
stantia propria, and called the sphincter papillae. 
The other is composed of scattered radiate muscular 
fibres and called the dilatorpapillae as well as abund- 
ant yellow elastic fibres radially arranged. (4) A 
basement membrane continuous with the lamina vitrea 
of the choroid, etc. (5) The pigmented epithelium 
of the tapetum nigrum and containing the pigment 
cells that give color to the iris. All these layers are 
devoid of pigment in albinos. 
The Retina. This membrane contains the functional 
end organs of the sense of vision. It is composed of 
nerve fibres and terminals, which are arranged as 
follows : The optic nerve leaving the chiasm passes 
forward and enters the eye through the perforations 
in the lamina cribrosa where the various nerve fibres 
spread out radially over the inner face of the choroid 
•as a membrane. If we will take a single nerve fibre 
and follow it we will get a clear conception of the 
structure of the retina. . After leaving the optic disk 
this fibre will be found to run outward under the 
internal limiting membrane of the retina, to the ap- 
pointed place. Here it turns towards the choroid and 
expands into a ganglion cell giving off filaments which 
now pierce a thick layer of granular tissue held in a PHYSIOLOGY 
451 452 
PHYSIOLOGY 
reticulum of connective tissue continuous with the 
internal limiting- layer before mentioned. The nerve 
filaments, which are to form the rods and cones of the 
eye, now expand into smaller ganglion cells, pierce 
another granular layer, like the first but thinner, 
expand ag-ain into oval g-angdion cells, pierce a very 
thin external limiting- membrane and end alternately 
as rod-shaped or cone-shaped cylinders, whose ends* 
are embedded in the pigrnent of the simple polygonal 
squamous cells which form the external layer of the 
retina, the tepetum nigrum, which rests on the choroid. 
Counted from within outward this gdves the classical 
ten layers of the retina. This arrangement exists over 
the entire retina except at the following- points : (1) 
Just behind the ciliary bodies the nervous elements of 
the retina end in an irregular jagged line forming the 
so-called ora serrata. Beyond this only the connective 
tissue elements of the retina continue forward as the 
pars ciliaris retinae and as the tapetura nigrum. (2) 
In the optic disk only nerve fibres are found ; hence 
we have here no power of vision, and this give us the 
“blind spot” of the eye. (3) At a point four millimeters 
to the outer (temporal) side of the centre of the optic 
disk is a tawny yellowish spot called the macula lutea 
and about its centre a depression the fovea centralis. 
In the fovea of man no rods are found, only cones, and 
these are more slender than elsewhere. To produce 
the relative thinness of the retina at this point all the 
internal layers are reduced in thickness. This area is 
functionally the most active of the entire retina. The 
rods (and cones) of the retina during life contain in 
their terminals a peculiar pigment, which they seem 
to extract from the pigment cells of the tapetum 
nigrum, called rhodopsin or visual purple. Darkness 
seems necessary to its formation, and when abundant PHYSIOLOGY 
453 454 
PHYSIOLOGY 
the eye is most sensitive to light. The retina is sup- 
plied with nutriment through the arteria centralis 
retinae, a small vessel which pierces the optic nerve 
and lamina cribrosa and about the centre of the optic 
disk divides it into five or six branches which subdivide 
and ramify in the inner layers of the retina. No large 
branches run in the region of the macula lutea. This 
aiteiy forms no anastomosis with neighboring- vessels 
and its blood is returned by veins that accompany the 
ai teries. In foetal life a branch of this artery, called 
the lenticular artery, extends from the centre of the 
optic disk to the posterior face of the lens. It passes 
through the vitreous and should the artery fail to 
atrophy it seriously affects vision. 
The Lens or crystalline humor of the eye lies just 
behind the iris and separates the aqueous from the vit- 
reous humor. It is clear biconvex solid body having 
an equatorial diameter of about nine millimeters with a 
radius of curvature for the anterior service of about 
eight, and for the posterior service of about six milli- 
meters. It is composed of cellular lens fibres and inter- 
stitial substance., The fibres are chiefly on the surface 
and are bent over the border of the lens to meet on 
either face in triradiate lines. E}ach lens fibril is 
hexagonal on section, from pressure, and seems to con- 
sist of an external envelope containing globulin. The 
nuclear or central portion is more dense than the corti- 
cal portion and less fibrillar. The combined action of 
these elastic fibres bent over the margin of the lens 
makes it tend to expand antero-posteriorly and of 
course contract equatorially. The lens is encased in a 
delicate transparent capsule of epithelium thicker in 
front, especially at the margins of the front surface. 
At this thickened anterior border the radiate suspen- 
sary ligament of the lens, or the zonule of £inn, is. PHYSIOLOGY 
455 PHYSIOLOGY 
attached. This ligament is the anterior prolongation 
of the pars ciliaris retinae, which is intimate!}7 adherent 
to the inner face and apex of ciliary bodies, from which 
point it is reflected radially inward to be attached 
to the capsule of the lens as stated. It is not a solid 
membrane, the alternate elevations of the ciliary pro- 
cesses making it rather a series of radiate ligaments. 
The Vitreous humor of the eyes fills the entire 
cavity of the globe behind the lens. It is bounded 
peripherally by a thin clear hyaloid membrane which 
lies on the retina behind, and on the pars ciliaris ret- 
inae, more anteriorly. When the ciliary bodies are 
reached this membrane is carried direct to the poste- 
rior surface of the lens and does not touch the suspen- 
sary ligament of the lens, except at the periphery. 
Thus a space is left between the hyaloid membrane 
and suspensary ligament around the border of the lens 
and this forms the canal of Petit. Within the hyaloid 
membrane is the substance of the vitreous, an albu- 
minous jelly containing a few isolated branched cells 
and irregular connecting fibrils (muscae volitantes). 
There is a wide tube of hyaloid membrane extending 
through the humor from the optic disk to the posterior 
face of the lens. This produces the canal of Stilling, 
is filled with watery fluid and must not be confused 
with the foetal canal for the lenticular artery. 
The Aqueous humor fills all the chambers of the eye 
lying in front of the lens, etc. The large space situ- 
ated between the cornea in front and the iris and lens 
behind is called the anterior chamber, while the 
smaller space lying between the iris in front and the 
zonule of 2finn behind is called the posterior chamber. 
Both of these are filled with aqueous humor which, 
unlike the vitreous, is not a fixed “humor” but is re- 
newed regularly by flow from the ciliary vessels be- PHYSIOLOGY 
457 458 
PHYSIOLOGY 
hind and discharges in front through the foramina of 
Fontana and the canal of Schlemm. This humor is a 
clear, slightly albuminous fluid, closely resembling a 
diluted lymph. It transudes from the iritic and ciliary 
vessels, percolates through the canal of Petit and 
enters the posterior chamber of the eye. Here some 
percolates through the open structure of the iris, but 
the bulk of it passes through the open pupillary aper- 
ture and makes its way outward to the corneo-scleral 
duct or canal of Schlemm, whence it empties into the 
adiacent plexus of vessels. 
The Blood vessels of the eye, consist of the arteria 
centralis retinae previously mentioned and the poste- 
tioi and anterior ciliaries. (1) The posterior ciliaries 
are two, the long posterior and short posterior. The 
latter some dozen or more in number, are derived from 
the ophthalmic, and pierce the sclerotic around the 
optic nerve. They run forward in the substantia pro- 
pria choroidae giving off small vessels to the chorio- 
capillaris as they go. They finally supply the ciliary 
bodies and anastomose with the vessels of the iris, etc. 
The long posterior ciliaries two or three in number 
arise from the same source, pierce the sclerotic just 
external to the preceding and run forward in the cho- 
ioid, external to the others, to supply the iris and 
contiguous parts. (2) The anterior ciliaries, derived 
from the muscular branches of the ophthalmic, pierce 
the sclerotic just external to the corneo-sceleral junc- 
tion and give blood to the iris and ciliary bodies. The 
blood from all these vessels is gathered into the four 
venae vorticosae which pierce the sclerotic and emerge 
about the antero-posterior equator of the globe, to join 
the ophthalmic veins. 
The Nerves of the eye are ; (1) The optic, which is the 
nerve of the special sense of vision and also contains PHYSIOLOGY PHYSIOLOGY 
excito-reflex fibres for the pupil and lids, etc.; (2) The 
short ciliary nerves, some six or eight in number, run 
from the ophthalmic gang-lion to pierce the sclerotic 
around the optic nerve, run forward on its inner surface 
and are distribtued to the ciliary muscles, iris, etc. 
(3) The long ciliary nerves, two or three in number 
come direct from the naso-ciliary branch of the sth, 
join the short ciliaries and proceed with them to their 
point of distribution. The fibres of those nerves that 
come from the 3d cranial, supply with motion the 
ciliary and sphincter pupillae muscles, those from 
the sympathetic, supply motion to the dilator pupillae, 
and those from the sth, furnish sensation, etc., to the 
entire eye. The exact relation of the ganglion to the 
short ciliaries is not well understood. The centre for 
the control of pupillary contraction (excluding the 
cortex) is the nucleus of the 3d nerve in the aqueduct 
of Sylvius. The route of its reflex action is through 
the optic, to the ant’ corpora quadrigemina, through 
intercentral fibres to the nucleus of the 3d cranial and 
thence through it to the sphincter. The centre for 
the dilation of the pupil lies in the dorsal cord. Im- 
pulses from this centre pass out by the rami communi- 
cantes and up through the cervical sympathetics. Im- 
pulses from the cerebral cortex of control pass down 
(in the face tract) to the centres mentioned. 
The refractive power of the eye is such that, when 
it is absolutely at rest, parallel rays of light, entering 
the eye and pupillary opening- and passing through the 
lens, are refracted to form an image, of the object 
viewed, on the macula lutea and surrounding retina. 
Here they produce such chemical changes in the pig- 
ment of the retina as will stimulate the appropriate 
retinal terminals and produce impulses in the optic 
nerve. This refractive condition exists only for par- PHYSIOLOGY 
461 PHYSIOLOGY 
allel rays. Rays entering- the pupil from a distance 
of twenty feet and beyond are practically parallel. 
Rays from a point nearer than twenty feet (or diverg'- 
ing- rays) must of necessity (in such an eye at rest) be 
focussed behind the retina, g-iving- imperfect or no 
vision. If the eye could be lengthened, of course the 
retina, could be brought to the point of focus. We are, 
however, provided with an apparatus by which we can 
change the curvature of the lens and thus its focal dis- 
tance, accommodating the eye for an object at practi- 
cally any distance. 
The mechanism of accommodation is as follows : 
The ciliary or tensor choroidae muscle, when stim- 
ulated, stretches the elastic choroid and draws the 
ciliary processes forward towards its point of origin. 
This, with the action of the circular ciliary (Muller’s) 
muscle, relaxes the suspensory ligament of the lens and 
its inherent elasticity causes it to bulge forward, chang- 
ing in curvature and focus. When the action of the 
ciliary muscles ceases, the elastic choroid draws back 
the ciliary processes, tightens the suspensory ligament 
and compresses the lens to its previous curvature. 
The increased curvature of the lens brought about bv 
the act of accommodation is called the accessory 
meniscus of curvature. (3. D.) When the eyeball is 
too short (hyperopia or far sight) even parallel rays are 
focussed behind the retina and muscular accommoda- 
tion must be used at all times, producing eye strain, 
headache, etc. When the eye ball is too long (myopia 
or near sight) parallel rays are focussed in front of the 
retina and only fall on the retina when the object 
viewed is brought near. When one becomes forty or 
more years of age the lens fibres begin to lose their 
elasticity and the lens will not change its curve even 
when its ligament is relaxed but remains set in a con- PHYSIOLOGY 
463 464 
PHYSIOLOGY 
dition to focus parallel rays only (presbyopia). To 
enable such persons to see near objects, read, etc., we 
give a'glass equal to the accessory meniscus of curvature 
needed for such work when young-. The lens for the 
relief of far-sigdit must be convex (+) and that for the 
relief of near-sig-ht must be concave (—). The ante- 
rior surface of the cornea (or lens) should present the 
equal curvatures of a segment of a sphere. If the 
radius of curvature of the cornea in one meridian be 
greater or less than in the other, the lens will not 
bring the rays to a point and we have the condition 
known as astigmatism. A cylindrical lens, that is one 
cut from the inner (—) or outer (+) surface of a 
hollow cylinder will correct this refractive error, as 
the rays are focussed in front or behind the retina 
respectively. 
The relation of the eyes to each other. The visual 
(antero-posterior) axis of the eye, is a line prolonged 
from the fovea centralis through the nodal point of the 
lens and the vertex of the cornea. Where this line 
pierces the cornea and sclera it establishes the anterior 
and posterior poles of the eye, respectively. All 
movements of the eye are made around a point two mm. 
behind the centre of the visual axis called the “point 
of rotation.” The transverse axis of the eye is a line 
prolonged through the point of rotation of both eyes. 
The vertical axis passes through the point of rotation 
at right angles to the visual and horizontal axes, re- 
spectively. Planes passing through these axes divide 
the eye by vertical, horizontal and equatorial sections. 
The position of rest, (muscular equilibrium) is when 
the visual axes are parallel with each other and with 
the sagittal plane of the body and are in the same hori 
zontal plane. To keep the visual axes fixed on any 
point, even at Infinity, the visual axes must converge PHYSIOLOGY 
465 466 
PHYSIOLOGY 
and the nearer the point the greater the convergence 
till the “near point of convergence” is reached. This 
convergence is frequently combined with an upward 
or downward movement. The nerve action for all 
such movements must be harmonious, and for this rea- 
son a single nerve (3d cranial) supplies the muscles of 
pupillary contraction, accommodation, convergence, etc. 
This is an “associated movement” and is greatly simpli- 
fied by unity of nerve supply. Conversely the movements 
of divergence, pupillary dilation, etc., which bring 
about the condition the reverse of this (viz., distant 
vision) are brought about by varied nerve impulses. 
The less frequently used muscles of rotation (obliques) 
also have different sources of nerve supply. 
Binocular vision is of service in that it increases the 
held of vision, gives perception of depth, and also 
allows estimation of size and distance. The formation 
of the eye, so that corresponding points of the retina 
will be stimulated by rays of light from the same point 
in the held of vision, allows binocular vision. 
If we could, without other disturbance than lateral 
shift, place one retina immediately over the other, we 
would find that while the optic disks (blind spots) would 
not coincide practically all other points would. In 
other words the light rays from the (experimentally) 
now single lens would pierce the transparent retinae 
at practically the same points as if each were in its 
own globe. Moreover, while separated for a time, 
anatomically the hbres unite in the same tract and 
impulses from these coincident points go ultimately to 
the same cortical centres. Here by experience the 
images, althongh differing as they must from differing 
points of view, etc., give rise to a single percept. 
This slight difference in the respective images from 
different points of view, gives us stereoscopic vision 
.and all the benefits that arise from it. PHYSIOLOGY 
467 468 
PHYSIOLOGY 
Color perception. We have reason to believe (Young- 
Helmholtz theory) that the retina contains three sets 
of terminals for the appreciation of rays of the three 
primary colors,—red\ green and violet. The ming- 
ling of these rays in varying proportions, would pro- 
duce stimulation of the terminals in varying degrees of 
intensity, and give perceptions of all the shades of 
color. If the terminals of one color be stimulated for 
quite a time, these terminals become fatigued and if we 
then shut our eyes we will receive feeble impressions 
from the terminals of the complementary color, which 
are not fatigued, but apparently excited. Thus we 
attempt to explain the after sensations of color so often 
seen. The absence of terminals for the appreciation of 
red is marked in that part of the retina near the ora 
serrata. When from congenital or acquired causes 
(tobacco, etc.), defective color perception extends over 
the remainder of the retina we have what is called 
“color blindness.’’ GENERAL INDEX 
Abducens nerve 346 
Bilirubin 46, 60, 188 
Absorption, in intestines 196 
in stomach 182 
Biliverdin 60, 190 
Binocular vision 466 
Accessorius nerve 358 
Accommodation,mechanism of 462 
Acid fermentation, of urine. .. 258 
Birth ' 22 
Bladder, capacity of 254 
structure of 254 
Afferent nerves 302 
Agraphia, etc 392 
Blood, abnormal conditions of SO 
amount of 50 
Air, atmospheric 150 
Agminated glands (Peyer’s).. 110 
as a whole 50 
coagulation of 42 
expired, changes in ..... 150 
ratio of contamination 
allowed 156 
comparative histology.. 42 
gas-es of 48 
residual...' 146 
tidal 146 
glands 98 
histological character ... 38 
influence of reagents 40 
Ala cinerea 334 
Albumin, tests for 246 
-—— organisms of 52 
physical properties 36 
Albumins, varieties of 59 
Albumin-sparing action of 
fats 264 
Blood cells, amoeboid move’nts 40 
Blood circuit, time of 90 
Albuminuria 246 
Blood, circulation of 66 
Blood corpuscles, red 38 
Albuminoids 56 
Alkaline fermentation of urine 258 
Application of skeletal muse’s 282 
white 40 
Blood current, speed of 90 
Blood vessels of brain 374 
Amoeba 20 
Amnesic aphasia 396 
of eye 458 
structure of 72 
Amylopsin 180 
Anabolic metabolism 260 
of cord and medu11a...... 376 
Brain and its functions 360 
Analysis of heat production ... 270 
of metabolic processes. . . 260 
Breathing, modes of 150 
Brunner’s glands 176 
Anode 386 
Ano-spinal centre 202, 330 
Aphonia 386 
Burdach’s column . 316 
Calamous scriptorius 334 
Canal of Petit 456 
Aqueduct of Sylvius 334, 322 
Aqueous humor 456 
Canal of Schlemm 444 
Capacity of thorax 144 
Arnolds nerve 354 
Arterial pressure 88 
Carbohydrates as foods... 160, 264 
varieties 0f... . 58 
factors of 82 
Ascending degenerations 310 
Cardiac cycle 76 
ganglia ....74, 90 
Asphyxia 154 
Ataxic aphasia 386 
Auditory nerve 350 
muscle 34 
Cartilaginous tissue. 32 
Casts, in urine ;... 250 
ossicles 422 
Auricle, structure of 66 
Cathode 306 
Cells, structure of 18 
Basal Ganglia. 362 
Bile 188 
Centres of pupillary control. .. 460 
spinal cord 330 
—— functions of 190 
Bile pigments 60, 188 
Cerebellum 37 2 
Cerebrum, gray matter of. . . . 36g 
salts 60 
secretion of 190 
white matter of 37q 
Chemistry of the body 5 4 GENERAL INDEX 
intestinal digestion 194 
of insalivation 164 
Cycle of muscular contraction 28S 
Cyon’s nerve 86, 356 
muscular tissue 280 
stomach dig-estion 180 
Chemical composition of liv- 
ing- bodies ... 14 
Death 24 
somatic 26 
Cholesterin 62 
molecular 24 
Decline, time of 24 
Deep reflexes 330 
Chorda tympani 358 
Choroid 446 
Degeneration of nerves. . 308 
Deglutition 172 
Chyle 50 
Chyme 180 
Descending degeneration 308 
Development 24 
Cilia, movements of 20, 280 
Ciliary muscle 448 
Cilio-spinal centre 330, 460 
Diapedesis 40 
Diastase, from barley 172 
Circle of Willis ... 374 
Circulatory apparatus 66 
Diet, amount of water free.. .. 162 
variations in 162 
Digestion 162 
Circulation 66 
——of lymph 94 
intestinal 182 
mouth 164 
portal 94 
Clarke’s column 326 
——- stomach 124 
—— temporary products 0f.... 60 
Clot, formation... 42 
Coagulation, influencing con- 
ditions 44 
Digestive ferments, adminis- 
tration of 204 
Cochlea 430 
Cochlear branch of the eighth 
nerve 350, 434 
Diffusion of gases 146 
Dilator pupillae 450 
Disturbance of language 384 
Cold, influence on the body. . . 274 
Diuretics, their influence 246 
Ductless glands ~ 98 
Color blindness 468 
Color perception 432 
Dyspnoea 154 
Earthy phosphates 242 
Colostrum 216 
Comparative growth of body 
and viscera 266 
Efferent nerves 302 
Eighth cranial nerve 350 
Comparison of animal and 
vegetable life .... 10 
Elasticity of muscle 286 
Electrical properties of nerves 304 
Electrical currents in muscle. 382 
Comparison of foods and ex- 
cretory products 262 
Electrotonus 306 
Eleventh cranial nerve 336 
Conductile tissues 34 
Connective tissues 30 
Eminentia teres 334 
Endocardium 70 
Contractile tissues 32, 280 
Contamination of air allowed, 156 
Endolymph 424 
Endothelium, forms of 30 
Co-ordinate reflexes 330 
Copulation centre 330 
Corium, of skin 208 
Epidermal appendages 210 
Epidermis, of skin 206 
Epithelium, forms of 28 
Cornea 444 
Corona radiata 370 
Evidences of life 10 
Expiration, forces of 128 
Corpora quadrigemina, ....... 368 
Corpora striata 364 
External ear 416 
External muscles of eye 440 
Corpulence and its prevention 266 
Corpus callosum 370 
Eye, appendages of 438 
Eyes, relation to each other... 464 
Corpuscles, ratio of white and 
red 40 
Cranial nerves 332 
Eyeball, structure of 442 
Facial nerve 348 
Fatigue stuffs 290 
Cura cerebri 322 
Crusta 322 
Fats, in starvation 264 
varieties of 58 
Cuneus 338, 362 
Cutaneous respiration 156 
Fatty foods 160 
Fever. 276 
Cycle of life 22 
Fibrin 42 GENERAL INDEX 
Hemiplegia 382 
Fibrin ferment 42 
Fibrinogen 42 
Fifth cranial nerve 340 
crossed 382 
normal.... 382 
Fillet tract 322 
First cranial nerve 336 
—— spinal 382 
Hippuric acid . 64 
Fluid tissues 36 
Foods, varieties of 158 
Homoiot hernial animals 274 
Hydrochloric acid in digestion 180 
preparation of 160 
Forced movements 368, 374 
Foreign gases, respiration of. 156 
Hyperopic eyes 462 
Hyperphyrexia 278 
Hypoglossal nerve 358 
Formatio reticularis 300 
Forms of gustatory sensation 412 
Inferior maxillary branch of 
fifth 344 
Fourth cranial nerve 340 
Fourth ventricle, floor of. 318, 332 
Inorganic foods 160 
Insalivation 164 
Functions of bile 190 
Function, definition of 6 
chemistry of 170 
Intercentral nerves 302 
of the skin 222 
—— of spinal tracts 324 
Functional classification 0f... 
nerves 310 
Internal capsule 364 
Internal ear 424 
Intestine, small 182 
Ganglia of heart 72, 90 
large 192 
gases found in 198 
Gases, diffusion of 146 
of blood 48 
putrefactive phenomena 
in 198 
Gasserian ganglion 342 
Gastric secretion 180 
Intestinal absorption 198 
digestion 194 
Geniculate ganglion 348 
Golfs column 318 
Glands, changes in cells of. .. 176 
digestion, chemistry of. . 194 
Iris, structure of 450 
Isodynamic ratios 272 
of skin 214 
Globulin 56 
Jacobson’s branch of ninth... 352 
Katabolic metabolism 260 
Glosso pharyngeal nerve 352 
Glycogen 58 
Kidney, blood vessels of 230 
nerves of 234 
Glycogenic function of liver.. 190 
Glycosuria 392, 248 
structure 228 
uriniferous tubule 0f.... 232 
Growth 22 
its limitations 216 
Gubler’s line 292, 350 
Lachrymal canals 440 
Lachrymal gland 440 
Lacteals 52 
Hair, structure of 210 
varieties of 212 
Large intestine. 192 
Latent period 288, 292 
Haematoidin 46 
Haemin 46 
Law of peripheral reference.. 396 
Lens, structure of 454 
Haematin 46 
Haemogoblin 44 
Lenses, for refractive errors. . 464 
Lenticulo-striate artery 376 
union with gases 48 
Hearing, sense of ■ 416 
Heart, framework of 68 
Leucomaines 150 
Lid of eye 408 
Leiberkuhn crypts of 184 
nerve supply of 72 
pathological condition of 92 
Life, definition of 8 
Liver 186, 272 
sounds of 78 
valves of 70 
blood supply of 188 
glycogenic function of.. . 190 
Heart cavity, capacity 0f.... . 90 
Heart’s impulse 78 
Locus coerulius 334 
Lung, nerves of 138 
Heat, sources of 270 
saving of by clothing. . .. 276 
gaseous interchange in. . 150 
traction of on heart, etc. 136 
substance in foetus 124 
Hemiatrophy 346 
Hemianopia 338 
Hemipeptones 196 
Lungs, blood supply of 124 
. ... lympatics of. 126 IV 
GENERAL INDEX 
... . structure of 122 
Lymph 52 
Nervous system 294 
Ninth cranial nerve 352 
circulation 94 
.... organisms of 52 
Non-striated muscle 34, 280 
Nutrition 20 
Lymphatic glands 110 
Macula lutea 452 
Oesophagus 174 
Odor of faeces 198 
Mammary glands structure of 214 
Manometer.. 88 
Mastication...., 164 
Olfactory bulb 338 
nerves 336 
Ophethalraic branch of fifth.. 342 
Mechanism of accommodation 462 
auditory perception 434 
ganglion 342 
Optic chiasm 338 
—— heart’s action 74 
defaecation 200 
nerve 338 
thalamus 366 
intestinal movements.... 200 
micturation 256 
Optical axes 464 
Organ of Corti 432 
—— stomach digestion 174 
■ respiration 130 
vomiting 204 
Organic elements 14 
Osseous or bony tissue 32 
Otic ganglion 316 
Medulla oblongata 318 
Meneires disease 430 
Ovum 22 
Oxy haemoglobin 48 
Membranes of brain and cord 374 
Membranous labarynth 428 
Pain, impulses in cord 326 
sense of 396 
Metabolic equilibrium 262 
Metabolic phenomena 260 
Pancreas 184, 272 
nerve supply 186 
Metabolic process, analysis of 269 
Metazoa 22 
Methods of study, nervfes 294 
Pancreatic ferments 186 
Papillae of tongue 410 
Paraglobulin 44 
Microcytes 38 
Microscopial anatomy 26 
Paraplegia 384 
Parotid gland 166 
Middle ear 418 
Milk, human, composition of. 206 
Parturition centre 330, 300 
Peptones 56, 182 
Monoplegia 382 
Motor cortex of brain 362 
Pepsin 182 
Perilymph 424 
Motor oculi nerve 340 
Motor speech centre 384 
Mucous glands. 166 
Pericardium 70 
Perverted reflexes 380 
Phagocytosis 40 
Muscle, active state of 284 
Muscle stimuli 284 
Phosphates of urine 242 
Physiology, definition of . 6 
Muscle tone 292 
Muscles as heat producers. . . . 272 
Pineal gland 108 
Pituitary body. . . 108 
Muscular contraction, cycle of 288 
Muscular fatigue 290 
Plants, functions of 10 
Plasma 42 
Muscular tissue, chemistry of. 280 
Myograph 268 
Myopic eyes 462 
Poikilothermal animals 270 
Pons varolii 320 
Portal circulation 94 
Nails 212 
Negative pressure in veins. . . 88 
Post mortem digestion 206 
Posterior root of spinal nerve. 314 
Negative variation in muscle. 286 
Negative variation in nerve.. 314 
Pressure sense 400 
Proteids 54 
Nerve cells, functions of 310 
Nerve corpuscles 34 
as foods 158, 262 
percent, composition.... 14 
Nerve fibres '. 36 
Nerve mechanism of defaeca- 
tion 200 
Protozoa 16 
Pseudopodia 40 
Ptyalin 164 
Nerve mechanism of urination 256 
Nerve stimuli 302 
Pulse, cause of 78 
dicrotic 80 
Nerves of eye 458 
tracings of 80 GENERAL INDEX 
V 
Senses vague 396 
Pulvinar 368 
Radiating reflex 308, 380 
Ramus communicans.B6, 316 
Sensory cortex of brain 362 
Sensory decussation 328 
Ratio of urea and uric acid. . . 240 
Reaction of degeneration 310 
Serum.... 42 
Setchenow’s centre 382 
Reciprocal action of skin and 
kidney 220 
Seventh cranial nerve 348 
Sight, sense of 498 
Rectum 194 
Red corpuscles, origin of 38 
Simple reflex 328, 380 
Sixth cranial nerve 346 
Skeletal tissues, varieties of. . 30 
Reflexes of the cord 328 
Refractive powers of the eye.. 460 
Regio olfactoria 338, 408 
Skin, functions of 222 
glands of 214 
Regio respiratoria 118 
Relation of respiration to pulse 148 
pathology of 224 
structure of 206 
Reproduction 22 
Rennin 160 
Small intestine 182 
Smell, sense of 406 
Respiration, cutaneous 156 
Respiration, beginning of. ... 132 
Soemmering’s classification.. 332 
Solitary blood glands 110 
definition 110 
interstitial 116 
muscles of 128 
Spasm 382 
Speech tract 384 
Speed of contraction wave in 
muscle 288 
of foreign gases 156 
nerve mechanism of ... 130 
Speed of nerve impulse wave.. 306 
pulmonary 116 
Respirations, number of 146 
Spermatozoon . 22 
Spirometer 146 
Respiratory apparatus 116 
Respiratory centres 138 
Spheno-palatine ganglion.... 344 
Sphincter ani 194 
Respiratory centres subordi- 
nate 142 
Respiratory movements, mod- 
ified form 144 
Sphincter pupillae 450 
Sphygmograph 80 
Spinal cord, centres of 330 
Respiratory reflexes 144 
gray matter of 316 
structure of . . 316 
Respiratory tract accessory.. . 118 
Respiratory tract true 120 
white matter of 318 
nerves 314 
Saliva 166 
chorda 168 
Spleen 98 
Starvation, effects of 264 
sympathetic 168 
Salivary glands, nerve supply 168 
Scala media 432 
Steapsin 186 
Stomach digestion 174 
nerves of 178 
Scala tympani 432 
Scala vestibuli 432 
Stomach, structure of 174 
Streaming of protoplasm 20 
Sclerotic 442 
Sebaceous glands 218 
Striated muscle 32 
Structural properties of living 
bodies 16 
Sebum 218 
Second cranial nerve 338 
Stuttering 384 
Secretion of bile 190 
Semi-circular canals 426 
Sense of hearing 416 
Sublingual gland 166 
Submaxillary gland 166 
Submaxillary gangliotl 346 
of muscle tension 402 
of smell 406 
Substantia niger 322 
Succus entericus 194 
of sight 438 
——of taste 410 
Sugar in urine 248 
tests for 248 
of temperature 400 
of touch 398 
Summation of muscular con- 
tractions 288 
Senses cephalic 396 
Senses fixed 396 
Senses somatic 396 
Superior maxillary branch of 
fifth 344 
Superficial reflexes 330 VI 
GENERAL INDEX 
Supra renal capsule 106 
Urethra 254 
Sweat, amount daily 200 
sweat glands 220 
Uric acid .62, 240 
Urinary deposits 250 
secretion of 220 
Taste, sense of 418 
Urinary pigments 240 
Urinary tract 252 
Teichmans crystals ... 46 
Temperature, conditions influ- 
encing 272 
Urine, abnormal constituents. 246 
amount per diem .. 236 
normal body 270 
regulation Of . ... 274 
constituents of 238 
changes in, after expul- 
sion 258 
sense of . 400 
Tenth cranial nerve 354 
inorganic constituents of 242 
physical characters of 236 
Tensor choroidae... .... .448, 462 
Tetanus, physiological 288 
secretion of 234 
Uriniferous tubule of kidney.. 232 
Theory of Weber 400 
Thermogenesis 274 
Urino-spinal centre 256, 330 
Vagus nerve 354 
Thermolysis 274 
Thermotaxis 274 
Third cranial nerve 346 
Valvulae conniventes 182 
Variations in diet 162 
Thorax 126 
capacity of 144 
Thymus gland 102 
Variations in tactile sensibility 400 
Vaso-motor centre 
Vaso-motor centre influencing 84 
Thyroid gland 104 
Vaso-motor fibres in cord 324 
conditions 84 
Time of digestion 202 
Tissues, gaseous interchange 
in 152 
Vaso motor impulses 86 
Ventricle, structure 68 
study of 26 
Tonsils 106 
Vestibular branch of eighth 
350, 428 
Touch, sense of. . 398 
Trachea 120 
Villi 184 
Vital capacity 146 
Vital capacity, influences on.. 146 
Training 290 
Trigeminus nerve 340 
Vital phenomena 18 
Vitreous humor 456 
Trochlearis nerve 340 
Trypsin 186 
Voluntary motion 18 
Vomiting, mechanism of 204 
Twelfth cranial nerve 358 
Uncinate gyrus 336 
Ureamia 244 
Waste products 62 
Weber’s theory 400 
Urea 62, 238 
effects of retention 244 
Word blindness. 390 
Word deafness 390 
Word forming centre 384, 386 
increase in fever 276 
Uterus masculinus .... 254 
Writer’s cramp 394 
Young Helmholtz’s theory. .. . 468 
Ureter 252 
Zonule of Zinn 454