A TOPICAL 
SYNOPSIS OF LECTURES 
ON 
ANIMAL PHYSIOLOGY 
BY 
HENRY SEWALL, Ph. D., 
PROFESSOR OK PHYSIOLOGY IS THE UNIVERSITY OF M1CHIOAK. 
PART I. 
AM ARBOR, MICHIGAN: 
SHEEHAN & COMPANY. 
1882. ANN ARBOR REGISTER PRINTING AND PUBLISHING COMPANY. AUTHOR’S NOTE. 
This imperfect skeleton of a course of lectures on physiology 
has been prepared at intervals with the sole object of helping 
students to fix the attention upon the main facts of the subject. 
The topics have served simply as points of departure in the lecture 
room, and no effort has been made to render the “Synopsis” clear to 
any for whom the spaces between the paragraphs have not already 
been filled in. The author has been burdened by no desire for orig- 
inality, and for good reasons the admirable text-books of Professor 
Martin and of Dr. Foster, especially the latter, have frequently been 
followed in both order and substance in the preparation of these 
notes. ERRATA. 
The following are some of the more important errors of the print: 
Page 7,15th line from bottom, for fibrogen read fibrinogen. 
“ 9, 16th “ “ top, “ plamine read plasmine. 
“ 18, 17th “ “ “ “ lanceloate read lanceolate. 
“ 21,20th “ “ “ “ contractlity read contractility. 
“ 27,20th “ “ “ “ envolved read evolved. 
“ 28, 9th “ “ bottom, “ is read it. 
“ 28, 4th “ “ “ “ of read if. 
“ 35, 4th “ “ “ “ is read is to. 
“ 39, 5th “ “ “ “ pneumogatric read pneumogastric. 
“ 72, 18th “ “ top, “ direct of read direct. 
“ 82,10th “ “ bottom, “ elimation read elimination. 
“ 102, 15th “ “ top, “ astigmation read astigmatism. 
“ 104, 9th “ “ bottom, “ complemetary read complemen- 
tary. 
“ 106,19th “ “ top, “ instrinsic read intrinsic. I. THE OBJECT OF PHYSIOLOGY AND THE FUNCTIONS OF 
LIVING MATTEL. 
Physiology is the study of the chemistry and physics of the 
living body. 
Physiologically Life is the sum of the functions of matter 
called Protoplasm. 
Protoplasm is made up of the elements C, H, 0, N; traces 
of P and S; some inorganic salts. Contains much water and 
probably residues of proteids, fats and carbohydrates. 
To make protoplasm needs building material and building 
energy. 
In the animal both are supplied by the food and oxygen 
taken in. 
In the green plant sunlight supplies building energy. 
Living protoplasm is continually wasting. 
In the animal the waste matter contains less potential 
energy than the food; the energy difference is the vital force of 
the animal. 
The general functions of all protoplasm are exhibited by 
the simplest living thing, as an amoeba, or white blood corpuscle. 
These functions are: 
Contractility. 
Spontaneity. 
Irritability. 
Conductivity. 
Coordination. 
Assimilation. This leads to Growth by Intussusception. 
Growth stops when the weight of egesta equals that 
of ingesta. As the amount of waste matter depends 
upon the mass of protoplasm and the amount of 
matter assimilated upon its surface, growth must have 
its limit according to the law of unequal increase of 
mass and surface. 4 
Reproduction. 
The highest animal exists first as an egg, a single cell. 
Multiplication of cells by fission. 
The body is composed of cells, modified cells and inter- 
cellular matter. 
Differentiation of tissues. 
Physiological classification of tissues into;— 
Undifferentiated. 
Supporting. 
Nutritive; including assimilative; secretory; receptive; elim- 
inative; respiratory; metabolic. 
Storage. 
Irritable. 
Conductive. 
Coordinating and Automatic. 
Motor. 
Protective. 
Reproductive. 
II. THE NATURE OF THE LAWS SUPPOSED TO RULE THE 
ACTIVITIES OF THE BODY. 
The physiologist studies vitality as a manifestation of 
chemical and physical energy and believes the laws governing 
living and not living things to be equally inflexible. 
Energy exists in two states, Potential and Actual or Kinetic. 
Potential energy; represented in the position of masses; by 
position of atoms in molecules. 
Kinetic energy; represented in the motion of masses and 
of molecules and atoms. 
The different kinds of energy. 
One kind of energy may be changed into another. 
Energy is indistructible. 
Energy cannot be created. 
The uses of a machine as illustrated by the steam engine, 
the pulley and the watch spring. 
The principle of the dissipation of energy. 5 
Consider the whole history of the energy represented in a 
stone thrown by the arm into the air. 
III. THE LYMPH AND BLOOD. 
The fluid parts consists of food matters dissolved and 
altered by digestion and the activity of metabolic tissues, and 
of the products of tissue change. 
LYMPH 
The tissue elements are bathed in lymph, 
Physical and chemical characters of lymph. Lymph cor- 
puscles. 
Lymph derived from blood by diffusion. 
Nature of diffusion; influence of temperature; of the divid- 
ing membrane; of the concentration and composition of the 
diffusing fluids. 
Effect of blood pressure on the diffusion from the blood 
vessels. The use of the lymphathic vessels. 
Various directions of the lymph currents of diffusion in the 
body. 
Influence of the blood circulation on the rate of diffusion 
by the supply of new and removal of waste matter. 
Physical and vital characters of lymph corpuscles. 
Coagulation of lymph. 
BLOOD. 
Consists physically of straw colored fluid plasma and of 
solid red and white corpuscles. 
Relative number of red and white corpuscles. Conditions 
of its physiological variation. 
Size, shape, physical and vital characters of white corpusles. 
Number, size, shape, physical characters and function of 
human red corpuscles. 
Distinction between the red corpuscles of mammals and of 
other vertebrates. 
Rouleaux of red corpuscles in drawn blood. 6 
Stroma and hajmoglobin of red corpuscles. 
Cause of opacity of blood. “ Laky ” blood and means of 
producing it. 
Composition of haemoglobin; haemoglobin crystals. 
Characters and production of haemin crystals. 
COAGULATION OF BLOOD. 
Physical changes in blood on coagulating; jelly stage; solid 
clot; cupping; serum; “resolution” of clot. 
Demonstration of fibrin threads in the clot produced on a 
microscope slide. 
Phenomena of clotting in a capillary tube. 
Effect of whipping fresh blood. 
Plasma. 
Corpuscles. 
Before clotting 
Physical components of blood 
Clot=fibrin~}- 
corpuscles. 
Serum. 
After clotting 
Whipped blood=corpuscles-fserum. 
Red corpuscles have nothing to do with coagulation. 
The huffy coat; its nature and conditions of occurrence. 
The reason for its occurrence in blood in inflammatory 
disease. 
Relation of the shape of the clot to that of the containing 
vessel. 
Color of clot at different distances from the free surface. 
Uses of clotting to a wounded animal. 
CAUSES OF COAGULATION AND INFUENCES MODI- 
FYING IT. 
Old theories that clotting was due to escape of ammonia; 
to taking up of oxygen. 
Significance of blood clotting under mercury. 
Hypothesis that the internal coats of the blood vessels pre- 
vent coagulation. 
Evidence as to influence of internal coat. 7 
View that blood does not tend to clot until chemically 
altered. 
Influence on coagulation, of temperature; of strong solu- 
tions of mineral salts; of stirring. 
White blood corpuscles always found in spontaneously 
coagulating fluids. 
The deposit of fibrin around a foreign object in flowing 
blood is preceded by accumulation of white corpuscles. 
In the thin clot upon a microscope slide the fibrin threads 
start from white corpuscles. 
In slowly clotting horse’s blood the firmest clot is at the 
level of greatest accumulation of white corpuscles. 
Direct observation under the microscope of thrombus for- 
mation in a frog’s tongue. 
The disintegration of wdiite corpuscles and transition forms 
on drawing blood from the body. 
Denis’ plasmine. 
Clotting of the solution of plasmine. 
Plasmine is a mixture of two fibrin factors, fibrinoplastin 
and fibrinogen. 
Fibrinoplastin is in solution in blood serum; i» precipitated 
by saturating with salines; is dissolved by dilute salines. 
Fibrogen is found in solution in transudation fluids; is pre- 
cipitated by saturating with salines; is dissolved by dilute 
salines. 
Artificial clot from mixture of serum with transudation fluid; 
or from mixture of saline precipitates of the fibrin factors. 
Physical characters of the two fibrin factors. 
Necessity of salines to coagulation. 
The action of the fibrin ferment. 
The nature of animal ferments; conditions of action. 
'' The origin of fibrin ferment and method of obtaining it. 
The weight of the clot is less than that of the fibrin factors 
employed. 
Fibrinoplastin is left over after clotting. 
' Part played by white corpuscles in the production of fibrin 
factors and of fibrin ferment. 8- 
THE TRANSFUSION OF BLOOD. 
Transfusion as practiced on the isolated hearts of the frog 
and dog. 
The nature of the foreign blood is not indifferent. 
Danger in direct transfusion of clotting in the transmission 
tube. 
Danger of injection of whipped blood because of its con- 
tained fibrinoplastin and fibrin ferment. 
Experiments illustrating this point. 
CHEMISTRY OF BLOOD. 
Specific gravity of blood; relative weight of corpuscles and 
plasma. 
Comparison of mass of corpuscles and plasma. 
Reaction of blood; its variation in clotting. 
The amount and kinds of gas given off in vacuum by a 
volume of blood; by serum. 
Chemical composition of serum; nature of its solid matters. 
The ash of serum contrasted with the ash of corpuscles. 
Chemical composition of the red corpuscles; of the white. 
HISTORY OF BLOOD CORPUSCLES. 
Evidence for the transitory nature of the corpuscles; varia- 
tion in number at different times; probable derivation of urin- 
ary and bile pigments; normal number quickly regained after 
hemorrhage. 
Origin of the red corpuscles in the embryo; metamorphosis 
of mesoblastic cells; transformation of white corpuscles arising 
in the liver and spleen; from the protoplasm of connective tis- 
sue corpuscles. 
Origin of red corpuscles in the adult; metamorphosed from 
transitional forms of white corpuscles found in the spleen and 
red medulla of bones. 
Fate of red corpuscles; probably destroyed in the spleen. 
White corpuscles; physiological variation in number. Arise 
in lymphatic glands and similar organs. They probably serve 
as occasional tissue builders, and give rise to red corpuscles. 9 
THE QUANTITY AND DISTRIBUTION OF BLOOD IN 
BODY. 
About one-thirteenth of body weight is blood: of this is 
contained 
One-fourth in heart, lungs, large arteries and veins. 
One-fourth in the liver. 
One-fourth in skeletal muscles. 
One-fourth in the remaining organs. 
DEMONSTATIONS. 
Whipped beef’s blood. 
Laky blood. 
Method of obtaining haemin crystals. 
Separation of corpuscles and plasma in horse’s blood pre- 
vented from clotting. 
The clotting of plasma from horse’s blood. 
Plamine of Denis. 
Precipitated fibrinoplastin. 
Clotted horse’s blood showing buffy coat. 
Clot and serum. 
The phenomena presented in the clotting of freshly drawn 
blood. 
Effect of whipping freshly drawn blood; character of the 
fibrin obtained. 
The clotting of blood under mercury. 
IV. THE CHEMISTRY OF ANIMAL TISSUES. 
All the activities of the body are due in the end to chemi- 
cal processes. 
The body is composed of living matter, protoplasm, and of 
not living matter which is made by protoplasm; otherwise, the 
body is composed of Formative and of Formed matter. In 
general, formative matter exists in cells while formed matter 
is intercellular. 
The molecule of protoplasm contains residues of proteids, 
fats, and carbohydrates, besides salines and extractives. 10 
PROTEIDS. 
These form the principal solids of active tissues, of blood 
and of lymph. 
The molecule is very complex; composed of many atoms of 
O, H, N, C, and S. 
Proteids are amorphous. 
All are non-diffusible except Peptones. 
Mostly coagulated by alcohol and ether. 
Soluble with change in strong acids and alkalis. 
Chemical reactions; xanthoproteic; Millon’s; caustic soda 
and copper sulphate, etc. 
1. Native albumins; serum and egg albumin. Soluble in 
water. 
2. Derived albumins or albuminates; acid and alkali 
albumin; casein. Not soluble in water but in dilute acids and 
alkalis. Not precipitated by boiling. Ail proteids dissolved 
in acid or alkali become albuminates. 
3 Globulins; globulin; fibrinoplastin; fibrinogen; myosin. 
Not soluble in water but in dilute salines; precipitated by 
strong salines. 
4. Fibrin. Insoluble in water and dilute salines. Soluble 
with difficulty in strong salines and dilute acids and alkalis. 
5. Coagulated proteids, soluble only in strong acids and 
alkalis. 
6. Peptones. Soluble in water. Not precipitated by acids, 
alkalis or boiling. Diffusible. Product of all proteid diges- 
tion. Many varieties. 
NITROGENOUS NON-CRYSTALLINE BODIES DERIVED 
FROM AND ALLIED TO PROTEIDS, BUT NOT CAPA- 
BLE OF REPLACING PROTEIDS IN THE FOOD. 
They contain the elements C, H, N, 0, and sometimes S. 
Mucin; a secretion of mucous epithelium. 
Chondrin; the organic basis of cartilage. Its solutions set 
on cooling. 
CLASSES OF PROTEIDS. 11 
Gelatin; organic basis of bone, teeth and tendon. Solutions 
set on cooling. 
Elastin; from elastic tissue. Its solutions do not gelatinize. 
Keratin; from hair; nails; epidermis. 
Nuclein; from nuclei of pus corpuscles. 
COMPLEX NITROGENOUS FATS CHIEFLY FORMING 
PARTS OF NERVE TISSUES. 
Lecithin. 
Protogon. 
Cerebrin. 
STORE MATERIALS LAID UP IN THE BODY AS FOOD 
FOR THE TISSUES; FATS AND CARBOHYDRATES. 
FATS. 
Neutral fats are compounds of a fatty acid with glycerine. 
They are made up of the elements C, H, 0. 
Insoluble in water. Soluble in ether, chloroform and hot 
alcohol. 
Are decomposed by caustic alkalis forming soaps with them, 
leaving the glycerine free. 
Palmitin. 
Stearin. 
Olein. 
The fats occur mixed together in the body. Their fusion 
points differ. Their molecule contains much more C and H 
in proportion to 0 than does that of carbohydrates. 
CARBOHYDRATES.— Composed of C, H, and 0. 
Dextrose or grape sugar; capable of alcoholic fermentation; 
of lactic acid fermentation. 
Lactose or milk sugar; capable of lactic acid fermentaiion. 
Inosit; capable of lactic acid fermentation. 
Glycogen; convertible into dextrose. 
Dextrin; convertible into dextrose. 12 
SOME OF THE SUBSTANCES FORMED IN THE BODY; 
FOR THE MOST PART “WASTE” PRODUCTS OF 
TISSUE CHANGE. 
NGN-NITROGENOUS METABOLITES. 
Lactic acid. 
Oxalic acid, in oxalate of lime 
Succinic acid. 
NITROGENOUS METABOLITES. 
Urea; and its oxalate and nitrate. 
Uric acid; and salts. 
Kreatin. 
Kreatinin. 
Sarkin. 
Leucin. 
Tyrosin. 
Hippuric acid. 
Taurocholic acid. 
Glycocholic acid. 
DEMONSTRATIONS. 
The reactions of proteids and characteristics of their groups. 
The indiffusibility of albumin and dialysis of common salt. 
V. EPITHELIUM, CONNECTIVE TISSUE, BONE, AND PHYSIO- 
LOGY OF THE SKELETON. 
EPITHELIUM. 
The typical animal cell; cell membrane; protoplasm; gran- 
ules ; nucleus and nucleoli; fibrillar net-work. 
Scaly or squamous epithelium; epidermis and buccal 
mucous membrane. 
Columnar epithelium; intestine. 
Pavement epithelium; mesentery. 
Polyhedral epithelium; glands. 
Ciliated epithelium; trachea, 13 
THE CONNECTIVE TISSUES. 
Function and distribution in the body. 
White fibrous tissue; physical characters; swelled by acids; 
distribution. 
Yellow elastic tissue; physical characters; unaffected by 
acids; distribution. 
Cement substance. 
Connective tissue corpuscles; varieties of form and function ; 
distribution. 
Gelatinous tissue; vitreous humor; umbilical cord. 
Areolar tissue ; composition and distribution. 
The development and condition of fat in the body. 
THE PERMANENT SKELETON.—CARTILAGE. 
Hyaline cartilage; its physical characters; the perichon- 
drium; contains no blood vessels; histological appearance; 
cells and matrix; method of formation of matrix; transition 
forms between round cartilage cells and branched periosteal 
cells; distribution and function. 
Fibro-cartilage; physical and histological characters; action 
of acids; distribution and function. 
Parenchymatous cartilage; physical and 
histological characters; unaffected by acids; distribution and 
functions. 
THE BONY SKELETON. 
The skeleton should be made of parts which are strong 
light, inflexible and symmetrical. 
Bones are composed of a mixture of organic and earthy 
matter. 
The former is flexible, the latter stifi‘ and brittle; the 
original size and shape of the bone are retained when either is 
removed. 
Two thirds of the weight of dry bone is mineral, chiefly 
Ca3 2 (P 0<). 
Mechanical advantage of this combination. 14 
THE LONG BONES. 
The periosteum. 
The expanded articular end of long bones allows distribu- 
tion of strain. 
The advantage gained by the hollow cylindrical form of 
the bone. 
The cancellated extremities and the red and white marrow. 
Histological structure of a long bone; the perfection of 
adaptation for firmness, lightness and elasticity. 
THE SKULL. 
Advantage of its curved shape. 
The two bony tables with diploe between. 
The outer bony plate is thicker, tough and fibrous. 
The inner bony plate is thinner, dense and brittle. 
Use of diploe in deadening jars. 
Use of the sutures in limiting the extension of jars. 
THE BACKBONE. 
The separate vertebrae allow the bending of the spine. 
The intervertebral pads allow bending without separation of 
vertebrae, and deaden jars. 
The curved shape of the spine gives it a wide range of elas- 
ticity. 
JOINTS. 
Ball and socket joints. 
Hinge joints. 
Pivot joints. 
Gliding joints. 
The synovial sac and its influence. 
The capsular ligament. 
Bones are held together by atmospheric pressure. 15 
THE BONY LEVERS. 
Lever of the first order; nodding motion 
of the head 
Lever of the second order; raising the body 
on the toes by the calf muscles. 
Lever of the third order; raising of forearm 
by the biceps muscle. 
DEMONSTRATIONS. 
Tendon. 
Ligamentum nuclne. 
Mesentery. 
Costal cartilage. 
Articular cartilage. 
Intervertebral cartilage. 
Elastic cartilage. 
Decalcified bone. 
Sections of long bone and skull. 
The skeleton. VI. THE CONTRACTILE TISSUES. 
AMCEBOID CELLS. CILIATED CELLS. MUSCLES. 
Contractility is a function of Protoplasm irrespective of any 
special form in which this matter may be found. 
All visible movements of higher animals are due to the con- 
traction of a special set of organs, the muscles, which are in no 
case able to set up movements spontaneously. 
The amoeboid cells contract throughout their body substance 
and have usually the power of locomotion. 
CILIATED CELLS. 
Ciliated cells are fixed and are usually columnar in shape 
The free margin of the cell is thick and firm, and has pro- 
jecting from it from ten to thirty long protoplasmic lashes, the 
cilia. 
The movement of the cilia is a to and fro whipping motion. 
The movement is two or three times quicker in one direction 
than in the other. 
Foreign bodies resting resting upon the cilia are urged in the 
direction of the more rapid motion. 
The function of cilia in the trachea and bronchi: they cause 
expulsion of solid particles and aid the mixture of gases. 
The movement is automatic and coordinated. The move, 
ment of a series of cilia is not isochronous, but proceeds in a 
wave form along the row. 
The impulse to the movement is probably conveyed directly, 
from the protoplasm of one cell to that of the next. 
The energy produced by each cell is calculated as sufficient 
to raise its own weight each minute 4-1 metres. 18 
THE MUSCLES. 
The muscles are not automatically contractile. 
They are usually red in color from contained haemoglobin, 
but the color is not essential. 
There are two great groups which are distinguished histo- 
logically and physiologically: (1) Plain or unstriated muscle; 
sometimes called visceral or organic or involuntary muscle. (2) 
Cross striated muscle; sometimes called skeletal or voluntary 
muscle. 
All striated muscles contract quickly after a short latent 
period. 
All non-striated muscles contract slowly after a long latent 
period. 
The visceral or involuntary muscles of some animals are 
striated. 
HISTOLOGY OF NON-STRIATED MUSCLE. 
The flattened lanceloate cell; the rod shaped nucleus. 
The method of aggregation of the muscle cells, and their dis- 
tribution in the body. 
THE STRIATED MUSCLES. 
The manner of aggregation of muscle and other tissues as 
shown in the cross sefction of a limb. Each muscle is made up 
of separate bundles of fibres. 
The fibres may be oblique or parallel to the long axis of the 
muscle. 
The length of the muscle fibre in man varies from twro feet 
to one quarter of an inch. 
HISTOLOGY OF STRIATED MUSCLE. 
The muscle fibre; the sarcolemma; the nuclei; the cross 
markings. 
The cross marking is due to alternate bright, dark and dim 
bands. 
The juncture of muscle fibres by their beveled endings. 
Two modes of ending in tendon. 
The greater part of the living muscle fibre is semi-fluid in 
consistency. 19 
PHYSIOLOGY OF STRIATED MUSCLE. 
The function of the muscle fibre is to contract or to draw its 
two ends nearer together. 
Muscle exists in the body in two natural conditions, in an 
active and a passive state; the shape and elastic properties of the 
muscle are different in the two conditions. 
The shortening of the muscle is active and due to distinct 
chemical processes; the elongation is passive. 
The shortening is caused by the tranverse swelling of the 
fibres. 
The muscle does not preceptibly alter in volume in contrac- 
tion. 
The molecular cause of contraction is probably the absorp- 
tion of the more fluid parts of the muscle fibres within definite 
layers of more solid particles. 
Whatever excites a muscle to contract is called a stimulus. 
The contraction begins at the point stimulated, and moves 
along the fibre in the form of a wave, which travels in the frog’s 
muscle with a velocity of about three metres per second. The 
wave moves slower the lower the temperature. 
THE PHYSICAL PROPERTIES OP MUSCLE. 
Compare the curve of elasticity of muscle with that of steel. 
Compare the curves of elasticity of resting and active mus- 
cle. 
The elasticity of resting muscle is perfect within narrow 
limits. 
When a muscle contracts, its elasticity decreases and its 
extensibility increases. 
The resting muscles in the body are always slightly stretched 
between their attachments. Proof of this and significance for 
the welfare of the body. 
The protective use to the body of the increased extensibility 
of contracted muscle. 
The elasticit}T of the muscle enables it to store up its energy 
of contraction. 
The lifting power of the muscle diminishes with contraction. 20 
Show how in the movements of the bony levers the contrac- 
tile energy of the muscle is economized according to the pro- 
ceeding principle. 
The muscle posesses the distinct properties of contractility, 
conductivity and irritability. 
Irritability is the capability possessed by some tissues of 
being stirred up to functional activity by a stimulus. 
Its peculiarity is the disproportion between the amount of 
energy represented in the stimulus and in the effect produced. 
Irritability is decreased by low temperatures, by fatigue, by 
various drugs. 
The old view that contraction of muscle was due to swelling 
of its subtance by the inflow of‘‘animal spirits.” 
Proofs of the independent irritability of muscle; contraction 
of embryonic muscles before the establishment of nervous con- 
nections; the “idio-muscular” contraction; the nerve free ends 
of the sartorius; the manner of action of curare. 
The various kinds of stimuli capable of exciting muscle; 
nervous; mechanical; thermal; chemical; electrical. 
The character of a muscular contraction caused by the 
application of a galvanic current. 
The contraction caused by a single inductive shock. 
The general law for the stimulation of irritable tissues: It is 
only the change of intensity of a stim ulus that excites an irrita- 
ble organ. 
The most favorable rate of cha nge of intensity of the stimu- 
lus differs for different kinds of tissues; the intensity should 
vary most rapidly for nerve, less so for striped muscle and still 
more slowly for unstriped muscle. 
The muscle answers a single stimulation by a single twutch 
or contraction. 
The contraction is prolonged by cold, by fatigue, by various 
drugs. 
The curve of a single muscular contraction; the latent period 
of stimulation: the phases of the contraction curve; the “con- 
tractur.” 21 
The latent period of stimulation is the interval elapsing 
between the application of a stimulus and the beginning of com 
traction. Its average duration in the frog’s muscle is .01 second. 
During the latent period the muscle molecules are undergoing 
chemical, electrical, thermal and mechanical changes. The 
period is lengthened by cold, by fatigue, by increased load. 
The “ contractor ” is due to the “ elastic after action ” of the 
muscle substance, not to vital changes. Influence of fatigue 
and of load upon the contractor. 
Maximal and sub-maximal single contractions; with a certain 
strength of stimulus the muscle gives a barely visible contrac- 
tion; with increase of stimulus the height of contraction 
increases to a certain extent, and then no stronger stimulus 
causes a greater contraction. 
The fatigue curve of muscle excited to single contractions 
repeated at a definite rate is a straight line. The line falls more 
rapidly with a shorter interval between the stimuli. The effect 
of rest is to increase the height of the succeeding contraction. 
The waste products of contraction diminish the irritability 
and contractlity of the muscle. A blood free muscle exhaus- 
ted by stimulation may be made to contract again after wash- 
ing out with dilute salt solution. 
The work done by a contracting muscle is measured by the 
load X height of lift. The work done increases with the load 
to a certain extent and then diminishes as the load becomes 
greater. 
The lift power of a muscle increases with its thickness, or 
the number of fibres side by side. The extent of the shortening 
increases with the length of the fibres. 
PHYSIOLOGICAL TETANUS 
When one contraction succeeds another in a muscle before 
the first is finished, the result is a longer and more extensive 
contraction or tetanus. The tetanus is smooth when each con- 
traction begins during the ascending phase of the preceeding 
one. The tetanus is vibratory when the muscle has time to 
relax from one contraction before another engages it. 22 
Proof of the formation of tetanus by the summation of sin- 
gle contractions. 
A tetanus may be sub-maximal or maximal in extent. 
A muscle may be shortened by tetanus to one-third its orig- 
inal length. 
In tetanus the duration, the amplitude, and the power of the 
contraction may be made greater than by the use of a single 
stimulus. 
The natural contractions of the living body are sub-maximal 
and tetanic in character. 
Proofs of the foregoing statement: comparsion of the power 
of voluntary and artificially excited contractions. The dura- 
tion of the shortest voluntary contraction compared with that 
excited by a single artificial stimulation. The muscle note and 
its pitch. 
Voluntary contractions are probably due not to the simul- 
taneous, but to the successive stimulation of the different fibres 
of a muscle. 
Free circulation of blood in the muscle is necessary to volun- 
tary contraction. 
THE ELECTRICAL PHENOMENA OF ACTIVE MUSCLE. 
When a muscle is stimulated, the part excited becomes 
electro-negative to the resting parts. 
The electric change is due to the chemical changes of the 
active molecules. 
The chemical change set up in the muscle by stimulation is 
conducted along the fibres, and the electro-negative condition 
accompanies it. 
The rate of this progression in the frog’s muscle is about 
three metres per second. It has already finished its course 
during the latent period of stimulation. 
If an electric conductor be made to connect the excited elec- 
tro-negative part of the muscle with its resting electro-positive 
part, a current of electricity will flow through the conductor. 
This current is called the “action current” of the muscle. 
Experiment of the “rheoscopic frog.” The secondary mus- 23 
cie is thrown into tetanus when the primary muscle istetanised, 
thus proving the interrupted nature of the electric changes in 
the latter. 
When the vital continuity of the nerve supplying the first 
muscle is broken by tying a string around it, the tetanus fails 
in both muscles. 
An action current is set up in a muscle by any stimulus, 
electrical or otherwise. 
The secondary contraction of a frog’s nerve-muscle prepara- 
tion caused by the beat of the mammalian heart. 
COMPARISON OF THE PHYSICAL AND CHEMICAL CHARAC- 
TERS OF LIVING AND DEAD MUSCLE. 
Living resting muscle is soft, glistening, elastic, semi-transpar- 
ent and alkaline or amphichroic in reaction. 
Living working muscle is less elastic, but more extensible 
and becomes acid in reaction. 
Dead muscle is dull, opaque, inelastic and is acid in reaction. 
A dying muscle loses gradually its irritability, and then goes 
rather suddenly into rigor mortis. Rigor is attended by a con- 
siderable production of sarcolactic and carbonic acids, by a rise 
of temperature and by a shortening of the muscle. Rigor passes 
off1 as decomposition sets in. 
THE CHEMICAL CHANGES OF WORKING MUSCLE 
The excised muscle gives off no oxygen under the air pump, 
but when made to contract it develops sarcolactic and carbonic 
acids in an oxygen free atmosphere. • 
The living muscle in the body consumes rn ore oxygen, and 
produces more carbonic acid in the active than in the resting 
condition. 
The weight of muscle substance soluble in water decreases, 
while that soluble in alcohol increases in the active as compared 
with the resting condition. 
The amount of acid produced by tetanising an excised mus- 
cle is substracted from the amount finally produced by the 
death of the muscle. 24 
The living muscle molecule probably consists of an essential 
nitrogenous part capable of building on to itself certain carbon 
compounds by whose oxidation the energy of contraction is 
produced. 
Every contraction is attended by an evolution of heat. 
Comparison of the muscle with the steam engine. 
THE CHEMISTRY OF LIVING MUSCLE. 
The contents of the living muscle fibre are chiefly semi-fluid 
in consistency. This matter is the muscle plasma. 
The artificial preparation of muscle plasma. 
The clotting of muscle plasma and its separation into clot 
and serum. 
The muscle clot is myosin; its formation in dead muscle 
causes rigor mortis. 
The clot of myosin is granular; its formation is accompanied 
by the development of acid. 
The dead muscle contains seventy-five per cent, water. Its 
dry substance contains:— 
Proteids; myosin; serum albumin. 
Extractives; kreatin; sarcolactic acid ; xanthin; hypoxan- 
thin; uric acid; inosit (in the heart); inosinic acid; sugar. 
No urea. 
Fats in quantity. 
In living muscle there is glycogen which is changed to sugar 
on death. The nitrogenous extractives are products of the chemi- 
cal changes of the muscle substance. Myosin does not exist in 
living muscle. 
THE CHEMISTRY OF DEAD MUSCLE. 
THE PHYSIOLOGY OF UNSTRIATED MUSCLE. 
Unstriated muscle is not found unmixed with other tissues 
of the body. 
Organs containing unstriated muscle have to some extent 
power of automatic contraction, which may be due to contained 
nervous elements. 
The contraction progresses slowly in a wave form from the 
spot stimulated, and is preceeded by a long latent period. • 2o 
In striated muscle the contraction waves passes only length- 
wise throughout the fibre; in unstriated muscle the wave may 
pass both in the direction of the length and the breadth of the 
cell. 
The impulse to contraction may probably be communicated 
directly by one muscle cell to another without the intervention 
of nerves. 
Unstriated muscle is more readily stimulated by the make 
and break of a galvanic current than by induction currents. 
Consider the action of unstriated muscle as seen in the 
peristaltic action of the intestine and ureter and in the contrac- 
tion of the urinary bladder. 
DEMONSTRATIONS. 
The motor power of cilia. 
Comparison of the contractions of striated and unstriated 
muscle in the rabbit. 
The contraction of muscle on mercury. 
The diminution of lifting power with the shortening. 
The single muscular contraction and its curve. 
Physiological tetanus and its curve. 
The analysis of tetanus. 
Maximal and sub-maximal contractions. 
Contraction with the constant current. 
The action of curare. 
The rheoscopic frog; secondary tetanus. 
Secondary contraction of frog’s muscle from the beat of the 
mammalian heart. 
Formation of acid with the death of the muscle. 
VII. NERVOUS TISSUES. 
The nervous tissues consist of the nerves and of the peripheral 
and central irritable non-contractile organs in which they end. 
Nerve fibres are bound together in bundles, the funiculi. 
Each funiculus is inclosed in several sheets of membrane, 
the neurilemma. Each nerve is composed of many funiculi 
inclosd in a common sheath. 
THE MINUTE STRUCTURE OF NERVES. 26 
The lymph channels of nerves. 
Nerve fibres fall into two groups: (1) Medullated or white 
nerve fibres. (2) Non-medullated, gray or sympathetic nerve 
fibres. 
Histology of the medullated fibre; the primitive sheath; the 
medullary sheath or white substance; the axis cylinder; the 
neuro-keratin frame work; the nodes of Ranvier; the cement 
substance; the nuclei. 
Significance of the nodes to the nutrition of the nerve. 
The medullary sheath is chiefly fat, and is invisible in per- 
fectly fresh nerve. 
The axis cylinder is protoplasmic and is the conductor of 
the nervous impulse. 
Nerves lose their medullary sheath before reaching their 
peripheral, and central terminations. 
The ending of nerves in voluntary muscles; ending in invol- 
untary muscle. 
Histology of gray nerve fibre; absence of medullary sheath; 
nuclei found in the substance of the fibre. 
The physiology of gray nerve fibre. 
In general, the gray nerve fibres arise from the sympathetic 
system and are distributed to organs whose function does no 
involve consciousness. 
CLASSIFICATION OF NERVES ACCORDING TO THEIR 
FUNCTIONS. 
Sensory. 
Reflex. 
Excito-motor. 
Vaso-motor. 
Inhibitory ? 
Afferent 
Peripheral Nerves 
' Motor. 
Vasomotor. 
Secretory. 
Trophic? 
Inhibitory. 
Efferent 
Intercentral Nerves. 
Exciting. 
Inhibitory. 
Commisural. -27 
PHYSIOLOGY OF NERVES. 
The nerve is not automatic, but possesses to a high degree 
irritability and conductivity. 
The nerve is excited only by the change of intensity of a 
stimulus. 
The nerve is excited by a much weaker induction shock than 
is the muscle. 
Various nerve stimuli; mechanical; thermal; chemical; 
electrical. 
The chemical change started by an artificial stimulation 
travels as a nervous impulse along the nerve in both directions. 
As in the muscle, the excited parts of the nerve are electro- 
negative to the resting parts. The action current and the chem- 
ical change causing it travel along the nerve of the frog at the 
rate of about twenty-eight metres per second, and of man’thirty- 
three metres per second. 
The irritability of the nerve and its rate of conduction 
increase with the temperature. 
The energy of the nervous impulse is small in amount. No 
heat can be shown to be envolved and no chemical change to 
take place as a result of nervous activity. 
All the phenomena of muscular contraction obtained by the 
direct stimulation of the muscle substance may be obtaind by 
its indirect stimulation through the nerve. 
The degeneration and regeneration of cut nerves. 
ELECTROTONUS. 
When a motor nerve is subjected to the passage of a con- 
stant current of electricity the muscle supplied by it contracts 
only at the make and break of the current in the nerve, and 
remains at rest during the passage of the current. 
The passage of a galvanic current modifies the irritability 
and conductivity of the nerve. 
The irritability and conductivity of the nerve are diminished 
in the neighborhood of the anode, and increased in that of the 
kathode of the constant current. 
Inthe region of diminished irritability the nerve is said to ■ 28 
be in the state of anelectrotonus. In the area of exalted irritabil- 
ity the nerve is said to be in kathelectrotonus. 
The electrotonic conditions are more marked the stronger 
the galvanic current used. 
Proofs of the electrotonic modifications of irritability as 
exhibited on the excised nerve-muscle of the frog and on the 
human arm. 
DEMONSTRATIONS. 
The indirect stimulation of muscle through the nerve. 
Maximal, sub-maximal contractions and tetanus indirectly 
obtained. 
Proof of the greater irritability of nerve-muscle than of cura- 
rised muscle toward induction shocks. 
Various nerve stimuli; chemical; mechanical; thermal. 
Contraction with the use of the galvanic current. 
The electrotonic modification of irritability of nerve. 
YIII. REFLEX ACTION AND THE MECHANISMS INVOLVED 
IN IT. 
The origin of nerves from nerve cells. 
Various forms of ganglion cells. Nerve cells in sporadic 
ganglia; in the spinal cord; in the cerebellum; in the cerebrum. 
In the living body every contraction of the skeletal mus- 
cles is due to stimuli proceeding from nerve cells. 
NATURE OF THE CONTRACTIONS PRODUCED BY THE 
DIRECT STIMULATION OF THE NERVE CELLS. 
Make one cut across a motor nerve and the muscle supplied 
by is contracts but once. 
Cut across the spinal cord of a frog and its muscles are 
thrown into tetanus. 
The tetanus involves only the flexor muscles if the section 
be made across the anterior part of the cord. Only the exten- 
sor muscles are contracted of the section severs the posterior part 
of the cord. 
The experiment indicates that a nerve cell when artificially 
excited may continue to send out discharges after cessation of - 29 
the stimulation. Also that there is localization of motor func- 
tion in the spinal cord. 
REFLEX ACTION 
Nerve cells communicates with the exterior by means of 
afferent nerve fibres. 
External phenomena excite afferent nerves through the 
medium of sense organs in which those nerves terminate peri- 
pherally. 
The nervous organs in which nerves terminate are excited 
only by a change in the intensity of a stimulous. 
Examples of sense organs; the retina; the organ of Corti; 
tactile corpuscles. 
The reflex action obtained by dipping the toe of a headless 
frog into dilute acid. 
Characters of the reflex. The latent period or reflex time 
The apparently purposeful character of the reflex in removing 
irritating substances. 
Purposeful character of a reflex as shown in sneezing and 
coughing. 
A single stimulus with difficulty provokes a reflex, but a 
succession of stimuli readily does so. Summation of stimuli in 
the spinal cord. 
Increase of strength of stimulation or increase of its rate 
shortens reflex time. 
The reflex time is the period occupied chiefly by processes 
in the nerve cells. 
The uncoordinate nature of reflexes obtained by direct stim- 
ulation of the afferent nerve. 
The value of the peripheral nervous organ in reflex action. 
Each sense organ is differentiated to be specially irritable toward 
one certain form of energy. 
Radiation of nervous impulses in the cord. 
The purposful character of reflex actions explained not by 
consciousness of the cord but by the choice of paths of least resist- 
ance which determines the direction taken in the cord by impul- 
ses arising from any quarter. 30 
■Any segment of the spinal cord may act as a reflex centre. 
The typical mechanisms employed in a normal reflex action 
are: A peripheral organ for the reception of the stimulus, an 
afferent nerve fibre, a single nerve cell or a sensory and a motor 
cell, an efferent nerve fibre, a peripheral motor or glandular 
organ. 
The essential characters of a reflex action are: (1) Its uncon- 
sciousness; (2) the want of likeness between the effects pro- 
duced and the nature and method of the stimulation employed; 
(3) the usually coordinated nature of the action. 
The most rapid action of which the central nervous system 
is capable is manifested in reflexes. 
Modification of the conductivity of the spinal cord in strych- 
nia poisoning. 
INHIBITION. 
The activity of a nervous centre is the resultant of two forces, 
one exciting to discharge and the other resisting discharge. 
Forces resisting or depressing activity are termed Inhibitory. 
The resistance to the action of any nerve cell seems to be 
increased by its association with the nerve cells in physiolgical 
connection with it. 
Inhibitory influences may reach an active nerve cell from 
any quarter, as along any afferent nerve. 
Consider the inhibition of a reflex action’through the strong 
stimulation of an efferent nerve. 
There appear to be in the brain special inhibitory centres 
whose business it is to send out impulses to retard or depress 
the activities of the body. 
Consider the inhibitory effect upon reflex action in the frog 
of stimulation of the optic lobes. The inhibition of the beat 
of the heart. 
Reflex time is the period occupied by a stimulus in over- 
coming the resistence to discharge offered by the nerve cell. 
The physiological relation of reflex and voluntary actions. 
Cerebral time. — 31 — 
The tendon reflex. 
Muscular tone. 
There is no proof that the sporadic ganglia of the body can 
serve as reflex centres. 
The physiological afferent and efferent nerve fibres are mixed 
together in the nerve trunks, but before reaching the spinal 
cord the sensory and motor fibres separate, the former joining 
the cord by the posterior spinal root, and the latter by the 
anterior root. 
DEMONSTRATIONS. 
Tetanus following section of the spinal cord in the frog. 
Reflex actions from headless frog brought about by mechani- 
cal, electrical and chemical stimulation. Influence of the 
strength of the stimulus. 
Reflex from stimulation of an afferent nerve. 
The summation of electrical stimuli in the nervous centre. 
The purposeful and coordinated character of the reflex shown 
in the removal of acid paper. 
Inhibition of reflex by stimulation of an afferent nerve. 
Influence upon reflex time of stimulation of the optic lobes 
in the frog. 
Effect of strychnia upon the frog. 
Demonstration upon the frog of the functions of the spinal 
nerve roots. IX. THE CIRCULATION OF THE BLOOD, AND THE ORGANS OF 
CIRCULATION. 
THE ANATOMY AND HISTOLOGY OF THE MAMMA- 
LIAN HEART. 
The pericardium; its shape, dimensions and manner of 
attachment to the heart and chest wall. 
The pericardial fluid. 
The division of the heart cavity into four distinct chambers, 
those of the two auricles and the two ventricles. 
The marked difference in thickness between the walls of the 
auricles and ventricles. The difference between the walls of 
the walls of the right and left ventricle. 
An inner layer of muscle is peculiar to each auricle and an 
outer layer is common to both. 
The spiral arrangement of the ventricular muscle fibres. 
The comparative volume of the auricle when collapsed and 
when distended. The auricular appendage. 
Compare the relative size of the four chambers of the empty 
heart. 
Notice the size, shape and manner of attachment of the 
mitral and tricuspid valves. The muscle fibres upon the upper 
surface of the valves. The papillary muscles and the chordae 
tendineas. 
Notice the form and structure of the vessels springing from 
the heart. 
Notice the shape, structure and manner of attachment of the 
semilunar valves. 
Notice the shape of the aorta at its base, and the position 
of the openings of the two coronary arteries. 
Observe the fibrous rings surrounding the auriculo-ventricular 
and arterial orifices. 
The columnse carnese. -34- 
Notice the muscle fibres continuing from the heart upon the 
surface of its great veins. 
The endocardium. 
The histological characters of the heart muscle. The mus- 
cle is made up of striated, nucleated cells not enclosed in sar- 
colemma. 
The intrinsic ganglia of the heart. 
The extra-cardiac nerves:—(1) fibres from the vagus 
including physiological efferent cardio-inhibitory and physio- 
logical afferent “depressor” fibres. (2) Fibres from the spinal 
cord by way of sympathetic ganglia, including physiological 
efferent “ accelerator ” fibres. 
THE STRUCTURE OF THE BLOODVESSELS. 
Tunica adventitia of the arteries. 
The thick arterial wall and open lumen of the empty vessel. 
The thin walled veins, collapsing when empty. 
Minute structure of a small artery:—The lining epithelium. 
The thickness of the wall composed of three distinct coats; (1) 
a narrow internal coat composed chiefly of white fibrous con- 
nective tissue; (2) a thicker middle coat of circularly ar- 
ranged unstriped muscle; (3) an outer less firm coat composed 
of mixed yellow elastic and white fibrous tissue. 
In the larger arteries the constituents of the three coats 
intermingle, while in the arterioles the coats are sharply defined 
one from the other. 
The muscular element becomes proportionally more prom- 
inent as we proceed from the larger to the smaller arteries. 
The capillaries, composed intirely of the vascular endothe- 
lium cells joined edge to edge. 
The structure of the veins corresponds in general with that 
of the arteries, except that the layer of muscle is not so well 
defined nor relatively so thick. 
The valves in the veins. 
Compare the elasticity of the artery with that of the vein. 
The artery is very elastic, its walls thick and strong. Curve 35 
of elasticity of the arterial wall. The vein is more extensible 
than the artery and more easily ruptured when fully distended- 
THE PHYSIOLOGY OF THE HEART. 
THE AURICULO-VENTRICULAR VALVES. 
Notice that the surface of the valves is considerably greater 
than is necessary to separate completely the cavity of the auri- 
cle from that of the ventricle on each side of the heart. 
Notice that the chordse. tendinese are attached externally not 
directly to the heart wall, but through the medium of the 
papillary muscles. The function of these muscles in keeping 
their tendons tense as the heart cavity becomes smaller in con- 
traction. 
The inner ends of chordse springing from each papillary 
muscle are attached to the edges not of a single valve but to 
those of two adjacent ones. 
The use of the muscle fibres upon the upper surface of each 
valve. 
The floating upward of the auriculo-ventricular valves dur- 
ing the pause of the ventricle. 
The function of the auricle in completely closing by its con- 
traction the auriculo-ventricular valves. 
The manner of action of the semilunar valves. 
THE FUNCTION AND COMPARATIVE PHYSIOLOGY OF 
THE HEART. 
The heart acts simply as a pump whose valves enable it to 
send fluid round a continuous circuit. 
Diagrams illustrating the action of simple and complex 
pumps. 
The object of the circulation is bring new material to the 
tissues and remove waste matters from them. 
The mammalian heart is a double pump; one-half of which 
forces out venous blood and the other half arterial blood. The -36 — 
use to the animal of this complex form of the mammalian 
heart. 
Demonstration of the movement of fluid in the sheep’s 
heart. 
The coordination throughout the animal kingdom of the 
anatomical structure of the heart with the physiological needs 
of the organism;—The contractile circulatory apparatus of the 
amoeba; of a worm; of a snail; of a frog. 
THE PHENOMENA INVOLVED IN THE CARDIAC CYCLE. 
The beat of the excised heart of the frog. The active sys- 
tole and the passive diastole. The rounder base and shorter 
long axis of the heart in systole. 
The position of the mammalian heart in the living body; 
the change of position on opening the chest wall. 
The movements of the living heart within the chest:—The 
slight rotation round the long axis. The marked movement of 
base toward the apex, and its cause. Effect upon the position 
of the heart and on the movement of its base, of bleeding. The 
absence of locomotion in the apex. 
The phases of the cardiac cycle:—The duration of the auri- 
cular systole and the condition of the rest of the heart during 
it. The duration of the ventricular systole and the condition 
of the rest of the heart during it. The duration of the common 
diastole of the heart. The length of the whole cardiac cycle. 
The nature and time relations of the changes going on 
within the various chambers of the heart throughout the car- 
diac cycle. The experiments of Chauveau and Marey. 
The cardiac systole begins in the great veins. 
The quick peristaltic contraction of the auricles. 
The simultaneous contraction of all the ventricular fibres. 
The long persistence of the phase of extreme contraction in 
the ventricle. 
The ventricles probably empty themselves completely at 
each systole. The auricles never do. -37- 
THE WORK DONE BY THE HEART. 
Factors which determine the amount of work done by the 
heart:—(1) The amount of blood pumped out at each beat; 
(2) the resistance to be overcome; (3) the frequency of the 
beats. 
The work power of the heart is alone quite sufficient to 
cause the blood to circulate through the whole body. 
THE SECONDARY MECHANICAL AIDS TO THE WORK OF THE 
HEART. 
The assistance given to the filling of the auricles by the 
movements of inspiration. 
The suction of blood into the auricles due to the movement 
of the base of the ventricle when the latter contracts. 
The help offered by the coronary circulation to the filling 
of the ventricle. 
The help offered by the elasticity of the ventricular wall to 
the filling of the ventricle. 
The circulatory variations in organs outside the heart as 
shown by the plethysmograph. 
The aid rendered to the filling of the ventricle by the slip- 
ping of the ventricle over the auricle in ventricular diastole, due 
to the aortic pull. 
THE INFLUENCES WHICH INITIATE AND MAY MOD- 
IFY THE BEAT OF THE HEART. 
The cardiac beat is an automatic action and may be carried 
on in a normal manner by the excised organ. 
The impulse to activity is discharged rhythmically, proba- 
bly from certain nerve centres within the substance of the 
heart. But the rate and nature of the beat are profoundly 
modified by various secondary influences. The following are 
the secondary influences which may be shown to operate on 
the heart, and to their variation must be due any alteration in 
the character and rhythm of the automatic beat:— 38 
1. The intra-cardiac blood pressure. The diastolic intra- 
cardiac pressure depends upon the volume of blood which 
flows into the heart. The systolic intra-cardiac pressure depends 
upon the resistence to the flow of blood from the heart, or upon 
the blood pressure within the aorta and pulmonary artery. 
2. The temperature of the blood entering the heart. 
3. The chemical constitution of the blood supplying the 
heart. 
4. The efferent nerves reaching the heart from extra-cardise 
centres. 
THE INFLUENCE UPON THE HEART BEAT OF INTRA-CAR- 
DIAC BLOOD PRESSURE. 
The heart of the frog cut out front the body and empty 
beats very feebly or comes to rest after a while; pass through 
its cavities a weak saline solution under pressure and the beats 
become much stronger or go on again for a time. Distension of 
the cardiac wall is a stimidus to the activity of the heart. The effect 
is more striking and lasting if blood instead of salt solution be 
used. 
When the excised heart is normally beating with an artifi- 
cial supply of blood, neither variation of arterial pressure nor 
variation of venous pressure produces any definite alteration 
in the rhythm of the heart beat. The rhythm of the heart beat 
is not directly affected by changes of intra-cardiac pressure. 
The work done by the heart and the force of its beat in- 
creases with intra-cardiac blood pressure. 
The normal heart is at any moment able to accomplish 
much more than it is normally required to do. 
INFLUENCE OF THE TEMPERATURE OF THE BLOOD ENTER- 
ING THE HEART. 
The heart muscle is extremely susceptible to changes of 
temperature. The rhythm of the beat is uniformly quicker 
with a higher and slower with a lower temperature, Changes — 39 — 
in the temperature of the blood amounting to a fration of a 
degree alter the rhythm of the mammalian heart beat. 
INFLUENCE OF THE CHEMICAL CONSTITUTION OF THE 
BLOOD SUPPLYING THE HEART. 
The heart is remarkably insensitive to deterioration in the 
nutritive fluid supplying it. The action of the frog’s heart 
under minute quantities of nutritive material. The beat of the 
isolated mammalian heart supplied by blood poor in oxygen 
and rich in waste matters. 
But the heart is very sensitive to the action of certain drugs. 
Certain of these affect the muscle of the heart directly, others 
operate on various parts of its intrinsic nervous mechanism. 
The action of alkali on the heart muscle. 
The action of acid on the heart muscle. 
The action of digitalin on the heart muscle. 
The action of atropin on the nervous mechanism. 
The action of muscarin on the nervous mechanism. 
THE INFLUENCE OF EFFERENT NERVES REACHING THE 
HEART FROM EXTRA-CARDIAC CENTRES. 
Modifications of the heart beat are probably normally 
nearly altogether due to impulses proceeding along the heart 
nerves whose centres are no doubt much more sensitive to 
changes of external conditions than is the heart itself. The 
heart is merely the pump, the extra-cardiac centres the intelli- 
gence that modifies the action of the pump according to the 
needs of the body. 
The cardio-inhibitory nerve:—fibres arising from the spinal 
accessory nerve join the pneumogatric trunk within the skull 
and are given oft’ from this nerve again in the neighborhood of 
the heart. Stimulation of the peripheral end of the cut vagus 
causes slowing of the heart beat if the stimulation be weak, 
stops the beat if stimulation be strong. — 40 — 
The inhibition due to stimulation is preceded by a latent 
period of one or two heart beats. 
Exhaustion of the inhibitory fibres: after being brought to 
a standstill, the heart soon commences to beat again though the 
stimulation be kept up. 
Evidence for the constant action of the vagus inhibitory 
fibres upon the heart. 
The vagus probably contains two other separate sets of 
fibres whose action in the one case strengthens, in the other 
causes weakening of the heart beat, without alteration of its 
rhythm. Evidence derived from the heart of the frog and 
terrapin. 
The cardiac accelerator fibres arise from the spinal cord and 
reach the heart through the last cervical and first thoracic 
sympathetic ganglia. 
Effect of stimulating the peripheral end of the spinal cord 
divided in the neck, or the peripheral ends of the divided 
accelerator fibres. 
The heart beat is quickened by the stimulation. The stim- 
ulus required is much stronger than for the inhibitory nerve. 
The latent period is long, and the effect of the stimulation per- 
sists for some time after the cessation of the latter. 
When the cardio-inhibitory and the accelerator fibres are 
simultaneously stimulated, the heart is brought to a standstill 
as if the vagus alone were irritated. 
THE AUTOMATICITY OF THE HEART. 
The phenomena offered by the frog’s heart when it is cut 
in different directions and when its various parts are separated 
from each other. 
The graded automaticity of the different parts of the heart; 
the decline of physiological resistance to discharge from the 
venous sinus to the ventricle. 
The isolated ventricle of the frog’s heart does not beat spon- 
taneously, but rhythmic beats follow when it is distended with 
fluid. — 41 — 
The function of the ventricles is to drive the blood respec- 
tively in its pulmonary and systemic circulation. 
The function of the auricles is, by the frequency and char- 
acter of their pulsation, to regulate the rate and character of 
the ventricular contraction. And also by its heat to complete 
the closure of the auriculo-ventricular valves. 
The law for the contraction of cardiac muscle:—Every stim- 
ulus that can call forth a beat at all produces a maximal beat. 
Stimuli of whatever strength are succeeded by contractions of 
the same force. Unlike the skeletal muscles, cardiac muscle 
refuses to give suh-maximal contractions on applying weaker 
stimuli. 
The heart’s contraction is probably not a tetanus but a long 
continued single contraction. 
The action current of the heart. 
THE APEX BEAT AND THE SOUNDS OF THE HEART. 
The apex beat felt outside the chest wall lasts throughout 
the systole of the ventricle and is due to this. The impulse is 
due probably not to a blow of the heart’s apex against the 
chest wall, but simply to the hardening of the heart muscle. 
The two sounds of the heart; the time of their occurrence 
in the cardiac cycle and their difference of quality. 
The first sound; probably both muscular and vaivular in 
origin. 
The second sound; due to the snapping to of the semilunar 
valves. 
THE CIRCULATION OF THE BLOOD. 
Proof that the work power of the heart is sufficient to com- 
plete the circulation of the blood. 
Rate of the circulation; the blood completes its circuit from 
ventricle to ventricle in man in about 23 seconds. 
The area of the arterial vascular bed increase from the 
heart to the capillaries and then decreases in the veins 
to the heart. The flow of blood is slowest where it passes -42- 
through the greatest area, that of the capillaries. The sum of 
the areas of cross section of the systemic capiliaries is prob- 
ably eight hundred times as great as that of the aorta. 
The circulation of the blood as observed in a frog under the 
miscroscope. The comparison of the flow in arteries, capilla- 
ries and veins. 
The “axial” current; the “inert” layer; the respective 
movements of white and red corpuscles. 
The changes in the circulation brought about by the pro- 
cess of inflammation. 
THE HYDRAULICS OF THE CIRCULATION. 
The agents concerned in the circulation;—(1) An incom- 
pressible fluid; (2) A pump of intermittent action; (3) Aset 
of elastic tubes. 
If an artery be cut across there is a continuous flow of 
blood from its central end with an increased spurt at each 
heart-beat. Cut across a vein and there is steady flow of blood 
without pulsation from its peripheral end. 
If a mercury manometer be attached to an artery of a 
living animal the position of the mercury will show that the 
blood in the artery is under considerable pressure, the blood 
'pressure, which fluctuates with each beat of the heart. 
If a manometer be attached to a vein the mercury will 
show a very small blood pressure and no pulsations. 
Consider the causes:—(1) of the high arterial and low 
venous blood pressure; (2) of the continuous flow of blood 
brought about by the intermittent action of the pump; (3) of 
the loss of the pulse in the veins. 
The law of the fall of fluid pressure in a tube offering equal 
resistance to flow in all its parts. 
The minor arterial schema. 
The major arterial schema. 
The resistance to the movement of the blood is internal; 
that is, due to the friction of the fluid particles against each 
other. Conditions determining internal and external friction 
in the movements of fluids. -43 — 
The internal friction increases fast as the calibre of the ves- 
sels decreases; hence the chief resistance to the circulation is 
in the capillaries, or is peripheral. 
Because of the peripheral resistance the arterial walls are. 
stretched by the blood pumped from the heart, and the strained 
wall reacting on the fluid produces the high arterial pressure. 
The arterial walls being kept constantly stretched, they 
squeeze constantly upon the inclosed fluid; hence the flow 
from a cut artery is continuous. 
If the heart stop, the circulation continues to go on until the 
arteries have come to a condition in which they are not 
stretched. 
The blood pressure is the immediate cause of the circulation. 
The action of the heart is its remote cause and operates through 
keeping the arteries stretched by forcing into them fresh quan- 
tities of fluid. 
The energy of the blood pressure is used up in overcoming 
resistance to the circulation and as the chief resistance is 
offered by the capillaries, there is a sudden fall of pressure 
between the arteries and the veins. 
Weber’s Schema. 
Each new quantity of fluid thrown into the base of the 
aorta distends the vessel there and this distension runs along 
the artery as the 'pulse wave. 
The rate and height of the pulse wave depend upon the 
elastic qualities of the arterial wall. 
The pulse wave started at any systole of the heart, travels 
much faster than the blood whose entrance into the aorta 
caused it. 
The energy of the pulse wave is used up in stretching the 
vascular wall; hence the height of the wave decreases from 
the heart outwards. 
Primary and secondary pulse waves. 
Study of sphygmographic tracings. 
The veins alone could contain all the blood of the body. 
The arteries are overfull. — 44 — 
THE USE OF ARTERIAL ELASTICITY. 
A greater amount of fluid is forced by a pump in a given 
time through an elastic tube than through a rigid one of the 
same calibre. 
The energy of the heart’s systole is stored in the arterial 
wall and acts throughout the cardiac cycle as driving force of 
the blood. By this means the useful energy of the heart is 
not limited in time to its systole, but is distributed through the 
whole cardiac -cycle. Consider the analogy of many artificial 
machines. Consider the results to the heart and the circula- 
tion of the arteries being rigid tubes. 
All the energy of motion that is lost to the blood in its cir- 
culation reappears as heat and goes to warming the tissues. 
As the arterial blood pressure is the force which drives the 
blood round its circuit, it is of vital importance to the animal 
that a pretty constant mean pressure be maintained. 
MEANS BY WHICH ARE REGULATED THE GENERAL 
BLOOD PRESSURE AND LOCAL BLOOD SUPPLY. 
The factors which determine the power of the blood pressure 
are three:—(1) The force and frequency of the heart beat as 
determining the quantity of blood pumped into the arteries. 
Other things being equal, blood pressure increases with the 
quantity of blood forced out of the heart in a given time. 
(2) The peripheral resistance; arterial pressure increases 
and venous pressure proportionately decreases as the peri- 
pheral resistance becomes greater, other factors remaining the 
same. 
(3) The elasticity of the arteries; other things remaining 
equal, blood pressure increases with increase of elasticity, or 
resistance to distension, of the arterial walls. 
Inhibition of the heart’s action through stimulation of the 
vagus nerve causes a sudden fall of blood pressure. — 45 — 
Quickening of the heart’s action by stimulation of the 
accelerator nerves does not alter the blood pressure. 
THE VASOMOTOR REGULATION OF BLOOD PRESSURE. 
Withdrawal of a large quantity of blood from an animal 
does not lower, except momentarily, the blood pressure. 
The injection of a large quantity of foreign blood into the 
vessels of an animal produces no permanent rise of blood 
pressure. 
When the spinal cord of an animal is divided in the neck 
the mean arterial blood pressure decreases to a small fraction 
of it former value. When the peripheral end of the cut cord 
is stimulated arterial pressure rises again. Both the fall and 
the rise of pressure are somewhat gradual. 
The vaso-motor centres in the medulla oblongata. 
Efferent impulses proceed from the vaso-motor centre along 
vaso-motor nerves to all parts of the body and keep the mus- 
cular coats of the small arteries and arterioles in a state of 
tonic contraction, thus increasing the peripheral resistance to 
the flow of blood. 
Secondary vaso-motor centres in parts of the brain other than 
the medulla oblongata. 
It is not proven, but is not improbable that the capillaries 
are under vaso-motor control. 
The experiment of cutting and stimulating the cord of a 
frog while its circulation is observed under the microscope. 
THE REGULATION OF LOCAL BLOOD SUPPLY. 
The various organs of the body require an increase of blood 
supply during their period of activity and a lesser quantity in 
the intervals between. 
Stimulation of sympathetic nerve branches supplying any 
area nearly always produces contraction of the vessels in that 
area. 
Efferent vaso-dilator as distinguished from vaso-constrictor 
nerves. — 46 — 
The vasomotor effect of stimulating the peripheral end of 
the mylo-hyoid nerve in the frog. 
The effect of stimulating the peripheral end of the chorda 
tympani upon the circulation in the sub-maxillary gland of 
the dog. 
The physiology of blushing. 
The functional vaso-motor changes of erectile tissues. 
The changes in the circulation of a vascular area on stim- 
ulating its vaso-dilator nerve: The increased calibre of the 
arterioles; the more rapid blood current; the flow of red 
blood through the veins; the venous pulse. 
The evidence for the presence in the medulla of a double 
vaso-motor centre, one part sending out vaso-constrictor nerves, 
the other part supplying vaso-dilator nerves. When one organ 
receives more or less blood than usual, there must be an alter- 
ation of vaso-motor tone in the blood vessels of other districts 
in order that the mean blood pressure shall remain constant. 
The influence of temperature and mechanical disturbances 
on vaso-motor activity. 
Gradual recovery of vascular tone in any area after cutting 
off its vaso-motor nerves. 
THE REFLEX EXCITEMENT OF THE VASO-MOTOR CENTRES. 
Stimulation of the central end of nearly any sensory nerve 
produces general reflex vaso-motor constriction and a conse- 
quent rise of blood pressure. 
The function of the depressor nerve, which in the cat and 
rabbit finds its way to the heart in a path independent of the 
vagus. The depressor is an afferent nerve; when divided 
stimulation of its central end brings about a fall of blood pres-i 
sure without marked change in the pulse rate. 
The reflex dilatation of the vessels in a rabbit’s ear through 
stimulation of the great auricular nerve. 
The reflex dilatation of the blood vessels of glands due to the 
stimulating effect of food upon the appropriate mucous mem- 
branes. 47 
Remembering that arterial pressure is the driving force of 
the blood, consider the difference of physiological effect between 
rapidly drawing a certain amount of blood from an artery and 
from a vein. 
THE LYMPHATIC VESSELS AND THE FLOW OF LYMPH. 
Two modes of origen of lymphatic vessels;—;plexiform and 
lacunar. 
The relative size and direction of lymph and blood capil- 
laries. 
The thin vein like walls of lymphatic vessels; their numer- 
ous valves. 
The stomata of serous membranes. 
Every tissue element probably lies in a lymphatic space 
from which fluid rapidly reaches lymphatic channels. 
The direction of flow in the Ipmphatic vessels. 
Influences modifying the flow of lymph;—muscular action; 
position of the body; respiratory movement. Flow from the 
opened thoracic duct of a dog. 
The lymphatic hearts of birds, reptiles and batrachians. 
Difference between lymph and chyle. 
Lymphatic glands; their position, structure and function. 
The general purpose and cause of the existence of lymph. 
DEMONSTRATIONS. 
Comparison of the elasticity of arteries and veins. 
The valves in the veins. 
Dissection of a sheep’s heart. 
Artificial circulation through a sheeps heart. 
The movement of needles in the mammalian heart. 
The beat of the isolated heart with an artificial supply of 
blood. 
The influence upon the beat, of valuable pressures; of tem- 
perature changes; of various drugs. 
The rhythm of beat in the isolated heart of the frog. — 48 — 
The beat of the pigeon’s heart directly observed. 
The behavior of the ganglion free apex of the frog’s heart. 
Vagus inhibition of the heart beat in a frog. 
The minor arterial schema. 
Weber’s schema. 
Comparison of blood pressures in the carotid and femoral 
arteries of mammal. Effect on the blood pressure of vagus 
stimulation. The graphic method of recording physiological 
observations. 
Comparison of the blood pressure and its fluctuations in 
the femoral vein and femoral artery. 
The effect upon blood pressure of stimulating the depressor 
nerve. 
The effect upon blood pressure of cutting, and then stimu- 
lating the spinal cord. X. THE PHYSIOLOGY OF SECRETION. 
All the phenomena of secretion probably depend in the end 
for their occurrence on the physical laws of diffusion and filtra- 
tion. 
The nature of the laws regulating the diffusion and filtration 
of fluids and of gases. 
Simple applications of the laws of diffusion in the living 
body. The production of diarrhoea by the presence of magne- 
sium salts in the intestine. The interchange of matter between 
the lymph and the blood and the relation of the animal cell to 
the process. The gas exchange in the lungs. 
Secretion is not simply a process of diffusion and filtration 
through dead membranes. The diffusion membrane of secre- 
tion is alive. 
In the simplest form of true secretion certain substances are 
selected by and passed through the secreting membrane. But 
most secreted fluids contain specific matters which have been 
produced by the vital activity of the secretory cells. 
The typical secretory animal membrane: (1) the secretory 
cell; (2) the basement membrane; (3) the capillary network. 
The modification of the typical secretory membrane into 
glands. 
Various forms of glands: tubular and racemose glands. 
The parts of a gland: the duct; the acinus or alveolus. 
The circulation in glandular tissue. 
Enzym. Mucous and albuminous glands. 
THE PHENOMENA OF SECRETION AS DETERMINED 
IN THE SUB-MAXILLARY GLAND. 
The nerve supply of the gland, and the processes of normal 
secretion. — 50 — 
THE CHEMICAL CONSTITUTION Otf SALIVA. 
The proportions of water, salts and organic matters. The 
relative diffusibility of the constituents. The specific bodies of 
the secretion. 
THE CHANGES PRODUCED IN THE SUB-MAXILLARY GLAND 
BY STIMULATING THE PERIPHERAL END OF THE CHORDA 
TYMPAN1 NERVE. 
The dilation of the blood vessels; the venous pulse and red 
blood in the veins. Vaso-dilator nerves. 
The volume of fluid continuously secreted may exceed that 
of the gland; the fluid could therefore not have been all stored 
in the resting gland, but must have come from the blood during 
the stimulation. 
The saliva is not simply filtered from the blood, for the 
secretion still goes on when the pressure of saliva within the 
duct exceeds that of the blood in the artery of the gland. 
Fibres of the chorda tympani must control the secretory 
activity of the gland cells; for, after poisoning with atropin, 
stimulation of the chorda still produces vasomotor dilatation 
in the gland but causes no secretion. 
The antagonistic actions of atropin and pilocarpine. 
The watery fluid of the secretion must have been contained 
in, and actively forced out of the gland cells. 
The secretion obtained by artificial stimulation from the 
gland of a decapitated animal. 
The chief volume of the secretion consists of the easily 
filtered and diffusible water with salts in solution. 
The volume of fluid secreted in*a given time does not mark- 
edly diminish during a series of stimulations. 
The organic matters of the saliva are not readily diffusible. 
The organic matters decrease in quantity as secretion pro- 
gresses. They are probably made by and stored up within the 
gland cells. — 51 — 
NERVES WHICH REGULATE THE CHEMICAL NATURE OF 
THE GLAND CELL SUBSTANCE. 
When the sympathetic nerve supplying the sub-maxillary 
gland of the dog is stimulated, the blood vessels of the gland 
contract and the amount of secretion is insignificant. But after 
previous excitement of the sympathetic, stimulation of the 
chorda tympani causes a secretion much richer in organic mat- 
ters than otherwise would be the case. 
Stimulation of the peripheral end of the nerve of Jacobson 
in the dog produces an abundant secretion from the parotid 
gland. 
Stimulation of the peripheral end of the sympathetic sup 
plying the parotid gland of the dog causes no secretion, but 
greatly increases the organic content of the secretion produced 
by subsequent stimulation of the nerve of Jacobson. 
Nerves of three distinct physiological varieties can be shown 
to take part in secretion: (1) Vaso-motor nerves, which regulate 
the calibre of the blood vessels; (2) secretory nerves, which 
bring about the active diffusion of water and salts through the 
gland cells; (3) trophic nerves, which produce chemical changes 
in the gland substance giving rise to more soluble organic mat- 
ters in it. 
THE HISTOLOGICAL CHANGES OF THE SALIVARY GLANDS 
IN SECRETION. 
Comparison of the appearance and reaction toward staining 
reagents of a resting sub-maxillary gland with one which has 
abundantly secreted. 
Comparison of the histological characters of the parotid 
gland before and after stimulation of the sympathetic nerve. 
The paralytic secretion of saliva. 
The theory of secretion suggested by the facts that have 
been advanced. — 52 — 
THE ABSORPTION OF MATTER INTO THE BODY. 
Absorption into the tissues is probably chiefly a process of 
simple diffusion. 
Absorption by the skin. 
Absorption by the lungs. 
Absorption in the alimentary canal. The preparation in 
digestion of food matters for absorption. The absorption of 
fats. 
The influence of the nervous system in the process of ab- 
sorption. 
DEMONSTRATIONS 
Stimulation of the chorda tympani. 
Comparison of the pressure of saliva in the gland duct with 
that of the blood in the femoral artery. 
The action of atropin and of pilocarpin on the gland. 
XL THE VARIETIES AND FUNCTIONS OF INGESTA. 
The'body must depend upon food matters for the mainte- 
nance of its structure and as the source of its energy. The 
nature of the alimentary substances which might be supposed 
most readily to fulfill these functions. 
The loss of energy to the food in the body. 
The source of energy of plant life. 
The different kinds and chemical composition of the sub- 
stances entering into food stuffs: proteids; albuminoids; fats; 
carbo-hydrates; salts and water; condiments, etc. 
The physical and chemical characters, and chemical reac- 
tions of the various kinds of alimentary substances, 
Proteids form the only class of foods which can probably 
alone maintain life; but the normal diet contains all the differ- 
ent kinds of food matter. 
The history of the various food stuffs in the body, and the 
form under which they appear in the egesta. 
Liebig’s classification of foods into plastic and respiratory. 
Objections to this division. -53- 
CLASSIFICATION OF INGESTA. 
Supply material for the formation 
and restoration of tissues. Sup- 
ply the energy for the construc- 
tion and activity of the body. 
Foods- 
Ingesta: 
Do not as such form a part of the 
living tissues, but are media ne- 
cessary to their activity. A sec- 
ond class of them acts as a collec 
tion of stimulating substances 
which produce effects out of pro- 
portion to the amount of material 
employed. 
Force regulators - 
Any ingested substance is not restricted in its function to 
one of the above classes, but may probably at the same time 
supply energy and tissue material to the body, and serve as a 
force regulator to the activities of the body. 
The two kinds of force regulators represented by a saline 
solution and a condiment. 
The usefulness of cooking. 
DEMONSTRATIONS. 
The chemical reactions of proteids. 
The chemical reactions of fats. 
The chemical reactions of starch, dextrin, glycogen and 
glucose. 
XII. DIGESTION; AND THE ACTIVITIES AND STRUCTURE OF 
THE PARTS INVOLVED IN IT, 
THE STRUCTURE AND ARRANGEMENT OF THE MOUTH 
PARTS. 
The anatomy of the buccal cavity and parts in connection 
with it. The silb-maxillary, the parotid and the lingual glands 
and their openings. 
Structure of the buccal mucous membrane. 
The tongue; its muscles, nerves and papillae. 
The teeth; the two sets of permanent and milk teeth; the — 54 — 
number in each. The shape and parts of the various teeth. 
The Crusta petrosa; dentine; enamel. 
THE PHYSIOLOGY OF SALIVA. 
Saliva as found in the mouth is the mixed product of the 
three pairs of salivary glands, of the glands of the tongue and 
adjacent parts, and of the buccal epithelium. 
The physical and chemical characters of saliva. 
The solid bodies found in saliva; the food detritus; epithel- 
ium cells; “salivary corpuscles.” 
The function of saliva in assisting deglutition. 
The physiological process of secretion and influences modi- 
fying it. “Watering” of the mouth; the “rice ordeal.” The 
normal reflex. 
Quantity of saliva secreted. 
THE DIASTATIC ACTION OF SALIVA. 
The conversion of starch into sugar under the action of 
saliva. The chemical change consists in the addition of a mole- 
cule of water to one of starch. 
The influence of temperature on the rapidity of the diastatic 
action. 
Exposure to the temperature of boiling water destroys the 
diastatic power of saliva. The action is arrested in a medium 
containing as much as 0.1 HC1, and strong alkalis destroy the 
body in the saliva which produces the change. 
The amount of starch which may be changed into sugar 
bears no definite relation to the amount of saliva employed. 
The diastatic power of the saliva does not seem to decrease pro- 
portionately to the extent of the change which it brings about. 
The diastatic action of saliva is due to the presence in it of 
an animal ferment, Ptyalin, which is probably an organic but 
non-proteid product of the activity of the salivary glands. 
The distinctive characters of ferments. Organized and un- 
organized ferments. 
The special characters of the saliva obtained from different 
glands. — db — 
THE PROCESS OF DEGLUTITION. 
The masticated mouthful of food is brought together in a 
heap upon the back of the tongue, and thence, by a complicated 
series of coordinated movements, is transferred to the stomach. 
The protective movements of the respiratory apparatus, and 
the function of the epiglottis. 
The process of deglutition may be divided into three stages; 
(1) while the food is still within the mouth, the movement is 
purely voluntary and may be slow or rapid. (2) When the 
food reaches the common buccal and respiratory chamber of 
the pharynx, the movement is nearly purely reflex, or involun- 
tary, and is then most rapid. (3) When the food reaches the 
oesophagus its movement is again slower and quite involuntary, 
and the mouthful is carried by a peristaltic contraction to the 
stomach. 
The nervous mechanisms involved in the swallowing move- 
ment. The centre in the medulla. 
The histological structure of the oesophagus. 
The mechanisms and processes involved in vomiting. 
The stimulus to the movement may be either peripheral or 
central. Majendie’s experiment. Nausea. 
THE STRUCTURE AND PHYSIOLOGY OF THE STOMACH. 
THE ANATOMY AND HISTOLOGY OF THE STOMACH. 
The shape, anatomical connections, and nervous and vascu- 
lar supply of the stomach. The fundus. 
The empty stomach is always contracted. 
The three coats of the stomach; (1) muscular; (2) areolar. 
(3) mucous. 
The muscular coat is composed of unstriated tissue. Its 
layers of longitudinal, oblique and circular fibres. 
The cardiac and pyloric sphincters. The pyloric “ valve.” 
The areolar coat. Division of blood-vessels in it. 
• The mucous membrane. The rugse and their cause. — 56 — 
The shape and cellular elements of the glands of the mucous 
membrane. The difference between the glands of the pyloric 
and other regions of the stomach. The blood and lymph ves- 
sels of the mucous membrane. 
The nerve cells within the stomach wall. 
THE GASTRIC JUICE AND ITS SECRETION. 
The fluid obtained from the stomach of a dog with gastric 
fistula by means of electrical, mechanical or chemical stimula- 
tion of the mucous membrane. Dilute alkalis readily excite 
the secretion. 
The quantity of gastric juice secreted in 24 hours. 
THE CHEMISTRY OF THE GASTRIC JUICE. 
The gastric juice of the dog contains about 0.45 p. c. solid 
matter, of which half is inorganic saline, and half organic mat- 
ter, the ferment pepsin, mucus, etc. The reaction is always acid, 
due to the presence of free HC1. Lactic and butyric acids, 
which are frequently present, are probably due to fermentations 
of the food matter, and not to the secretory activity of the 
stomach. The amount of free HC1 is about 0.2 p. c. of that of 
the normal juice. 
THE DIGESTIVE POWERS OF THE GASTRIC JUICE. 
The digestive powers of the gastric juice are due to the action 
of a ferment pepsin, which is made in and secreted by the cells 
of the stomach glands. Pepsin is probably an organic but non- 
proteid body. 
The presence of free acid is necessary to the action of gastric 
juice. The power of the juice is destroyed by the temperature 
of boiling water. The rapidity of digestion depends upon the 
temperature. 
On starch the gastric juice has no effect, though it may set 
free starch grains which are held together by proteid substances. 
On sugars the gastric juice has no effect; though there ap- 
pears to be a ferment in the mucus, which is secreted by the 
epithelium covering the mucous membrane, which has the — 57 — 
power of converting cane into grape sugar. An excess of cane 
sugar in the food causes an increased secretion of mucus. 
The mechanical function of the mucus as a cleanser of the 
alimentary canal. 
On fats the gastric juice has no effect, though they are set 
free by the solution of the proteid and gelatiniferous portion of 
their cell envelopes. 
Albuminoid substances are dissolved by the gastric juice. 
Such mineral salts as are soluble in dilute acids are dissolved 
by gastric juice. 
The chief digestive power of the gastric juice consists in its 
decomposition of proteids by which they are converted into 
soluble, diffusible substances called peptones. 
Experiments upon the digestive power of gastric juice may 
be carried out either with natural or artificial juice. 
Artificial gastric juice may be prepared by extracting the 
minced mucous membrane of the stomach, (1) with water, (2) 
with dilute hydrochloric acid (0.2 p, c.), (3) with glycerine, (4) 
or with glycerine after standing under strong alcohol. 
Gastric juice acts most rapidly at about the body tempera- 
ture, and is inert at 0°C. 
The presence of free acid, best HC1 0.2 p. c., is necessary to 
the activity of the juice. 
The acid is used up in digestion and gradually disappears 
from an artificial solution. 
The ferment, pepsin, does not appear to be used up in diges- 
tion. 
Evidence that pepsin is formed by changes in the stomach 
glands after death; that it is made during secretion and not 
stored up in the cells. 
The pro-ferment, pepsinogen. 
The activity of the gastric juice is greatly hindered by the 
accumulation of the products of digestion. 
The histological changes which the gastric gland cells under- 
go in digestion. 
The changes as to granulation which digestive cells in gen- 
eral go through in their activity. — 58 - 
The functions of the different kinds of cells of the stomach 
glands. The relation of the glands in the pyloric part of the 
stomach to those in other regions of the organ. 
THE CHANGES OF PROTEIDS IN GASTRIC DIGESTION 
The characteristic swelling of the proteid substance and its 
gradual solution. 
The formation of soluble albumin, precipitable by boiling. 
The formation of parapeptone or acid albumin. Dilute acid 
alone may effect these changes. 
The formation of peptone. Dyspeptone. 
Complete and incomplete peptones. 
Characters of perfect peptones: peptones are soluble in 
water, but are not precipitated by boiling; they answer the 
chemical tests for proteids; they, unlike other proteids, are 
readily diffusible. They are not precipitated by strong acetic 
acid and potassium ferrocyanide, as are the incomplete pep- 
tones. 
Kiihne’s theory of the division of proteid substances by gas- 
tric digestion into two groups—Hemi-peptone and Anti-peptone. 
The formation of peptones appears to be brought about by 
a hydration of the proteid. 
The milk ferment. Rennet. 
THE HISTORY OF THE FOOD WITHIN THE MOUTH 
AND STOMACH. 
The effect of mastication and the mechanical and chemical 
functions of saliva. 
The swallowed saliva excites the flow of gastric juice, as 
does probably the mere smell of food. 
The digestive action of saliva upon - starch is not interfered 
with by the acidity of the gastric juice to the same extent as 
would be the case in a pure acid of the same strength. 
The mechanical and chemical changes of the food in the 
stomach. The usefulness of thorough mastication. The me- 
chanical dissolution of the fats, starches and proteids. The 
nature of the movement of food in the stomach. The chyme. — 59 — 
The processes of solution, absorption and passage into the 
intestine. 
The rapidity of digestion in the stomach and influence 
modifying it; nature of the food; method of cooking; state o 
division; temperature; ‘rate of absorption; the efficiency of the 
gastric juice and rapidity of its secretion; the energy of move- 
ment which mixes the food. 
THE MECHANISMS OF SECRETION AND OF MOVE- 
MENT IN THE STOMACH. 
The only nerves reaching the stomach are branches from the 
vagi and the splanchnics. 
Normal gastric juice is secreted after division of both sets of 
nerves. The essential secretory mechanism seems to be local. 
The food is brought directly into contact with the secretory 
membrane. 
The influence of emotions on secretion. 
The normal mucous membrane is flushed during digestion; 
it becomes pale on cutting through the vagi, and reddens again 
when the central ends of these nerves are stimulated. 
Afferent vaso-motor impulses seem to travel from the 
stomach along the vagi, while efferent vaso-motor impulses 
descend to the stomach in the splanchnic fibres. 
The nature and cause of the movements of the stomach. 
The empty stomach is contracted; the empty intestine is 
relaxed. 
The influence of mechanical distension on movement of the 
stomach. 
The influence of extrinsic nerves. 
THE CHANGES WHICH THE FOOD UNDERGOES IN 
THE INTESTINE, AND THE DIGESTIVE ORGANS 
INVOLVED IN THEM. 
The digestive fluids which are poured into the intestine are 
all alkaline in reaction and come from three sources: (1) the 
Pancreas, pancreatic juice; (2) the Intestinal Mucous Membrane 
mccus entericus ; the Liver, bile. — 60 - 
THE ANATOMY AND HISTOLOGY OF THE PANCREAS. 
The relative position of the openings of the bile and pan- 
creatic ducts into the intestine in man and in other animals. 
The lobulated structure of the gland. 
The histological appearance of the pancreas. The ducts; 
the single acini; the gland cells, their outer hyaline and inner 
granular zone. 
The phases of histological change which the gland cells 
undergo in digestion. The observation of the pancreas in a 
living rabbit. 
In general, the granular matter of a resting secretory cell is 
distributed throughout the whole of the cell; while as a result 
of activity, the granules are fewer in number and are accumu- 
lated round the lumen of the gland on the inner border of the 
cells. 
The difficulty of establishing a permanent pancreatic fistula. 
The pancreatic juice begins to flow from a fistula immedi- 
ately on food being .taken; the rate of secretion increases till 
about the fourth hour, then decreases for an hour, and then 
increases again, reaching a second maximum at the eighth hour 
after taking food, afterward declining. 
The amount of pancreatic juice secreted in 24 hours. 
THE CHARACTERS AND POWERS OF PANCREATIC JUICE. 
Normal pancreatic juice is a clear, viscid fluid, frothing 
when shaken. It has a decided alkaline reaction. 
- The fluid contains about 8 p. c. solids, consisting of albumin, 
alkali albumin, leucin and tyrosin, some fats and soaps and a 
considerable amount of soda carbonate. The presence of leucin, 
tyrosin and soaps is probably due to digestive changes in the 
juice after its secretion. 
The pancreatic juice is probably the most important of all 
the digestive fluids. It probably normally contains several 
distinct kinds of ferment. 
The action of the pancreatic juice upon starch is similar to 
that of saliva, but is apparently more powerful. 61 
Neutral fats are emulsified by pancreatic juice, and are 
partly decomposed into glycerine and a fatty acid. 
Unlike the gastric juice, pancreatic juice does not dissolve 
gelatiniferous substances. 
On proteids, pancreatic juice exercises a powerful solvent 
action, converting them into peptones. 
The digestion of proteids does not cease at this stage, but 
peptones are farther decomposed into two nitrogenous crystal- 
line bodies, leucin and tyrosin. 
The complicated changes undergone by proteids in their 
digestion; the bye-products formed are alkali-albuminates in- 
stead of acid-albuminates as in the case of gastric digestion. 
The special proteid ferment of the pancreatic juice is called 
trypsin. 
Kiihne’s theory of the changes undergone by proteids in 
gastric and pancreatic digestions. 
The digestion of proteids by natural or artificial pancreatic 
juice in an alkaline medium is attended with the formation of 
indol, a substance having an offensive fsecal odor. 
Indol is not formed when the digestion is carried on in the 
presence of salicylic acid. It is probably not a product of 
digestion, but of the activity of adventitious organized fer- 
ments. 
A proteid, as fibrin, undergoing pancreatic digestion appears 
to be gradually corroded and crumbled; it does not swell as 
when acted on by the gastric juice. 
If the pancreatic ferments be exposed to the temperature of 
boiling water their digestive power is destroyed. 
An artificial extract of the pancreas may be made which 
shall have all the powers of the natural juice. 
The extract of the perfectly fresh gland has little or no 
digestive power. 
The fully formed ferment does not exist stored up in the 
gland cells during life. The living cells do not contain trypsin 
but hold an antecedent to this ferment, called zymogen. 
Trypsin is quickly formed in the excised pancreas when 
this is exposed to a warm temperature. — 62 — 
Addition of strong acetic acid rapidly converts zymogen 
into trypsin, and a powerful digestive fluid can than be made 
by extracting the gland with a 1 p. c. solution of soda car- 
bonate. 
THE RELATION OF THE PROTEID FERMENTS OF THE GAS- 
TRIC AND PANCREATIC JUICES. 
Gastric juice can digest only in an acid medium. Pancre- 
atic juice digests best in an alkaline fluid, 1 to 2 p. c. soda car- 
bonate, but is still active in a neutral or slightly acid solution. 
When pepsin and the pancreatic ferments are mixed 
together in an acid solution, pepsin acts upon and destroys 
the trypsin. 
THE STRUCTURE OF THE INTESTINE AND THE 
SECRETION PRODUCED BY ITS GLANDS. 
ANATOMY AND HISTOLOGY OF THE INTESTINE. 
The arbitrary division of the small intestine into duodenum, 
jejunum and ileum. 
The three coats; muscular, areolar and mucous. The circular 
and longitudinal muscle fibres. 
The nerve plexuses of Auerbach and of Meissner. 
The valvulx conniventes. 
The villi of the small intestine; their capillary and lymph 
vessels ; the layer of muscle cells ; the striated borders of the 
covering epithelium. 
The glands of Brunner, 
The “ crypts ” of Lieberkiihn. 
Fever’s “patches.” 
The secretion of the intestinal glands, the Succus Entericus, 
is an alkaline fluid having slight proleotytic and amylolytic 
digestive powers. 
THE BILE. 
The bile is the secretion of the liver cells, and in the inter- 
vals between digestive activity is stored up in the gall bladder. 63 
CHEMICAL AND PHYSICAL CHARACTERS OF BILE. 
The bile is decidedly alkaline in reaction. 
The green bile of herbivora and the yellow bile of car- 
nivora. 
The biliary pigments biliverdin and bilirubin. 
The clay color of the faeces when bile is prevented from 
entering the intestine. 
Pettenkofer’s test for bile acids. 
The bile salts; taurocholate and glycocholate of soda. 
Gmelin’s test for bile pigments. 
THE PROCESS OF SECRETION AND THE DIGESTIVE FUNC- 
TION OF BILE. 
The secretion of the bile increases rapidly after taking food 
and reaches its maximum in 4 to 10 hours after a meal. The 
bile, unlike the saliva, is secreted under a pressure much less 
than that of the blood. 
The passage of dilute acid, as of the contents of the stom- 
ach, over the intestinal orifice of the bile duct, causes a gush of 
bile into the intestine occasioned by contraction of the mus- 
cles of the gall bladder. This action is purely reflex. 
If bile, or a solution of bile salts, be added to a fluid con- 
taining the products of gastric digestion, the complete and in- 
complete peptones in solution are precipitated. Most of the 
pepsin is carried down mechanically by the precipitate. Excess 
of bile redissolves the precipitate and the resulting solution is 
alkaline in reaction. 
The precipitation of the dissolved gastric peptones prevents 
their too rapid progress along the intestine, and removes the 
pepsin whose action is destructive to trypsin. 
Bile has a slight emulsifying power over fats which is much 
increased when mixed with pancreatic juice. 
It probably mechanically assists in the absorption of fats, 
as these pass more readily through membranes moistened with 
bile. — 64 — 
Bile may furnish alkali for the formation of soaps in diges- 
tion. 
The amount of bile secreted in 24 hours. 
The effect of withdrawing bile from the body. 
The history of the food in the small intestine. The chyle. 
ABSORPTION FROM THE SMALL INTESTINE. 
The diffusion of liquids. The absorption of fats. 
The pumping action of the villi which assists absorption. 
The diffusion of water through the wall of the small intes- 
tine is about equal in both directions, for the contents of the 
ileum are as fluid as those of the duodenum. The action 
of purges. 
The mucous membrane of the large intestine is crowded 
with tubular glands but supports no villi. 
The contents of the large intestine rapidly lose water and 
become dry. They become acid in reaction from the products 
of intrinsic fermentation. The csecal digestion of herbivorous 
animals. 
The gases found in the large intestine:—C02, N, CH4, H, 
SH2. 
The chemistry of the fgeces. 
The function of mucus as a cleanser of the alimentary canal. 
THE MOVEMENTS OF THE INTESTINE. 
Fibres from the vagi and splanchnics unite the intestine 
with the brain. 
The peristaltic contraction of the excised intestine. 
The normal movements of the intestine and their stimulus. 
DEMONSTRATIONS. 
The conversion of starch into sugar by saliva: influence of 
temperature. 
The effect upon its amylolytic power of boiling saliva. 
The reaction and digestive power of natural gastric juice. 
Digestion of proteids with artificial gastric juice. The in- — 65 — 
fluence of the state of division of the proteid; the acidity of 
the juice; the temperature. 
Effect of boiling the juice. 
Products and bye-products formed during proteid digestion. 
The characters, solubility and diffusibility, of perfect pep- 
tones. 
Pancreatic digestion; of fats; of starch; of proteids. The 
formation of leucin and tyrosin. The formation of indol. 
Pancreatic digestion without formation of indol. 
Bile; the acid test of Pettenkofer. 
Gmelin’s test for bile pigments. 
The precipitation and resolution by bile of gastric peptones. 
The emulsion of oil in bile and pancreatic juice. 
The peristaltic movement of the intestines. 
The demonstration of the lacteals after their natural injec- 
tion with chyle. XIII. THE RESPIRATION. 
THE RESPIRATORY MECHANISM AND ITS FUNCTIONS- 
The object of the respiration is the removal from the body 
of waste products of tissue change and the renewal of oxy- 
gen to the tissues. 
This interchange of matter is brought about by the process 
of diffusion. 
The function of respiratory movement is to hasten the pro- 
cess of diffusion. 
The modification of the respiratory apparatus in different 
animals. Respiration in an amoeba; in a marine worm; in a 
fish; in an insect; in a frog; in a mammal. 
THE STRUCTURE OF THE RESPIRATORY ORGANS IN MAN- 
The trachea and bronchi; the incomplete cartilaginous 
rings; the mucous glands; the ciliated epithelium. 
The lungs; the lung alveoli; the air cells and their flattened 
lining epithelium; the capillary circulation in the lung. 
Comparison of the lungs of the batrachian, reptile and 
mammal. 
The muscular and elastic tissue of the lung. 
The topographical relations of the lungs. The pleura 
THE MOVEMENTS OF RESPIRATION. 
The lungs are extremely elastic and extensible. They are 
but semi-distended in the thorax. The pressure exerted by the 
elasticity of the lungs in man is about that of a column of mer- 
cury five millimetres high. 
The atmospheric pressure upon the inside of the lungs 
keeps them distended while in the closed chest. 
When the chest cavity is enlarged in inspiration the atmos- 
pheric pressure causes the lungs to fill the new space; and — 68 — 
when the cavity becomes smaller in expiration the elasticity of 
the lung substance causes a corresponding diminution in the 
bulk of the lungs. 
Demonstration on an artificial diagram and on a rabbit of 
the effects of the respiratory movements upon the contents of 
the chest. 
In ordinary breathing, inspiration only involves muscular 
effort, the expiration being performed by the elastic reaction of 
the parts. 
The cavity of the chest is increased vertically by the con- 
traction of the muscle of the diaphragm. The effect of violent 
contraction of the diaphagm upon the lower ribs and upon the 
abdominal viscera. 
The movements of the ribs and sternum in respiration. 
The external intercostals, the scaleni and the levatores costarum 
are the elevators of the ribs in ordinary inspiration. 
In laboured inspiration the following muscles are also called 
into play: Serratus magnus, pectoralis minor, pectoralis major, 
latissimus dorsi, serratus posticus superior, serratus posticus inferior, 
quadratus lumborum, sacro-lumbalis. 
The internal intercostals are probably muscles of ordinary 
expiration. 
In laboured expiration the abdominal muscles are the chief 
active agents. 
The action of the intercostal muscles as illustrated on Ham- 
berger’s schema. 
In the human species costal respiration is relatively most 
marked in the female, abdominal respiration in the male. 
The movements of the face and larynx in respiration. 
The rhythm of respiration. 
THE QUANTITY OF AIR IN THE LUNGS AND ITS 
VARIATION. 
After the most violent expiration the lungs still contain 
about 100 cubic inches air, called the residual air. At the end 
of an ordinary expiration the lungs contain an additional 100 
cubic inches of supplemental air. Thus there are 200 cubic — 69 — 
inches of stationary air which in ordinary breathing never leave 
the chest. In ordinary inspiration an additional 30 cubic inches 
of tidal air are drawn in. By a forced inspiration there may still 
be added about 98 cubic inches of complemental air. The full 
capacity of the lungs then is 328 cubic inches; the vital capacity 
the amount of air capable of being taken in after the most 
powerful expiration, is 228 cubic inches. These capacities are 
estimated from the lungs of a man of medium size. 
The process of gas interchange in the lungs under these con- 
ditions. 
The quantity of air breathed daily. 
The effect of respiration upon the movement of blood and 
lymph. » 
THE CHANGES OF AIR IN RESPIRATION. 
The air expired is nearly always warmer than that inspired. 
The air expired is nearly saturated with moisture. 
Oxy- 
Nitro- 
Carbonic 
gen. 
gen. 
acid. 
20.81 
79.15 
.04 
16.033 
79.557 
4.38 
Pure dried air contains in 100 vols. 
Expired air contains in 100 vols 
The expired air also contains small but important quanti- 
ties of volatile organic matters. 
The volume and weight of oxygen absorbed and carbonic 
acid given off in a day. 
Owing to its higher temperature and contained watery vapour 
the volume of air expired is greater than that inspired; but 
when dried and measured at the same temperature the air 
inspired is found to have diminished in bulk, having lost a 
greater volume of oxygen than it has gained of carbonic acid in 
respiration. 
Ventilation. The hurtful qualities of air which has been 
respired are due not so much to its carbonic acid as to the ani- 
mal matter contained in it. 
THE CHANGES UNDERGONE BY THE BLOOD IN THE 
LUNGS. 
The losses and gains of the blood in the lungs. 
The difference in color belween the venous and arterial 
blood. — 70 — 
When exposed to a vacuum 100 vols. blood give off about 
72 vols. gas, measured at 0°C. and 750 millimetres pressure. 
Arterial blood • „ „ 
100 vols. Venoug bl0Qd give 
Oxygen. Carbonic acid.Nit’og’H' 
20 50 
o 
10 60 
2 
The color of the blood of an asphyxiated animal. 
The color of the blood is due to the haemoglobin contained 
in the red corpuscles. 
Oxyhaemoglobin and reduced-hasmoglobin. Haemoglobin 
crystals. 
The amount of gas given off to a vacuum by blood is greatly 
in excess of that which could be obtained from an equal vol- 
ume of blood serum. 
The laws which govern the absorption of gases by liquids. 
The explanation of the large quantity of gas found in blood 
is the chemical union of the oxygen with the haemoglobin. 
The combination of oxygen with haemoglobin is not a stable 
one, but the gas is given off when the partial pressure of oxy- 
gen upon the blood falls below one inch of mercury. 
Comparison of the partial pressures of gases in the lung 
alveoli and in the blood. 
The carbonic acid of the blood exists chiefly in loose chemi- 
cal combination with substances in the plasma. 
The respiration of the tissues. The same laws determine 
the gas interchange in the tissues as in the lungs. 
The ratio of the amount of oxygen absorbed and of carbonic 
acid given off by the tissues in a certain time is not constant. 
During the day more oxygen is given off in carbonic acid than 
is taken up in the same time; during the night the pro- 
portions are reversed. The same relation holds for periods of 
activity and of rest. 
The amount of oxygen taken into the blood depends not 
upon the amount supplied to the lungs but upon the amount 
which has been used by the tissues. The haemoglobin of arter- 
ial blood is normally nearly or quite saturated with oxygen. 
The oxidations of the body occur not in the blood but in 
the tissues. 71 
THE NERVOUS MECHANISM OF THE RESPIRATION. 
The mixed voluntary and involuntary characters of the re- 
spiratory movements. 
The respiratory centre in the medulla oblongata. Instant 
cessation of respiratory movement follows destruction of this 
centre. 
The phrenic nerves spring from the spinal cord at about the 
level of the 4th pair of cervical nerves; the intercostal nerves 
leave the cord throughout the dorsal region. 
The coordination of the various respiratory movements. 
The effect upon the movement of cutting a nerve supplying 
any part of the respiratory apparatus. 
THE CONDITIONS UNDER WHICH THE RESPIRATORY 
CENTRE ACTS. 
The movements of respiration are remarkably susceptible 
to modification under the influence of stimuli foreign to their 
nervous centre; effect of a dash of cold water; effect of emo- 
tions. 
When any single efferent respiratory nerve is cut the part 
supplied by it remains quiescent; and when the spinal cord is 
divided below the medulla the failure in the income of oxygen 
is accompanied by an exalted action of the respiratory centre 
as shown by the more powerful action of the remaining respir- 
atory movements of the mouth parts, though these are ineffici- 
ent to aerate the blood. 
When the vagi are divided on each side of the neck the 
respiratory movements become slower and deeper, but do not 
cease. 
When the central end of the cut vagus is gently stimulated 
the respiration is quickened, and it may be so hastened that 
the respirations are fused together and the muscles come to a 
tetanic standstill in the phase of inspiration. 
The same is true, but to a slighter extent, of the inferior 
laryngeal nerve. -72- 
It is not improbable that the mere mechanical conditions of 
the lungs in the phases of expiration and inspiration excite the 
respective movements of inspiration and expiration. 
It is clear, then, that the respiratory centre is under the 
modifying control of stimuli proceeding to it along afferent 
nerves. But that the essential activity of the centre is quite 
independent of any stimulus reaching it from without. 
THE EXCITING CAUSE OF THE RESPIRATORY MOVEMENT. 
The action of the respiratory centre is determined by the 
condition of the blood supplying it. 
The centre is made active by venous blood but is not ex- 
cited by arterial blood. 
It appears to be the want of oxygen and not the excess of 
carbonic acid which stimulates the centre, as shown by the 
respiratory disturbance of an animal breathing in an atmos- 
phere of hydrogen. 
The activity of the respiratory centre is determined by the. 
direct of influence of the blood upon it, irrespective of the con- 
dition of the blood in other parts of the body. 
We may suppose that the activity of the respiratory centre 
causes an accumulation of stimulating waste products in it, 
and that the oxygen supplied by arterial blood combines with 
and renders these inert. 
The change of normal respiratory rhythm into that of 
dyspnoea. 
The breathing of dyspnoea owes its character to lack of oxy- 
gen. In ordinary dyspnoea the breathing is deeper than usual 
and the rhythm generally slower, as after section of the phrenic 
nerves. In the dyspnoea of asthma, however, the respirations 
are quicker and rather less deep than usual. 
Physiolgical apnoea is the condition of rest in the respira- 
tory centre due to excessive respiration. 
THE RHYTHMIC ACTION OF THE RESPIRATORY CENTRE, 
The respiratory discharge is probably the resultant of two 
forces, one exciting to discharge and the other resisting it. — 73 — 
Many mechanical analogies can be cited showing how, under 
similar conditions, rhythmic'action is brought about. 
The waste products of tissue change in the respiratory cen- 
tre are probably the stimuli to its discharge. 
The function of the afferent respiratory nerves is probably 
to either increase or diminish the exciting as compared with 
the resisting force in in the centre. 
The resistance theory. 
The double nature of the respiratory centre; the inspiratory 
centre; the expiratory centre. 
The phenomena and means of production of asphyxia. 
Poisoning by carbonic oxide. 
Modified respiratory movements:—yawning; sighing; cough- 
ing ; hiccough; [sneezing; laughing; sobbing. 
DEMONSTRATIONS. 
Diagram illustrating the effect upon lungs and heart of the 
respiratory movements. 
Hamberger’s schema illustrating the action of the intercos- 
t?d muscles. 
Proof of the absorption of oxygen and the production of 
carbonic acid in respiration. 
The respiratory rhythm, and the phenomena of dyspnoea, 
apnoea and asphyxia. 
The effect of stimulating the afferent respiratory nerves. 
Puncture of the nceud vital. 
XIV. THE SKIN AND ITS APPENDAGES. 
The skin consists of two layers, an outer cellular layer the 
epidermis or cuticle, and an inner layer composed chiefly of con- 
nective tissue, the dermis, cutis vera or corium. 
The hairs and nails are local modifications of the epidermis. 
HISTOLOGICAL STRUCTURE OF THE SKIN AND ITS 
APPENDAGES. 
The dermis:—its structural tissue; the papillse—their ar- 
rangement into rows; its blood vessels; tactile corpuscles and 
Pacinian bodies ; groups of fat cells. — 74 — 
The epidermis :—soft and horny epidermis; the lower layer 
of perpendicular cells; the pigmented cells of dark races; 
nerve endings; cause of the external ridges. 
The nails. 
The sudoriparous or sweat glands; the spiral opening and 
the coiled inner termination. 
Hair; the papilla and hair follicle; the hair muscles; the 
erectile tissue about the base of sensory hairs. 
The sebaceous or oil glands. 
THE SECRETION OF THE SWEAT GLANDS 
The functions of the perspiration are to remove waste mat- 
ters from the body, and to serve as a regulator of the body 
temperature. 
The conditions determining the amount of perspiration:— 
temperature; moisture of the air; exercise; nature of food. 
The quantity of sweat secreted in twenty-four hours. 
Sensible and insensible perspiration. 
The sweat is acid in reaction and owes its odour to volatile 
oils. 
Composition of the perspiration; — water; fatty acids; 
sodium chloride; urea. 
THE MECHANISM OF THE SWEAT SECRETION, 
An increased flow of blood to the skin usually attends the 
production of perspiration, but is not the cause of it. The dry 
skin of fevered patients. 
The emotion of terror may cause sweating from a pale skin 
Sweat is produced by the activity of the cells of the sudori- 
parous glands under control of the nervous system. 
Section of the sciatic nerve of the cat causes reddening of 
the balls of the feet but no sweating. Stimulation of the per- 
ipheral end of the nerve causes the secretion to appear upon 
the balls of the feet, even of a freshly amputated leg. 
Sweating as a reflex action. 
Pilocarpin excites to activity the sweat glands; atropin 
abolishes their functions. 
Absorption by the skin. 
The secretion of the sebaceous glands. — 75 — 
XV. THE KIDNEYS AND THEIR SECRETION. 
GROSS STRUCTURE OF THE KIDNEY. 
The capsule surrounding and vessels entering the kidney. 
The kilns; 'pelvis; calices. The cortical and medullary por- 
tions of the opened kidney; the papillae. The pyramids of 
Malpighi and of Ferrein. 
MICROSCOPIC STRUCTURE OF THE KIDNEY. 
The uriniferous tubules; the Malpighian corpuscles; the 
loops of Henle; the convoluted and collecting parts of the 
tubules. 
The lining cells peculiar to different parts of the tubules. 
The blood supply of the kidney; the glomeruli. ' 
THE URINE. 
The quantity secreted in 24 hours varies from 40 to 60 fluid 
ounces. 
The complementary activity of skin and kidneys. 
The color, reaction and specific gravity of urine. 
The variation of color and specific gravity. 
THE AMOUNT AND COMPOSITION OF URINE PASSED BY A 
MEDIUM SIZED MAN IN TWENTY-FOUR HOURS. (Foster’s 
Physiology). 
Water 1500.000 grammes 
Total solids 72.000 grammes 
Urea 33.180 grammes Chlorine 7.000 grammes 
Uric acid 555 grammes Ammonia 770 grammes 
Hippuric acid 400 grammes Potassium 2.500 grammes 
Pigment, fats,&c 10.000 grammes Sodium 11.090 grammes 
Sulphuric acid.. 2.012 grammes Calcium 260 grammes 
Phosphoric acid 3.164 grammes Magnesium 207 grammes 
The general nature and origin of the various substances 
found in the urine. — 76 — 
THE SECRETORY MECHANISM. 
The uriniferous tubule consist of two parts each of which 
probably serves special purposes. The thin walled capsules 
round the glomeruli probably allow rapid filtration of water and 
salts through them, while the cells lining the tubules proper 
have no doubt the function of active secretion. 
INFLUENCES DETERMINING THE AMOUNT OF THE SECRE- 
TION. 
Increased flow of blood to the kidney, bringing about a 
high blood pressure in the glomeruli, increases the amount of 
urine secreted. This may follow general rise of blood pressure 
or local dilation of the renal arteries. 
The effect of cold in constricting the vessels of the skin is 
to raise general blood pressure. 
Dilution of the blood increases the secretion. 
Stoppage of the secretion after section of the spinal cord. 
THE SECRETORY EPITHELIUM OF THE TUBULES. 
It is probable that the cells lining the tubules have the 
power of active secretion independent of blood flow. 
The passage of indigo-carmine through the renal cells. 
The injection of urea or urates excites the flow of urine. 
The process of secretion as studied in the kidney of an 
amphibian. 
The distinction between selection by the kidney cells of 
urea from the blood and the manufacture of it by them from 
certain antecedents. 
The evidences as to the part played by the kidney cells in 
the elimination of urea. 
The physiology of micturition. 
DEMONSTRATIONS. 
The secretion as collected from the ureter; the effect of 
blood pressure upon the rate of secretion. 
The effect of dilution of the blood and of the addition of 
urea to it, upon the rate of secretion. XVI. THE PHYSIOLOGY OF NUTRITION. 
The subject of nutrition is a chemical study, and it has to 
do with the changes which matters entering the living body 
undergo there. 
The waste matters of the body are at a lower chemical 
potential than the food matters, and it is believed that this 
energy difference is exactly represented by the vital force of 
the animal. 
The food matter absorbed into the body does not necessarily 
fall directly to the chemical standpoint of the wastes, but it 
probably most often reaches the condition of the latter after 
passing through a series of synthetic as well as analytic changes. 
The products of digestion must be worked over by living 
tissues before they form part of the normal blood. 
THE STRUCTURE OF THE LIVER. 
The liver is the chief seat of changes undergone by the 
digested food in its preparation for the tissues. The blood 
coming from this organ is probably the warmest in the body. 
In the embryo the liver is proportionately large, and is there 
probably the seat of the formation of blood corpuscles. In 
many lower animals the liver secretes digestive juices; among 
mammals its only secretion, and that is partly an excretion, is 
bile. 
Most of the blood of the liver is collected from the viscera 
into its portal circulation, from which the circulation in the 
hepatic arteries and capillaries is distinct. 
The division of the liver substance into lobules. 
Glisson’s capsule and the three interlobular vessels, the 
hepatic artery, the portal vein and the bile duct, inclosed by 
it. The intra-lobular, the sub-lobular and the hepatic veins. — 78 — 
The hepatic cells; granular polyhedral bodies without cell 
membrane, often containing globules of fat and masses of 
glycogen. 
The histological changes of the hepatic cells during diges- 
tion. 
The origin of the bile ducts between the liver cells. 
CONSTRUCTIVE METABOLISM OF THE BODY. 
THE PART PLAYED BY THE LIVER IN THE HISTORY OF 
GLYCOGEN. 
The liver is preeminently the organ of those chemical 
changes in the body which do not involve the formation or 
disintegration of permanent tissues. 
Glycogen may be found in considerable quantity in the 
liver cells of normal animals; it may also be extracted in small 
amounts from probably any living tissue. 
When food is withheld from an animal the quantity of 
glycogen in its liver begins immediately to diminish, and finally 
probably completely disappears. 
If food be again given, the accumulation of glycogen in the 
liver proceeds rapidly till it has reached its former amount. 
Carbohydrate foods are particularly favorable to the laying up 
of glycogen by the liver. 
The glycogen is no doubt constructed by the activity of the 
liver cells out of the food matter coming from the digestive 
tract. 
When the liver is removed from the body and allowed to lie 
in a warm place, after a time it is found that the glycogen has 
disappeared and that sugar has been produced in its place. If 
the liver be boiled while quite fresh, it is found to contain much 
glycogen but little or no sugar. When the liver is removed 
from the body its store of glycogen is turned into sugar by the 
action of a ferment, probably produced within the liver cells. 
It is probable that the glycogenetic function of the liver 
consists in the storage within the liver cells of the carbohy- —79 — 
drate moieties of the food matter in the comparatively insolu- 
ble form of glycogen. Under normal conditions this glycogen 
is transformed into soluble sugar at a certain definite rate, the 
sugar passing into the general circulation for the supply of the 
tissues. Through this function of the liver, both the overload- 
ing of the tissues with carbohydrate matter at the time of feed- 
ing and their suffering for want of it in time of hunger, are 
prevented. 
DIABETES. 
Temporary diabetes may be artificially produced in an 
animal. If a well-fed rabbit be punctured in the vaso-motor 
region of the medulla the flow of urine will be increased and 
in one to two hours it will contain considerable sugar, which 
after a day or two will have disappeared again. If the animal 
be previously starved so that the liver contains little or no 
glycogen, the urine after the operation will contain little or no 
sugar. The sugar found, then, has come from stored up gly- 
cogen. 
The obscurity of the cause of this diabetes. 
Mild and severe forms of natural diabetes and the relation 
of the nature of the food supply to them. 
FORMATION OF FAT IN THE BODY. 
The fluctuation in the quantity of fat in the body. 
Histological changes in the connective tissue corpuscle which 
is being converted into a fat cell. 
Fatty degeneration of proteid containing tissues. 
The ripening of cheese. 
The fat of the body may be produced from the metabolism 
of food matters other than fat. A greater quantity of fat may 
appear in the milk of a cow than was contained in the food of 
the animal. The amount of wax produced by bees far exceeds 
that of the fat found in the saccharine food of the creatures. 
It has been shown, in one instance, that for every 100 parts of 
fat in the food of a fattening pig, 472 parts were laid up as fat 
in the body. -80- 
Proteid foods as a source of fat. 
The fat of the living body consists of certain average pro-1 
portions of tri-olein, tri-palmitin and tri-stearin which are 
unaltered by the variation of the proportions of those sub- 
stances in the food; therefore the fat of the body is not simply 
that of the food stored up unchanged. 
THE STRUCTURE AND SECRETION OF THE MAMMARY 
GLANDS. 
Each human mammary gland is composed of a number of 
distinct lobes which are bound together by connective tissue 
containing much fat. Each lobe is farther divided into smaller 
and smaller lobules. The ductules of neighboring acini unite, 
and the ducts, from 15 to 20 in number, of the various lobes 
thus formed open separately upon the nipple. The ducts are 
dilated near their external openings so as to form small milk 
reservoirs. The ducts and the terminal acini are lined by short 
columnar epithelium. 
Fresh milk is alkaline in reaction but may become acid 
while yet in the gland ducts. Its chemical constituents are,— 
water; casein, serum albumin; fats ; milk sugar; potassium 
phosphate, calcium phosphate, potassium chloride, magnesium 
phosphate. 
The fatty globules forming the emulsion are surrounded by 
albuminous envelopes. 
Colostrum differs from ordinary milk in being deficient in 
casein and proportionately rich in albumin. 
Milk sugar is readily changed by fermentation into lactic 
acid which then causes coagulation of the casein. 
The protoplasm of the mammary gland cell probably forms 
all the organic constituents of the milk. 
Histological changes in the gland cells during lactation. 
The fats of milk are increased by proteid feeding and the 
amount of milk sugar is not dependent on the carbohydrates 
eaten. — 81 — 
THE STRUCTURE AND PHYSIOLOGY OF THE SPLEEN. 
The structure of the spleen is much like that of a lym- 
phatic gland. The organ consists of a reticular frame- 
work of bands of elastic tissue, in the interspaces of which 
rests the red-brown spleen pulp which consists of a network of 
branched connective tissue corpuscles, through the interstices of 
which oozes blood in which are found red corpuscles apparently 
undergoing destructive metamorphosis. The trabecular sub- 
stance of the spleen contains much plain muscular tissue. The 
outer connective tissue coat of the smaller arteries is frequently 
dilated into small spheroidal bodies which have the structure 
of lymph follicles, the so-called Malpighian corpuscles. 
The spleen may be extirpated without danger to the life of 
the animal. After such an operation there seems to be an 
increase in the size of the lymphatic glands and in the activity 
of the medulla of bones. 
The spleen increases in size up to about the fifth hour of 
digestion, and then diminishes again. 
The amount of blood passing through the spleen is prob- 
ably regulated by the action of the muscle fibres found in the 
trabecular tissue of the organ. 
The spleen is probably a seat of the formation of white cor- 
puscles and destruction of red corpuscles of the blood. The 
peculiar “spleen corpuscles” which contain fragments of red 
blood disks. 
The pulp of the spleen is very rich in so-called extractive 
matters. 
THE ORIGIN OF UREA. 
The living tissues are continually being wasted and restored, 
and the nitrogen of the wastes is nearly all contained in the 
urea excreted. 
Muscular tissue contains kreatin, uric acid and other crys- 
talline nitrogenous bodies, but no urea. — 82 — 
THE RELATION OF THE KIDNEYS TO THE FORMATION 
OF UREA. 
It is probable that the nitrogenous crystalline substances of 
the muscle are waste products of the tissue and in part antece- 
dents of urea. 
There is some reason to believe that the cells of the renal 
tubules may effect the conversion into urea of certain antece- 
dents of the latter which are found in the blood. 
THE RELATION OF PANCREATIC DIGESTION AND OF THE 
LIVER TO THE FORMATION OF UREA. 
The pancreatic digestion of proteids may give rise in the 
intestine to considerable amounts of leucin and tyrosin. Leucin 
injected into the alimentary canal reappears as urea in the 
urine. The liver always contains urea in its substance. It is 
not improbable that the liver cells turn into urea the leucin 
produced by excessive proteid digestion in the intestine. 
The possible chemical process by which the liver forms 
urea from leucin, as indicated by the results which follow the 
ingestion of sarcosin. 
Uric acid though less oxidized than urea is probably not an 
antecedent of the latter. Uric acid replaces the urea in the 
excrement of birds. 
The chemical functions of the liver which are indicated in 
the elimation of hippuric acid. 
STATISTICAL STUDY OF NUTRITION. 
The proportion in which the various tissues exist in the 
body. The relative diminution of the tissues during starva- 
tion. 
The history of nitrogen excretion in the urine of a starving 
animal. Luxus consumption. 
The study of the changes taking place in the body by a 
comparison of the substances entering it with those coming out 
of it. — 83 — 
The effect of nitrogenous foods on the chemical processes of 
the body. Nitrogen equilibrium. 
The Banting system of dietetics. 
The effects of fatty, of carbohydrate food and of gelatine. 
The functions of these foods as force regulators. 
The effects of salts in the food. 
It is probable that the urea excreted has at least two dif- 
ferent sources; arising in pretty definite quantities from the 
nitrogenous tissues, and also coming in fluctuating quantities 
from the decomposition of proteid matter which never forms 
part of the general tissues. 
The dietetic value of the various food stuffs. 
THE NATURE OF THE PROCESSES WHICH GIVE RISE 
TO THE BODILY ENERGY. 
The amount of energy evolved by the body is represented 
by the difference between the chemical potentials of the food 
and the waste matter and is wholly unaffected by the manner 
in which this degradation is brought about. 
In every change of matter in the body by which molecules 
are made more unstable, energy is absorbed; in every change 
in which the reverse takes place, energy is evolved. 
Those movements of the body which involve friction are 
attended with a loss of heat. The difference between the 
mechanical energy of the blood in the aorta and in the venae 
cavae must be represented by an equivalent of heat, produced 
by friction in the blood-vessels. The heat lost by radiation, 
conduction and evaporation, owes its origin to chemical 
changes in the body. 
The energy set free in the body all reappears either as heat 
or mechanical energy. 
THE ENERGY SUPPLY OF THE BODY. 
The amount of energy stored up in the various food matters 
may be determined in heat unites when these are completely 
burned. — 84 — 
The direct oxidation of the following. 
Gives rise to 
dried at 100° Centigrade: 
Gram, degree, 
Met.-Kilo 
1 gram Beef-fat 
3841 
1 gram Arrowroot 
1657 
1 gram Beef-muscle purified with ether 
5103 
2161 
1 gram Urea 
934 
Supposing that all the nitrogen of proteid food goes out as 
urea, 1 gram of dry proteid, such as dried beef-muscle, would 
give rise to about one-third gram of urea, hence : 
Gram degree, 
Met-Kilo. 
1 gram Proteid 
5103 
2161 
Less 
J gram Urea 
331 
Available energy of 1 gram of Proteid 
4368 
1850 
(Foster’s Physiology). 
THE SOURCE OF ENERGY OF MUSCULAR WORK. 
It was the belief of Liebig that the non-nitrogenous, or 
“ respiratory,” foods were oxidized in the body to maintain its 
temperature, while the nitrogenous, or “ plastic,” foods went to 
form the living tissues and that the functional changes of the 
latter gave rise to the nitrogen of the egesta. 
It is probable that muscular labor does not involve the 
destruction of the nitrogenous part of the muscle molecule. 
The amount of nitrogen excreted is not increased by muscular 
work. 
The experiments of Parkes, of Pick and Wislicenus. The 
experiments of Flint. 
The amount of carbonic acid excreted is immediately and 
greatly increased by muscular work. 
The experiments of Pettenkofer and Voit, comparing the 
oxidations of the body while in a state of rest and at work. 
The oxidations of the body occur in the tissues and not in 
the blood or the lungs. These oxidations are not immediately 
dependent upon the respiration. Excess of carbonic acid given 
off during the day and of oxygen absorbed in the night. 
The muscle molecule probably consists of an essential nitro- — 85 — 
g&noiis portion capable of adding to itself certain combustible 
non-nitrogenous matters, which latter, during functional activ- 
ity, are oxidized and give rise to free energy. 
ANIMAL HEAT. 
The energy difference between the food and waste matters 
all reappears as heat in a resting animal. During work, the 
oxidations of the body and the heat produced are increased. 
The muscles, glands and central nervous tissues are the 
chief seats of heat production in the body. 
The mechanical energy of the circulating blood finally re- 
appears as heat. 
The body temperature of different animals. 
The difference between the temperatures of difference parts 
of the body and the variation of temperature in the same part* 
The blood coming from the liver is the warmest in the 
body. 
THE MAINTENANCE OF A CONSTANT BODY TEMPER- 
ATURE. 
THE REGULATION OF THE LOSS OF HEAT. 
The loss of heat through various chanels is calculated as 
follows: 
In warming faeces and urine 2.5 p. c. 
In warming expired air 5.2 p. c.. 
In evaporating the water of respiration...14.7 p. c. 
In conduction, radiation and evaporation 
by the skin 77.5 p. c. 
The means by which the loss of heat through the lungs and 
skin is controlled. 
The perfection of this regulation as shown by the high tem- 
peratures which can be borne in a dry atmosphere. 
In some hair-covered animals the chief loss of heat is by 
means of the lungs. 
The function of the non-conducting layer of subcutaneous 
fat. — 86 — 
THE REGULATION OF HEAT PRODUCTION. 
The oxidations in the body of a warm-blooded animal are 
increased by a low surrounding temperature; those of a cold- 
blooded animal are decreased. 
This increased production of heat in warm-blooded animals 
is probably the result of a reflex action in which the activity of 
a thermogenic nerve-centre is involved. A curarised animal* 
or one whose spinal cord has been divided, shows, like a cold- 
blooded creature, diminished oxidations when the surrounding 
temperature is lowered. 
The action of the thermogenic centre increases the chemical 
changes of the tissues, leading to an excessive absorption of 
gen and evolution of carbonic acid. 
It has been made certain that the loss of heat from the 
body is under nervous control, chiefly through means of, 1, the 
vaso-motor centres; 2, the sweat centres; 3, the respiratory 
centres. 
It has been made highly probable that the production of 
heat is under the nervous control of centres which cause, 1, an 
increase of heat production; 2, a diminution of heat produc- 
tion. That is, there are probably heat producing and heat 
inhibitory nerve-centres. 
THE INFLUENCE OF THE NERVOVS SYSTEM ON THE 
NUTRITIVE PROCESSES OF THE BODY. 
Many obscure facts point to a nervous regulation of the 
nutritive processes of the body, but in no instance has such an 
action been proven. Inflammation of the cornea which follows 
section of the trigeminal nerve. Pneumonia which succeeds 
division of the vagi. 
It is at present safest to consider that the healthy nutrition 
of a part depends upon the sum total of its physiological 
actions rather than on the influence exerted by a special 
“trophic” nerve. 
DEMONSTRATION. 
Extraction of glycogen from the fresh liver, and the con- 
version, by the liver ferment, of glycogen into sugar. mi THE SPINAL CORD. 
STRUCTURE OF THE SPINAL CORD AND ACCESSORY 
PARTS. 
The spinal cord is closely invested by the vascular pm mater 
which gives rise to the connective tissue frame-work of the cord. 
Outside the pia mater is the arachnoid membrane, and 
between the two sheets of tissue is found the cerebro-spinal 
fluid. 
Surrounding the parts just described is a dense mem- 
brane, the dura mater, which is at points attached to the wall 
of the neural canal. 
The spinal cord is held in position by the spinal nerves 
entering it, and by ligaments passing from the pia mater to the 
dura mater. 
The cervical and lumbar enlargements of the cord. 
The cauda equina and the filum terminate. 
Each spinal nerve divides into two branches, the anterior 
and posterior spinal roots, just after entering the neural canal. 
All the sensory fibres of the spinal nerves enter the cord by the 
'posterior roots; all the motor fibres leave the cord by the anterior 
roots. Each posterior root bears a ganglion near the point 
of its juncture with the anterior root. 
The spinal cord is divided longitudinally on its anterior 
side by a broad shallow groove, the anterior median fissure. 
Posteriorly the cord is similarly divided by a deeper and nar- 
rower posterior median fissure, which is filled by a sheet of inflected 
connective tissue. The two sets of spinal nerve-roots enter the 
cord along tolerably definite lines, the lateral fissures. As marked 
out by these fissures, the cord may be considered to be made 
up of a pair of anterior, a pair of lateral and a pair of posterior 
columns. The posterior columns have further indicated on 
their surface a narrow posterior median column. — 88 — 
The central canal of the spinal cord, lined by cuboidal cilh 
ated epithelium. 
Running through the cord is a core of gray matter which 
has a double crescent shape in cross section. 
The nervous matter of the white substance of the cord is 
composed of medullated nerve fibres; that of the gray sub‘ 
stance is made of nerve cells, and nerve fibres chiefly without the 
fatty sheath. 
The variation in form and mass of the gray matter in dif- 
ferent parts of the cord. The gelatinous substance in the pos- 
terior cornua. 
The shape and distribution of the nerve cells and the con- 
nection of nerves with them. 
The anterior white commissure and the gray commissures. 
Most, if not all, the nerve fibres reaching the spinal cord 
sooner or later enter its gray substance. 
The nervous elements of the cord are intimately bound and 
supported by a connective tissue frame-work. The neuroglia. 
THE SPINAL CORD AS A CENTRE FOR REFLEX 
ACTIONS. 
The spinal cord contains nervous centres capable of sending 
out nervous discharges which may stir up complicated, coor- 
dinated and adaptive movements. 
These movements are never initiated in the cord, but are 
brought about by impulses reaching the cord from without; 
that is, they are not spontaneous, but reflex in character. 
The stimulation of the terminal organs of the afferent 
nerves is much better adapted for arousing reflexes than the 
direct stimulation of a nerve trunk. 
The nerve cell requires time to cause an efferent nervous 
discharge after having received an impulse from an afferent 
nerve. The reflex nerve cell is readily excited to action by a 
succession of distinct impulses reaching it, but rarely by a 
single one. 
The inhibition of a reflex action may be occasioned by the 
strong stimulation of any afferent nerve, or by the influence -89- 
of nerve centres in the brain or spinal cord other than the 
reflex centre. 
The peculiar movements of a mammal with divided spinal 
cord. 
The spinal cord has no power of learning to adapt its activ- 
ities to new conditions. 
In a certain sense the spinal cord may be looked on as a 
servant of the centres of intelligence which has learned, under 
their instruction, to carry out alone certain oft repeated ac- 
tions. 
There is no evidence of the spinal cord possessing a con- 
scious intelligence. 
THE SPINAL CORD AS A COLLECTION OF AUTOMATIC 
CENTRES. 
One of the functions of the spinal cord, probably, is to act 
nearly independently by means of special centres whose duty it 
is to preserve the organic welfare of the body, and whose pow- 
ers in part are, no doubt, automatic. The nervous control of the 
sphincter muscles of the body; the sexual centres; muscular 
tonicity; subsidiary vaso-motor centres. 
THE PATHS OF CONDUCTION IN THE SPINAL CORD. 
We usually have conscious sensation of the impulses reach- 
ing the spinal cord; in such cases the impulses must be trans- 
mitted to the brain. 
We cannot suppose that all the nerve fibres entering the 
cord are individually represented by fibres passing to the brain 
in that organ, for the number of nerve fibres in the spinal cord 
is not great enough to admit of this. 
We may suppose that the fibres, or most of them, from the 
periphery on the one hand and from the brain on the other, 
are connected with certain nerve centres in the gray matter of 
the spinal cord, by whose mediation impulses reaching the 
cord from many different sources may be sent out of it 
bv a single channel, or conversely. In this sense the nerve cen- — 90 — 
tres of the cord act as relay stations for the transmission of 
impulses reaching them from any quarter. 
The segmental distribution of the gray matter in the cord. 
The area of gray matter in a cross section of the cord rises and 
falls with the sectional area of the nerve fibres entering the 
cord at that level. 
It has been attempted to determine the anatomical and 
physiological grouping of the nerve fibres of the spinal cord, (1) 
by a study of the direction in which cut fibres degenerate; (2) 
by the different periods at which various collections of the 
fibres assume the medullary sheath; (3) by pathological data; 
(4) by observation of the results following physiological exper- 
iment. 
All impulses, whether sensory or motor, passing between 
the brain and the body at large cross the middle line and end 
in the side opposite to that in which they originated. 
This decussation occurs at the level of, and below the pons 
varolii. 
Sensory impulses probably cross to the opposite side lower 
down in the spinal cord than do the volitional impulses. 
Volitional impulses cross most largely in the medulla and 
travel along the cord in the lateral, and perhaps anterior, col- 
umns and enter the nervous centres of the anterior cornua o 
the gray matter of the cord, whence they emerge in the anterior 
spinal roots. 
Sensory impulses reaching the cord, enter the posterior cor- 
nua of its gray matter or its posterior white columns, and soon 
crossing, proceed to the brain chiefly in the lateral columns. 
The most marked results of lateral hemi-section of the spinal 
cord is a paralysis of voluntary motion and hypersesthesia on the 
same side below the injury, with a loss of sensation on the op- 
posite side; probably neither of these effects is complete. 
The functions, sensory and motor, which are abolished by 
a hemi-section of the cord may be gradually recovered without 
reunion of the divided parts. 
Purely tactual, and painful sensory impulses probably pass 
through the cord along different paths. — 91 — 
The gray matter of the cord can no doubt conduct in any 
direction the impulses which reach it. 
DEMONSTRATIONS. 
Comparison of the reflex actions obtained by stimulating 
the skin and a nerve trunk of a beheaded frog. 
The purposeful character of reflex actions. 
The summation of stimuli in the spinal cord. 
The inhibition of reflex action in a frog, (a) through the 
strong stimulation of an afferent nerve; (b) through stimulation 
of the optic lobes. 
XVIII. THE BRAIN. 
THE MEDULLA OBLONGATA. 
The medulla, besides being the pathway of nerve fibres con- 
necting the brain and spinal cord, contains a number of auto- 
matic and reflex nerve centres which especially preside over 
the organic” functions of the body. Among the nerve centres 
are included,—a respiratory centre; a cardio-inhibitory cen- 
tre ; a diabetic centre; a vaso-motor centre; centre for degluti- 
tion; centre for reflex secretion of saliva; a vomiting centre; 
centre for movements of oesophagus and stomach; and probably 
centres for the coordination of movements of the body. 
The medullary centres, though capable of independent 
action, are no doubt normally under the influence of other sim- 
ilar centres in higher parts of the brain. 
THE CHANGES PRODUCED IN AN ANIMAL BY THE 
REMOVAL OF ITS CEREBRUM. 
A frog or a pigeon bears well the extirpation of the cere- 
brum, but a mammal sooner or later succumbs to such an oper- 
ation. 
The loss of the cerebrum involves the loss of spontaneous 
movement; an animal without that organ stirs only in answer 
to a stimulus. — 92 — 
With the loss of its cerebrum an animal appears to lose its 
faculty of perception and its power of forming judgments. The 
deterioration of the animal is in its psychical powers. 
The aspects of a frog and of a pigeon after removal of the 
cerebral lobes are nearly normal. Food is not voluntarily 
taken, though it is swallowed when placed in the mouth. No 
sign of fear can be aroused. 
The most complex cobrdinated movements may still be 
carried out. The balancing and swimming of a frog, and the 
flight of a pigeon whose cerebral hemispheres have been removed. 
Such an animal appears to retain its normal sensations. A frog 
deprived of its cerebrum avoids obstacles in leaping. 
The same general results follow the destruction of the cere- 
brum in a mammal. A rabbit or a rat so treated ceases to 
notice food. Its gaze is attracted by a moving light, and it may 
utter plaintive cries and leap on being stimulated. Its sensa- 
tions are preserved but its perceptions are lost. 
THE LOCALIZATION OF FUNCTION IN THE 
CEREBRUM. 
THE STRUCTURE OF THE CEREBRUM. 
The interior of the cerebral hemispheres is chiefly composed 
of masses of nerve fibres which terminate in the cortex. The 
nerve cells of the cerebrum are contained in the cortical sub- 
stance, a thin sheet of gray matter which overlies the convo- 
luted surface of the hemispheres. 
In general, the cerebrum may be considered to be the seat 
of thought, of consciousness, and of will power. 
It is not certain whether the manifold functions of the cere- 
bral cortex are separately localized in the various convolutions, 
or whether the whole brain is to be regarded as a complicated 
machine in which the activity of one part involves that of all 
the rest. 
The effect of gradual removal of a pigeon’s brain is a grad- 
ual loss of psychical power in the animal. — 93 — 
In certain pathological conditions, as in the disease aphasia, 
there is strong suggestion of a localization of function in the 
cortex. 
There may be produced in an animal definite movements or 
signs of sensation, as a result of the electrical stimulation of 
well defined areas of the cerebral convolutions. Mechanical or 
chemical stimulation of the cortex is not followed by positive 
results. 
Removal of a “motorarea of the cortex is said by some to 
be followed by a loss of voluntary control over the muscles for- 
merly excited by the stimulation of that area. Removal of a 
“sensory ” area is said in like manner to involve a loss of the 
appropriate sensations. 
The results supporting the theory of localization, as ob- 
tained in the experiments of Fritsch and Hitzig, of Ferrier and 
of Munk. 
The nature of the phenomena brought out by artificial 
stimulation of the cortex, and of those which follow the extir- 
pation of various areas. 
There is a gradual recovery from the motor paralysis or 
loss of sensation which follows removal of a limited area of the 
cortex. 
In this recovery the function of the lost part has not been 
assumed by any definite homologous area in another part of 
the brain. 
According to the experiments of Goltz, there is no distinct 
localization of function in the cerebral cortex; but a grad- 
ual loss of psychical power, of sensation and of definite volun- 
tary motion follows extirpation of any part of the cerebral 
convolutions in the dog, and these disturbances are more ex- 
tensive and less readily recovered from, the more widespread 
the lesion. 
After suffering such an operation an animal responds in 
a reflex manner to stimuli much more readily than usual. 
Parts of the brain below the cerebrum are no doubt capa- 
ble of carrying out independently complicated activities in which 
simple sensations are involved. — 94 — 
The difference between psychoses and neuroses. 
Cerebral “ reaction time.” 
THE CORPORA STRIATA AND THE OPTIC THALAMI. 
The so-called “ basal ganglia ” are masses of gray tissue con- 
taining many nerve cells. Most of the fibres of the crura 
cerebri pass into the basal ganglia before proceeding to the cor- 
tex of the brain. The anterior fibres of the peduncles enter 
the corpora striata and the posterior fibres join the optic that- 
ami, before continuing into the cerebral substance. The nerve 
fibres which enter the basal ganglia are no doubt largely con- 
nected with nerve cells found there. 
When a lesion involves both the corpus striatum and optic 
thalamus of one side, there is loss of voluntary motion and of 
sensation on the opposite side of the body, without necessary 
impairment of intellectual faculties. 
It probable that the basal ganglia act as sets of relay sta- 
tions which mediate between the cerebral cortex and nervous 
centres in lower parts of the brain and spinal cord. 
There is some reason to believe that the corpora striata are 
chiefly concerned in the modification of volitional impulses 
passing to it from the cerebral convolutions; and that the optic 
thalami receive the sensory impulses before they proceed to the 
surface of the brain. 
Injury to the optic thalami is followed by blindness or 
imperfection of vision. 
THE CORPORA QUADRIGEMINA. 
These bodies correspond to the corpora bigemina, or optic 
lobes, of the frog and pigeon. 
The nervous centres for the coordination of the movement 
of the eyeballs with the contraction of the pupils lie in or 
below the anterior half of the corpora quadrigemina. 
The manner in which the actions of these centres are asso- — 95 — 
ciated; when the visual axes are converged the pupils contract, 
when the axes becomes parallel the pupils dilate. 
Movements of the opposite eye are brought about by the 
stimulation of the corpora quadrigemina on one side. 
Extirpation of the corpora quadrigemina, or of the optic 
lobes, on one side produces blindness in the opposite eye. 
The seat of visual sensations appears to be in the corpora 
quadrigemina, but visual perceptions are lost when the cerebral 
cortex is destroyed. 
Other physiological functions, as that of respiration, proba- 
bly are regulated by special centres situated in the corpora 
quadrigemina. 
THE CEREBELLUM. 
The structure of the cerebellum and the manner of its asso- 
ciation with the rest of the brain. 
The chief function of the cerebellum is to serve as a collection 
of nerve centres whose action maintains the equilibrium of 
the body and coordinates its movements. 
Lesions of the cerebellum artificially produced are followed 
by unsteadiness of gait, and when a large amount of nervous 
substance is lost complete failure of coordination is the result. 
Lateral lesions produce more effect than those established in 
the median line. 
Extensive asymmetrical injury of the cerebellum, as of sec- 
tion of the middle peduncle on one side, produces remarkable 
forced movements of the animal, together with a peculiar rolling 
back and forth of the eyes. 
Section of one of the crura cerebri is also followed by forced 
movements, as also are injuries of the corpora striata and optic 
thalami, or even of the cerebral cortex alone. 
The passage of a galvanic current through the back part of 
the head produces a sensation of giddiness and a rolling 
motion of the eyes. 
There is no reason to believe that the cerebellum is con- 
nected with the sexual functions. The special sexual centres 
appear to be situated in the lumbar region of the spinal cord. 96 
THE SEMICIRCULAR CANALS AND THEIR RELATION 
TO THE MAINTENANCE OF THE EQUILIBRIUM 
OF THE BODY. 
THE STRUCTURE OF THE SEMICIRCULAR CANALS. 
The planes of the three membranous canals lie approxi- 
mately in the three dimensions of space. 
The ampullar enlargement of each canal and the modified 
termination of the filaments of the auditory nerve within it. 
The cavity of each canal communicates with that of the 
utricle. 
The whole membranous labyrinth is filled with endolymph. 
THE EFFECT OF CUTTING THE SEMICIRCULAR CANALS IN 
A PIGEON. 
When one of the semicircular canals of a pigeon is divided, 
remarkable disturbances of equilibrium immediately follow. 
When one of the horizontal canals is cut the head moves from 
side to side; when one of the vertical canals is operated on the 
movement is up and down. These disturbances of equilibrium 
become more marked when a number of canals is divided, and 
the animal places its head in unusual positions with respect to 
to the body. Gradual recovery takes place if but one or two 
canals be injured. 
Injury of the semicircular canals of the mammal is fol- 
lowed by the same general results as in the case of the pigeon. 
These results are not due to partial muscular paralysis, nor 
probably to unusual auditory sensations. 
THE SENSE OF EQUILIBRIUM. 
The maintenance of the equilibrium of the body requires 
the coordinated activity of complicated nerve-muscular mech- 
anisms. The afferent impulses which determine the action of 
this motor apparatus, may arrive from different sources. 
The body must know its position in reference to surround- 
ing objects in order to maintain its equilibrium. Such a knowl- 
edge of the body’s position may be attained through visual sen- 
sations, tactile sensations and muscular sensations. — 97 — 
But it has been shown that a person may be conscious of a 
change of position without the excitement of any of the foregoing 
sensations. The impulses which bring this information are 
supposed by some to arise in the semicircular canals. It is 
possible that movements of the body may cause a change of 
pressure of the endolymph within the semicircular canals upon 
the nervous mechanisms there, the intensity of excitement in 
each ampulla depending upon the direction of the movement. 
The truth of this hypothesis is not established. 
The various means by which vertigo may be produced. 
THE CRURA CEREBRI AND PONS VAROLII. 
These bodies contained considerable gray matter, but the 
chief functions we can ascribe to them are those in which they 
serve as connecting links between different parts of the central 
nervous system. Marked disturbance of equilibrium follows 
injury of either the crura cerebri or the pons varolii. 
THE BLOOD SUPPLY OF THE BRAIN. 
The amount of blood supplied to the brain is, in proportion 
to the size of the organ, probably small. 
When the brain is exposed it is found to undergo rhythmic 
alterations of volume occasioned by the heart beats and respir- 
atory movements. 
During its periods of activity the brain appears to receive 
more blood than when at rest. 
Owing to the rigid cranial envelope sudden variations of the 
amount of blood in the brain subject its substance to such 
changes of pressure as may affect the consciousness. 
The blood supply of the brain is no doubt under elaborate 
vaso-motor regulation. 
DEMONSTRATIONS. 
The phenomena exhibited by a pigeon and by a frog after 
removal of the cerebral hemispheres. 
The phenomena of “forced movements.” 
The effects following section of the semicircular canals in 
the pigeon and the frog. XIX. THE EYE AND SIGHT. 
The anatomical mechanism whose excitement gives rise to 
a simple sensation consists of (1) a peripheral “sense organ,” 
(2) an afferent nerve, (3) a central nerve-cell organ. 
It is only the activity of the central organ which directly 
affects consciousness. It is often difficult to determine in which 
part of the sense apparatus the disturbance which gives rise to 
a sensation originates. 
Specific nerve energy. 
The difference between simple sensations and judgments. 
THE STRUCTURE OF THE EYE AND PARTS NEAR IT. 
The small third eyelid which represents the nictitating 
membrane of some animals. 
The perforated lachrymal papillae. The lachrymal gland. 
The Meibomian glands. 
The six muscles for the movement of the eyeball. 
The eyeball. The oblique entrance of the optic nerve. The 
sclerotic coat and cornea continuous with it. The radius of cur- 
vature of the cornea is smaller than that of the remaining sur- 
face of the eyeball. The choroid coat; its blood-vessels, pigment- 
cells and ciliary processes. The iris) its inner circular and outer 
radial plain muscle fibres; its vessels, nerves and pigment. 
The ciliary muscles. The crystalline lens; its suspensory liga- 
ment. The vitreous humour and hyaloid membrane. The aqueous 
humour. The anterior and posterior chambers of the eye. The 
canal of Schlemm,. The retina; the ora serrata; the macida lutea 
and fovea centralis; the blood-vessels of the optic nerve and 
their distribution in the retina. 
Commencing at its anterior surface there may be recognized 
in the human retina ten distinct layers; (1) Membrana limi- 
tans interna; (2) layer of nerve fibres; (3) layer of nerve cells; — 99 — 
(4) inner molecular layer; (5) inner nuclear layer; (6) outer 
molecular layer; (7) outer nuclear layer; (8) membrana lim- 
itans externa; (9) layer of rods and cones; (10) layer of tessel- 
lated, pigment-holding cells. 
The macula lutea or yellow spot is free from blood-vessels 
except at its margin. The blood-vessels of the retina 
ramify in the nerve fibre layer and their capilarlies do not 
extend outward beyond the inner nuclear layer. 
-The fovea centralis contains only the retinal cones, the rods 
being there absent. 
The pigment-free part of the choroid which forms the tapetum 
in some animals. 
THE EYE AS AN OPTICAL INSTRUMENT. 
When a ray of light falls on the retina we become conscious 
of a sensation of light. 
In order that we may become aware of the form of a dis- 
tant object an image of it must be thrown upon the retina. 
The eye is a camera made up of a dark chamber to which 
the light is admitted through a diaphragm, the iris; two refract- 
ing media, the cornea and crystalline lens, intercept the light 
before its entrance into the retinal chamber. 
The refracting power of a lens depends (a) upon the curva- 
ture of its surface, (&) upon the refracting power of its sub- 
stance. 
The foci of all the refracting media of the eye fall upon an 
optic axis which meets the retina a little above and inside of the 
fovea centralis. 
We may calculate the path of all oblique rays entering the 
eye by assuming that they meet the optical axis at a “ nodal ” 
point and leave the axis in a direction parallel to the 
first from a second nodal point. The nodal points are near 
together on the optical axis within the lens. 
The refraction of a ray of light entering the eye occurs chiefly 
at the anterior surface of the cornea and at the anterior and pos- 
terior surfaces of the lens. 
When the head is plunged under water the refraction by —100 — 
the cornea is nearly done away with; hence the marked com- 
pensatory curvature of the fish’s lens. 
The anterior and posterior surfaces of the cornea being 
nearly parallel, they may be regarded as one. 
The refractive powers of the aqueous and vitreous humours 
being nearly the same as that of the cornea, we may regard the 
refracting surfaces of the lens as three, the anterior surface of 
the cornea, the anterior and posterior surfaces of the lens. 
It is calculated that the focus of the refracting media of the 
eye lies, for parallel rays, 14.647 mm. behind the posterior sur- 
face of the lens and 22.647 mm, behind the anterior surface 
of the cornea. 
ACCOMMODATION. 
The focal distance at which a distinct image of an object 
may be formed by light passing through a refracting surface, 
the refractive index remaining the same, depends, (a) upon the 
curvature of the surface, (b) on the angle which the entering 
rays form with it. In order that an image which is thrown 
upon a certain fixed plane may remain distinct when one of 
those factors is changed, the other factor must undergo a com- 
pensatory change. 
If this accommodation is not brought about, the image is 
replaced by a series of blurred “diffusion circles.” 
Accommodation in the human eye as illustrated by “Schei- 
ner’s experiment.” The near limit of distinct vision. 
In the normal or emmetropic eye, the near limit is at a dis- 
tance of ten to twelve centimetres; the far limit may be 
regarded as at an infinite distance. In the short sighted or 
myopic eye the near limit is brought within five to six centi- 
metres distance of the cornea and the far limit at a variable 
but not considerable distance. In the far-sighted or hyperme- 
tropic eye, the near limit of distinct vision is some distance away 
and a far limit does not exist. In the three cases, an image 
formed by rays parallel to the optical axis falls respectively on 
the retina, before it and behind it, — 101 — 
THE APPARATUS OF ACCOMMODATION. 
While at rest, the eye is accommodated for objects at an 
extreme distance. 
In accommodating for near objects two movements may be 
observed in the eye, (1) a narrowing of the pupil, (2) a change 
in the curvature of the anterior surface of the lens by which it 
become more convex. 
In its normal condition the lens is an elastic body whose 
curved surfaces are somewhat flattened by the pressure of the in- 
closing suspensory ligament which is kept stretched by its attach- 
ment to the choroid. When the ciliary muscles contract, the 
choroid is pulled forward and the suspensory ligament is slack- 
ened, thus allowing the anterior surface of the lens to bulge 
outward. 
THE MOVEMENTS OF THE PUPIL. 
The pupil is contracted when light falls upon the retina, but 
is dilated in the dark. It is contracted when we accomodate 
for near objects, but it is dilated when we accommodate for 
distant ones. It is contracted when the optical axes converge 
and dilated when they become parallel. 
The contraction and dilation of the pupil are active move- 
ments brought about respectively by the circular and the radial 
muscular fibres of the iris. 
These movement of the pupil are the result of reflex and 
associated actions. When the movement is brought about by 
light falling upon the retina, the optic nerve is the afferent 
nerve of the reflex apparatus; the third or oculo-motor nerve is 
the efferent nerve whose excitement causes contraction, and 
the sympathetic is the efferent dilator nerve. 
There is union between the reflex centres for movement 
of the pupils; for subjecting one eye to changes of illumination 
produces movement of the opposite pupil. 
The action of drugs upon the pupil, as of atropin or physo- 
stigmin, is probably wholly local, -102- 
DEFECTS OF THE EYE AS AN OPTICAL APPARATUS. 
The special defects of the myopic, hypermetropic and pres- 
byopic eye. 
The spherical aberration due to the form of the lens is prob- 
ably insignificant in comparison with other optical defects of 
the eye. The refractive power of the lens varies in different 
parts of it. The most obvious use of the iris is to diminish 
spherical aberration by cutting off circumferential rays. 
When light passes though a spherical lens it can throw a 
well defined image of larger dimensions upon a curved surface, 
like that of the retina, than upon a plane surface. 
The refracting surfaces of the eye are not perfect sections 
of a sphere, but are often more convex along one meridian 
than another. Hence, lines having different directions cannot 
all be brought simultaneously to focus on the retina. This 
leads to the defect known as astigmation. 
Methods of determinating the chromatic aberration of the eye. 
Entoptic phenomena.—Floating particles in the vitreous 
humour, the muscse volitantes. Imperfections in the lens. Tears 
on the cornea. The observation of the margin of the pupil. 
The luminosity and the floating coloured clouds of the retina. 
The refracting surfaces of the eye are not centred on the 
optic axis. 
SENSATIONS OF VISION. 
The part of the retina which is directly excited by light is 
the posterior layer of rods and cones. 
The optic nerve itself is nnirritable towards light. The 
blind spot. The shadows of the retinal blood-vessels seen as 
Purkinje’s figures. 
The amount of energy contained in a luminous wave may 
be exceedingly small. 
The movement of pigment in the retinal epithelium under 
the influence of light. 
The retinal pigments which are altered by light. 
Both rods and cones are probably directly irritated by light; 
in certain animals the first and in others the second of these —103 — 
elements seems to be absent. It has been conjectured that rods 
serve chiefly to give mere sensation of light, while the cones 
are adapted to permit of distinctness of vision. 
The alternate spontaneous blindness of the two eyes. 
Temporary blindness produced by pressure on the bulb. 
THE RELATION OF THE DURATION AND STRENGTH OF THE 
STIMULUS TO THE SENSATION. 
The sensation produ ced by a momentary flash of light has 
a much longer duration than the stimulus itself, when single 
flashes follow each other sufficiently rapidly the separate sen- 
sations are fused. The intervals between the flashes must be 
smaller the stronger the light in order that the separate sensa- 
tions may be completely fused. The duration of the “ after- 
image” is longer the stronger the light which caused the sen- 
sation. 
The intensity of sensation varies with the intensity of illu- 
mination; but the relation of the variation of the intensities 
is not a sinple one. 
Weber’s law.—The increase of stimulus which is necessary 
to produce the smallest increase of sensation bears always the 
same proportion to the whole intensity of the stimulus which 
has already been applied. 
THE DISTINCTION AND FUSION OF SIMULTANEOUS SENSA- 
TIONS. 
Two objects appear as one if brought near enough together. 
In order to appear as two objects, the distance between their 
images on the retina must not be less than the diameter of a 
single retinal cone. In the human eye objects thrown thus 
near together in the fovea of the retina may still be distin- 
guished apart. Tow ard the periphery of the retina the dis- 
tinction is not nearly as fine. 
Cause of the broken outline of fine lines which are drawn 
close together. 
The distinction between cerebral and retinal visual areas. — 104 — 
The number of cones in the retina is much greater than 
that of the fibres in the optic nerve. 
COLOUR SENSATIONS. 
Besides the sensations of white and black, we may attain 
certain sensations of colour, the quality of each of which is 
determined by the wave length of the incident light. The 
spectral colours are red, orange, yellow, green, blue, violet. The 
fusion of blue and red produces another simple color, purple, 
not found in the spectrum. 
All the hues of nature may be imitated by the proper 
fusion of the primary color sensations with each other or with 
white or black. 
The origin of browns, and olive greens. Various methods 
and the results of mixing simple colour sensations. 
The cause of the difference between the sensation obtained 
by the mixture of two colours on the retina and that derived 
from the mixture of the pigments themselves. 
A colour is said to be more or less saturated according as it 
contains less or more of white light. No colour is absolutely 
saturated. 
Every colour which is sufficiently illuminated appears white. 
Colour sensation produced by electric stimulation of the eye. 
Gray is a mixture of white and black. 
Complementary colours are those which, when mixed on the 
retina, produce the sensation of white light. 
The following are complemetary colours;—Red and green- 
blue; orange and cyan-blue; yellow and ultramarine-blue; 
greenish-yellow and violet; green and purple. 
Any three colours, situated in the spectrum as far apart as 
possible, may, in proper porportions, together produced white; 
by varying the proportions, all of the other spectral colours 
may be derived from the three primary colours. 
The Hexing theory of colour sensation. 
The Young-Helmholtz theory of colour sensation. — 105 — 
AFTER IMAGES. 
The sensation of light lasting longer than the stimulus, an 
object may still be seen for a time after its removal from the 
field of vision; such sensations are known as after images. The 
after image is at first positive, or of the same brightness and 
colour as the stimulus ; soon it becomes negative, or of brightness 
and colour complementary to the original stimulus. 
Explanation of changes in after images as a result of retinal 
fatigue. I 
The successive fading of the colours of an after image. 
The intrinsic light of the retina. 
COLOUR BLINDNESS. 
Some persons are incapable of acquiring certain colour 
tions. The most common form of the defect is that of “red- 
blindness.” To persons suffering from it, the colours rose-red 
and bluish-green are identical. They distinguish in the spec- 
trum but two colors, calling th em yellow and blue; under the 
yellow they include the red, orange, yellow and green, and blue 
and violet are called blue. 
About 5 p. c., of the population are affected to some degree 
with red-blindness. 
Temporary c olour blindness induced by wearing coloured 
glasses, and by the ingestion of santonin. 
A rarer form of colour-blindness is said to occur in which 
the sensation of red is preserved, but that of green is lost. 
The demonstration of the yellow pigment of the macula lutea. 
The perception of the mosaic of rods and cones of one’s 
own retina. 
In the w aning twilight the red disappears first and the blue 
last; hence, red objects first become dark. 
The psychical effects produced by viewing a landscape 
through differently coloured glasses. 
VISUAL PERCEPTIONS. 
The mind derives ideas from simple visual sensations; sen• 
sations give rise to visual perceptions. — 106 — 
The perception of the positions of objects. The localization 
of objects by vision is a subjective process. The images of 
objects are inverted on the retina. 
Distinctness of vision diminishes from the centre to the per- 
iphery of the retina, as does also the appreciation of colour dif- 
ferences. 
MODIFIED PERCEPTIONS 
Irradiation: bright objects appear larger than dark ones of 
the same size. 
Simultaneous contrast: light and dark surfaces appear res- 
pectively brighter and darker when viewed together. The phe- 
nomena of coloured shadows. When a piece of gray paper is 
laid on a coloured surface and covered with tissue paper, the 
gray slip appears to have a colour complementary to that of 
the surface. 
The blind spot is not perceived chiefly because no sensation 
is aroused by it. 
The retina itself gives rise in the dark to luminous sensations. 
Instrinsic coloured images of the retina. Lights produced 
by pressure on the eyeball. Effect of stimulating the eye or 
optic nerve.- 
Visual judgments of size. The only method of determin- 
ing the relative size of objects is the comparison of the magni- 
tude of their images thrown upon the retina; our estimation of 
their real size depends upon the distance from the eye at which 
they are believed to be situated. This distance seems greater 
when sub-divided by intervening objects; the apparent size of 
the moon in mid-sky and on the horizon; comparison of the 
lengths of two equal lines, one of which is sub-divided and the 
other not; the greater apparent size of objects in a fog. The 
appreciation of difference of size by contrast. 
Judgments of the magnitude of angles. 
VISION WITH TWO EYES. 
In general, the reason why an object viewed with two eyes 
appears single is that the image of each point on it falls upon — 107 — 
“ corresponding ” or “ identical ” areas of the two retinas. Points 
on the inner side of one retina have their corresponding points 
on homologous parts of the outer side of the other. 
MOVEMENTS OF THE EYEBALL. 
The orbit and the eyeball form a ball and socket joint, the 
centre of rotation being 1.8 mm. behind the centre of the eye. 
The reflex fixation of external objects which keeps the eye- 
balls at rest when the head is moved. 
The “ primary ” and “ secondary ” positions of the eye. The 
position of the resting eye. 
The rotation of the eye around its visual axis when the lat- 
ter is changed from a primary to an oblique position. 
The muscles of the eyeball and the movements brought 
about by their action. 
The coordination of the movements of the eyeball. The dou- 
ble images that result when the coordination centre fails to act. 
Apparent rotation of toothed wheels brought about by the 
rinsing motion. 
False judgments of motion. 
THE HOROPTEI 
Distinct vision of objects can be had only when the images 
of their parts fall upon corresponding points of the two retinas. 
In any given position of the visuah$axes such corresponding 
points are projected outward upon some definite line or surface 
and this line or area of distinct vision is known as the horopter. 
The horopter changes its form or position with changes of direc- 
tion of the visual axes. When standing erect and looking 
toward the horizon the ho ropter is upon the ground before the 
eyes. The precautions n ecessary in walking upon a hillside, or 
upon a level while looking through a prism. 
THE JUDGMENTS THAT ARISE FROM BINOCULAR 
VISION. 
By means of the movements of the two eye-balls and the 
images falling upon corresponding point of the two retinas, we — 108 — 
are enabled to form certain judgments concerning the form 
size and distance of objects. 
Illustrations of the judgments concerning size and distance 
as depending upon the “muscular sen se” of innervation of the 
eye-muscles. 
When a solid object is viewed the images falling upon the 
two retinas cannot be identical; they, however, do not give rise 
to double vision, but are fused in the cerebrum so as to give 
the perception of single solid objects. The shading of an object 
largely assists in the formation of a judgment of its solidity. 
Applications of the stereoscope. 
When two different colours or white and black are viewed 
at the same time each by one eye, there is not a fusion of colour 
in the sensation but an alternate mastery one and the other. 
The action of the accessory glandular and muscular mech- 
anisms of the eye. 
The reflex secretion from the lachrymal glands and the aid 
rendered by winking movements to the emptying of the lachry- 
mal canals. 
DEMONSTRATIONS. 
Schemer’s experiment. Observation of the movements of 
the pupil. Astigmatism. The blind spot. Purkinje’s figures. 
The mixture of colours upon a rotating disc. Complementary 
colours. After images. Tests for colour-blindness. The yellow 
spot. Irradiation. Simultaneous contrast. Judgments of 
distance. Judgments of motion. The stereoscope. 
XX. THE EAR AND HEARING. 
THE STRUCTURE OF THE EAR. 
The organ of hearing may be considered to be made up of 
three parts;—an external ear, composed of the pinna and audi- 
tory meatus, the latter being separated by the tympanic mem- 
brane from the middle ear or tympanum. The tympanum 
contains the auditory ossicles, malleus, incus and stapes, and — 109 - 
its cavity opens upon the upper wall of the pharynx by means 
of the Eustachian tube; an internal ear, consisting of a mem- 
branous labyrinth, to which the auditory nerve is distributed, 
which is contained within a bony labyrinth; the two labyrinths 
are filled with fluid known respectively as the endolymph and 
the perilymph. The division of the bony labyrinth into vesti- 
bule, semicircular canals and cochlea. The fenestra rotunda and 
fenestra ovale are placed in the bony wall separating the tym- 
panum respectively from the scala tympani of the cochlea, and 
from the vestibule. The membranous vestibule is composed of 
two sacs, the saccule and utricle, whose cavities are indirectly 
united. The membranous semicircular canals spring from the 
utricle, and the cavity of the saccule is continuous with that of 
the membranous canal of the cochlea. The auditory hair-cells 
upon the maculse of the vestibular sacs and on the cristse of the 
ampullae of the semicircular canals. The otoliths within the 
sacs and canals. 
The microscopic structure of the membranous cochlea and 
of the organ of Corti contained in it. 
THE SPECIAL FUNCTIONS OF THE PARTS OF THE 
ACOUSTIC APPARATUS. 
THE PINNA OR EXTERNAL EAR. 
The modification of the concha in different animals. Its 
purpose is to collect the waves of sound from the external air. 
THE MEMBRANA TYMPANI. 
The curved surface and funnel-shape of the tympanic mem- 
brane. This membrane is easily set vibrating by air waves, 
and has no fundamental note of its own. Its peculiar shape 
adapts it for transmitting motions of great amplitude and small 
energy as motions of small amplitude and great energy. 
The movements of the auditory ossicles. The ossicles form 
a sort of compound lever by which the oscillations of the tym- 
panic membrane are exactly transferred to the membrane of the — 110 — 
fenestra ovale, but with diminished amplitude and correspond- 
ingly increased force. 
The tensor tympani muscle serves by its contraction to pre- 
vent the tympanic membrane being pushed out too far. 
The laxator 'tympani muscle probably by its contraction 
causes the ear-drum to move outward. 
The stapedius muscle probably acts to prevent the stapes 
being driven too far into the fenestra ovale. 
THE EUSTACHIAN TUBE 
This channel connecting the middle ear and the pharynx 
serves to keep the pressure within the tympanic cavity equal to 
that of the atmosphere. The tube is probably only opened 
during the act of swallowing. 
THE GENERATION OF AUDITORY SENSATIONS. 
AUDITORY SENSATIONS. 
THE MEMBRANOUS LABYRINTH. 
The filaments of the auditory nerve end in the maculse and 
cristse of the internal ear and in the basilar membrane of the 
cochlea. It is supposed that vibrations of the endolymph 
set these end-organs in corresponding motion, thus mechan- 
ically stimulating the auditory nerve. 
The transmission of sound through the bones of the skull; 
hearing without a tympanic membrane. 
Sounds may be divided into musical tones which are caused 
by rhythmic or periodic vibrations of the air, and noises which 
are due to non-periodic vibrations. 
Sounds are distinguished by the three characters of loud- 
ness, pitch and quality. The physical peculiarities implied in 
these terms. 
The physical range of audible tones. 
Each musical tone is made up of a fundamental note, which 
determines the pitch, with which a greater or less number of 
overtones are combined, the latter determining the quality of the 
tone. —Ill — 
Nearly every body capable of periodic vibration has a fun* 
damental note of its own. 
Sympathetic vibrations. The analysis and synthesis of 
musical tones. 
There is reason to think that the organ of Corti may be 
regarded as a musical instrument capable of responding by 
sympathetic vibration to all audible tones. 
It has been supposed that the auditory hairs upon and the 
otoliths near the maculae and cristee of the labyrinth are con- 
cerned in the reproduction of irregular vibrations known as 
noises. 
The simplest aural apparatus known is a mere sac whose 
walls are set with hair-cells, and whose cavity is filled with 
fluid containing otoliths. 
When single sounds are repeatsd with sufficient rapidity 
they fuse into a continuous tone whose pitch is determined by 
the rate at which the single sounds succeed each other. 
Tones produced by vibrations recurring less than 30 times 
a second are not heard. The upper limit of auditory sensation 
is reached when vibrations recur 38,000 times per second. 
The power of distinguishing pitch differs much in different 
parts of the scale. 
The subjective nature of sound. Individual differences in 
the appreciation of tones. 
AUDITORY JUDGMENTS. 
Any stimulation of the auditory nervous apparatus is inter- 
preted as due to sound waves. 
From the loudness, quality and pitch of sounds, we form 
judgments as to their direction or distance. The nature of 
ventriloquism. 
XII. THE ORGAN AND SENSE OF SMELI 
The cavity of the nose on each side of the nasal septum is 
divided functionally into a lower respiratory and upper olfac- 
tory chamber. The olfactory mucous membrane, to which the — 112 — 
olfactory nerve is distributed, lines the upper and middle tur- 
binated parts of the fossae and the upper part of the septum. 
The ciliated epithelium and mucous glands of the respiratory 
chambers of the nose. ff 
The termination of the nerve fibres in the olfactory cells of 
the upper chamber. 
THE ORIGIN OF SENSATIONS OF SMELI 
Odorous particles are carried by diffusion into the olfactory 
chamber of the nose, or drawn into it by active inhalation. 
Odorous bodies must come into contact with the olfactory 
mucous membrane in order to produce a sensation, and the 
particles must not be in liquid form. Filling the nose with an 
odorous liquid causes no sensation of smell. When several 
odours are simultaneously inhaled, the peculiarity of each may 
be distinguished. 
Localization of an odour by the sense of smell is very im- 
perfect. 
The sensation requires some time to develop itself after 
application of the stimulus and may last for a considerable time. 
Certain pungent substances, as ammonia, give rise to sensa- 
tions through the nose which are not thos e of smell proper, but 
are probably due to stimulation of the fifth nerve. There may 
be sensations of smell of purely subjective origin. 
XXII. THE ORGAN AND SENSE OF TASTE. 
The glossopharyngeal and the lingual nerves are the special 
nerves of taste. 
The modified termination of the gustatory nerves in the 
mucous membrane of the tongue and palate. 
Many sensations which 'avc are accustomed to distinguish 
as those of taste are really sensations of smell. 
Sapid substances may be classified as sweet, sour, saline 
and bitter. They act in solution as chemical stimuli. 
Sensations of taste may arise from mechanical or electrical 
stimulation of the gustatory apparatus. 113 
XXIII. GENERAL SENSIBILITY AND SENSATIONS OF TOUCH. 
The distribution and modified terminations of sensory nerves, 
possess a certain faculty of general sensibility which 
gives rise to a consciousness of irritation in the body without 
enabling as to localize the stimulus or distinguish its nature. 
Such are the sensations due to irritation of a nerve trunk or of 
the viscera. Such sensations readily merge into those of pain. 
The more special sensations of feeling are those derived 
from touch, temperature and muscular activity. 
TACTILE SENSATIONS 
SENSATIONS OF PRESSURE. 
The smallest difference which can be distinguished between 
two unequal weights laid upon the skin is proportional to the 
magnitude of the weights. 
When separate sensations of contact succeed each other 
with sufficient rapidity they become fused. 
Not all parts of the skin are equally sensible to variations 
of pressure. 
Sensations of contact are present when the intensity of the 
pressure is varied, and fade away when it becomes constant. 
A cold body is judged to be heavier than a warm one of 
equal weight. 
There is reason to believe t hat there exist tactual nerves dis- 
tinct from those of general sensibility. 
TACTILE PERCEPTIONS AND JUDGMENTS. 
Sensations of contact are referred generally to definite local- 
ities on the skin. The erroneous judgme nts that arise from the 
irritation of 'the nerves of an amputated limb. Mistaken 
judgments arising when a marble is rolled between the tips of 
two crossed fingers. 
The power localizing contact upon the skin is not the same 
in all parts. The division of the skin into tactual areas. 114 
The power of localization is most marked upon the tip of 
the tongue and the palmar surface of the finger, and least 
marked upon the forearm, sternum and back. 
The fineness of tactile perception is greatly increased by 
exercise. 
THE TEMPERATURE SENSE. 
Bodies warmer or colder than the skin when in contact with 
it give rise to sensations of heat or cold. The erroneous judg- 
ments that may arise from artificially rendering the two hands 
of different temperatures. 
The range of finest distinction of temperature is included 
between limits which lie near the body temperature. 
Not all parts are equally sensitive to variations of tempera- 
ture. 
There are probably special afferent temperature nerves which 
are irritated by variations of temperature. 
THE MUSCULAR SENSE. 
We commonly estimate the weight of bodies by observing 
the intensity of muscular exertion necessary to lift them. 
Muscular sensations are probably peripheral in origin. 
The effects following diminution of tactile and muscular 
sensibility in locomotor ataxy. 
Judgments which arise from the muscular sense. INDEX. 
1. The object of physiology and the functions of living 
matter 3 
II. The nature of the laws supposed to rule the activities of 
the body 4 
III. The lymph and blood 5 
IV. The chemistry of animal tissues 9 
Y. Epithelium, connective tissue, bone and physiology of 
the skeleton ...... 12 
VI. The contractile tissues 17 
VII. Nervous tissues * 25 
VIII. Reflex action and the mechanisms involved in it 28 
IX. The circulation of the blood and the organs of circula- 
tion 33 
X. The physiology of secretion.; 49 
X. The varieties and functions of ingesta... 52 
XII. Digestion ; and the activites and structure of the parts 
involved in it 53 
XIII. The respiration . G7 
XIV. The skin and its appendages 73 
XV. The kidneys and their secretion . 75 
XVI. The physiology of nutrition 77 
XVII. The spinal cord 87 
XVIII. The brain 91 
XIX, The eye and sight 98 
XX. The ear and hearing 108 
XXI. The organ and sense of smell Ill 
XXII. The organ and sense of taste 112 
XXIII. General sensibility and sensations of touch 113 
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