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QUESTION BOOKS. No. 1. 
PHYSIOLOGY. QUESTIONS AND ANSWERS 
ON THE 
ESSENTIALS OF PHYSIOLOGY 
PREPARED ESPECIALLY FOR 
STUDENTS OF MEDICINE. 
BY 
H. A. HARE, B.Sc., M.D. (Univ, of Pa.), 
DEMONSTRATOR OF THERAPEUTICS AND INSTRUCTOR IN PHYSICAL DIAGNOSIS IN THE MEDICAL 
DEPARTMENT, AND INSTRUCTOR IN PHYSIOLOGY IN THE BIOLOGICAL DEPARTMENT OF 
THE UNIVERSITY OF PENNSYLVANIA ; PHYSICIAN TO THE DISPENSARY FOR THE 
DISEASES OF CHILDREN, AND ASSISTANT PHYSICIAN TO THE NERVOUS 
DISPENSARY OF THE UNIVERSITY HOSPITAL; PHYSICIAN TO ST. 
CLEMENT’S DISPENSARY AND HOSPITAL ; MEMBER OF THE 
AMERICAN SOCIETY OF PHYSIOLOGISTS AND OF THE 
AMERICAN SOCIETY OF NATURALISTS. 
with Illustrations. 
PHILADELPHIA: 
W. B. SAUNDERS. 
1888. Entered according to Act of Congress in the year 1888, by 
W. B. SAUNDERS, 
In the Office of the Librarian of Congress, at Washington. 
DORNA N, PRINTER, 
PHILADELPHIA. PREFACE. 
At the present time, when the student is forced by the 
rapid progress of medical science to imbibe an amount of 
knowledge which is far too great to permit of an attempt 
on his part to master it, any book which contains the 
“essentials” of a science in a concise yet readable form 
must of necessity be of value. The trite saying that “ there 
is no short road to knowledge ” is, of course, as true as it 
is old, and for this reason many of the medical profession 
have looked with disfavor on books of this character, as 
being the means by which students might attempt the 
shorter path. • ’ ‘ 
No one desires more than the writer that the depth and 
scope of medical education may be increased, but in his 
belief the evil at present in existence consists in the fact 
that medical institutions, by granting a degree too early, 
make the short road to knowledge the only one which the 
student with the average amount of cerebral gray matter 
can possibly travel. The evil lies with the small amount 
of time required for the obtaining of the degree, not with 
those books which are called into existence by the short- 
ness of the medical curriculum. 
V VI 
PREFACE. 
The usefulness of arranging the subject in the form of 
questions and answers will, the writer thinks, be apparent, 
since the student, in reading the standard works on Phys- 
iology, often is at a loss to discover the important points 
to be remembered, and is equally puzzled when he attempts 
to formulate ideas as to the manner in which the question 
could be put in the examination-room. 
A manual of this character is in no one way intended to 
supplant any of the text-books, but to contain, as its title 
declares, the essence of those physiological facts with which 
the average student must be familiar. 
After considerable thought, it has been considered 
advisable to exclude points which may be called purely 
anatomical, and which deprive some of the smaller books 
on Physiology of the space which might otherwise be 
occupied by purely physiological statements. The results 
reached every day by physiological experimenters are 
many of them so contradictory that no attempt to give 
individual opinions or teachings has been attempted, the 
statements made being supposed to represent those facts 
most generally accepted and taught. The student will, 
therefore, find statements which are not in accord with 
those taught by his instructor, and it is for this purpose 
that the interleaved edition has been published, in order 
that individual teachings may be noted and remembered. 
In the compilation of the facts here rehearsed, the standard 
works of Landois, Yeo, Foster, Dalton, Baker, Hermann, 
and Chapman have all been consulted. CONTENTS. 
PAGE 
Proteids 18 
Carbo-hydrates ......... 20 
The blood 21 
Coagulation of blood 28 
Respiration 45 
The nervous mechanism of respiration . . . - . 50 
Digestion 51 
The stomach . . . . . . . . . .56 
Pancreatic digestion ........ 61 
The liver .......... 62 
Absorption 67 
Animal heat 68 
The kidneys .......... 73 
The urine 82 
The skin 87 
Secretion .......... 89 
General view of the most important substances used as food 91 
Milk - .... 91 
The muscles 96 
The nervous system 103 
The physiology of the cerebro-spinal nervous system . . 108 
The functions of the spinal cord Ill 
The cranial nerves 123 
The special senses 127 
The sensibility of the skin ...... 128 
The sense of taste 129 
The sense of smell 130 
The sense of sight 131 
VII VIII 
CONTENTS. 
PAGE 
Hearing 139 
The voice and speech ....... 141 
The sympathetic nerve ....... 144 
Generation and development 146 
Generative organs of the female . . . .147 
The male sexual organs . . . . • . .150 
Development 152 
The development of organs ....... 158 
Vertebral column and cranium ..... 158 
Extremities . . . . . . . . .159 
Heart and bloodvessels 159 
Nervous system 160 
Eye 161 
Ear 162 
Nose 162 
Alimentary canal and organs ...... 162 
The foetal circulation ....... 163 ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is physiology? 
Physiology is the study of vital phenomena which are always 
present in living things be they animal or vegetable. As a con- 
sequence of this we divide physiology into two subdivisions, known 
as animal physiology and vegetable physiology, but it should be 
remembered that the line of demarcation between animals and 
vegetables in the lower forms of life is very ill-defined. The word 
physiology is derived from the Greek word <f>uais, nature, and Adyof, 
a discourse, and in its original meaning was applied to the study 
of natural history in general. Physiology is really synonymous 
with the term biology, since it is necessary for the study of either 
one that vital properties be present in the thing studied. The term 
biology, however, has a wider scope with certain persons, as under 
some circumstances it is divided up into morphology, which treats 
of the forms and structure of living bodies, while physiology at- 
tempts to explain the modes of activity exhibited by them during 
their lifetime. In other words, morphology stands in the same 
position in reference to physiology as does anatomy. The term 
vital phenomena is applied to the changes which constantly go on 
in all living bodies, the primary causes of which are not at all 
understood; in other words, while we note the ultimate object of 
each function we can give no cause for the setting in motion of 
that function. 
What is the chemical basis of the body? 
Of the sixty-three elements known to chemists, a very small 
number, comparatively speaking, are found in any quantity in 
living animal matter, although traces of them are frequently 
present. Oxygen, carbon, hydrogen, and nitrogen are present in 
very large proportions in every tissue, and together make up about 
97 per cent, of the whole body, while the sulphur, phosphorus, 
chlorine, fluorine, silica, potassium, sodium, magnesium, calcium, 18 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
and iron are indispensable to the economy, but are widely distrib- 
uted and occur in much smaller quantities. Since to investigate 
the chemical composition of a tissue must require analysis, the 
composition of the tissues during life is, strictly speaking, un- 
known, since by the very analysis death is produced. An im- 
portant point to be remembered is that all animal bodies, be they 
simple or complex, are made up of protoplasm more or less differ- 
entiated according to the function which it is to fulfil. 
What two great groups of substances make up the body? 
Physiological chemistry teaches us that we have in the body two 
sets or groups of substances known as nitrogenous and non-nitro- 
genous. The nitrogenous perform the most important functions, 
and, indeed, form all the active portions of the organism. As the 
simplest representative of these nitrogenous bodies may be men- 
tioned protoplasm itself. Derived from this and entering into the 
formation of it are albumens, serum-albumens, and, thirdly, by 
the outcome of still further differentiation we have albuminoids, 
chiefly represented by gelatine. Last of all are those products 
which, though nitrogenous, differ from the others in that they are 
intermediate or effete products of tissue manufacture or waste, as, 
for example, urea, uric acid, kreatin, and kreatinin. The non- 
nitrogenous substances consist chiefly of the carbohydrates, which 
contain hydrogen and oxygen in the proportion found in water, as, 
for example, starch and sugar. Then we have substances contain- 
ing oxygen in less proportion than the above, namely, fats. Salts 
occur all through the tissue, as does also water. 
PROTEIDS. 
AU compounds included in the group of proteids contain carbon, 
hydrogen, nitrogen, oxygen, and sulphur. 
They are amorphous, with variable solubility in water and acids, 
usually soluble in alkalies, almost insoluble in alcohol and ether. 
They are precipitated from their solutions by excess of strong 
mineral acids, by acetic or hydrochloric acid, potassium ferro- 
cyanide, and the basic acetate of lead, mercury bichloride, tannin, 
and potassium carbonate in powder. CLASSIFICATION OF PROTEIDS. 
19 
The following table, taken from Gamgee’s Physiological Chem- 
istry, is of great importance, and gives the points to be remembered 
most tersely. This will be, of necessity, frequently referred to 
later on. 
Class 1.—Albumens are proteid bodies which are soluble in water, and 
which are not precipitated by alkaline carbonates, by sodium chlo- 
ride, or by very dilute acids. If dried at a temperature below 40° 
C. they become transparent and yellow, break with vitreous frac- 
ture, and are soluble in water. Coagulation occurs between 65° 
and 73° C. 
1. Serum-albumen, not precipitated from its solutions by the 
addition of ether. 
2. Egg-albumen, precipitated from its solution by agitation with 
ether. 
Class 2.—Peptones, proteid bodies exceedingly soluble in water. Solu- 
tions are not coagulated by heat when precipitated by sodium chlo- 
ride, nor by acids or alkalies; precipitated by a large excess of 
absolute alkali and by tannic acid in the presence of much caustic 
potash or soda. A trace of a solution of copper sulphate produces a 
beautiful rose color. 
Soluble in 
pure water 
Class 3.— Globulins, proteid substances which are insoluble in pure 
water but soluble in dilute solutions of NaCl. These solutions are 
coagulated by heat They are soluble in dilute hydrochloric acid, 
being converted by alkalies into alkali-albumen. 
1. Vitellin, not precipitated from its solution when saturated 
with common salt. 
2. Myosin, precipitated from its solution by weak common 
salt. When saturated with sodium chloride it coagulates 
at 55° to 60° C. Solutions in common salt are not coagu- 
lated by a solution of fibrin-ferment. 
3. Fibrinogen, soluble in weak solutions of NaCl, precipitated 
from them completely on the addition of NaCl when this 
amounts to twelve or sixteen percent. Solutions coagulate 
on the addition of fibrin-ferment and at the temperature of 
60° C. 
4. Paraglobulin, soluble in weak solutions of NaCl, and pre- 
cipitated from weak alkaline solutions by the addition of a 
small quantity of NaCl. A further addition of this body 
redissolves the precipitate, which is again precipitated, 
although not so completely as before. When the amount 
of NaCl in solution exceeds twenty per cent, paraglobulin 
is completely precipitated when the solution is saturated 
with ammonium sulphate. Its solutions are not precipitated 
by the addition of the fibrin ferment It coagulates at 
different temperatures according to the amount of salts 
present and the mode of heating, but generally between 
68° and 80° C. 
Insoluble in 
pure water, 
but soluble 
in weak 
solutions of 
common salt 20 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Class 4.—Derived albumens, proteid bodies insoluble in pure water and in solutions of 
NaCl, but readily soluble in dilute HC1 and in dilute alkaline solutions. Solutions 
are not coagulated by heat 
1. Acid-albumens, obtained by the action of dilute acids, especially HC1, on 
solutions of proteids, and by action of strong acids upon solid proteids. 
They occur as first products in the action of gastric juice. NaCl added to 
saturation precipitates them. 
2. (a) Alkali-albumens, obtained by the action of dilute alkalies upon the pro- 
teids, possessing the properties of acid-albumen with the exception that in 
the presence of an alkaline phosphate the solutions are not precipitated by 
neutralization. They occur as the first products of pancreatic digestion 
(6) Casein, the chief proteid constituent of milk, has the same properties as 
alkali-albumen, but when treated with a strong solution of caustic potash 
potassium sulphide is formed ; with alkali-albumen it is not formed. 
Class 5.—Fibrin is insoluble in water and in weak solutions of NaCl, and becomes 
swelled up in cold hydrochloric acid of one-tenth per cent, solution, but does not 
dissolve unless pepsin is added and heat is applied. 
1. What test have we for proteids? 
The nitric acid test, which consists in heating the liquid, and 
adding nitric acid until the reaction is strongly acid, when a pre- 
cipitate occurs. 
2. What is the xantho-proteic reaction? 
Heat with concentrated nitric acid, when, if aproteid be present, 
a yellow tint appears, which becomes reddish-orange on the 
addition of alkalies. 
3. What is Millon’s reagent? 
It is made by dissolving in the cold one part of mercury in its 
weight of concentrated nitric acid, the solution being completed 
by applying gentle warmth; two volumes of distilled water are 
then added, and the fluid decanted. This test gives a red color 
with liquids containing proteids, which is more marked when they 
are heated to 60° C. or 70° C. 
CARBO-HYDRATES. 
These include the starches and sugars. 
What test have we for starch ? 
Starch, when added to free iodine, strikes a blue color which dis- 
appears on the application of heat, but returns if the liquid be THE BLOOD. 
21 
suddenly cooled. If heated to the temperature of 210° C. starch is 
converted into dextrin, and, as we shall learn later, the digestive 
fluids change starch into glucose or grape sugar. 
Sugars are substances having a more or less sweet taste, usually 
soluble in water, destroyed by strong H2SO4, which abstracts water 
from these compounds, and leaves only the carbon. The most 
important of this group are glucose, lactose, saccharose, and gly- 
cogen. On fermentation they yield CO2 and alcohol. 
What test have we for sugars ? 
Trommer’s test, which depends upon the fact that sugar in an 
alkaline solution acts as a reducing agent. To the saccharine 
fluid about one-fourth of its bulk of caustic potash or soda is added, 
and a dilute solution of copper sulphate. A slight clouding occurs 
which disappears on shaking, but boiling strikes a brick-red color. 
Fats are widely distributed in plants and in animals. They 
contain very little oxygen, and are soluble in ether, benzole, chloro- 
form, and in boiling alcohol. When fats are boiled with solutions 
of the alkaline hydrates or carbonates they undergo saponification, 
and are decomposed into glycerin and fatty acids. The latter 
immediately combine with the alkali and form soap. 
THE BLOOD. 
What is the function of the blood.? 
In all animals, except those which form the lowest class, a liquid 
medium corresponding, in function at least, to the blood of man, 
circulates. It serves in the distribution of nutritious materials to 
the various parts of the system and, equally important, it collects 
those substances which have resulted from the changes which are 
constantly going on in the tissues and bears them to those organs 
whose function it is to discharge them from the body. Quite as 
important is the constant intercourse which it keeps up between 
the tissues and the air, supplying them with oxygen. 22 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the color of the blood in the different portions of 
the circulatory system? 
The color of the blood as it occurs in the arteries is of a bright 
scarlet-red, while in the veins it is of a dark bluish color. 
What is the cause of this variation ? 
The cause of the variation in these two positions is due to the 
oxygen of the air, which, entering into a chemical composition with 
the haemoglobin of the red blood corpuscles, produces oxyhaemo- 
globin, which gives up some of its oxygen to the tissues of the 
body as it passes through the capillaries, and returns in the veins 
partly decomposed into reduced haemoglobin, which gives to the 
venous blood its dark hue. 
Is the entire amount of oxyhaemoglobin reduced in venous 
blood ? 
No. The reduction of haemoglobin amounts to only about five 
per cent. 
Are the red blood corpuscles really red ? 
The blood corpuscles, while they appear red in bulk, are in 
reality, as is seen when they are spread out in a thin layer on a 
piece of glass under the microscope, bright yellow; the red hue 
being chiefly produced by the refraction of light when in large 
numbers. 
What is the reaction of the blood? 
The reaction is alkaline, owing to the presence of sodium carbo- 
nate and disodic phosphate, Na.2HPO4. 
Does it always retain its alkalinity ? 
Always during life, but after blood is shed its alkalinity rapidly 
diminishes, and the greater the alkalinity of the blood is, the more 
rapidly this change occurs. Finally, the reaction becomes 
strongly acid, this change coming at about the time of coagula- 
tion. 
What is the odor of the blood ? 
The odor which the blood possesses differs in the various 
animals, and in some animals is very characteristic. This odor 
depends upon the presence of volatile fatty acids. THE BLOOD. 
23 
What is the taste ? 
It is saline in taste, which is dependent upon the salts contained 
in it. 
What is the specific gravity of the blood ? 
The specific gravity is 1055, the extreme limits being from 
1045 to 1075. The specific gravity of the blood corpuscles alone 
is 1105, that of the plasma 1027. As a consequence of this, blood 
corpuscles tend to sink to the bottom of the beaker. 
What is the temperature of the blood ? 
It varies from 98° F. at the surface of the body to 107° in the 
hepatic vein. 
Of what does the blood consist? 
Blood, when flowing in a normal condition through the blood- 
vessels, consists of an almost colorless fluid, the plasma, in which 
are suspended a number of small solid bodies, known as the red 
and white blood corpuscles. The liquid portion of the blood, or 
the blood plasma or liquor sanguinis, is of a pale straw color when 
free from blood corpuscles or other coloring matter, and is the 
liquid which keeps the corpuscles afloat. The blood plasma is not 
identical with the serum of the blood, since radical changes take 
place in its composition during coagulation, and the serum results 
after the clot is formed. Serum will not form of itself a clot, 
plasma will; in other words, one of the differences between 
liquor sanguinis, or plasma, and serum, is that the first contains 
the fibrin factors, while the second is without one of them, namely, 
fibrinogen. 
Is there any variation in the character of the blood in 
different parts of the circulatory system ? 
The arterial blood contains more oxygen and less CO2, and is 
more coagulable. The blood of the portal vein varies with the 
stages of digestion, during which time it is richer in water, albu- 
minous matters, and sugars, with a diminished number of cor- 
puscles. In the hepatic vein the sugar is increased, but the 
albumin and fibrin diminished. 24 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What are the two varieties of blood corpuscles ? 
Red and white. 
What others have we ? 
Very small ones, known as microcytes, and the so-called blood 
plaque of Bizzozero. 
What is the function of these microcytes ? 
Most physiologists believe them to be young red blood corpuscles, 
others that they are worn-out red blood corpuscles. 
What is the function of the corpuscle of Bizzozero ? 
It is not known, but they are found in large numbers in thrombi. 
Describe the white corpuscles. 
They are small protoplasmic cells, differing in no way from the 
pale round cells found in most portions of the body, and occur in 
large quantities in the lymph. For this reason they are sometimes 
called lymphoid cells or leucocytes. They possess a finely granular 
structure and nuclei, and these nuclei may often be recognized 
near the centre of the cell. The nuclei may be made more marked 
by the action of certain reagents, notably acetic acid. They pos- 
sess an amoeboid movement, and so are enabled to migrate not 
only through the bloodvessel wall, but also through the tissues. 
They are somewhat larger than the red disks, and do not possess 
a cell wall. 
What do you mean by diapedesis ? 
The passage of the white blood corpuscles through the blood- 
vessel wall. The white corpuscles constantly pass through 
normally, but in very large numbers in inflammation. The red 
only under morbid conditions, as in injury or inflammation. 
What are the relative positions of the red and white cor- 
puscles in the blood stream of the smaller arterioles 
and capillaries ? 
The red move along rapidly in the centre, while the white slowly 
roll along the walls. If inflammation occurs, they stop and block 
the vessel. The layer of blood in which the white corpuscles lie 
is called the “ still layer.” THE BLOOD. 
25 
Where are they formed ? 
According to the best physiologists, in the lymphatic glands and 
the spleen, and very similar cells develop in the connective tissues 
by multiplication by division. 
What is their function, and what is their ultimate end ? 
To form red blood corpuscles. They probably are destroyed 
in this way. 
Describe the red blood corpuscles. 
The red blood corpuscles give the red color to the blood of all 
vertebrated animals except the amphioxus, but are not found in 
the blood of invertebrates. They differ in their shape in almost 
all animals, in the mammalia they are biconcave disks. Their 
size differs in each class of animals, but the size of the animal has 
no relation to the size of the corpuscle, for in the frog all the 
corpuscular elements are of great size. They are soft and elastic, 
and bend and alter their shape when necessary to pass through a 
narrow bloodvessel, but return immediately to their normal shape 
as soon as the pressure is removed. If blood be withdrawn from 
the body, even for a few moments, and then returned to the circu- 
lation, death of the corpuscles takes place, and in a short time 
evidences of their destruction may be noticed by the presence of 
haemoglobin in the urine. 
What is one of the peculiarities of the red blood corpuscles 
outside the body ? 
They form themselves into rouleaux, which resemble very 
closely the appearance of a large number of coins placed side by 
side. This peculiarity is rather due to a physical law than to any 
action of the corpuscles themselves, since it has been found that 
small disks of cork will do very much the same thing when placed 
in water. 
Have the red blood corpuscles any nuclei ? 
No, but owing to their biconcave shape the refraction is such 
that under the microscope a dark spot is apparently situated near 
their centre. 26 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Are the red blood corpuscles few, or are they exceedingly 
great in number ? 
Their quantity is enormous; a cubic millimetre contains be- 
tween four and five millions. Approximate mathematical estimates 
show that the red blood corpuscles of an adult present an aggre- 
gate surface of about three thousand square yards, while the 
surface they represent for the absorption of oxygen in the lungs 
in one second is about eighty square yards. 
How are they formed ? 
The red blood corpuscles are probably derived from the spleen, 
liver, and red medulla of bones, where they are found in tran- 
sitional states, and are probably the offspring of the white corpus- 
cles to a certain extent. 
What is the end of the life history of the red blood 
corpuscles ? 
Most physiologists regard the liver as one of the chief places 
where the disintegration of the red blood corpuscles takes place, 
and this is supported by the facts that the bile-pigments are formed 
from haemoglobin and that the blood of the hepatic vein contains 
fewer red blood corpuscles than the blood of the portal vein. The 
spleen is also regarded as one of the organs in which the red blood 
corpuscle is disintegrated. 
What are the functions of the red corpuscles, and their rela- 
tive number to the white corpuscles ? 
The function of the red blood corpuscles is entirely different 
from that of the white blood corpuscles. The red blood corpuscle 
contains in its stroma a large amount of haemoglobin which, when 
exposed to the air in the lung, takes up oxygen, thereby forming 
the chemical compound known as oxy-haemoglobin. By these 
means the tissues, even in the most distantly removed parts of the 
body from the lung, receive their oxygen, the exchange of oxygen 
from the corpuscles to the tissues taking place in the capillaries. 
By this means, oxidation, with the resulting tissue break-down, 
and the development of heat, takes place in every portion of the 
body. THE BLOOD. 
27 
The relative number of the red blood corpuscles to the white has 
been much discussed, some observers insisting that it is one to fifty, 
while the majority insist that it is more frequently one to four 
hundred. 
Do changes ever occur in the relative number of red and 
white corpuscles in health ? 
Very frequently ; since many circumstances arising in every-day 
life may produce great changes in this respect. The variation may 
go all the way from one in fifty to one to twelve hundred. Preg- 
nancy decreases the proportion ; meals also have a very powerful 
effect on their relative numbers. Certain diseases also alter the 
proportion greatly. 
What is haemoglobin ? 
It is the substance which gives the red color to the corpuscles, 
and carries by their aid the oxygen to the tissues. 
What is haematin ? 
A result of the decomposition of haemoglobin. Haematin is 
synonymous with haemin, while haematoidin occurs only when 
blood coagulates outside the circulation, or becomes decomposed, 
as in extravasations into the tissues. A third substance derived 
from haemoglobin is known as the colorless proteid of haemoglobin. 
What are the gases of the blood ? 
Chiefly oxygen, carbonic acid, and nitrogen. The oxygen exists, 
as before stated, in chemical combination with the haemoglobin, 
and also in small amounts is simply absorbed in the blood plasma. 
Carbonic acid occurs in small amount in arterial blood, in much 
larger amount in venous blood. 
Nitrogen exists in the blood in very small amounts, and appears 
to be simply absorbed. 
Does C02 unite with the haemoglobin ? 
No. It is held in solution chiefly by the plasma, and in very 
small amounts in the red blood corpuscles. 28 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the quantity of the blood ? 
The quantity of the blood is equal to one-thirteenth part of the 
body weight. 
COAGULATION OF BLOOD. 
Blood, on being withdrawn from a vessel, is perfectly fluid, but 
rapidly becomes thick, and then forms a clot resembling a solid 
gelatinous mass. 
What is this clotting1 due to ? 
The presence of fibrin. 
What is fibrin ? 
Fibrin is that substance which, becoming solid in shed blood, or 
in lymph, causes coagulation. 
Does fibrin exist already formed in the blood ? 
No. 
How is it produced ? 
It is produced by the coming together of two proteid substances 
which occur dissolved in the plasma, namely, fibrinogen and fibri- 
noplastin, or paraglobulin, and a ferment necessarily present, 
known as the fibrin-J'erment. 
What is the difference between fibrinogen and fibrinoplastin ? 
The difference is not well marked. Fibrinogen is found in 
serous exudations, as in the pericardium and peritoneum, in 
pleural cavities, and in hydrocele. In these fluids no fibrinoplastin 
exists. Fibrinoplastin may be readily prepared from blood serum, 
in which, however, there is no fibrinogen. 
The liquid of serous effusions will not coagulate, neither will 
blood serum, occurring after clotting, clot of itself; but if one fluid 
be added to the other coagulation occurs. One liquid contains one 
fibrin factor, the other, the other. 
How is the clot made up ? 
The fibrin forms in fibrils, which entangle the blood corpuscles, 
as in a spider’s web, and thereby form a complete blood-clot. COAGULATION OF BLOOD. 
29 
The blood in the body is made up as follows : 
Blood 
I 
Plasma 
Corpuscles (red and white) 
Albumen 
Water 
Fibrin-ferment (?) 
I 
Salts 
I 
I 
Fibrin factors 
Blood when it has undergone coagulation is as follows: 
Blood 
I 
Corpuscles, red and white 
Plasma 
Serum 
Fibrin 
Clot 
I 
Containing fibrin, corpuscles, and serum. 
What changes take place after the clot is formed? 
The clot leaves the sides of the vessel, and on its surface there 
appear small transparent drops of yellowish liquid known as serum. 
These drops running together form a layer of yellowish fluid. 
In what way is the serum expelled from the clot? 
The fine fibrils of fibrin ramifying all through the clot contract, 
and squeeze out the serum. These fibrils also entangle the 
corpuscles. 
How long1 does this contraction and displacement of the 
serum last? 
From twenty-four to thirty-six hours. 
How do you defibrinate blood? 
By beating it with twigs or a glass rod. The fibrin adheres in 
sticky masses to the rods, and the remaining fluid will not clot. 
The corpuscles are left, most of them in the serum. 30 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What conditions hinder or delay coagulation? 
The addition of small quantities of alkalies or of concentrated 
solutions of neutral salts of alkalies, notably magnesic sulphate; 
the addition of egg-albumen, syrup, glycerine, and much water; 
and by covering the blood with oil, or by cold at freezing point. 
What hastens coagulation ? 
Coagulation is accelerated by contact with any foreign body, by 
heating from 39° to 55° C., and by constant agitation. 
What do you mean by the huffy coat? 
In blood which is drawn from a body during inflammation the 
fibrin coagulates slowly, and the corpuscles subside to the bottom 
of the vessel, so that the upper stratum of the clot is not red but 
only yellowish, containing scarcely any red blood corpuscles. 
This occurs physiologically in horses’ blood. 
What prevents coagulation of the blood in the bloodvessels? 
This is not positively known; some relationship exists between 
living tissues and the blood. 
Under what circumstances do you get clotting in the blood- 
vessels? 
As soon as the endothelial layer of the bloodvessels is in any 
way injured. 
How long after death does the blood coagulate in the 
body ? 
From ten to twenty-four hours. 
Do pathological changes ever take place in the blood ? 
Yes. Plethora is an increase in the quantity and quality of the 
blood, the red corpuscular elements being greatly increased in 
number 
Anaemia is a decrease in the corpuscular elements of the blood, 
without necessarily any increase in the liquids. 
Leucocythemia is a term applied to a condition in which the white 
blood corpuscles are in greater proportion to the red than normal, 
the proportion often being one to one to twenty-five or thirty. THE HEART. 
31 
Uraemia cannot be considered a disease of the blood, but simply 
an accumulation of urea in that fluid, owing to kidney disorders. 
THE HEART. 
What is the function of the heart? 
To propel blood through the body. 
How many cavities has it ? 
Four. 
What is the difference between the right and left side of the 
heart ? 
The right side of the heart takes the venous blood from the 
vena cavse and pumps it through the lungs to the left side of the 
heart. This circulation is much more limited, of course, than that 
produced by the left side, and is known as the pulmonic circulation. 
The left side of the heart receives the arterialized blood from the 
lung and drives it into the general arteries. This is known as the 
systemic circulation. 
Which, is the strongest, the right or left side of the heart? 
The left side is not only much stronger, but its walls are much 
thicker on account of the greater amount of work which it is 
forced to perform. 
What is the difference between the contraction of the 
auricles and the contraction of the ventricles? 
The contraction of the ventricles takes place synchronously 
from all sides, so that the pressure within is equal in any direc- 
tion. The auricles contract peristaltically from the opening of the 
supplying vessel toward the auriculo-ventricular orifice. 
Which have the thickest walls, the ventricles or the 
auricles ? 
The ventricles, owing to the greater force which they are re- 
quired to put out. 32 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the function of the auricle ? 
To force the blood through the auriculo-ventricular opening and 
so supply the ventricles. 
Has the heart any suction power enabling it to aid the 
circulation, not only by pushing but by sucking? 
According to the latest researches it has not.1 
What are the valves of the heart ? 
They are fibrous flaps arranged in one of two ways, which open 
and shut the orifices which they guard. The edges of the auriculo- 
ventricular valves are attached by what are known as chordae ten- 
dineae to the walls of the ventricles. 
What is the function of the valves ? 
To prevent the regurgitation of blood from a heart cavity, or 
bloodvessel, back into the area from which it has been propelled. 
What two sets of valves have we ? 
The auriculo-ventricular and semilunar. 
Where are they situated ? 
The semilunars guard the opening of the aorta and pulmonary 
artery. 
At the right auriculo-ventricular orifice we have the tricuspid 
valve, at the left auriculo-ventricular we have the mitral or 
bicuspid valve. 
How many cusps make up the semilunars ? 
Three at each opening. 
Are there any valves at the opening of the cavse into the 
right auricle ? 
No. 
Why are they not needed ? 
Because the peristaltic action of the auricle prevents a tendency 
1 The muscular arrangement of the heart is probably already known to the student; 
if not, he must turn to his anatomical text-books. THE HEART. 
33 
to regurgitation, except in rare conditions. For the same reason 
we have no valve at the opening of the pulmonary vein into the 
left auricle. 
What are the chordae tendineae ? 
The chordae tendineae are small bands running from the mus- 
cular fibres of the heart wall to the edges of the valves. 
What is the function of the chordae tendineae ? 
To prevent the everting of the auriculo-ventricular valves into 
the auricles by a sudden pressure of blood during ventricular 
systole. 
What are the columnae carneae ? 
They are small ridges of muscular tissue lying on the ventricular 
wall. 
What are the musculi papillares ? 
They are small teat-like muscular projections arising from the 
inner portion of the ventricular wall, to which the chordae tendineae 
are generally attached. 
What is their function ? 
As the ventricle contracts they pull the chordae tendineae tense. 
I 
In what way does the blood circulate through the heart ? 
Entering the right auricle from the cavae, it passes from the 
right auriculo-ventricular opening into the right ventricle, then 
through the pulmonary artery into the lungs, from the lungs 
through the pulmonary veins to the left auricle, and through the 
left auriculo-ventricular orifice to the left ventr cle, from the 
ventricle through the aorta, and so on through t e arterial system. 
How much blood is sent out of the left ventricle ordinarily 
in the adult at one contraction ? 
About four to six ounces. 
How much force does the heart put out at each systole ? 
Enough to lift three foot-pounds.1 Of this the left ventricle 
1 A foot-pound represents the force required to lift one pound one foot. 34 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
does two and a quarter pounds. In twenty-four hours the heart 
puts out enough force to lift one hundred and twenty-four foot-Zons, 
or enough to lift one ton one hundred and twenty-four feet. 
What are the movements of the heart ? 
The chief movements are those of contraction, or systole, and 
expansion, or diastole. 
The two auricles contract synchronously, thereby filling the 
ventricles, then the ventricles contract together, and then follows 
diastole. Following ventricular diastole there is a pause. 
Systole, diastole, and the pause, therefore, make up one cardiac 
revolution. 
Does the heart change its position during contraction or 
expansion ? 
Yes, somewhat; for, with contraction, the base of the heart de- 
scends, the base of the ventricle goes toward the left but the whole 
heart rotates a little to the right, and the apex is tilted a little for- 
ward. The vertical movement of the apex amounts to nothing. 
At what time does the impulse of the heart take place 
against the chest ? 
During systole. 
When the heart is slowed or quickened, is the change in 
speed due to a change in systole or diastole, or 
both ? 
Systole remains unaltered, diastole is prolonged when slowing 
occurs, shortened when quickening occurs. 
How many heart sounds have we ? 
Two; the long, dull “lub,” and the short, sharp “dup.” 
What are the sounds of the heart due to ? 
The first sound is due to the vibration of the auriculo-ven- 
tricular valves made tense by the systolic force of the ventricles, 
and also the sudden contraction of the muscular fibres of the heart 
walls. The striking of the apex against the chest wall does not 
even help the first sound, since it can be heard after the wall is THE HEART. 
35 
removed. The second sound is produced by the closure of the 
aortic valves. 
At what rate does the heart beat ? 
Before birth, per minute, the beats are 140-150. 
During first year, per minute, the beats are 125-135. 
During third year, per minute, the beats are 95-100. 
During eighth, ninth, and tenth to fourteenth year, 85-90. 
In the adult, about 72. 
In very old age, or decrepitude, the pulse once more becomes fast. 
In which sex is the pulse most rapid ? 
In females. 
What effect has posture on the pulse ? 
The erect posture causes a more rapid pulse than when lying 
down. 
What other conditions influence its rate ? 
Respiratory changes, drinking water in small repeated swallows, 
and many similar conditions. 
What is the intrinsic nervous mechanism of the heart ? 
The intrinsic nervous mechanism of the heart consists in three 
centres, which have been proved to exist in the heart of the frog, 
and are generally received as the centres for the mammalian heart. 
The three centres are: 
1. The motor ganglion, or that of Remak. 
2. The accelerator, or second motor ganglion, or that of Bidder. 
3. The inhibitory ganglion, or that of Ludwig. 
Fig. 1. will serve to illustrate the matter : 
The motor ganglion (a) sends out through its radiating fibres 
impulses which drive the heart. 
The accelerator motor ganglion (6), when it acts, quickens the 
irradiation of these impulses. 
The inhibitory ganglion (c) prevents the heart from beating too 
fast. 36 
ESSENTIALS OF HUMAN PHYSIOLOGY 
a. The motor centre, that of Rernak. b. The accelerator motor centre, that of Bidder, 
c. The inhibitory centre, that of Ludwig, d. The accelerator nerves, e. The pneumo- 
gastric or inhibitory nerves. The arrows represent direction in which impulses travel. 
What keeps up the contraction of the muscle ? 
The constant circulation of the blood over the endothelium, 
thereby stimulating and sending reflex impulses to the motor 
ganglion. 
What are the extrinsic cardiac nerves ? 
The accelerators and the pneumogastric or inhibitory nerves, 
which arise in the base of the brain and are governed by centres 
.there. 
What is their function ? 
They govern the ganglia in the heart muscle. 
Are the pneumogastric nerves and the accelerators, 
strictly speaking, antagonists ? 
They are not, for the accelerators do not act all the time, while 
the pneumogastrics do, and the vagi can always overcome readily 
any accelerator influence. 
What effect on the heart has stimulation of the pneumo- 
gastrics 
It slows the pulse and produces large and full diastole. THE HEART. 
37 
What effect has section of the vagus ? 
It produces an exceedingly rapid pulse. 
What effect has stimulation of the accelerators ? 
Stimulation of the accelerators makes a very rapid pulse. 
What is the depressor nerve, and what is its function ? 
The depressor nerve is given off from the superior laryngeal 
nerve and the trunk of the vagus in the rabbit, and passes into the 
cardiac plexus It conducts impulses from the heart to the vaso- 
motor centre, and lowers the activity of that centre, thereby relax- 
ing the bloodvessels somewhat. In this way the heart when over- 
worked, owing to the increased resistance of high blood pressure 
(vasomotor spasm), can be relieved as soon as is necessary. 
What is the function of the so-called pressor fibres of the 
laryngeal nerves ? 
They stimulate the vasomotor centre, causing a rise of blood 
pressure. They are, therefore, the direct opponents of the depres- 
sor fibres. 
What are the functions of the bloodvessels ? 
The bloodvessels carry blood to and from the various tissues and 
organs. They are divided up into three divisions, known as: 1, 
arteries and arterioles ; 2, capillaries; 3, veins. Of these three, 
the capillaries are most important in their function, since they not 
only carry blood, but, owing to the peculiarity of their walls, 
bring the blood into intimate relation with the tissues. The fluid 
which escapes from the capillaries is known as lymph, and the 
function of lymph is to irrigate and nourish. 
What is the difference between arteries, veins, and 
capillaries ? 
Arteries differ from veins in having thicker walls, owing to a 
greater development of their outer coats. 
Remember! The fact that arteries do not contain valves is not 
a differential point, since some veins contain no valves. 
How many coats have the arteries ? 
They contain three coats, known as the outer, or tunica adventitia; 38 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
the middle, or tunica media; the inner, or tunica intima. The last 
of these is made up of transparent endothelium, composed of 
irregular, long, fusiform cells held together by a cement substance 
which is stained black by nitrate of silver (AgNO3). Outside 
the endothelial coat lies a very thin, more or less fibrous layer, the 
sub-endothelial; and outside of this is the elastic lamina, which in 
the smallest arteries amounts to nothing more than a structureless 
or fibrous membrane, whilst in the other vessels its function is 
most important. It is known as the fenestrated membrane. The 
tunica media contains much unstriped muscular fibre, which 
increases in amount as the vessel grows larger. Most of these 
fibres are circular, completely surrounding the vessel, while a 
much smaller number run longitudinally. The tunica adventitia, 
or the outer coat in the smallest arteries, is a structureless mem- 
brane which changes into a fibrous membrane as the vessel 
increases in size. 
What are the functions of these coats ? 
The endothelial layer forms a smooth surface over which the 
blood may pass, and the importance of this will be understood when 
it is remembered that rough surfaces aid in the coagulation of 
the blood. The muscular coat regulates the amount of blood 
received by each part and governs the elastic coat. This is neces- 
sary, since it is manifest that the heart cannot regulate the blood 
supply of each portion of the body. 
Does the muscular coat aid in the propulsion of the blood? 
No; it must be distinctly remembered that in the higher 
animals, particularly in man, the muscular coat probably aids very 
slightly in the propulsion of blood. 
In what way do these coats aid in arresting hemorrhage? 
The muscular coat aids, in conjunction with the elastic coat, in 
the prevention of extensive hemorrhage by contracting the open- 
ing in the bloodvessel, turning in its edges so that the opening is 
greatly decreased in calibre. THE HEART. 
39 
What other function has the elastic coat? 
A more important function of the elastic coat is the prevention 
of sudden pressure in any portion of the body by yielding partially 
to a sudden strain or controlling a tendency to too great a dilata- 
tion. It, therefore, equalizes blood pressure during diastole and 
systole, and were it not for this important coat the arteries would 
be entirely emptied during diastole and filled to bursting during 
systole. 
What is the function of the outer fibrous coat of the larger 
bloodvessels ? 
To protect the bloodvessels from injuries from the exterior and 
to give the bloodvessel walls support. If it were not for the fibrous 
coat a ligature applied to a vessel would cut through. 
What have we in the veins which do not occur in arteries ? 
Valves which flap back against the wall of the vessel as the blood 
flows onward, but which prevent any reflux should the current 
be reversed by any cause. 
How are these valves arranged, singly or in pairs ? 
In pairs. 
Is there any difference in the capacity of the various por- 
tions of the vascular system ? 
The combined calibre of the branches of an artery exceed in 
their capacity that of the parent trunk, and so soon as the muscular 
coat of an artery is past the capacity of the vascular system is 
enormously increased. The capillaries are capable of holding 
eight hundred times as much blood as the aorta. The veins 
diminish in area as they come toward the heart, whilst the arteries 
increase as they go toward the periphery. The capacity of a vein 
is always greater than that of a corresponding artery; even at the 
heart the capacity of the venae cavae is twice as great as that of the 
aorta. 
What do you mean by blood pressure ? 
The pressure under which the blood stream is kept by the action 
of the heart and the walls of the bloodvessels. 40 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Is the blood pressure always constant in man and animals? 
The blood pressure varies from many causes, and differs in nearly 
all animals. In the rabbit it can support a column of mercury 
from two to three and a half inches in height, in the dog from four 
to five and a half inches, in the horse from eight to twelve inches, 
while in man the pressure will hold a column of mercury as high 
as five and three-fourths inches. The pressure in the human aorta 
is estimated at four pounds and four ounces, in the horse eleven 
pounds and nine ounces, in the radial artery of man at four drachms, 
in the pulmonary artery two pounds and two ounces. But it must 
be remembered that these figures represent the maximum amounts 
at the moment of ventricular systole. The pressure is least in the 
capillaries, greatest in the aorta. The venous pressure is only 
one-tenth .that of the arterial pressure. 
What is the influence of the nervous system on blood 
pressure ? 
Nerves supply all the arteries and arterioles, and even the capil- 
laries and veins, and belong to the so-called sympathetic system. 
What are these nerves called ? 
Vaso-motor nerves. 
How are they arranged and governed ? 
By a centre in the medulla oblongata known as the vaso-motor 
centre, which is situated near the calamus scriptorius and the cor- 
pora quadrigemina, the tension of the vascular system is governed. 
Fibres from this centre pass down in the neck through the spinal 
cord, and find exit with the anterior roots of the spinal nerves. 
The vaso-motor centre is probably always at work, and to aid it we 
have scattered through the spinal cord, and in various portions of 
the body, lesser centres under its control, but capable of originating 
impulses themselves. 
What proof have we that this is so ? 
If the cervical sympathetic be cut on one side in the rabbit, or 
in any animal, that side of the head becomes very rapidly deeply 
suffused and congested, and remains in this condition for many 
hours. Finally, however, the color returns almost to normal, and THE HEART. 
41 
congestion goes down. The first dilatation was due to the fact that 
the governing centre in the medulla by the section, was cut off from 
that side, and the minor centre not being accustomed to send out 
powerful impulses, is unable to govern its tributary bloodvessels. 
In a short time, however, the local centre gathers power, and once 
more exerts not only its previous influence over the vascular supply 
of that side, but also is enabled to supplement the action of the 
higher centre in the medulla, which, before the section, constantly 
aided it in its efforts. 
What effect has stimulation of the vaso-motor system on 
blood pressure ? 
It raises it by contraction of the bloodvessels all over the body. 
What effect has depression of the vaso-motor system on 
blood pressure ? 
It lowers it by dilatation of the bloodvessels. 
What effect has division of a vaso-motor nerve on its 
tributary vessels ? 
It produces palsy, or relaxation, of its tributary muscles in the 
wall of the bloodvessel, and, as a consequence, a local or, if the 
vessels are large enough, indirectly a general fall in blood pressure, 
by drawing a large amount of blood from the general system. 
Stimulation of a nerve, on the other hand, produces a contraction 
of these muscles and a rise of pressure. Blushing is a good example 
of vaso-motor disturbance of the nervous apparatus governing the 
vascular system. 
What effect has galvanization of a sensory nerve on 
general blood pressure ? 
It raises it. 
What effect has it on bloodvessels of a leg in which the 
sensory nerve is galvanized ? 
It dilates them and locally lowers pressure. 
What effect has asphyxia on blood pressure? 
It increases it by stimulation of the vaso-motor centre in the 
medulla by the increased amount of CO2 in the blood. 42 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What effect has section of the spinal cord on blood pres- 
sure ? 
It produces a great fall in pressure, due to the cutting off of the 
vaso-motor centre in the medulla from the vascular system all 
through the body. 
What effect has paralysis of the vaso-motor nerves supply- 
ing- the abdominal bloodvessels ? 
A general fall in blood pressure all over the body. 
Why is this so ? 
Because these bloodvessels are capable of holding all the blood 
in the body, and so starve the rest of the vascular system. 
What other causes increase arterial pressure ? 
Increased heart action, whereby more blood is driven out into 
the bloodvessels in a given space of time. The increase in heart 
action may be by increased rate or force, the result is the same. 
What are the physical forces of the circulation ? 
Liquid always goes away from pressure, and the pressure depends 
on the ease of escape and the forces from behind. If a tube be 
elastic, and its distal end open and small, it will be found that 
though the liquid enters it in jerks at the proximal end, it will 
leave the distal end in a steady stream, but if the tube is rigid the 
liquid moves in jerks along its whole length. This is the key to the 
circulation. 
Under what conditions is the blood placed after being 
driven out of the ventricle into the arterial system? 
Just before the arteries are changed into capillaries they are 
known as arterioles; it is in these arterioles that we still have the 
muscular coat quite powerfully developed and governed by the 
vaso-motor system. These muscular coats are kept at a certain 
degree of tonicity, producing thereby a considerable narrowing 
of the blood paths, and they, therefore, prevent the blood from 
flowing out into the capillary system too rapidly. On the other 
hand, the force given to the blood by the heart has so distended THE HEART. 
43 
the arterial system, particularly in the larger trunks, that the 
elastic coats have been greatly stretched, and no sooner does 
the pressure from the heart muscle cease than they contract on 
the blood. Pressed upon in this manner on all sides, the blood 
endeavors to find some mode of exit, and is prevented from 
regurgitating back into the ventricle, in health,, by the valves 
at the aortic opening. As a consequence, the blood obeys the 
physical law already mentioned, and passes in the direction of least 
resistance, namely, through the contracted arterioles. 
What is the function, therefore, of the arterioles ? 
To prevent too rapid a flow into the capillary system, which, if 
permitted, would immediately starve both the arteries and veins of 
their proper amount of blood, since, as before noted, the capacity 
of the capillaries is extremely great. 
What aids blood flow in the capillaries ? 
Capillary attraction and pressure due to muscular movements of 
the body. Also to the action of the heart and arterial coats. 
What aids blood flow in the veins ? 
Lateral pressure exerted by contraction of the voluntary mus- 
cles of the body, the indirect action of the valves in the veins, and, 
to a slight degree, the heart force. Also, the suction produced by 
movements of the thorax in respiration (not the heart). 
Does the blood find it more difficult to return through the 
veins than to descend through the arteries ? 
No; the circulation in this respect resembles a U-shaped tube 
filled with mercury, in which the column rises on one side, due to 
pressure or displacement on the other. In othe words, the blood 
descending in the femoral artery shoves the blood up the corre- 
sponding vein. 
Is there difference in the rapidity of the flow of the blood 
in the arteries, capillaries, and veins ? 
Yes; in the artery the flow is very rapid and in spurts, in the 
capillaries it is many times slower and generally moves in a steady 44 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
stream. In the veins the rapidity of the flow increases as the 
blood nears the heart, but moves in a steady stream, and does not 
attain the speed of the blood in the arteries. 
What is the pulse ? 
The pulse is caused by a wave of force which travels along 
the column of" blood in an artery as a direct result of a single 
contraction of the heart; in other words, each pulse represents 
a heart beat, but not the blood thrown out at that beat. The 
stroke given by the heart in propelling the blood onward is 
expended in causing not only the forward movement of the whole 
mass of blood, but also the latter expansion already spoken of. 
As a consequence of this, each pulse is like an expansion wave, 
causing the vessel to expand by reason of the increased tension 
and force produced by the heart from behind. 
Is the rapidity of the pulse wave the same as the rapidity 
of the blood stream in the artery ? 
No; the main current passes along the vessel at a given rate of 
speed, while the force of each systole is transmitted along the 
blood stream as if it were a solid piece of metal or wood, which, 
having been struck at one end, transmits a wave of force to the 
other end. The blood being enclosed in partially rigid walls 
carries the impulse chiefly forward, not laterally. The pulse wave 
is twenty or thirty times as rapid as the blood current itself. 
Does the pulse cause simply a lateral dilatation of the 
bloodvessel? 
No ; the bloodvessel is not only widened, but lengthened, so that 
a straight artery may be seen not only to dilate, but also to become 
curved to make up for its elongation. 
Is the pulse wave equally strong1 in all portions of the 
body ? 
No; it diminishes in force and in speed as it travels onward, due 
to the force expended in distending successive parts of the blood- 
vessel, friction, and other causes. As a consequence of this, the 
pulse in certain portions of the body occurs an appreciable length 
of time after the cardiac contraction which has produced it. This RESPIRATION. 
45 
is noticed particularly in the radial artery, or markedly in the dor- 
salis pedis artery. The delay, however, even at the most distant 
point amounts to not more than one-sixth to one-eighth of a second. 
At what speed does the blood circulate ? 
About ten metres or thirty-five feet per second, and takes but 
one-third of a second to pass a given point. The length of each 
pulse wave is, therefore, about three metres (9J feet), or twice the 
length of the longest artery. When the last part of the pulse 
wave has passed the arch of the aorta the first part has just reached 
the arterioles. 
RESPIRATION. 
The respiratory apparatus is divided into the larynx, trachea, 
bronchial tubes, bronchioles, and vesicles in the lung. Surround- 
ing each lung are the pleurae, one layer of which is attached to the 
lung (visceral layer), the other to the chest wall (parietal layer). 
What is the object of respiration? 
In order to bring the oxygen of the air in close relationship 
with the haemoglobin in the blood, and to permit of the elimination 
of CO2 from the body, as well as other effete products in very 
minute amount. The enlargement of the chest occurs with inspi- 
ration, the contraction of the chest with expiration. 
How many varieties of blood-supply exist in the lung1 ? 
Two; the pulmonary artery supply, and the bronchial artery 
supply. 
What is the function of these two varieties ? 
The pulmonary artery supplies the blood for aeration, the 
bronchial artery that for the nourishment of the lung-tissue itself. 
In what manner is the blood brought to the vesicles and 
exposed to the air ? 
The smaller branches of the pulmonary artery split up more 
and more, and have the peculiarity that they do not anastomose with 
one another. The fine capillaries run between the air vesicles, the 46 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
thin wall of the vessel and vesicle permitting the free interchange 
of gases to take place. 
What difference do we have in the distribution of the 
bronchial and pulmonary veins from that of the 
arteries ? 
The pulmonary and bronchial veins anastomose with one 
another. 
Is the circulation more or less rapid in the lung capillaries 
than elsewhere ? 
More rapid, since their area is not so great. 
Why is the pulmonary vein slightly smaller than the 
artery ? 
On account of the lessening of fluid due to exhalation of moisture 
in respiration. 
Are the movements of the lung passive or active ? 
They are passive, merely following the movements of the chest 
walls. 
What are the movements of inspiration? 
The side walls and front of the chest move upward and outward. 
By this means a vacuum is made, and air rushes in to equalize the 
internal and external atmospheric pressure. The antero-posterior 
diameter of the chest is increased by the raising of the anterior 
part of the ribs, the posterior ends being fixed to the spinal column. 
The increase in the lateral diameter is due to the outward move- 
ment of the ribs; the increase in the vertical diameter by descent 
of the diaphragm, the dome-shaped surface of which becomes less 
arched. For this reason the diaphragm is the most important respi- 
ratory muscle. 
The intercostals and other muscles also aid in moving the ribs. 
What are the movements of expiration? 
They ordinarily take place passively by the weight of the chest, 
which sinks down, displacing the air. The elastic tissue of the 
lung aids it. When it is forced, the abdominal muscles pull down 
the chest. RESPIRATION. 
47 
What effect has sex on respiration ? 
In men respiration is largely abdominal; in women chiefly 
costal. In young children respiration is chiefly diaphragmatic. 
Diaphragmatic breathing would be impossible during pregnancy, 
therefore women breathe chiefly with the upper part of the chest. 
Which is longer, inspiration or expiration? 
Inspiration, nearly three times as long as expiration. 
What sounds do we hear on listening to the chest? 
The respiratory murmurs, which are produced by the passage of 
the air in and out of the respiratory apparatus. 
What do you mean by “tidal air”? 
The ordinary volume of air respired, amounting to about thirty 
cubic inches in the adult. 
What do you mean by “reserve air”? 
The air which can be voluntarily emitted after ordinary expira- 
tion. It amounts to about one hundred cubic inches. 
What do you mean by “complemental air”? 
The amount which can be taken in after an ordinary inspiration. 
What do you mean by “residual air”? 
It is the amount which remains after forced expiration, equalling 
about one hundred and twenty cubic inches. 
What does the term “vital capacity” mean? 
The greatest amount of air which can be emitted after forced 
inspiration, and is therefore the sum total of reserve, tidal, and 
complemental air. It varies with age, sex, and size. The total 
quantity in an adult, passing in and out in twenty-four hours, is 
680,000 cubic inches; in hard-working laborers, 1,568,390 cubic 
inches. For every inch of height above five feet one inch, the 
capacity should increase eight cubic inches. 
What influence has sex on capacity? 
Females have less capacity than males, where the chest has the 
same circumference. 48 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
How many respirations a minute ? 
Fourteen to twenty, but the number is influenced by sex, the 
age, and position, also by exertion. The size of the animal governs 
rapidity. The mouse breathes very rapidly; the elephant only 
eight times per minute. 
What effect has the law of the diffusion of gases on res- 
piration ? 
In the vessels we have a large amount of CO2, while in the air 
we breathe we have an excess of O. According to this law, there- 
fore, the O attempts to get in as the CO2 attempts to get out. This 
law also prevents the reserve and residual air from becoming laden 
with CO2. The change is assisted, too, by the different temperatures 
of the air within and without. 
What amount of work is performed by the respiratory 
muscles ? 
The work done by the respiratory muscles is estimated by 
Haughton at 21 foot-tons in twenty-four hours. 
What changes have we produced in the atmospheric air 
by respiration ? 
1. Increase in its temperature. 
2. Increase in CO2. 
3. Increase in organic matter and free ammonia. 
4. Watery vapor. 
5. Diminished amount of O. 
The expired air is hotter than the inspired as a general rule, 
but on a hot day, with the atmosphere above 98.8° F., it is cooler. 
The temperature varies from 97°-99j° F., according to the 
length of time the air remains in the lungs. 
Is the amount of C02 exhaled constant? 
It varies at all hours of the day, and is influenced by many con- 
ditions. The CO2 given off by a normal man in an hour equals 
1346 cubic inches, or 636 grains. Accordingly we have 173 grains 
of carbon given off in an hour, or 8 ounces in twenty-four hours. 
Time of day, varieties of food, and exercise, greatly influence 
the amount of CO2. RESPIRATION. 
49 
Does age affect the amount of CO2? 
Yes; CO2 increases in amount from 8 to 32 years, while from 
35 to 50 it remains stationary, or slightly falls. After 50 years it 
constantly diminishes. At 80 years it scarcely exceeds that of a 
child of 10 years. 
How much 0 is abstracted from every volume of air ? 
About 4£ per cent. 
What effect has quickening of the respiratory movements 
on the amount of C02? 
The quicker the respirations the less CO2 in each respiration, 
but the aggregate amount is increased. 
What portion of the expired air contains the most CO2? 
That of the last half of expiration. 
What effect has the condition of the atmosphere on the 
amount of C02? 
More CO2 is given off when air is moist than when it is dry. 
What influence has the time of day on the relative amounts 
of C02 and 0 ? 
During the day more CO2 is exhaled than O is taken in; while 
at night the reverse is the case. In other words, there is a reserve 
fund of O stored up at night to meet the exigencies of the day. 
Is a very large amount of watery vapor given off by the 
lungs ? 
Yes; almost enough to saturate the expired air. The amount 
equals 6 to 27 ounces in twenty-four hours. The average amount 
is from 9 to 10 ounces. 
Does ammonia exist as a physiological constituent of all 
expired air? 
No; it does not. It is chiefly derived from decomposition pro- 
ducts in the mouth. 50 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
THE NERVOUS MECHANISM OF 
RESPIRATION. 
Is respiration purely, an involuntary act? 
No, it is not; since we can “ hold the breath,” or breathe rapidly 
or slowly, superficially or deeply, as we choose. That it is in- 
voluntary to a great extent is proved by the fact that one does not 
stop breathing when asleep or unconscious. 
Respiration is governed by a centre, the respiratory centre, in 
the medulla oblongata near the calamus scriptorius. 
What keeps this centre active ? 
It is kept active by the condition of the blood. If the amount 
of O is too small the centre sends out impulses and increases 
respiration. 
What do you mean by eupnoea, apnoea, and dyspnoea? 
Eupnoea is normal breathing; apnoea is a condition in which too 
much O is absorbed into the blood, and is readily produced by 
forced artificial respiration. Remember, that the use of the word 
apnoea to indicate a condition in which breathing has ceased from 
the ordinary causes, is incorrect. Breathing in apnoea ceases from 
the excess, not the lack, of oxygen. Dyspnoea is labored or 
difficult breathing. 
What effect has the pneumogastric apparatus on respi- 
ration ? 
If both vagi are cut the respirations become somewhat deep and 
full. If these nerves are stimulated the respirations become very 
rapid and violent. 
Is this change due to a direct transmission of the 
stimulus along the nerves to the lungs, or to a 
reflex wave to the respiratory centre ? 
It is due to a reflex wave to the respiratory centre. Remember, 
that the vagus nerves are made up of both efferent and afferent 
fibres. Also remember that not only do we have an efferent and 
afferent set of fibres, but that the afferent fibres are made up them- DIGESTION. 
51 
selves of two sets of fibres, one of which, the central end of the 
superior laryngeal branch, after it has been cut, when stimulated 
slows the respirations, while stimulation of the central end of the 
vagus itself quickens the respirations. When the nerve is stimu- 
lated the impulse goes upward to the centre, and from there is 
irradiated down to the organs. 
Sighing is a long inspiration. When great attention is being 
paid we speak of “shallowbreathing.” In other words, we almost 
forget to breathe. Sighing always follows this condition, and makes 
up for the shallow breathing before it. 
Hiccough is a sudden inspiration due to descent of the diaphragm. 
Coughing is expiratory. 
Sneezing is expiratory, but is preceded by a full inspiration. 
In speaking we expire. 
Sobbing consists of a series of short inspirations, after each of 
which the glottis is closed. 
Laughing is a series of short and rapid expirations. 
DIGESTION. 
What three forms of digestion have we ? 
Salivary, gastric, and intestinal. 
What is the function of salivary digestion? 
To convert starch into sugar. 
On what does the gastric digestion act ? 
On the proteids, converting them into peptones. 
What part of digestion is carried on in the small in- 
testine ? 
The fats are prepared for assimilation and the proteids converted 
into peptones. 
The salivary secretion is derived from what three glands ? 
The submaxillary, sublingual, and parotid. The mucous glands 
present in the mouth are solely for the purpose of lubrication. 52 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Describe the characteristics of the saliva? 
It is a mixture of the secretion of the three glands named, and 
is a slightly turbid, tasteless fluid of a distinctly alkaline reaction. 
The specific gravity is 1.004 to 1.008. It contains five-tenths per 
cent, of solids, the greater part of which are organic, such as mucin, 
which produces the viscidity, traces of albumen and globulin, and 
a peculiar ferment, ptyalin. The inorganic constituents are salts, 
the chief one of which is sulpho-cyanate of potash, which may be 
readily perceived by its odor when saliva is kept for a short time 
in a test tube. The other portions of the saliva are made up of 
salivary corpuscles (which are rounded, protoplasmic masses con- 
taining nuclei or coarse granules which show Brownian move- 
ments), epithelial cells, and various forms of microorganisms. 
How much saliva is secreted in twenty-four hours ? 
From 7 to 70 ounces. 
What is the difference between parotid saliva and the 
others ? 
It contains more ptyalin, a smaller amount of urea, traces of 
a volatile acid, and some inorganic constituents, as salts of soda 
and potash; it is much thinner than is the secretion of the sub- 
maxillary or sublingual glands. 
Describe the submaxillary saliva. 
Submaxillary saliva is markedly alkaline, tenacious, and con- 
tains mucin ; it contains much less ptyalin than does parotid saliva. 
Describe the sublingual saliva. 
Sublingual saliva is more sticky and cohesive than either of the 
others, and contains much mucin, salivary corpuscles, and sulpho- 
cyanate of potash. 
What is the nerve supply of the salivary glands ? 
The submaxillary glands are supplied by the chorda tympani, 
which is derived from the facial nerve. It also receives filaments 
from the superior cervical ganglion of the sympathetic, and from 
the submaxillary ganglion, DIGESTION. 
53 
Remember, that the chorda tympani contains two sets of fibres: 
1st, true secretory fibres; 2d, vaso-dilator fibres. 
The sympathetic also contains two sets of fibres : 1st, true secre- 
tory ; 2d, vaso-constrictor fibres. 
The sublingual glands are supplied by the same nerves as supply 
the submaxillary. The parotid glands are supplied by branches of 
the facial which join the auriculo-temporal branches of the fifth 
pair of cranial nerves. 
What is the effect of section of the chorda tympani ? 
The flow of saliva is very greatly decreased. 
What is the effect of stimulation? 
Increased salivary flow and increased glandular vascularity. 
What is the effect of stimulation of the facial nerve at its 
origin in the floor of the fourth ventricle ? 
It increases the salivary flow from the submaxillary gland. 
What is the effect of stimulation of the sympathetic? 
It causes a decrease in the salivary flow, with contraction of the 
bloodvessels and consequent decrease in vascularity. 
Does the increase in salivary flow depend upon increased 
vascularity ? 
No ; since if all the bloodvessels going to the gland be tied, secre- 
tion is still increased either when the chorda tympani is stimulated, 
or when the sympathetic is paralyzed; under these circumstances 
the extra liquid required is obtained from the lymph vessels and 
spaces. Atropine and daturine are drugs which decrease salivary 
secretion by depressing the chorda tympani peripherally. 
Remember, that mere increase in vascularity in the salivary glands 
does not of necessity increase the flow of saliva. The only influence 
which increased vascularity exerts is a greater supply of liquid 
which escapes from the gland rather by leakage than by secretion. 
Is the pressure in the excretory ducts of the salivary glands 
very great? 
Yes; Ludwig has found that the pressure in these ducts may be 54 
ESSENTIALS OF HITMAN PHYSIOLOGY. 
twice as great as the blood-pressure in the carotid itself. The 
pressure in Wharton’s duct may equal 200 millimetres of mercury. 
What is the cause of the great pressure in the salivary- 
ducts ? 
It is due to the secreting power of the cells in the gland. 
What change in temperature occurs in the gland ? 
During secretion the temperature of the gland rises, so that it is 
often warmer than the arterial blood. 
How do you produce increased salivary flow from the 
parotid? 
By stimulation of the facial nerve after it has joined the auriculo- 
temporal branch of the fifth or trifacial nerve, or reflexly by stimu- 
lation of the glosso-pharyngeal nerve. 
In what way is secretion brought about when food enters 
the mouth ? 
Reflexly through the lingual branch of the glosso-pharyngeal 
and the inferior maxillary branch of the trifacial or fifth nerve, 
which carry the impulses up to the centre in the medulla. 
What effect has section of the chorda tympani on this 
reflex ? 
If the chorda tympani be cut previous to the introduction of a 
substance into the mouth no increase of flow comes from the glands 
which it supplies; but if the sympathetic be cut the reflex, although 
partially interfered with, is not prevented. 
What is the physiological action of saliva? 
Its most important action is its diastatic or amylolytic action, or, 
in other words, the transformation of starch into dextrin, and of 
dextrin into sugar. 
What do you mean by the term diastatic ? 
The power which certain substances have of acting on starch and 
converting it into sugar. 
Upon what does the diastatic power of saliva depend? 
Upon ptyalin. DIGESTION. 
55 
Is the ptyalin destroyed when it acts? 
Scarcely at all, for it acts by catalysis, or its mere presence. 
What is the sugar called which is formed by the action of 
the saliva? 
The sugar formed by the action of saliva on starch is called 
maltose, which differs from ordinary glucose by containing one less 
molecule of water. Finally, the ferment acts still further, and the 
maltose is converted into grape sugar proper. 
What is the object of boiling starchy foods? 
In order to break up the cellulose coverings of the starch gran- 
ules, and enable the diastatic ferment to attack the starch. 
What are the mechanical uses of saliva? 
It keeps the mouth moist, facilitates speaking and the mastication 
of food, also the movements of the tongue. It dissolves certain sub- 
stances, and renders them capable of being tasted; by mixing with 
food it forms a soft bolus which is easily swallowed and digested. 
What is the function of mastication? 
We divide, by this means, the food into small pieces, biting it 
off by the incisors, tearing it off by the canines, and grinding it up 
by the molars. Soft food is broken up by the tongue pressing it 
against the roof of the mouth. By this means the digestive fluids 
may attack the food more readily. 
What is the function of the tongue in mastication? 
To keep the food between the teeth, in which it is assisted by 
the muscles of the lips and the buccinator muscles. 
In what way is deglutition accomplished? 
1. The aperture of the mouth is closed by the orbicularis oris. 
2. The jaws are pressed .together by the muscles of mastication. 
3. The tip, middle, and root of the tongue, one after the other, 
are pressed against the hard palate, thereby propelling the food 
backward. Just at this time the levator palati draws the soft palate 
upward and backward, completely closes the posterior openings of 
the nasal cavities, and the intrinsic muscles of the larynx firmly 
close the rima glottidis. * 56 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
4. After the anterior palatine arch is passed, it is prevented from 
returning to the mouth by the palato-glossi muscles, lying in the 
anterior pillars of the fauces. 
5. The bolus is now urged on, first, by the action of the superior 
constrictors of the pharynx, next the middle, and third the inferior 
constrictors. 
6. Having reached the oesophagus, it is urged on by the outer 
longitudinal and the inner circular non-striped muscular fibres, 
which contract peristaltically. Recent experiments show that this 
peristalsis only occurs on forced deglutition, the food ordinarily 
being projected into the oesophagus by the voluntary muscles. 
What is the nervous mechanism of deglutition? 
The centre for swallowing is in the medulla oblongata. The 
efferent nerves which govern deglutition are: the hypo-glossal, 
which supplies the hyoid or tongue muscles ; the glosso-pharyngeal 
and vagus nerves to the pharyngeal plexus, which supply the con- 
strictor muscles; and the facial and fifth, which supply the fauces 
and palate. The movements of the oesophagus are governed both 
afferently and efferently by the vagus, which also acts with the 
superior maxillary branch of the trifacial. The afferent vagus fila- 
ments for the first part of deglutition, are the pharyngeal branches 
of the anterior laryngeal branches. 
THE STOMACH. 
What are the movements of the stomach ? 
When the stomach is empty it lies with its greater curvature 
downward and its lesser upward; when it is full the greater cur- 
vature swings forward against the abdominal wall, while the lesser 
curvature approximates itself to the spinal column. 
What other gastric movements have we ? 
We have two distinct varieties of gastric movement different 
from the two mentioned: the first is a rotatory or churning move- 
ment whereby the walls glide over the food, these movements occur 
periodically and last for several minutes, their function is to 
moisten the food by the gastric juice anckbreak it up ; the other is THE STOMACH. 
57 
the peristaltic movement whereby the food is pushed out into the 
duodenum through the pylorus. 
What are the intrinsic and extrinsic nerves of the stomach ? 
Auerbach’s plexus is the motor portion of the apparatus. The 
left vagus supplies the anterior surface of the stomach, the right 
vagus supplies the posterior surface. 
Describe the gastric juice. 
It is a tolerably clear, colorless fluid (straw-colored), of acid reac- 
tion, sour taste, and peculiar characteristic odor; it is not rendered 
turbid by boiling and resists putrefaction for a long time; its spe- 
cific gravity is 1002.5. The quantity secreted in twenty-four hours 
amounts to from eight to fourteen pints. 
What does the gastric juice contain? 
First, pepsin, the characteristic nitrogenous hydrolytic ferment, 
which dissolves proteids; second, hydrochloric acid, the chief acid 
present; also small amounts of lactic acid. The latter, however, is 
not secreted, but is due to decomposition of carbo-hydrates in the 
stomach. 
Which cells secrete the greatest amount of pepsin ? 
Those at the cardiac end of the stomach. 
Does pepsin exist in the glands ready formed? 
According to most physiologists it is due to the presence of a 
compound known as pepsinogen, which forms pepsin as soon as 
it comes in contact with hydrochloric acid in the stomach. 
What is the function of lactic acid ? 
It digests the proteids in much the same manner as does hydro- 
chloric acid. 
Does secretion go on constantly in the stomach ? 
No. Only on the entrance of stimuli, such as food, etc. 
What change takes place in the gastric mucous membrane 
on the entrance of food ? 
It becomes red and the circulation more active. 
What happens to the gastric juice when the food passes 
out of the stomach into the alkaline intestine ? 
It is neutralized and part of the pepsin reabsorbed. 58 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is chyme ? 
The mixture of food and gastric juice. 
What effect has gastric juice upon proteids ? 
It changes the proteids first into a substance known as syntonin 
or acid-albumen, which is immediately changed again into pro- 
peptone or hemi-albuminose or para-peptone. The para-peptone 
is now converted into peptone, which is absorbed into the blood 
from the small intestine and immediately converted back again 
into proteids, and so deposited in the tissues. 
Does pepsin suffer any change when acting ? 
It acts chiefly by catalysis, but is partially destroyed. 
(For properties of peptones and para-peptones, see page 19.) 
Is any albumen absorbed unchanged ? 
According to Yeo, a considerable quantity of albumen is absorbed 
unchanged, both from the stomach and intestines. 
What other special ferment have we in the stomach ? 
The milk-curdling ferment. 
What is the action of the gastric juice on carbo-hydrates ? 
It has no effect on starch, inutin, or the gums. Cane-sugar is 
slowly changed by it into glucose, while the fats are broken up, 
according to Cash and Ogata, into glycerine and fatty acids. 
Why does not the stomach digest itself ? 
There is much discussion in regard to this point, and it cannot 
be decided positively. Most physiologists teach that the protection 
which the coats of the stomach, during life, seem to have is due to 
the constantly circulating alkaline blood through them. This 
seems likely, since when the blood ceases to circulate, as in death, 
the stomach often digests itself. On the other hand, if the leg of 
a living frog or the ear of a living rabbit be put into a gastric fistula 
or into artificial gastric juice it will be digested. 
What gases have we in the stomach ? 
Those which are derived from the air which is swallowed with 
the saliva and those which regurgitate from the duodenum. Besides 
these we have gases which arise in cases of dyspepsia from fermen- 
tative and putrefactive changes in the food. THE STOMACH. 
59 
What is the mechanism of vomiting ? 
It is caused by contraction of the walls of the stomach, whereby 
the pyloric sphincters are closed. It occurs most easily when the 
stomach is distended, and in infants, owing to the peculiarity of the 
position of their stomachs, the regurgitations of milk are due to 
scarcely more than reversed peristalsis. In children, therefore, the 
abdominal muscles do not always aid in the expulsion of food. In 
adults they always do. 
In what way is vomiting produced ? 
Vomiting is produced either by an action on the peripheral ends 
of the nerves of the stomach or by direct action on the vomiting 
centre in the medulla. 
What effect has section of the vagi on vomiting ? 
It prevents it. 
Do we ever have bile in vomit ? 
Frequently when the vomiting is so severe as to cause the bile 
to flow out of the duodenum into the stomach. 
What is the movement called by which food is passed 
along through the intestines ? 
Peristalsis. 
In what portion of the intestinal tract is peristalsis most 
marked ? 
In the small intestine. 
What is peristalsis ? 
Peristalsis is the constantly moving onward of a contractile wave 
along the wall of the gut, or, in other words, is the progressive 
narrowing of the tube from above downward. • 
Do the movements of the stomach and intestine continue 
during sleep ? 
Some physiologists believe that they do; others that they do 
not. The matter is largely one of opinion, but it is probable that 
the first opinion is the correct one. 60 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What do you mean by reversed peristalsis ? 
A condition in which the peristaltic wave travels from below 
upward, the cause of which has been supposed by some to be due 
to the fact that one band of the muscular fibres in the gut misses 
a contraction. 
What are the functions of the muscular coat of the intes- 
tine ? 
To carry on peristalsis. 
What nervous influence is exercised over intestinal move- 
ments ? 
Auerbach’s plexus is the automatic motor centre which lies 
between the muscular coats and produces peristaltic movements 
in sections of the gut removed from the body. Meissner’s plexus 
is much less important, supplying only a few motor fibres to the 
muscular coats, and a few motor and sensory fibres to the muscularis, 
mucosee, and intestinal glands. 
What do you mean by aperistalsis ? 
An absolute abolition of peristaltic movement. Normal peris- 
talsis is known as euperistalsis. When peristalsis becomes very 
violent it is known as dysperistalsis. 
What influence has the circulation of the blood on peri- 
stalsis ? 
Violent peristaltic movement is produced by interrupting the 
circulation of blood in the wall of the gut, whether the stoppage is 
due to congestion or anaemia of the parts. This is the cause of the 
marked peristalsis preceding death. 
What are the inhibitory nerves of the gut? 
The splanchnics, which, however, also contain motor filaments. 
What effect has stimulation of the splanchnics on peri- 
stalsis ? 
If the blood supply is normal it slows or prevents them. If 
abnormal, it increases them. The reason of this is that the inhibi- 
tory fibres of the splanchnics are paralyzed by venous blood in the 
gut, but the motor fibres are not. PANCREATIC DIGESTION. 
61 
PANCREATIC DIGESTION. 
Describe the pancreatic juice ? 
Pancreatic j nice is thick, transparent, odorless, and saltish in 
taste. The saltish taste is due to the presence of sodium carbonate; 
if acid be added CO2 is liberated. It acts powerfully as a digestive 
agent. 
What is the appearance of the pancreas when at rest and 
at work ? 
During digestion it is red and turbid, and at other times pale 
and ansemic. 
What is the function of the pancreatic juice 
It contains at least four hydrolytic ferments and is, therefore, a 
most important digestive fluid. 
What are these four pancreatic ferments ? 
(1) The diastatic action is caused by a ferment known as amylop- 
sin, a substance which seems to be identical with the ptyalin of 
the saliva. 
What is the difference between the action of this ferment 
and ptyalin on starch ? 
It is much more powerful than ptyalin. 
(2) The tryptic action, which is caused by the presence of a sub- 
stance known as trypsin, or pancreatin, which acts on proteids 
converting them into peptones, or, as they are sometimes called, 
tryptones. The intermediary, product between a proteid and a 
tryptone is alkali-albumen, corresponding to the acid-albumen of 
gastric digestion. 
What are leucin and tyrosin ? 
Substances normally found in the small intestine produced by a 
t)o prolonged action of trypsin on its self-formed peptone. They 
are crystallizable nitrogenous bodies. 
What are skatol and indol ? 
Strong, stinking decomposition products resulting from the con- 
tinuation, pathologically, of this action of trypsin on peptone. 62 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the difference in the manner in which trypsin acts 
on albuminous matters from that of the gastric 
juice ? 
In gastric digestion fibres of meat swell up before they are 
dissolved. In pancreatic digestion they do not swell up but become 
eroded. 
What reaction is necessarily present for the pancreatic 
action to take place ? 
An alkaline reaction. 
• 
What is the alkali commonly present ? 
Sodium carbonate, the presence of which is as necessary to the 
pancreatic action as hydrochloric acid is to the peptic action. 
What two forms of tryptones have we ? 
One known as anti-peptone the other as hemi-peptone. 
What is the action of the pancreatic juice on fats ? 
It first forms them into a fine emulsion, and secondly causes 
them to take up a molecule of water and split up into glycerine and 
fatty acids. The action of the pancreatic juice is due to the third 
ferment, known as steapsin. 
According to Kiihne and Rorferts the pancreas contains, fourth, a 
milk-curdling ferment. The four are, therefore, as follows: amy- 
lopsin, trypsin, steapsin, and the milk-curdling ferment. 
At what time is the pancreatic juice poured out 1 
On the entrance of food into the small intestine coming from the 
stomach. 
THE LIVER. 
The anatomy of the liver is so closely concerned in its physio- 
logical functions that an outline seems necessary at this point. It 
will be remembered that the liver is made up of many little livers 
known as lobes and lobules, each lobule being a perfect gland in 
itself. The bloodvessels are derived from two sources, first, the 
venous, which enter by means of the vena porta; and which, branch- THE LIVER. 
63 
ing, give off numerous interlobular vessels or veins forming dense 
plexuses around the lobules. Branching off from these interlobular 
vessels are the capillaries which converge from the centre of the 
lobule, forming elongated meshes, between which are rows of cells. 
Fig. 2. 
Section of lobule of liver of rabbit in which the blood and bile capillaries have been 
injected (after Cadiat). a. Intralobular veins, b. Interlobular veins, c. Biliary 
canals beginning in fine capillaries. 
These capillaries on reaching the centre of the lobule form the 
interlobular vessel or central vein, which again joins together with 64 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
others and forms the radicles of the hepatic veins. The second set 
of bloodvessels are branches of the hepatic artery which dip down 
between the lobules to nourish the whole gland tissue whatever it 
may be. The third set of vessels which are present are known as 
the bile-ducts, which, arising from the centre of the lobule join 
one another and form the interlobular ducts which anastomose 
and finally form the common biliary duct. 
Fig. 3. 
Section of the liver of the newt, in which the bile ducts have been injected, and can 
be seen to form a network of fine capillaries around the liver cells, the outlines and 
nuclei of which can be seen. 
What is the chemical composition of the liver cells ? 
First, proteids or albuminous matters. Second, glycogen, or 
animal starch, which is a true carbo-hydrate, and is changed into 
sugar by a diastatic ferment. 
What conditions influence the quantity of glycogen ? 
The eating of large quantities of starch, milk, fruit, or cane-sugar 
increases it greatly, while purely albuminous or fatty diets decrease 
it greatly. 
What are the sources of glycogen ? 
It is probably derived from the carbo-hydrates of the food. THE LIVER. 
65 
What are the functions of the liver ? 
The functions of the liver are three—the secretion of bile, the 
formation of glycogen, and the destruction of worn-out blood cells. 
What is the use of glycogen in the body ? 
It is not really known. 
Describe the bile. 
Bile is a yellowish-brown or dark green transparent fluid with a 
neutral reaction and a bitter taste. Its specific gravity is 1.026 to 
1.032. 
What does bile contain? 
First, mucus, which makes it viscid, and which comes from the 
walls of the gall-bladder. Second, the bile acids, glyco-cholic and 
tauro-cholic acids, which unite with soda, forming cholates. 
Which of the bile acids is most abundant in man ? 
The tauro-cholic acid. 
What is Pettenkofer’s test for bile ? 
Add concentrated H2SO4 drop by drop, then add a ten per cent, 
solution of cane-sugar when a reddish purple color is struck. 
What is Heintz’s test ? 
Heintz’s test consists in adding nitric acid, when a play of colors 
results. 
What are the bile pigments ? 
Bilirubin, which is yellowish-brown ; biliverdin, which is green; 
bilifuscin, biliprasin, and hydro-bilirubin, the last being the normal 
coloring matter of the feces. 
What is cholestrin ? 
Cholesterin is an univalent alcohol which occurs in the yolk of 
eggs, and in solution in the bile. 
Is the secretion of bile a mere filtration of substances already 
in the blood ? 
No; it is a true secretion, being produced by the cells of the 
glands. 66 
ESSENTIALS OF HUMAN PHYSIOLOGY 
What is the quantity of bile secreted per day ? 
About seventeen ounces. 
What is the difference between the contents of the blood- 
stream in the hepatic vein and the portal vein ? 
The hepatic vein contains more sugar (?), cholesterin, and blood- 
corpuscles, and less albumen, fibrin, free haemoglobin, fats, water, 
and salts. 
In what way is the coloring matter of the bile obtained ? 
By destruction of worn-out blood corpuscles. 
What are the functions of the bile ? 
The emulsification of the fats, the lubrication of the walls of the 
intestine, and to increase the osmotic power of the wall of the gut 
in order to facilitate the absorption of fats. It also prevents to a 
very considerable extent decomposition and stimulates peristalic 
action. 
What is the fate of bile in the intestine ? 
Some of it passes out with the feces, and part is absorbed and 
eliminated as urobilin. The cholesterin is given off with the feces, 
and the bile salts are for the most part reabsorbed by the gut. 
Have the other juices of the small intestine any digestive 
power ? 
They probably have some power in the solution of the proteids, 
and perhaps a diastatic action. 
What is the fate of the salivary, gastric, and pancreatic 
ferments ? 
Ptyalin is destroyed in the stomach by the acid pepsin, and the 
milk-curdling ferment by the alkaline salts of the pancreatic and 
intestinal juices and by trypsin, the diastatic ferment of the pan- 
creas by acid fermentation in the large intestine. 
What is the function of the large intestine ? 
It absorbs the liquids from the fecal matter coming from the 
small intestine. 
What is the amount of feces in twenty-four hours ? 
Six to twenty ounces according to the character of the food. ABSORPTION. 
67 
ABSORPTION. 
The mucous membrane of the whole alimentary canal is capable of 
absorption, some portions more so than others. 
In what two ways does absorption occur ? 
By means of the blood-capillaries and the lacteals. 
What substances are absorbed by the capillaries and what 
by the lacteals ? 
The first absorbs sugars and proteids, the lacteals the fats. 
What portion of the gastro-intestinal tract carries on the 
greatest amount of absorption? 
The upper half of the small intestine. 
What is the position of the lacteal ? 
It lies in the axis of the villus, and is surrounded by a blood- 
vessel and a vein. The lacteals anastomose in the sub-adenoid 
tissue of the gut, and finally form lymphatic networks which 
end in the receptaculum chyli, the beginning of the thoracic 
duct which opens into the subclavian vein on the left side near 
the junction of the jugular. The villi are possessed of unstriped 
muscular fibres, which aid in emptying the lacteal, and the 
nerves which supply them are derived from Meissner’s plexus. 
What three forces are at work in the absorption of digested 
food? 
Endosmosis, diffusion, and filtration. 
What do you mean by endosmosis and diffusion? 
Endosmosis is the change which occurs between two fluids which 
are capable of forming an intimate mixture with each other through 
an animal membrane, but never between two fluids which do not 
form a perfect mixture, such as oil and water. Diffusion is the 
mixing of two liquids placed one over the other in a vessel without 
the presence of a septum. 
What is the law in regard to the diffusion of crystalloids 
and colloids ? 
Crystalloids will diffuse into colloids, but colloids will not diffuse 68 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
into crystalloids. Filtration occurs in the small intestine simply 
by the pressure which is exerted upon the fluid by the contraction 
of the walls, and also by a negative pressure or suction produced 
by the villi. 
What is the influence of the nervous system on absorption ? 
Our knowledge is limited, but it has been found that after extir- 
pation of the semilunar ganglion of Budge, or section of the mesen- 
teric nerves, the intestinal contents became very fluid, which may 
be due to diminished absortion. 
ANIMAL HEAT. 
What do you mean by the term animal heat? 
The temperature at which the body of a warm-blooded animal 
is maintained. 
What is the normal temperature of man ? 
98f° F. 
Is it constant in all persons ? 
It varies but a fraction of a degree. 
Do all animals have the same temperature as man ? 
No; birds have as high as 107° F., and dogs as high a tempera- 
ture as-103° F. In the lower animals the bodily temperature of 
members of the same species often varies. 
Upon what does the temperature of cold-blooded animals 
depend ? 
Upon the temperature of the surrounding medium. 
What conditions influence bodily temperature ? 
Age, sex, period of day, exercise, climate and season; food and 
drink also influence it. 
What is the effect of age ? 
The temperature of a newborn child is one degree above that 
proper to the adult. In full adult life the temperature is lower 
than at any other time since it rises again in old age. ANIMAL HEAT. 
69 
What effect has the period of day? 
The variation may equal one to one and a half degrees, the mini- 
mum late at night or early in the morning; the maximum late in 
the afternoon. 
What is the effect of exercise ? 
It raises the temperature; but physiologists differ as to the actual 
amount of increase thus, some state that the rise of temperature 
produced by exercise never raises the general bodily temperature 
more than about 1° F., while others believe that it raises it much 
more. Those who think the actual general rise is slight, believe 
that the great rise occurring in tetanus, where all the muscles con- 
tract, is due to some other concomitant pathological condition. 
Students must be governed in regard to this point by the opinion 
of their instructor. Climate and season have very slight influence 
over the bodily temperature. 
What variations in bodily temperature may we have in 
disease? 
In fever we may have a temperature as high as 106° and 110°, 
or even 115° F. In Asiatic cholera it sometimes falls to 77° or 79°. 
What difference is there in the temperature of different 
portions of the body ? 
The surfaces of the hands and feet are cooler than any other 
portion of the body, while the liver often is as high as 105° F. 
From what source is animal heat derived ? 
The ultimate source is contained in the potential energy taken 
into the body with food and with the oxygen during respiration, 
but the amount of heat formed depends upon the amount of kinetic 
energy liberated. The energy of the food stuffs may be called 
“latent heat.” (For definitions of these terms, see Bodily Me- 
tabolism.) 
What are the direct sources of heat ? 
The blood during digestion becomes laden with more carbon, 
hydrogen, and oxygen than is needful for the repair of the tissues, 
and these gases uniting with the sulphates develop heat by chemi- 70 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
cal means very rapidly, while the rest of the heat of the body is 
more slowly developed by a slower combustion. The brain, the 
muscles, and the glands manufacture heat, so that venous blood 
leaving one of these parts is warmer than arterial blood. 
Is there any difference in the heat-producing properties of 
different food stuffs ? 
Fat are particularly heating, giving more kinetic energy. 
What is the nervous mechanism of animal heat ? 
In the brain is seated a heat centre whose function it is to direct 
the rapidity of combustion or the development of heat in the body. 
Governing this centre are two others, the inhibitory heat centre 
(Wood), whose function it is to prevent a too rapid production of 
heat, and the accelerator heat centres (Sachs and Aronsohn), whose 
function it is to increase the production of heat. 
What two functions govern the temperature of the body? 
Heat production and heat dissipation. Heat production consists 
in the manufacture of a certain number of heat units or calories in 
a given space of time in the body, while heat dissipation is the 
function by which a certain number of heat units are given off 
from the body to the surrounding atmosphere or medium. 
What is the effect of increased heat production and de- 
creased dissipation? 
Increase in temperature, or, in other words, fever. 
What is the effect of a decrease in heat production or an 
increase in heat dissipation ? 
A fall of temperature. Remember that these two functions 
balance one another and that disorder of either of them either 
raises or lowers bodily temperature. 
Under what circumstances is the dissipation of heat in- 
creased ? 
By cold surroundings, by conditions which bring large quan- 
tities of heat to the surface of the body, and by contact of the body 
with substances which readily conduct the heat away. ANIMAL HEAT. 
71 
What keeps the temperature of the body uniform ? 
The circulation of the blood, which distributes the heat very 
evenly. 
What conditions of the vasomotor system influence the 
distribution of heat ? 
Local dilatations of the bloodvessels produce increased tempera- 
ture of the part and increased heat dissipation, and, indirectly, 
increased local heat production. 
What is the function of the perspiration in regard to 
bodily heat ? 
By its evaporation it aids enormously in the dissipation of heat 
when heat is formed in or added to the body too rapidly. 
Why can a person stand a high heat in a dry atmosphere 
better than in a moist atmosphere ? 
Because in a dry atmosphere the perspiration is evaporated so 
rapidly that the heat is readily dissipated. 
How high a temperature may the human being stand in 
an absolutely dry atmosphere ? 
According to Blagden, a temperature of 198° to 211° F. was 
supported in dry air for several moments, and on one occasion he 
stood 260° F. for eight minutes, having trained his skin to exces- 
sive secretion. Workmen in English iron furnaces sometimes 
stand on a furnace floor which is red hot and the air of which 
stands at 350° F. Chabert, the so called “fire-king,” is said to 
have stood from 400° to 600° F., according to Morrant Baker. 
Which one of the animal tissues is the best protector 
against cold? 
The fatty layer, which nearly always occurs in varying amounts 
under the skin in all warm-blooded animals, and forms a protective 
covering whereby the conduction of internal heat is almost im- 
possible. 
Fibrous tissues conduct heat more readily in the direction of 
their fibres than at right angles. The bones are the next best con- 
ductors of heat, and are followed by blood-clots. The spleen, liver, 72 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
cartilage, tendon, muscle and elastic tissue, and nails follow as 
conductors of heat. The skin is a poor conductor of heat. 
What influence has starvation on the bodily temperature ? 
It lowers it greatly. 
What effect has sleep and hemorrhage on temperature ? 
In those persons who sleep during the day and work at night 
the typical course of the temperature is inverted from that which 
has been already stated as normal. Hemorrhage causes at first a 
slight fall in temperature, and after that a rise of several tenths of 
a degree, which is curiously usually associated with a chill or slight 
rigor. Several days after this the temperature falls again. 
What is the cause of the fall of temperature after hemor- 
rhage ? 
The interference with oxidation. 
What effect has the artificial cooling of animals ? 
It produces great depression, but voluntary and reflex movements 
are not abolished. The pulse falls from 100 to 150 to 20 beats per 
minute, the blood pressure falls, the respirations become shallow, 
and death occurs with spasms and signs of asphyxia. 
What is the asphyxia due to ? 
Failure of respiration: for if artificial respiration be employed 
at this time the temperature rises fifteen to twenty degrees. Lan- 
dois asserted that if in addition to artificial respiration external 
warmth be applied, animals apparently dead for forty minutes can 
be resuscitated. 
What is hibernation ? 
A condition in which an animal has all its vital processes 
temporarily in abeyance. Respiratory and intestinal movements 
cease completely and the cardio-pneumatic movements alone 
sustain the slight exchange of oxygen in the lungs. If a warm- 
blooded animal be cooled to 30° F., it wakes before freezing. 
Varnishing the skin of an animal increases heat dissipation so 
enormously that death occurs, which is put aside if external heat 
be applied. THE KIDNEYS. 
73 
THE KIDNEYS. 
What are the kidneys? 
Compound tubular glands. 
What is the function of the kidneys ? 
Their function is the secretion of urine. 
What is the purpose of the large amount of fat around 
these organs ? 
It acts as a protective. 
What is the size of the adult kidney ? 
About four and four-tenths of an inch long, three inches thick, 
and two inches wide. In the male it weighs from four to six ounces, 
in the female from four to five and a half ounces. 
Of what two portions is the kidney made up ? 
The parenchyma, consisting of the outer or cortical layer, and 
the inner or medullary layer. The medullary layer is also some- 
times called the pyramidal portion. 
Into what two divisions is the medullary portion divided? 
It is subdivided into the boundary layer of Ludwig and the 
papillary portion. 
What appearance has the cortical portion of the kidney 
when torn ? 
It presents a granular aspect, due to the presence of the Mal- 
pighian corpuscles. Striae are also seen, due to the medullary rays. 
What is the difference between the boundary zone or layer 
of Ludwig, and the papillary portion of the kidney ? 
The boundary zone is darker, and often purplish in color, while 
the papillary zone is nearly white, and uniformly striated. The 
striae merge into the apex of the pyramid. 
Which is the least pliable, the cortex or medullary portion? 
The medulla of the kidney is less pliable than the cortex. This 74 
ESSENTIALS OF HUMAN PHYSIOLOGY 
is due to the greater amount of connective tissue, and the bundles 
of straight tubes which may be traced at regular intervals, running 
upward, and becoming smaller and smaller as they pass toward 
the periphery. 
Fig. 4. 
Longitudinal section through the kidney (after Tyson and Henle). 1. Cortex. 1'. 
Medullary rays. 1". Labyrinth. 2. Medulla. 2'. Papillary portion of medulla. 2". 
Boundary layer of medulla. 3. Transverse section of tubules in the boundary layer. 
4. Fat of renal sinus. 5. Artery. * Transverse medullary rays. A. Branch of renal 
artery. 0. Renal calyx. U Ureter. 
In what portion of the kidney is the labyrinth ? 
That portion of the cortex which occurs between the medullary 
rays is called the labyrinth, owing to the arrangement of its tubules. THE KIDNEYS. 
75 
How many pyramids have we in each kidney ? 
Usually about eight or twelve. The pyramids are sometimes 
called those of Malpighi or Ferrein. The apices of the pyramids 
are directed toward the pelvis of the kidney, while their bases 
are directed toward the cortex, and each one of them opens into 
a small saccule or calyx, which in turn forms with others a dilated 
pouch, situated at the pelvis of the kidney, forming the beginning 
of the ureter. 
How many times do we have the pelvis of the kidney 
divided ? 
First, into two or three divisions, and then again into eight or 
twelve smaller ones, which are called calyces. 
What is the function of a calyx ? 
It receives the point of one pyramid, generally, but sometimes 
two pyramids empty into one calyx. 
What do you mean by the tubuli uriniferi ? 
Fine, very elongated tubes, composed of a nearly homogeneous 
membrane, and lined by epithelium possessing the power of secre- 
tion. These tubes are, on the average, one six-hundredth of an 
inch in diameter. They begin at the Malpighian corpuscle in the 
cortical portion of the kidney, and, after passing through many 
convolutions, finally end in the pyramidal bodies, from the papilla- 
like point of which the urine drops into the saccules already men- 
tioned. 
In what portion of the kidney do we find the tubuli 
uriniferi ? 
Both in the medullary and cortical portions. 
Into how many divisions are they divided? 
Fifteen. 
Is there any difference in the function of each division ? 
Certain sections are supposed to secrete certain substances. 
What is the glomerulus or Malpighian body ? 
It is composed of a small tuft of bloodvessels covered with a 76 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
layer of cells and surrounded by a membranous covering, known 
as Bowman’s capsule, which is the beginning or dilated extremity 
Fig. 5. 
Subcapsular layer 
without Malpighian 
corpuscles. 
Inner stratum of cortex, without 
Malpighian corpuscles. 
Diagram of two uriniferous tubules. (Tyson and Brunton, after Klein and Noble 
Smith.) 1. Malpighian tuft surrounded by Bowman’s capsule. 2. Constriction, or neck. 
3. Proximal convoluted tubule. 4. Spinal tubule. 5. Descending limb of Henle’s loop. 
G. Henle’s loop. 7 and 8. Ascending limb of Henle’s loop. 9. Wavy part of ascending 
limb of Henle’s loop. 10. Irregular tubule. 11. Distal convoluted tubule. 12. First 
part of collecting tube. 13 and 14. Straight part of collecting tube. 15. Excretory 
ducts of Bellini. 
of the uriniferous tubule. They are apparent to the naked eye, 
in the cortical portion of the kidney, as little red points. Their 
average diameter is T|jtli of an inch. 
What is the function of the glomerulus or Malpighian 
tuft or corpuscles ? 
According to most physiologists, the Malpighian tuft secretes the THE KIDNEYS. 
77 
liquids and salts of the urine, while the epithelial lining of the 
uriniferous tubules secretes urea and uric acid, or any substance 
which taken into the body is eliminated by the kidneys. 
Fig. 6. 
Bowman’s capsule and glomerulus (after Landots). a. Vas afferens. e. Vas efferens. 
c. Capillary network of the cortex, k. Endothelial structure of the capsule, h. Origin 
of convoluted tubule. 
What peculiar arrangement have we in the blood supply 
of the Malpighian tuft ? 
The blood passes, by means of the afferent vessel or artery, to the 
Malpighian tuft and enters it, giving off immediately a capillary 
network. At the other side of this capillary network a vessel 
goes off, which, as a general rule, does not leave the Malpighian 
body on the opposite side from the entrance of the artery, but finds 
its exit from the same opening as that by which the artery entered. 
The uriniferous tubule, however, is given off from the Malpighian 
body on the opposite side from that at which the artery enters 
and the efferent vessel leaves. 
The capsule of Bowman, or the beginning of the uriniferous 
tubule, may be considered as a sac, into which is secreted the liquid 
by the Malpighian tuft. 
Is the efferent vessel called a vein ? 
The efferent vessel after leaving the Malpighian body forms a 78 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
second, capillary network, twisting around the uriniferous tubules. 
Not until these capillaries come together do they form one vessel, 
known as the vein. 
Why is the efferent vessel smaller than the artery ? 
It is somewhat smaller for the reason that it loses some of its 
liquid in the Malpighian body. 
What other vessels have we ? 
Besides the efferent and afferent vessels, we have those known as 
the vasa recta, which, instead of being concerned, in any way with 
the Malpighian tufts, pass directly out of the kidney, through the 
medullary portion. 
Fig. 7. 
Longitudinal section of kidney (after Ludwig and Tyson) PF. Pyramids of Ferrein. 
RA. Branch of renal artery. RV. Lumen of renal vein receiving an interlobular vein. 
VR. Vasa recta. PA. Apex of a renal papilla, b, b, embrace the bases of the renal 
lobules. THE KIDNEYS. 
79 
What is their function ? 
Their function is to afford a side stream for the blood in cases of 
congestion, so that all of it will not of necessity pass to the paren- 
chyma of the organ. 
What other vessels carry on a side stream ? 
Another side stream, which is less important, but for the same 
purpose, is produced by the fine interlobular arteries which, as 
they approach the surface of the kidney, communicate with the 
capillaries of the external capsule. 
In what way is the kidney nourished ? 
By bloodvessels which dip down from the capsule, and from the 
vasa recta. 
What are the nerves of the kidney ? 
They are derived from theTenal plexus and the lesser splanch- 
nics. 
Do these nerves govern secretion, or only the blood supply? 
We know that they govern blood supply, but it is not proven 
that they influence secretion. 
What effect has increased blood pressure on the urinary 
secretion ? 
According to most of the text-books, increased blood pressure 
increases urinary flow, and vice versa; but recent investigations 
have seemed to prove that blood pressure has no very great influ- 
ence over the kidney. The urine which is increased by pressure, 
contains less solids, proportionately, than urine formed by stimu- 
lation. “Pressure” urine is scarcely more than a leakage, and 
not a true secretion. 
What is the function of the ureters ? 
To carry the urine from the pelvis of each kidney to the bladder. 
Do the ureters possess any power of urging on the flow ? 
Yes; they have a slight peristaltic movement, and are supplied 
by motor and sensory nerves, the sensory nerves showing their 
presence in the human being when a calculus is being passed. 80 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
How long does it take the wave of contraction to travel 
along the ureters from the kidney to the bladder ? 
About one-tenth of a second. 
In what way do the ureters enter the bladder ? 
Obliquely. They enter the external wall of the bladder at one 
point, pass between its coats for a short distance, and then open on 
its inner surface. 
In what way is this opening, arranged ? 
A small papilla with a valve-like action, permits the urine to 
flow out but not to return, and the oblique manner in which the 
ureter enters the bladder forms a sharp bend in that tube which 
acts as a valve, particularly when the bladder is distended. 
What mechanical arrangement have we to prevent leakage 
from the bladder ? 
At the neck of the bladder the circular muscular fibres are 
strongly developed, and act as a sphincter, and in addition to this 
is the muscle known as the sphincter of the urethra, which also 
acts in very much the same way. Remember! Both these muscles 
must relax before urination can take place. 
What is the function of the bladder ? 
To retain the urine until a sufiicient quantity has been collected 
to pass, in order that a constant dribble may not take place. 
What is its capacity ? 
About one pint. 
In what condition is the mucous membrane of the bladder 
when the bladder is empty ? 
It is thrown into rugous folds. 
What is the cause of the movement of the urine ? 
First, it is formed under high pressure in the kidney; second, 
gravity, when the person is erect, aids its passage; and, third, 
the muscles of the ureter contract rhythmically, and so aid its 
onward flow. This movement of the ureter is reflex, and is due to 
the presence of the urine in it. 81 
THE KIDNEYS. 
Do both kidneys act constantly? 
No ; they act alternately. 
What influence has the ingestion of small or large quanti- 
ties of water on the urinary flow ? 
During thirst it amounts to but two or three drops every minute, 
when drinking it often runs in a steady stream. 
In what way is the urine discharged from the bladder ? 
By contraction of its muscular coats, which, it will be remem- 
bered, run in all directions. 
What muscles aid in the voluntary act of urination ? 
The respiratory muscles and abdominal muscles. The diaphragm 
is fixed, and the act is completed by the accelerator urinse muscle, 
which quickens the stream. 
In what portion of the spinal cord is the centre for the 
bladder ? 
In the lumbar region. 
What other muscle aids in the expulsion of the last drops 
of urine, other than the accelerator urinae ? 
The bulbo-cavernosus. 
What is the nervous mechanism of urination ? 
The sphincter vesicse is kept in a state of contraction by the 
motor centre governing it in the cord. 
When the urine collects in the bladder a sensory impulse travels 
to the cord and brain, and the brain and cord in turn send down 
motor impulses which contract the muscular walls of the bladder, 
while a second impulse relaxes the sphincters. 
Where is the spinal centre for urination situated ? 
About the point of origin of the third, fourth, and fifth sacral 
nerves. 82 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
THE URINE. 
How much, urine is secreted in twenty-four hours ? 
About three pints in the normal adult. 
At what time of the day does the minimum secretion take 
place? 
Between 2 and 4 A. m. 
At what time of the day does the maximum secretion take 
place? 
Between 2 and 4 p. m. 
What are some of the causes that diminish the quantity 
of urine ? 
It is diminished by increase in the sweat, diarrhoea, thirst, non- 
nitrogenous food, diminution of blood-pressure, and certain dis- 
eases. 
What are the causes which increase its quantity ? 
It is increased by increased blood-pressure, by copious drinking, 
by exposure to cold, by the use of nitrogenous food, and various 
conditions of the nervous system. Various drugs also influence 
the quantity. 
What is the specific gravity of the urine? 
It varies from 1.005 to 1.015 to 1.025. The minimum specific 
gravity occurs after copious drinking and may be 1.002; the maxi- 
mum after profuse sweating, and may be 1.040. The mean specific 
gravity is 1.020. 
What ready, but not strictly accurate, method have we 
for determining the amount of solids in a given 
specimen of urine ? 
By the use of Christison’s formula, which consists in multiplying 
the last two figures of the specific gravity by 2.33, which will give 
the amount of solids in one thousand cubic centimetres. THE URINE. 
83 
What is the color of the urine due to ? 
The color depends on the matters present in it, chiefly uro- 
chrome and urobilin, a derivative of hematin. The color varies 
greatly, but the difference in intensity is chiefly governed by the 
quantity of water which is present. 
What is the cause of the slight cloudiness which appears 
in the bottom of a vessel in which urine is placed 
for a length of time ? 
It is due to mucus, which is chiefly derived from the bladder. 
What is the taste and odor of urine ? 
Its taste is slightly alkaline or bitter; its odor characteristic and 
aromatic. The odor, however, is altered by various causes, par- 
ticularly by the administration of drugs. 
What is the reaction of the urine ? 
It is acid, owing to the presence of acid phosphate of soda. 
After standing for a while the acidity is increased, due to fer- 
mentation of the mucus and other similar products, and, at the 
same time, with this increase in acidity, urates and free uric acid 
are deposited. 
Under what circumstances outside the body does the 
reaction become alkaline ? 
After it has become acid it changes to an alkaline reaction, owing 
to the presence of ammonium carbonate derived from alterations 
of the urea. At the same time, a strong ammoniacal odor is 
noticeable, and fetor, with deposits of triple phosphates and alkaline 
urates, appears. 
Does the reaction of the urine vary in different animals ? 
In most herbivora it is alkaline and turbid, but this difference 
depends not upon a different mode of secretion, but upon the 
variety of diet. 
Into what three forms is the urine passed at different 
times divided ? 
Urinae potus, urinse cibi, and urinse sanguinis. 84 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the difference between each one of these ? 
Urinse potus is secreted immediately after drinking, urinse cibi 
after a solid meal, and urinae sanguinis is that which is secreted 
early in the morning when neither food nor drink has been 
ingested. 
What is the chief solid of the urine ? 
Urea is the chief solid constituent, and it is the most important 
ingredient since it is the substance by which the nitrogen of de- 
composed tissue is given off. 
What is the result when this urea is not freely eliminated 
from the body? 
It produces the condition known as uraemia, in which the patient 
has convulsions and low muttering delirium ending in death. 
Does urea exist in a state of solution, or in a solid form 
in the urine ? 
In a state of solution. 
What is its appearance in the solid state? 
It forms delicate, silvery acicular crystals. 
What is the quantity of urea excreted in twenty-four 
hours ? 
About five hundred grains. 
Is the quantity of urea per day influenced by diet ? 
Yes. Nitrogenous or animal foods increase the urea, while a 
purely vegetable diet decreases it. 
Is there any difference in the amount secreted by males 
and females ? 
Males secrete more than females, while middle-aged persons 
secrete more of it than the very young or old. Remember, 
however, that children secrete more in proportion to their weight 
than do grown persons. 
What is the origin of urea ? 
It is derived from two sources: first, portions of unassimilated 
elements of nitrogenous food; second, from the breaking down of 
tissue, or tissue waste. THE URINE. 
85 
Does urea exist, to a certain extent, preformed in the blood, 
or do the kidneys manufacture it from the blood ? 
Some of it certainly exists ready formed, the kidneys merely 
extracting it. 
What is uric acid? 
An acid which appears, as a general rule, in small quantities in 
the urine of the human being, and which is entirely absent in the 
cat tribe. The quantity of it varies greatly in different animals. 
In birds and serpents its amount greatly exceeds that of the urea. 
In what way is the quantity of uric acid increased? 
By nitrogenous food, but decreased by vegetable food. In gout 
it is deposited around the joints as the urate of soda. 
From what does uric acid arise ? 
From the destruction of albuminous matters. The relation 
between urea and uric acid is not well understood. 
What is hippuric acid ? 
It is found in man and is allied to benzoic acid. Benzoic acid 
is eliminated as hippuric acid. 
What are extractives of the urine ? 
They consist of kreatin and kreatinin, two crystallizable sub- 
stances derived from muscle metamorphosis. 
What are the saline matters of the urine ? 
H2SO4 in the urine forms a compound chiefly or entirely with 
soda or potash, thereby forming salts. The phosphoric acid also 
combines and forms salts. 
The breaking down of what tissues increases the amount of 
phosphates in the urine ? 
The nervous tissues. 
How are the chlorides formed? 
The chlorine combines with ammonia and potash to form chlo- 
rides. 86 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Do gases exist in large quantities in normal urine? 
No; in very small quantities. They are chiefly CO2 and 
nitrogen. 
What pathological conditions of the urine occur ? 
Albuminuria is a condition in which a certain amount of albu- 
men is allowed to escape from the system by the kidneys. At one 
time the presence of albumen in the urine was considered to be 
pathognomonic of Bright’s disease, but it has been proved that it 
may exist physiologically for a short time after the ingestion of 
large quantities of albumen. Hematuria is a condition in which 
there is blood in the urine, the blood coming from the kidney or 
any portion of the urinary apparatus. 
What is haemoglobinuria ? 
A condition in which free haemoglobin occurs in the urine. 
Remember, that haemoglobinuria is not haematuria. 
What is choluria? 
The presence of bile in the urine. It occurs in certain condi- 
tions in which the circulation of the portal vein is disordered, or 
after the ingestion of certain poisons, as, for example, phosphorus. 
What is glycosuria ? 
Glycosuria is the presence of sugar in the urine. It is termed 
diabetes mellitus. 
What is the cause of diabetes mellitus? 
It is either produced by a lesion occurring in the diabetic centre 
in the floor of the fourth ventricle, or is due to disorder of the 
circulation of the liver whereby the sugars ingested and manufac- 
tured in this organ are improperly distributed. 
What is chyluria ? 
It is a condition in which the chyle from the digestive tract is 
passed out in the urine. 
What is diabetes insipidus ? 
A condition in which a very large quantity of liquid, of a low 
specific gravity and containing no sugar, is passed. THE SKIN. 
87 
THE SKIN. 
What are the chief functions of the skin? 
It acts as an external integument for the protection of the 
deeper tissues, as a sensitive organ in the exercise of touch, as an 
important excretory and absorbing organ, and plays a highly 
important part in the regulation of the bodily temperature. 
Of what does the skin consist? 
The skin consists of a layer of vascular tissue named the corium, 
derma, or cutis vera, covered by a layer known as the cuticle or 
epidermis. Underneath and within the corium are embedded 
several organs with special functions, as follows: the sudoriferous 
glands, the sebaceous glands, and the hair follicles, while on its 
surface are sensitive papillae. 
Are the appendages of the skin, known as the hair and 
nails, formed frcm the corium or the epidermis ? 
They are modifications of the epidermis. 
What layer of the epidermis contains the pigment in colored 
races? 
The layer known as the rete mucosum. 
From what portion of the skin does the papillae arise? 
They are conical elevations of the corium or true skin. 
What is the function of the papillae? 
Nearly every one of them contains a nerve ending, thereby 
increasing the peripheral sensibility. (For the corpuscles of touch, 
etc., see the Special Senses, ‘‘Touch.”) 
What is the function of the cuticle ? 
It protects the papillae from injury and forms a check on undue 
evaporation from the skin. The manner in which it protects 
sensibility is made evident when we remember the tenderness of 
those areas, where, by constant rubbing, the epidermis is rubbed off. 88 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the function of the sudoriferous glands ? 
They pour out the sweat on the surface of the body through 
ducts which at first are spiral but which, as they approach the 
surface, become straight. 
Are the sudoriferous glands the glands which secrete the 
familiar odors in the axilla and elsewhere ? 
No; the glands which are odoriferous are like them save that 
they are larger and have very short, straight ducts. 
What is the difference between sweat and perspiration? 
Sweat is applied to the liquid which is secreted so fast that it 
collects in drops; perspiration, to the moisture which is continu- 
ously and unconsciously given off by the skin. 
What is the function of sweat and perspiration? 
They aid in the dissipation of heat by their evaporation and 
thereby reduce the bodily temperature. 
How much watery vapor is excreted by the skin in twenty- 
four hours? 
From one and one-half to two pints. 
How much C02 is lost in this manner per day ? 
An amount which is almost to of the amount exhaled by 
the lungs, and which differs enormously according to the condi- 
tions surrounding the individual, and exercise, food, and drink. 
What other impurities are given off by the skin other 
than CO., ? 
Urea and inorganic salts. 
Is the excretory function of the skin important? 
Exceedingly so, if interfered with it may produce death by 
throwing too great a strain on the kidneys, for remember that the 
skin is a supplementary organ to the kidneys. 
In what ways may the flow of perspiration be increased 
other than by exercise or exposure to heat ? 
If a localized vaso-motor palsy occurs sweating sometimes takes THE SKIN. 
89 
place; section of the cervical sympathetic produces copious sweat- 
ing of that side of the head. 
What are the objects of the sebaceous glands ? 
They secrete a lubricating fluid or oily matter which keeps the 
skin soft and pliable. 
What is the vernix caseosa? 
That sebaceous matter which covers the skin during intra-uterine 
life. 
What is the function of hair? 
It acts as a protection from cold, as when on the head, and pro- 
tects the skin from friction in the axilla or on the pubis. Besides 
protecting the head from changes in temperature, it wards off 
blows which might otherwise be serious in their results to the 
more vital tissues. 
What is the function of the nails? 
To protect the ends of the fingers from injury or the sensory 
papillae of the finger tips from contact with harsh, rough objects, 
which, if it occurred constantly, might deprive them of their deli- 
cacy of touch. 
Can absorption of certain substances take place rapidly 
through the skin? 
Very rapidly. A familiar example of this is the ptyalism pro- 
duced by mercurial inunctions. 
SECRETION. 
What is secretion ? 
The separation from the blood of some product, directly or indi- 
rectly, by the vital process peculiar to a gland or membrane. This 
product is called an excretion when it is passed out of the body as 
waste, or a secretion when it carries out some function in the animal 
economy. 
Give a good example of an excreting gland? 
The kidney. 90 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Give an example of a secreting gland. 
The pancreas or mammary gland? 
(For the manner in which secretion is carried on in each gland, 
see questions on each subject.) 
THE MAMMARY GLANDS. 
What changes take place in the mammary gland during 
gestation ? 
It becomes much larger, the areola around the nipple increases 
in width and deepens in color, the veins become more prominent, 
while the lobules can be plainly felt. 
How many lobes has the mammary gland? 
From fifteen to twenty, each one of which is divided into several 
lobules made up of acini. 
What is the function of the lactiferous ducts ? 
They carry the secretion to the nipple, on which they open by a 
number of orifices. Just before they enter the nipple they dilate, 
forming little sacs which collect the milk. 
In what way are the fat globules of milk formed ? 
They are supposed to be the results of a physiological fatty 
degeneration of the cells lining the acini and ducts. 
(For Milk, see Articles used as Foods.) 
THE BODILY METABOLISM. 
What do you mean by the term Bodily Metabolism? 
Those phenomena by which all living organisms are capable of 
taking substances derived from their food into their tissues, and 
making them an integral part of their own bodies; further than 
this, metabolism includes the breaking down of these tissues, and 
the removal of the results of their destruction; the first half of the 
process is termed assimilation, the second half excretion. MILK. 
91 
Does the body merely assimilate sufficient food to replace 
exactly those particles which are destroyed, or does 
it do more than this, and act as a storehouse, from 
which, on a sudden strain, energy may be derived? 
It acts as a storehouse of potential energy, which, when necessity 
arises, it may transform into kinetic energy. 
What do you mean by potential energy? 
That energy which possesses the power to move, but is quiescent. 
What do you mean by the term kinetic energy? 
Potential energy, when exerting its influence, either by pro- 
ducing motion or preventing it, is called kinetic energy ; in other 
words, potential energy is latent, kinetic energy is active. A 
coiled watch-spring held firmly represents potential energy, but 
if the pressure is removed, its force is transformed into kinetic 
energy. 
GENERAL VIEW OF THE MOST 
IMPORTANT SUBSTANCES 
USED AS FOOD. 
How much of the body is made up of water ? 
58.5 per cent, of the body consists of water, which is continually 
taken in and given off. 
What is the purpose of water in the organism ? 
The processes of digestion and absorption require the presence 
of water for the solution of the food, and it is also used to carry off 
the effete products. So much water exists in the tissues of all 
animals that Hoppe-Seyler has put it that all organisms live in 
water. 
Milk. 
What is the use of milk and its preparations ? 
Milk forms a complete typical food, in which are all the con- 
stituents necessary for life and growth. 92 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What are the constituents of milk ? 
In every ten parts of proteids we have ten parts of fats and 
twenty parts of sugar. 
Describe some of the characters of milk. 
It is an opaque, bluish-white liquid, with a sweetish taste and a 
characteristic odor. 
What is this odor due to ? 
Probably to the peculiar volatile aromatic substances derived 
from the cutaneous secretion of the glands. 
What is its specific gravity ? 
1.026 to 1.035. 
What is the reaction of human milk ? 
It is always alkaline; cows’ milk may be alkaline, sometimes 
acid, or even neutral. The milk of carnivora is always acid. 
What are milk globules ? 
Small, highly refractive, oil globules floating in a clear fluid, the 
milk plasma. The white color of milk is due to their presence. 
Of what do the globules consist ? 
Of fat or butter, surrounded by a coating of casein. 
What is the effect of churning on these milk globules ? 
This coating of casein is broken, and the butter globules are 
allowed to run together. 
What does the milk plasma contain aside from the globules? 
It contains free casein, serum-albumen, and, to a less extent, a 
body resembling albumen, the lacto-protein of Millon and Lieber- 
mann. 
What other substances have we in milk ? 
Galactin, albuminose, and globulin; very minute traces of pep- 
tone are also present. Milk sugar, a carbohydrate resembling 
dextrin; -and urea and extractives complete the list of its con- 
stituents. Remember, that the casein is the albuminous portion MILK. 
93 
of milk while the butter globules make up the hydro-carbon 
portion. 
When milk is boiled, what changes take place in it ? 
The serum-albumen coagulates, while the surface also becomes 
covered with a layer of casein which has become insoluble. 
Is raw or boiled milk most digestible ? 
The raw milk; if nature had intended that boiled milk should 
be more digestible than raw milk, raw milk would have been formed 
with the same, conditions present that exist in boiled milk. 
Upon what does the coagulation of milk depend ? 
Upon the coagulation of its casein. 
What salt in milk keeps the casein in solution ? 
Calcium phosphate; which is, of course, destroyed by the acid 
of the stomach. Remember, that milk coagulates in the stomach, 
not on account of the acid, but owing to the presence of a milk- 
curdling ferment. (See page 58, Digestion.) 
What causes the spontaneous coagulation or souring of 
milk? 
It is produced by the development of lactic acid, which is formed 
from the milk sugar by the action of the bacterium lacticum. 
What is the difference between human milk and cow’s 
milk ? 
It contains less albumen, and the albumen it does contain is 
more soluble than that in cow’s milk. It also contains more sugar 
and fats than does cow’s milk. 
What is colostrum ? 
It is the substance which is secreted at the beginning of lacta- 
tion, and contains much serum-albumen, and very little casein, 
while all the other substances, specially the fats, occur in large 
amount. 
What is the purpose of colostrum? 
Containing, as it does, a large amount of fat, it acts as a purga- 
tive, and sweeps out the meconium and other effete products from 
the alimentary canal of the infant. 94 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Are gases found in ordinary milk ? 
Only in minute traces. 
What salts are found in milk? 
The potash salts are much more plentiful than the soda salts; 
there is also a large amount of calcium phosphate present. 
What is the purpose of the calcium phosphate ? 
It is necessary in the formation of the bones of the infant. 
What difference is there in the composition of milk at 
various times? 
That drawn last is always richer in butter, while if the ducts 
are emptied frequently the butter decreases but the caseine increases. 
Are eggs a typically complete food ? 
They are not as complete a food as is milk, but are the most 
typical food next to milk. 
What is the object attained by cooking flesh? 
It breaks up to a certain extent the elastic coverings of the 
muscular fibre, softens the connective tissues, and renders it more 
tender and easy of digestion. 
In the vegetable foods, what are the chief nitrogenous 
substances? 
Gluten is the most abundant nitrogenous substance present, and 
occurs immediately under the husk. 
How many groups of foods are necessary for the main- 
tenance of health in man? 
Five. 
What substances make up these groups ? 
First, the starches, which are used for the purpose of adding 
heat to the body, and also fat; second, the fats, which are used 
for the purpose of maintaining the bodily heat and retaining it; 
third, albuminous foods, whose function is to add force to the 
system; fourth, water, which is necessary for the carrying out of 
the vital processes; and fifth, salts, which are also absolutely 
needful for the maintenance of health. MILK. 
95 
What is the absolute amount of the different food-stuffs 
required by an adult in twenty-four hours? 
It varies enormously according to the surrounding conditions, 
but, as a general rule, it should contain 130 grammes of proteids, 
84 grammes of fats, and 404 grammes of carbohydrates. Remember, 
that the carbohydrates should always be greatly in excess of the 
nitrogenous principles. 
What effect has the withdrawal of all forms of food-stuffs, 
with the exception of one particular class, upon 
nutrition ? 
The animal wastes, and finally dies with very much the same 
symptoms as would follow starvation. 
The manner in which effete products are taken up and excreted 
has already been considered (see Circulation, Respiration, and the 
Kidney and Urine). 
What process goes on during starvation ? 
All food being taken away from the body the organism is re- 
quired to abstract at first the unimportant tissues in order to keep 
up its vital processes. After this the wasting becomes marked, 
and the bodily weight falls. Weakness, the result of the breaking 
down of vital tissues, comes on, and finally death, after all sub- 
stances capable of supplying force in the body have been used up, 
save those actually concerned in the vital processes. 
How long will the average adult survive without food? 
About twenty-one to twenty-four days, although cases are on 
record of survival for forty-one days. 
How much bodily weight is lost before death? 
Four-tenths of the bodily weight. 
Are fats ever formed from proteids ? 
Yes; as an example of this, the cow does not consume as much 
fat in a day as she gives in butter. 96 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
THE MUSCLES.1 
What is the function of the muscles? 
To produce movements, which vary according to the rapidity 
and power of their contraction. 
In what way do the voluntary muscles act upon the bones? 
As levers. They are often attached to the short arm of the lever, 
and while this is apparently a disadvantage, since under these 
circumstances greater force is required to lift a given weight, it, in 
reality, is of the greatest service, since slight contractions of muscles 
cause very extensive and rapid movements of the part. 
How many orders of levers are met with in the movements 
of the different bones of the skeleton by the muscles ? 
All three; and in some cases all three occur at the same joint. 
Give an example of the first order of levers. 
When the triceps is the power which draws upon the olecranon, 
thus moving the hand and forearm around the trochlea, which acts 
as the fulcrum. 
Give an example of the second order. 
This occurs when the hand, resting on a point of support, acts as 
the fulcrum, and the triceps pulling on the olecranon is the power 
which raises the humerus, upon which is fixed the body or weight. 
Give an example of the third order. 
This is exemplified by the action of the biceps in ordinary flexion 
of the elbow, in which the biceps is attached to the upper portion 
of the forearm. 
What two varieties of muscular fibre have we ? 
Two; striped, or striated or voluntary ; unstriped, unstriated or 
involuntary. The first group are moved entirely by the will-power, 
or by centres under the control of the will-power. The second 
group, solely by nervous centres over which the will-power has no 
direct influence. 
1 The anatomy of muscles is to be found in anatomical text-books. THE MUSCLES. 
97 
What large mass of striped muscular fibre is an exception 
to this rule? 
The heart, which, although it is made up of striped muscle, beats 
independently of the will. The arrangement of the heart muscle, 
however, is somewhat different from striped muscular fibres else- 
where. 
What is the difference in the contraction of striped and 
unstriped muscular fibre ? 
The striped muscular fibre usually contracts more rapidly. 
What is the consistency of muscle ? 
The contractile substance of muscle is so soft as to be almost 
fluid, being of the consistency of jelly. 
What is the chemical composition of muscle ? 
As already pointed out elsewhere, it is impossible to determine 
this during life, since the analysis produces death. Muscle, how- 
ever, contains the substances known as muscle-serum and muscle-clot 
or myosin, which are the result of certain chemical changes occur- 
ring after death. 
What effect has coagulation of the myosin in muscle ? 
Its formation is followed by “rigor mortis,” or post-mortem 
rigidity. 
In what way can this coagulation be postponed? 
By keeping the muscle at a temperature but a few degrees above 
freezing point. If a muscle be kept in this manner, pressure will 
cause the exudation from it of a yellow, opalescent, alkaline juice, 
which on still further cooling changes into a jelly. 
What effect has warming of this jelly ? 
It passes through the stages of coagulation seen in ordinary 
muscle after death, producing the same fluid serum and muscle-clot 
or myosin. 
What is this muscle juice sometimes called? 
Muscle plasma, which is supposed to be the contractile matter in 
living muscle. 98 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What does the coagulation of muscle plasma very closely 
resemble ?. 
The coagulation of blood plasma, with the difference that the 
muscle clot is gelatinous and not in threads, as is fibrin. It is a 
globulin, and is soluble in a two per cent, solution of common salt. 
Remember, that this globulin forms the greater portion of albu- 
minous matter in muscle. 
What is the difference between the reaction of muscles 
before and after death ? 
Before death they are alkaline; after death, acid. 
Of what does the serum of the muscle consist beside the 
albuminous principles ? 
1st, kreatin, kreatinin, and xanthin; 2d, haemoglobin; 3d, grape 
sugar, muscle sugar or inosit, and glycogen; 4th, sarcolactic acid, 
made from the inosit by fermentation; 5th, carbonic acid; 6th, 
potassium salts; and, 7th, 75 per cent, of water. 
What do you mean by the elasticity of muscle ? 
The degree to which the muscle can be stretched and still return 
to its normal length. If a given weight be applied to the end of 
a muscle, it is stretched a certain distance; but an additional 
weight or weights do not produce by any means an elongation 
equal to the first. The elongation, on additional strain, is con- 
stantly decreased in extent. 
Is there any variation in the elasticity of muscles? 
At first a strain on a muscle produces very rapid extension; but 
this is constantly decreased as time goes on, finally ceasing. 
Muscles which ‘are fatigued are more readily stretched than fresh 
ones. 
What difference is there between the elasticity of dead 
and living muscle ? 
Dead muscle possesses less elasticity and requires a greater 
weight to stretch it. It can be stretched further than living 
muscle, but does not return to its former length as completely as 
the normal muscle. THE MUSCLES. 
99 
Are the muscles of the body always on the stretch, and if 
so, what is the object reached by this condition? 
They are always on the stretch, even when passive, and act as 
ligaments which bind together, in a compact mass, the entire body. 
Muscles nearly always have opposing muscles whose function it is 
when exercised, to produce opposite movements. The elasticity 
of these muscles, in a passive state, also opposes active contraction 
in the opposite muscle, which is, however, easily overcome. After 
the active contraction has taken place, the elasticity of the passive 
muscle acts as a weak spring, thereby keeping up the tonicity of 
the limb and preventing sudden jerkings of the body, as would 
occur if a muscle should contract suddenly and “ take up the 
slack” in the opposite muscle. 
What electrical phenomena have we in muscle ? 
In the normal living muscle we have invariably present an 
electric current known as the natural muscle current. 
What circumstances influence this current ? 
It is greatly reduced by fatigue and loss of vital power, and is 
generally supposed to be absent in perfectly normal passive muscle 
lying in situ. As soon as the muscle is moved or disturbed by 
partial removal from the body the current develops. 
What do you mean by “negative variation” in muscle? 
If a muscle be connected with a galvanometer so as to measure 
its natural current and then be stimulated to a contraction by 
means of the nerve trunks, a marked decrease occurs in the 
current. The galvanometric needle swings toward the zero point, 
showing that the current is weakened and destroyed. This is 
called the negative variation, and precedes the change to an active 
condition of the muscle. 
What do you mean by the irritability of the muscle ? 
The capability with which a muscle passes into contraction. 
What are the usual causes of contraction of the voluntary 
muscles ? 
They contract ordinarily in response to impulses communicated 100 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
to them by nerves, the impulse originating in the brain or spinal 
cord. The will power is the most common cause of contraction 
of the skeletal muscles. 
What other conditions may produce contractions of the 
muscles ? 
Contraction of the muscles may be produced either by the appli- 
cation to them directly of some irritating or stimulating substance, 
or by the application of stimulation to their supplying nerves. 
Is it possible to cause contraction in muscular fibre which 
is devoid of terminal nerve filaments, or, in other 
words, does the contraction of a muscle necessarily 
depend upon the presence of peripheral motor 
nerves ? 
That muscles may be stimulated to contraction without the in- 
tervention of nerve fibres, is proved by the fact that some parts 
of muscles, as the lower end of the sartorius, respond energetically 
to all forms of muscle stimuli, though they possess no nerve 
endings; there are some substances, too, which produce contrac- 
tion of muscles on direct application, which will not produce that 
contraction when applied to the nerve trunk, as, for example, 
ammonia. Again, the muscles will generally respond to various 
stimuli long after the nerve supplying them has been killed by 
exposure, and curare, which paralyzes the peripheral ends of the 
motor nerves in the muscles, in no way prevents the contraction 
of the muscle itself when it is directly stimulated. 
What forms of muscle stimuli have we ? 
First, mechanical stimulation, as by a sudden blow or pinch, 
resulting in momentary transient contraction. Second, thermic 
stimulation. Contraction of the muscle takes place if the tem- 
perature be raised or lowered. This contraction, however, is 
scarcely identical with ordinary muscular contractions, since it is 
a prolonged spastic contraction of an abnormal type. Third, 
chemical stimulation, which may produce contractions by irri- 
tating mineral and organic acids, various metallic and neutral 
salts. Fourth, electrical stimulation, which is the most common 
form employed, and gives the most satisfactory results. THE MUSCLES. 
101 
At what time during the application of an electrical current 
to a muscle does the contraction take place ? 
Remember that it takes place not while the current is passing 
through the muscle, but at the moment the current is turned on 
or turned off, or is suddenly increased or decreased in strength. 
A constant current of exactly even intensity may be made to pass 
through a muscle without exciting contraction. 
Is the stimulus necessary to produce contraction in a muscle 
when applied to its nerve trunk, sufficient to pro- 
duce the same degree of contraction in the muscle 
when applied to the muscle itself? 
No, it is not. 
What are the chemical changes resulting in a muscle 
during its contraction? 
Its neutral or faintly alkaline reaction becomes for the moment 
acid, owing to the formation of sarco-lactic acid. More oxygen 
is taken up from the blood than when the muscle is at rest. A 
greater amount of carbon dioxide is given off, but the change in 
the quantity of CO2 has no exact relation to the quantity of oxygen 
used. A diminution is said to occur in the glycogen of muscle, 
and a peculiar muscle sugar makes its appearance. 
What changes occur in the elasticity of the muscle during 
contraction? 
The elasticity is less than when it is in a passive state—that is, 
a given weight will stretch a contracted muscle more than a passive 
muscle, but the return to the normal length of the muscle is not 
so complete, or, in other words, extensibility is increased, elasticity 
is decreased. 
What effect, therefore, has stimulation of a muscle which 
is overloaded by a weight greater than it can lift ? 
When stimulation is applied to such a muscle we get elongation 
instead of contraction, because of the rule just now given, namely, 
that the active state lessens the elastic power of the muscle. 102 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What effect has stimulation of one part of a muscle upon 
the rest of the muscle ? 
A contraction wave passes from the part stimulated over the 
whole mass. 
What effect has the activity of muscle fibre upon its 
temperature ? 
It raises it very markedly, the production of heat being in 
direct proportion to the tension of the muscle. If the muscle be 
kept in a state of constant activity, so that fatigue is produced, the 
temperature falls. 
What change in shape takes place in the muscle on 
contraction? 
It shortens, and in direct ratio with its shortening its thickness 
increases. There is, therefore, but little change in bulk, but con- 
siderable change in shape. 
What do you mean by the “latent period” ? 
The short space of time which elapses between the moment of 
stimulation of a muscle and the beginning of its contraction. In 
the voluntary muscle of the frog this lasts only about one-tenth of 
a second. 
What do you mean by the period of “ rising energy”? 
The space of time during which contraction occurs first slowly, 
then more quickly, then more slowly. 
What do you mean by the term “falling energy”? 
The period at which relaxation of the muscle takes place. At 
first slowly, then more quickly, finally, more slowly. 
Is there any pause at the height of contraction before 
relaxation begins ? 
No, none at all. 
Is there any variation in the rapidity of contraction of 
different muscles ? 
Yes, an enormous difference exists not only in various animals, 
but in the same muscles of a single individual. As an example THE NERVOUS SYSTEM. 
103 
of the difference in rapidity of contraction in the muscles of diff- 
erent animals, may be mentioned the fact that while the unstriped 
muscular tissue of a mollusc occupies several minutes for its con- 
traction, the muscle of the wing of a horse-fly contracts 330 times 
a second. The variation and rapidity of contraction differ very 
largely with the needs and habits of the animal. 
What do you mean hy the “maximum contraction” of a 
muscle? 
The greatest shortening which can be produced by a single in- 
stantaneous impulse or stimulus. 
What do you mean by the term “summation”? 
If a muscle be caused to contract by a shock of medium strength 
it contracts to its maximum, but if a second shock be given while 
the muscle is contracting from the first shock, a new maximum 
contraction is added to that already under way. This is called 
the summation of effect. 
What do you mean by the “tetanus ”? 
A condition of a muscle in which it apparently remains in a 
constant state of contraction—or, in other words, a summation of 
contractions exists. To produce artificial tetanus, impulse after 
impulse must be transmitted to the muscle with great rapidity, 
otherwise between each stimulus the muscle will partially relax 
or attempt to pass into the condition known as falling energy. 
Upon what does the irritability and fatigue of a muscle 
depend ? 
This is governed by the amount of labor required and the nour- 
ishment supplied by the blood. Fatigue means lessened irrita- 
bility. 
THE NERVOUS SYSTEM. 
What is the function of the nervous system ? 
It is the apparatus by which distant parts of the body are 
kept in constant relationship with one another so that a change of 104 
ESSENTIALS OF HUMAN PHYSIOLOGY 
condition in any one spot is communicated to, and may set up 
corresponding changes in, remote parts. 
What two divisions have we of nerve fibres?, 
The afferent or centripetal, and the efferent or centrifugal; most 
nerves contain both sets of fibres. 
Do nerve fibres possess the power of generating force in 
themselves ? 
They do not. Neither are they capable of originating impulses. 
They are functionally inactive until they receive impulses from 
higher nerve centres. 
What is the arrangement of the sheaths of the nerve 
fibres ? 
In the centre of every nerve is a bundle of protoplasmic fibrils, 
always covered, and known as the axis-cylinder; in some nerves 
there is but one very thin transparent covering termed the primi- 
tive sheath, while in others there is a thick layer of fluid inside the 
primitive sheath in immediate contact with the axis-cylinder. 
The fluid, which is very viscid, is known as the white substance of 
Schwann ; it is also called the medullary sheath. 
What is the distinction between the white and the gray 
nerves? 
The white nerves contain the white substance of Schwann, the 
gray nerves do not. 
Which of these two varieties is the most common ? 
The white by far, since the gray are contained chiefly in the 
sympathetic system and parts of the organs of special sense. 
What is the function of an afferent, centripetal, or sensory 
nerve ? 
To carry impulses from the periphery to the centre which may 
receive them. 
What is the function of an efferent, centrifugal nerve? 
To carry impulses from the centre to the periphery, which THE NERVOUS SYSTEM. 
105 
impulses may arise of themselves in the central nervous system or 
be excited reflexly through a sensory nerve. 
Are impulses travelling along one nerve trunk ever trans- 
ferred to another nerve trunk running near by ? 
No, never, under any circumstances, if both nerves are intact. 
How many divisions have we of efferent nerves? 
First, motor, or nerves going to muscles causing them to contract; 
second, secretory, which call forth the activity of glands; third, 
inhibitory, which check or prevent some activity; fourth, vaso- 
motor nerves, which regulate the contraction of the muscular coat 
of the bloodvessels, and trophic, thermic, and electric nerves, all 
of which are doubtfully in existence, save the electric, which occur 
in animals capable of emitting electrical discharges. 
What do you mean by inter-central nerves ? 
Inter-central nerves are those which act as bonds of union be- 
tween the cells of nerve centres. 
What is the velocity of nerve force ? 
It is about at the rate of thirty metres per second, or the speed 
of a fast express train, so that impulses can only travel from one 
portion of a man’s body to another at about the same rate as an 
express, or about twice as fast as the fastest horse can gallop. 
What do you mean by “ negative variation” ? 
The natural current of a nerve, like that of a muscle, undergoes 
a diminution at the moment the nerve is stimulated; this is termed 
the negative variation. The negative variation travels along the 
nerve at just the same velocity as the impulse does from the point 
of stimulation, as a consequence of this the negative variation and 
nerve impulse are believed to be identical. 
What do you mean by electrotonus ? 
If one of two wires leading to a galvanometer be'applied to the 
centre, and the other to the end of the nerve so as to indicate the 
natural current, and at the same time another part of the nerve be 
placed in the circuit of a constant current from the battery, and 106 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
the current be turned on, a change is found to occur in the natural 
current; this is termed electrotonus. 
What do you mean by the terms anelectrotonus and 
katelectrotonus ? 
Anelectrotonus is the term applied to the condition of the nerve 
near the anode, or positive pole, during the passage of a constant 
electrical current, the irritability of the nerve being decreased in 
this region. Katelectrotonus is applied to the part of the nerve near 
the cathode, or negative pole, the irritability being here increased. 
What do you mean by the irritability of nerves ? 
The condition which permits of the transmission of impulses 
from more or less powerful stimuli. 
What conditions are necessary for this irritability ? 
A perfect supply of blood, to bring nourishment and carry away 
effete matters, an uninjured connection with the nerve centres, and 
a normal temperature. 
At what portion of the nerve trunk would you apply the 
stimulus to produce the greatest contraction in the 
tributary muscle, or, in other words, at what point 
would you find the greatest irritability of the nerve ? 
At some part of the nerve distant from the muscle. The further 
from the muscle the more powerful is the contraction produced. 
The impulse seems to gather force as it goes along the nerve. 
What do you mean by the “ indifferent point” of a nerve? 
As already stated, when a constant current is applied to a nerve 
its irritability is greater in the neighborhood of the cathode but is 
diminished in the neighborhood of the anode. Near the middle 
of the nerve, or rather a point about half way between each pole, 
we have an area known as the indifferent point, since at this portion 
the increased irritability of the cathode no longer exists, nor does 
the diminished irritability of the anode occur. This indifferent 
point is not always midway between the two poles, since variations 
in the strength of the current influence its position. PHYSIOLOGY OF THE SPINAL NERVES. 
107 
What are the laws of contraction ? 
1. In all muscles, when the current is broken, the disappearance 
of anelectrotonus is the cause of the stimulation. 2. When the 
current is made it is the appearance of katelectrotonus which 
causes the stimulation. 3. With the same current the contraction 
produced with the making of the current is more than the contraction 
which occurs on the breaking of the current. 4. Anelectrotonus 
causes reduction of irritability and conductivity. 5. Katelectrotonus 
causes increase of irritability. 6. With ascending currents, the 
portion of the nerve next to the muscle is in a state of reduced 
functional activity or anelectrotonus. 7. With descending cur- 
rents the part of the nerve next the muscle is in a state of exalted 
activity—katelectrotonus. 8. These changes are much weaker with 
weak currents than with strong ones. 
What do you mean by the term nerve corpuscles or terminals? 
Those small nerve bodies or corpuscles in which nerve fibres end 
and through which efferent nerve fibres give off their impulses 
and afferent nerve fibres receive their impulses. Those which are 
attached to the endings of sensory or afferent nerves of the skin 
are known as tactile corpuscles. 
PHYSIOLOGY OF THE SPINAL 
NERVES. 
It will be remembered that thirty-one pairs of spinal nerves 
leave the vertebral canal between the vertebrae, in contradistinc- 
tion to the cranial nerves which come out from the base of the 
skull, and that each pair of nerves is attached to the spinal cord 
by two roots known as the anterior and posterior, which becoming 
united pass throngh the intervertebral canal, forming one trunk. 
Just before the junction of the two roots it will also be remembered 
that the posterior root is enlarged by a ganglionic swelling. The 
spinal nerves are, therefore, sometimes called mixed nerves for the 
reason that they contain both efferent and afferent fibres. Those 
going from the anterior portion of the spinal cord carry the motor 
or efferent impulses, those coming to the posterior part of the 
spinal cord carry the afferent impulses. 108 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What do you mean by recurrent sensibility ? 
If after division of a motor nerve the peripheral portion of it be 
stimulated some pain is felt. This is due to what is known as 
recurrent sensibility, and depends on the fact that some of the fibres 
of the sensory root, after having joined the motor root, instead of 
going as usual to the periphery, revert to the spinal cord and enter 
it by the motor root. This condition of recurrent sensibility is 
also found in some of the peripheral mixed nerves. 
What is the function of the ganglia which occur on the 
posterior roots of the spinal nerves ? 
Their function is not clearly understood. There is no evidence 
of their being centres of reflex action, nor can they be shown to 
possess any marked automatic activity, but it is supposed that 
they preside over the nutrition of the nerve itself, for if the roots 
be cut off, that part of the posterior root attached to the cord 
degenerates, while the piece attached to the ganglion remains intact. 
This is not the case where the anterior or motor root is cut, since 
under these circumstances that portion of the nerve next the cord 
remains intact, while the divided portion undergoes degeneration. 
From this it would appear that the nutrition of the sensory nerves 
is governed by the ganglia, while that of the motor nerves is gov- 
erned by centres in the cord itself. 
THE PHYSIOLOGY OF THE CEREBRO- 
SPINAL NERVOUS SYSTEM. 
The physiology of the cerebro-spinal nervous system includes 
that of the spinal cord and the medulla oblongata, the brain, and 
the nerves given off from each one of them, and the functions of 
the ganglia on those nerves. 
What is the function of the membranes of the brain and 
spinal cord ? 
The dura mater is a tough membrane, and composed of bundles 
of connective tissue, whose function it is to enclose, and, to a cer- 
tain extent, protect the nervous tissue beneath it. The arachnoid CE REBRO-SPIN AL NERVOUS SYSTEM. 
109 
is a much more delicate membrane, similar in structure to the dura 
mater; the function of which is to secrete the cerebro-spinal fluid. 
The pia mater consists of immense numbers of bloodvessels, which 
dip down and nourish the surface of the brain. 
What do you mean by the neuroglia ? 
A special form of connective tissue which supports the nerve- 
fibres and the cells of the brain and spinal cord. 
Of what does the spinal cord consist ? 
It is a cylindriform column of nerve-substance connected with 
the brain through the medium of the medulla oblongata, and ter- 
minating in the midst of the roots of the many nerves which form 
the cauda equina. It is composed of white and gray nervous 
matter, of which the white is- situated externally, and constitutes 
the chief portion, while the gray occupies its central portion, and 
is so arranged that on the surface of a transverse section it appears 
like two somewhat crescentic masses, connected together by a 
narrow portion or isthmus. 
Is the spinal cord of the same size throughout its whole 
length ? 
No; it varies greatly. It is very large in the middle and lower 
part of the cervical region and at the lowest part of the dorsal 
region, since at these two points a large number of nerve fibres are 
given off. 
Of what does the white substance of the spinal cord consist? 
Of nerve fibres with a medullary sheath. 
What is the function of these nerve fibres ? 
The transference of impulses from cell to cell. 
Of what does the gray matter consist? 
Of a dense network of naked nerve fibrils with numerous gan- 
glionic cells scattered between them. The nerve fibres in this 
substance also transmit impulses from cell to cell. 
Does the white or the gray substance contain the ganglionic 
cells ? 
The gray substance. 110 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What are these cells called? 
Multipolar, bipolar, or unipolar cells, for the reason that they 
possess processes, one or more in number, which do not divide in 
the same way as do the interlaced nerve fibres. 
What groups of nerve cells have we in the gray matter ? 
1. In the anterior cornua are cells which are the points of origin 
for the motor spinal nerves. (See Fig. 8.) 
Fig. 8. 
direct pyrami- 
dal tracts. 
Cells of origin 
z of ant. nerve 
roots. 
Anterior column. 
Intermedio- - 
lateral tract. 
Vesicular 
column 
of Clark. 
Gelatinous 
substance of 
Rolando. 
Antero-lateral column. 
Lateral column. 
Gray substance. 
— Crossed pyramidal tract. 
Cerebellar tract. 
Column of Goll. 
Column of Burdach. 
Transverse section of the spinal cord at level of the upper dorsal vertebrae. 
2. The tractus intermedio-lateralis, a group of nerve cells mid- 
way between the anterior and posterior cornua, near the external 
surface of the gray matter. (See Fig. 8.) 
3. The posterior vesicular columns of Clark and Stilling are 
found in the posterior cornua near the inner surface. (See Fig. 8.) 
4. The substantia gelatinosa cinerea of Rolando is scattered 
throughout the gray matter, but is chiefly found in the posterior 
cornua. (See Fig. 8.) CEREBRO-SPINAL NERVOUS SYSTEM. 
111 
Into how many columns is the spinal cord divided? 
Three on each side. The following scheme will illustrate this 
more clearly than words, particularly if the figure is also examined: 
The direct or uncrossed pyramidal tracts. 
The anterior ground bundles or anterior radi- 
cular zones. 
1. Anterior columns . 
2. Posterior columns , 
Goll’s column, or the postero-median column 
Burdach’s columns, or the posterior radicular 
zones, the posterior lateral columns or the 
funiculus cuneatus. 
3. Lateral columns 
The anterior and lateral mixed paths. 
The crossed pyramidal paths. 
- The direct cerebellar paths. 
The Functions of the Spinal Cord. 
In what manner is conduction carried on by the spinal cord? 
It carries the sensory impulses transmitted to it by the sensory 
nerves up to the perceptive centres in the brain, and the motor im- 
pulses from the brain down to the nerves which are distributed to 
the muscles. 
Roughly speaking, what portion of the cord may be con- 
sidered motor, and what portion sensory ? 
The anterior portion is motor; the posterior, sensory. 
What difference is there in the function of the white and 
gray matter ? 
According to Schiff, and most physiologists, the gray matter 
transmits in all directions both sensory and motor impulses which 
are purely reflex in character, or, in other words, only intended to 
remain in the cord, while sensory impulses which are to go to the 
brain, or motor impulses which pass from the brain, must travel by 
the white matter. 
It will be remembered that both the anterior motor and the 
posterior sensory nerve roots d<? not arise from the white matter, 
but from the horns of the gray, 112 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
The function of the gray matter in the posterior horns is, there- 
fore, limited to the receipt and transmission of sensory impulses 
from the periphery to the white matter, which will conduct them 
to the brain, or across the cord to a motor cell to complete a reflex 
action.1 
The function of the gray matter of the anterior horns is limited 
to the transmission of motor impulses from the white matter to 
the motor nerve trunks, or to the originating of a reflex movement. 
What function is supposed to be possessed by the gray 
matter around the central canal of the spinal cord? 
To transmit sensory impulses up to the brain without their 
having to pass through the white columns. 
In what way can you prove, physiologically, that the anterior 
columns of the cord are motor and the posterior sensory? 
If the posterior columns be destroyed, the foot may be burnt off 
but no signs of pain are elicited. If, upon the other hand, the 
anterior columns be destroyed, burning of the foot produces vio- 
lent pain-cries, but the animal is unable to send the impulse from 
the brain to the leg and draw it away from the injury. 
What is the function of the direct or uncrossed pyramidal 
tracts of the anterior columns and the crossed 
pyramidal tracts of the lateral columns ? 
They carry all the impulses from the central convolutions of the 
cerebrum, by which voluntary movements are executed. 
What is the function of the direct cerebellar paths of the 
lateral columns ? 
They connect with the cerebellum directly by ascending fibres, 
which proceed through the restifonn bodies from Clarke’s columns 
of nerve cells in the gray matter. They connect the posterior nerve 
roots of the trunk (not of the extremities) with the cerebellum. 
1 For definition of a reflex movement, see page 114, CE REB R O - SP IN AL SYSTEM. 
113 
What is the function of the anterior ground bundles of 
the anterior columns, and the anterior and lateral 
mixed paths of the lateral columns ? 
They connect the gray matter of the spinal cord with that of the 
medulla, and carry reflex impulses. They also contain those fibres 
which are the direct continuation of the anterior spinal nerve 
roots which have entered the gray matter. The anterior and 
lateral mixed paths of the lateral columns also contain some sen- 
sory paths. 
What is the function of Goll’s column ? 
It unites the posterior roots with the gray nuclei of the posterior 
pyramids, otherwise known as the funiculi gracili, and carries 
impulses centripetally. 
By what is the nutrition of these various conducting paths 
governed ? 
By nutritive centres, in the case of the centripetal tracts, situated 
in the cerebrum. In the centrifugal, or motor, tracts these centres 
are situated in the anterior cornua of the cord. 
What classifications can we make in the functions of the 
nervous centres in the cord ? 
Their functions can be divided into conduction, transference, reflec- 
tion, and automatism, or the power of originating impulses in them- 
selves. 
Give an example of conduction through a nerve centre. 
If an impulse travels from a peripheral sensory nerve to a single 
centre in the spinal cord reflexly it may produce contraction in 
the muscles which are tributary to the motor centre next to it. 
This stimulation, if strong enough, may cause an impulse to travel 
to all the other centres in the cord, so that general muscular move- 
ments may take place. 114 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Give an example of the transference of nerve force. 
The pain in the knee or ankle occurring during hip disease is a 
good example of this condition, and is supposed to be due to the 
fact that the sensory nerves running from the hip carry impulses 
up to the sensory cells in the spinal cord, which again transfer the 
sensation they receive to sensory centres in direct communication 
with the area of the knee or ankle. Under these circumstances 
the brain receives the impulse from the two sets of fibres and mis- 
interprets the real cause of the sensory impulse. The impulse, 
under these circumstances, may be divided into two portions, the 
first, which is the primary, and goes to the brain directly from the 
cells in communication with the hip, while the other is the second- 
ary, and is due to the transference to other centres of the impulse 
before it reaches the brain. If the primary and secondary impulses 
reach the brain together the pain is referred to both the hip and 
knee. 
What do you mean by the reflexion of nerve force, or reflex 
action? 
Reflex action is due to the fact that an impulse travelling from 
the periphery to the body along the sensory nerve reaches the same 
point at which a sensory or receptive cell and a motor or expulsive 
cell exist side by side. Under these circumstances the sensory cell 
transfers an impulse to the motor cell, by conduction, which in 
turn starts an impulse down along its tributary motor nerve, with 
the result of contraction in the muscle which it supplies. 
Give an example of this. 
If the foot of a frog be pricked the leg which is pricked, and, to a 
certain extent, the other leg, are immediately jerked away. That 
this jerking away of the leg is not due to the fact that the brain 
desires to remove the leg from the irritation, is proved by the fact 
that if the spinal cord be cut, thereby preventing any impulses 
from reaching the brain, reflex action is as marked as if the cord 
was intact. CE REBRO-SPIN AL SYSTEM. 
115 
What is Setschenow’s reflex inhibitory centre? 
A centre situated in the upper portion of the spinal cord whose 
function it is to prevent excessive reflex action. If it were not for 
this centre the pricking of a pin would cause but a slight reflex 
contraction of the leg, while a violent blow would send such an 
impulse to the reflex centres that a severe convulsion or tonic 
spasm might result. Under these circumstances, however, the 
reflex inhibitory centre controls the motor centres of the spinal 
cord and prevents their sending out impulses which would be too 
violent. 
What is automatism? 
The originating, entirely independent of any external cause, of 
an impulse in a nerve cell. 
What special centres have we in the spinal cord ? 
Centres which govern the bladder and genital organs. 
What effect has irritation applied directly to the anterior 
and lateral white columns ? 
It produces muscular movements but no pain, and they are con- 
sequently excitable but insensible. 
Are the posterior columns, when irritated, sensitive or 
insensitive ? 
They are very sensitive, particularly near the origin of the pos- 
terior roots. 
Is this sensibility due to the presence of sensory nerve 
filaments belonging to these columns, or simply to 
the presence of the fibres of the posterior roots ? 
It is simply due to the fibres of the roots. 
What effect has section of the antero-lateral columns ? 
It abolishes all power of voluntary movement in the lower 
extremities. 116 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What effect has section of the posterior column ? 
The power of muscular coordination is lost. It is these columns 
which are diseased in locomotor ataxia. 
Does the gray matter respond in any way under the 
influence of direct stimulation? 
No, it does not. 
What is the result of a lesion of the spinal cord in the 
lower part of the sacral region ? 
There is paralysis of the sphincters of the rectum and bladder 
and of the accelerator urinae, and the compressor urethrae muscles. 
What is the result of a lesion high up in the sacral region ? 
Paralysis of the muscles of the bladder, rectum, and anus; loss 
of sensation and motion in the muscles of the leg, except those 
supplied by the anterior crural and obturator nerves. 
What is the effect of a lesion on the upper part of the 
lumbar region ? 
Loss of motion and sensation in both legs; loss of power over 
rectum and bladder; paralysis of the muscles of the abdominal 
walls. As a result of this, there is some interference with respira- 
tion. 
What effect has lesion of the cervical part of the cord ? 
It produces palsy, as do the other lesions named, with, in addi- 
tion, paralysis of all the intercostal muscles, and, as a result, great 
interference with respiration. There is paralysis of the muscles 
of the upper extremities except those of the shoulders. If a lesion 
occurs at the upper cervical region, death is instantaneous from 
respiratory failure. 117 
THE MEDULLA OBLONGATA. 
The points to be remembered concerning this portion of the nervous 
system are as follows: 
Its columns are continuous with those of the spinal cord, and 
each half of it may be considered to be divided into three columns 
or tracts of fibres, in the same manner as they occur in the spinal 
cord. 
What difference exists between the columns here and in 
the cord? 
They are more prominent, and separated from each other by 
deeper grooves. 
What are these columns of the medulla called ? 
B 
Pyramids; the anterior columns are called the anterior pyramids, 
those of the posterior columns restiform bodies. 
The Medulla Oblongata. 
Fig. 9. 
Anterior median fissure. 
Pyramid. 
’ Hypoglossal 
nerve. 
Olivary body. 
— Vagus nerve. 
Membrana reti- 
culata. 
Origin of the tri- 
facial. 
Respiratory 
centre 
—' Continuation of 
cerebellar tracts. 
'•» Posterior column 
Diagram showing cross section at level of fourth ventricle. 118 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What are the direct pyramidal tracts ? 
The anterior pyramids which pass directly upward to the cere- 
brum without crossing to the other side. 
What are the crossed pyramidal tracts? 
Those fibres of the lateral columns which cross to the opposite 
anterior pyramid. 
What is the olivary body ? 
On the outer side of each anterior pyramid is a small oval mass 
of gray matter, the olivary body. 
What is the posterior pyramid ? 
A small tract marked off from the posterior part of the restiform 
bodies on each side by a slight groove. 
What forms the fourth ventricle ? 
The restiform bodies diverge, and by so doing lay open a space— 
the fourth ventricle. 
What is the distribution of the fibres of the medulla 
oblongata ? 
The anterior pyramids receive fibres from the middle fibres of 
the lateral columns of the cord, not only from the same side but 
from opposite sides. In other words, some of the lateral fibres of 
the left side enter the anterior pyramid of the right side and vice 
versa. These are the crossed pyramidal tracts already mentioned. 
What is the crossing from one side to the other called ? 
Decussation. 
After this occurs, what happens next ? 
The anterior pyramids with their new fibres pass on upward, 
the greater part going through the pons to the cerebrum, while a 
smaller part joins some fibres from the olivary body forming the 
olivary fasciculus or fillet. Still another small mass of fibres pro- 
ceeds to the cerebellum. 
What course do the fibres of the lateral columns pursue ? 
The outer fibres go with the restiform tract to the cerebellum, 
the middle decussate to the anterior pyramids as already stated, THE MEDULLA OBLONGATA. 
119 
and the inner pass on to the cerebrum along the floor of the fourth 
ventricle. 
What is the direct cerebellar tract ? 
The outer fibres of the lateral columns first named. 
Do the impulses of the will which arise in the brain pass 
down each side of the spinal cord directly and 
produce contractions in muscles of the same side ? 
No, they do not. The fibres carrying these impulses cross each 
other in such a way that impulses arising in the left side of the 
brain are made manifest on the right side of the body, while those 
arising in the right side of the brain are made manifest in the left 
side of the body. 
Why is this so ? 
The decussation of part of the fibres of the anterior pyramids of 
the medulla transfer impulses across the cord. 
Does this same transference of impulses take place in the 
sensory tract, or, in other words, is a sensation 
occurring in the left foot recognized in the right 
hemisphere of the brain ? 
Yes. 
Does the transference take place in the medulla ? 
No, it does not. The posterior fibres do not decussate in the 
medulla, but Brown-Sequard has shown that the crossing takes 
place in the spinal cord. 
What is the function of the medulla oblongata ? 
In many ways it is similar to that of the spinal cord for it carries 
on conduction, transference, reflexion, and automatism. It is in 
this portion of the nervous apparatus that the decussation of part 
of the fibres of the anterior cornua of the medulla takes place, ex- 
plaining the phenomenon which has just been mentioned in regard 
to paralysis occurring on the opposite side from the lesion. 
What special centres exist in the medulla oblongata ? 
First, the respiratory centre, whose function it is to send out 
those impulses which result in respiratory movements, and the 120 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
interference with which causes great disorder of respiration or 
death; second, it contains the centre of deglutition which sends 
out the impulses which produce the movements necessary to the 
acts of swallowing; third, a centre for the movements of mastica- 
tion; fourth, the chief vaso-motor centre which governs the blood- 
vessels all over the body (see Circulation); fifth, the cardio-in- 
hibitory centre for the regulation of the movements of the heart 
through the pneumogastrics; sixth, the cilio-spinal centre which 
governs the movement of the iris; seventh and eighth, the centres 
of the special senses of hearing and taste; ninth, the centre for 
speech; tenth, the centre for vomiting ; eleventh, the centre which 
governs the secretion of saliva. 
How do you know that the medulla contains all those 
centres which are necessary for the continuance of 
life? 
Because the brain and cerebellum can be destroyed and yet the 
respiration and heart go on unimpaired. 
What is the function of the pons Varolii? 
It contains a large number of nerve fibres both transverse and 
longitudinal and is a conductor of impressions from one part of 
the spinal axis to another. Concerning its functions as a nerve 
centre little or nothing is certainly known. 
What are the functions of the crura cerebri? 
They are formed of nerve fibres, of which the inferior or super- 
ficial are continuous with those of the anterior pyramidal tracts of 
the medulla, and the superior or deeper fibres with the lateral and 
posterior pyramidal tracts, and with the olivary fasciculus. Each 
crus cerebri contains among its fibres a mass of gray substance 
known as the locus niger. They act principally as conducting 
organs. As nerve centres they are probably connected with the 
functions of the oculo-motor nerve which arises from the locus 
niger, and through which are directed the numerous movements 
of the eyeball. They are also connected with the coordination of 
other movements than those of the eye. THE MEDULLA OBLONGATA. 
121 
What is the result of injury to the crus cerebri ? 
Either rotatory or disorderly movements, with loss of coordina- 
tion, result. 
What is the function of the corpora quadrigemina ? 
Removal of those bodies produces total loss of vision; destruc- 
tion of one of them produces blindness in the eye of the opposite 
side. It also produces rotatory movements of the body resembling 
those occurring after division of the crus cerebri, save that the 
movements are slower. 
What is the function of the corpora striata and the optic 
thalami ? 
Injury to the corpora striata on one side prevents the communi- 
cation between the will and the muscles of the opposite half of the 
body, so that palsy results, or, in other words, hemiplegia. The 
corpus striatum may, therefore, be considered as the motor con- 
nection between the cerebrum and the crus cerebri. If the optic 
thalamus is destroyed on one side sensation of the opposite side of 
the body is impaired or lost. It is, therefore, regarded as the sen- 
sory band between the cerebrum and the crus cerebri. 
What are the functions of the cerebellum ? 
It is absolutely insensible to irritation and may be cut away 
without any signs of pain ; its removal from the body or destruc- 
tion by disease is generally unaccompanied by loss or disorder of 
sensibility. Animals from which it is removed can see, hear, and 
feel pain to all appearance as perfectly as before. It governs the 
coordination of movements, and while irritation of the cerebellum 
produces no movements at all, remarkable results are produced by 
removing part of its substance. As portion after portion of it is 
cut away the animal gradually loses the power of springing, walk- 
ing, standing, or preserving its equilibrium. If laid upon its back 
it cannot recover its normal posture but struggles to get up, and 
if a blow is threatened tries to avoid it. 
What results do we gain, therefore, from these experiments? 
We know that the cerebellum has no connection with volition, 
sensation, and memory, but merely has the faculty of combining 122 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
the action of the muscles and producing thereby the movements 
intended by the higher nervous centres. Remember that the 
influence of each half of the cerebellum is directed to the govern- 
ment of the opposite side of the body, and that both halves must 
act in unison, or, otherwise, strange disorders of motility result. 
What is the function of the cerebrum ? 
The cerebral hemispheres are the organs by which perception is 
carried on. They contain the organ of the will; they possess 
memory, or the means of retaining impressions of sensible influ- 
ences ; and they are the medium of all the higher emotions and 
feelings—imagination, understanding, reflection, and judgment. 
How do we know that consciousness depends upon the 
action of the cerebral hemispheres ? 
If they are injured in any way, consciousness is lost—as, for 
example, during an apoplectic fit. 
How do we know that it is in the cerebral hemispheres 
that the intellect is situated ? 
Because the higher the intellect is the greater development is 
possessed by the brain and because destruction of the cerebrum 
stops intellection. Congenital and other morbid conditions of the 
hemispheres always produce disorders of the intellect. 
What do you mean by cerebral localization ? 
The determination of the areas in the cerebral hemispheres 
governing various portions or functions in the body. 
Where is the speech centre located in the cerebrum ? 
In the third frontal convolution and the Island of Reil. 
On which side of the brain is the speech centre best 
developed? 
The left side. 
What is aphasia ? 
The partial or complete loss of the power of articulate speech 
from causes arising in the cerebrum. THE CRANIAL NERVES. 
123 
THE CRANIAL NERVES. 
It will be remembered that, according to most anatomists, the 
cranial nerves are divided into twelve pairs. 
1. What is the function of the olfactory nerve ? 
It is the nerve of special sense by which odors are distinguished; 
in other words, it is the nerve of smell. It is distributed to the 
mucous membrane of the nose, and arises superficially from the 
lower part of the frontal lobe in advance of the anterior perforated 
space, passing through the cribriform plate of the ethmoid bone. 
2. What is the function of the optic nerve ? 
It is the nerve of sight, and is distributed to the retina of the 
eye. It arises superficially from the geniculate and quadrigeminal 
bodies and thalamus, and passes out through the optic foramen of 
the orbit. It conveys no other impulses than those of sight. 
What is the effect of division of one of the optic nerves ? 
It produces complete blindness in the eye of the corresponding 
side. 
What is the effect of division of the optic tract ? 
It produces loss of sight in the outer half of the eye of the same 
side, and of the inner half of the eye of the opposite side. 
What is the effect of injury to the anterior part of the 
optic chiasm ? 
It causes blindness in the inner half of both eyes. 
3. What is the function of the oculo-motor nerve ? 
It is the motor nerve of the levator palpebrarum, the superior, 
internal, and inferior rectus, and the inferior oblique muscle of the 
eye. Its superficial origin is the inner side of the cerebral crus, 
and it finds its exit from the sphenoidal foramen. It also supplies 
filaments to the ciliary ganglia from which the ciliary nerves 
arise, which enter the eyeball and are distributed to the circular 
fibres of the iris and the ciliary muscle. It governs the accommo- 
dation of the eye. 124 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What effect has stimulation of the oculo-motor on the 
pupil ? 
It causes contraction of the pupil, internal strabismus, and mus- 
cular movements of the eye, but no pain. Section of the nerve is 
followed by ptosis, or drooping of the upper eyelid, internal stra- 
bismus, due to the supposed action of the external rectus muscle, 
and paralysis of the accommodation of the eye. 
4. What is the function of the pathetic nerve ? 
It governs the movements of the eyeball so far as those are con- 
cerned which are produced by the action of the superior oblique 
muscle; it arises from the valve of Vieussens and passes through 
the sphenoidal foramen. 
5 What is the function of the trifacial nerve ? 
It is a nerve of sensation, motion, and taste. It arises from the 
side of the pons by a smaller motor and a larger sensory root, and 
is divided into three divisions, the first of which supplies the 
conjunctiva, the lachrymal gland, the eyeball, the upper eyelid, 
the integument of the forehead, and the mucous membrane and 
integument of the nose. The second division supplies the lower 
lid and conjunctiva, the temple, upper lip, nose, cheeks, and teeth 
of the upper jaw. These two divisions are purely sensory. The 
third division supplies the muscles and skin of the lower part of 
the face, the muscles of mastication, the teeth in the lower jaw, the 
tongue, the parotid gland, and the auricle of the ear. This di- 
vision contains motor, sensory, and other filaments which carry 
the sense of taste. 
What is the effect of irritation of the larger root of the 
trifacial nerve ? 
It produces marked evidence of pain, which is always felt in the 
periphery of the nerve, since it will be remembered that pain 
arising at the origin of a sensory nerve is always referred to its 
peripheral filaments. Irritation of the small root produces move- 
ments of the muscles of mastication, whilst section of this root 
causes paralysis of these muscles. Section of the large root is THE CRANIAL NERVES. 
125 
followed by a complete abolition of sensibility in the head and 
face, but no disturbance of motion. 
6. What is the function of the abducent or sixth pair of 
nerves ? 
Motion, which results in turning the eyeball outward. They 
arise from the anterior pyramids, and supply the external rectus 
muscle of the eye. Stimulation of this nerve causes outward 
rotation of the eyeball, while paralysis of it causes internal stra- 
bismus. 
7. What is the function of the facial nerve ? 
It supplies the motor filaments of the muscles of the ear, scalp, 
and face—platysma, digastric, and stylohyoid muscles—and arises 
between the olivary and restiform bodies. It finds its exit through 
the internal auditory meatus, the facial canal, and the stylo- 
mastoid foramen. 
What is the peculiarity of the facial nerve? 
It is a motor nerve in its origin, but in its course receives sensory 
filaments from the fifth pair and the pneumogastric. Irritation of 
the facial produces muscular contractions, while division produces 
paralysis of the muscles of the face. Remember, that it is this 
nerve which gives off the chorda tympani, that branch which 
supplies the bloodvessels and secretion of the sublingual and sub- 
maxillary glands and the sense of taste in the anterior two-thirds 
of the tongue. 
8. What is the function of the auditory nerve ? 
It governs the sense of hearing, conducting the impulses from 
the exterior to the brain. It rises in the floor of the fourth ven- 
tricle, and is distributed to the labyrinth of the ear. Destruction 
of this nerve produces deafness. 
9. What is the function of the glosso-pharyngeal nerve ? 
It governs the sensibility of the pharynx, and therefore influences 
taste. It has also motor filaments which pass to the root of the 
tongue, the tonsils, the soft palate, the pharynx, and the tympanum. 126 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
10. What is the function of the pneumogastric or vagus 
nerve ? 
It is chiefly made up of sensory filaments which anastomose 
with motor filaments from other sources. It influences deglutition, 
the action of the heart, the circulatory and respiratory systems, 
the voice, and the stomach. It arises from the fore part of the 
restiform body and the vagal nucleus of the floor of the fourth 
ventricle. The functions of its branches have been considered 
when studying the circulation, respiration, etc. 
11. What is the function of the spinal accessory nerve ? 
It is made up of motor filaments, some of which pass to the 
vagus nerve, while others supply the sterno-mastoid and trapezius 
muscles. It arises from the lateral columns of the spinal cord and 
the gray substance within. It will be remembered that it consists 
of two parts, a smaller accessory root whose deep origin is in a 
nucleus of gray matter at the back of the medulla below the origin 
of the vagus, and a large spinal root from the lateral columns of 
the cord. 
What is the effect of destruction of its medullary root? 
It produces paralysis of the laryngeal muscles, resulting in 
aphonia, and impairs the action of the muscles of deglutition. 
Irritation of the spinal root produces contractions of the trapezius 
and sterno-mastoid muscles, but section of this branch does not 
produce absolute palsy in these muscles, since they are supplied 
by motor filaments from elsewhere. 
12. What is the function of the hypoglossal or sublingual 
nerve ? 
Its function is motor and it governs all the movements of the 
tongue, influences mastication, deglutition, and articulate language. 
It rises from the anterior pyramid, the olivary body, and the 
hypoglossal neucleus. Irritation of it produces convulsive move- 
ments of the tongue, while division of it abolishes all these move- 
ments and interferes considerably with deglutition ; articulation 
is considerably impaired, and mastication is performed with diffi- 
culty from inability to retain the food between the teeth. THE SPECIAL SENSES. 
127 
THE SPECIAL SENSES. 
What do you mean by the term “nerves of special sense”? 
Those nerves which carry, as do sensory nerves, impulses from 
the periphery to those centres in the brain which may perceive 
and interpret them, and which differ from the ordinary sensory 
nerves in that, as a general rule, the impulses are not the result of 
ordinary stimulation by contact, but of one special form of irrita- 
tion. As an example of this the optic nerve appreciates light, yet 
light can never be said to produce activity of the nervous proto- 
plasm by contact; nor do the vibrations of air produced by sound 
cause any impulses to travel along any sensory nerves save the 
auditory; neither can we say that the olfactory nerves are stimu- 
lated mechanically by the presence of substances so small that 
they cannot be distinguished by spectrum analysis, but which, 
nevertheless, are perceived by the nostrils; this is the reason why 
each one of the nerves carrying the impressions of sight, smell, 
taste, or sound, are called special, since each one of them can 
transmit but one variety of impulse. 
Do the nerves which carry these impulses of special sense 
differ from other nerves in their structure and 
ordinary capabilities ? 
No; they differ in no way at all from ordinary afferent nerves, 
with one or two exceptions. 
Is the sensation recognized at the point at which the cause 
exists, or by the special centres in the brain ? 
It is recognized in the centre, but, as has been stated before, 
impulses in sensory nerves are always referred to the periphery, 
and, therefore, we are accustomed to say that we feel the burn or 
other injury at the spot where it occurs. 
By what means is this peculiar condition in regard to 
sensation governed ? 
It is solely governed by the mind itself, which has been taught 
to do this as the result of education, experience, and habit, acquired 
by a long series of unconscious experiments in early youth. 128 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is necessarily present for a complete special sense 
apparatus ? 
First, a special nerve ending, only capable of being excited by 
special forms of stimuli; second, an afferent nerve to conduct the 
impulse from the special end organ to the nerve centre; third, 
nerve cells forming a centre, which is capable of translating the 
impulse received into a sensation and of referring that sensation to 
some local point; fourth, associated nerve centres capable of per- 
ceiving sensations, forming ideas, and drawing conclusions there- 
from, with the object of determining the position, character, and 
intensity of the external influence. 
The Sensibility of the Skin. 
Those impulses which are received through the skin are obtained 
through the sense of touch. 
Into how many divisions is this sense of touch subdivided ? 
First, tactile sensibility, by means of which we appreciate the 
slightest touch and recognize the exact point at which the skin 
receives the impulse. Second, the sense of pressure, by which we are 
enabled to judge of the compression which is being exerted on a 
certain area; this sense, however, is by no means so well developed 
as the tactile sense. Third, the sense of temperature, by which we 
are enabled to determine whether an object is hot or cold. This 
sense, also, is not perfectly developed, since for a moment we are 
unable to determine whether an object is hot or cold unless the 
eye or other special sense aids us. 
What is the object of tactile sensibility? 
In order that we may judge of the position, character, and shape 
of bodies. 
Is tactile sensibility exceedingly important to the animal 
organism ? 
Very important, since without it nothing could be held firmly 
in the hand, and all the movements of the body would be seriously 
interfered with. THE SENSE OF TASTE. 
129 
In what way are the nerves arranged for tactile sensi- 
bility ? 
The sensory nerves running to the skin are endowed with 
endings of various forms according to their function; these forms 
are divided into five varieties: First, the touch corpuscles, which 
are egg-shaped bodies situated in the papillae of the true skin, 
directly under the epithelial cells of the rete mucosum; they vary 
in size considerably, according to the amount of work which they 
are forced to perform; in these the axis cylinder of the nerve 
ends. Second, the end bulbs, which are smaller than the last and 
differ from them in that they are only distributed to localized 
areas; they are made up of a little vesicle containing fluid in 
which the axis-cylinder terminates, the wall of the vesicle joining 
the sheath of the nerve. Third, touch cells, which differ from the 
others in that they exist in the deeper layer of the epiderm. 
Fourth, free nerve endings, which occur on the surface of the epi- 
thelium of mucous membranes. Fifth, Pacinian corpuscles, which 
are ovoid bodies made up of concentric layers of varying con- 
sistence, with a collection of fluid in the centre, in which the axis- 
cylinder ends. 
The Sense of Taste. 
In what way is taste produced ? 
By the contact of sapid substances with the endings of the 
gustatory nerves of the tongue in the various papillae. 
What are these papillae sometimes called ? 
“Taste buds” or “ taste goblets.” 
Is it possible to taste a dry substance ? 
No; when a dry substance is placed on the tongue the moisture 
dissolves or moistens at least some of it. 
What proof have we that this is so? 
If the tongue be thoroughly dried no taste is perceived. 
Where is the chief sense of taste situated? 
In the tongue. 130 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What other surfaces aid the tongue in tasting ? 
The soft palate and its arches, the uvula, tonsils, and upper 
pharynx. The hard palate has little taste power. 
What is the nerve supply of the back part of the tongue? 
The glosso-pharyngeal. 
What is the nerve supply of the tip of the tongue ? 
The lingual branch of the trifacial nerve. 
What portion of the tongue perceives taste the best ? 
The back portion. The tip and middle of the tongue are not so 
well endowed with nerves.1 The sense of smell aids the sense of 
taste when eating. If the nostrils be closed and the eyes shut no 
distinction can be exercised between a piece of apple, potato, or 
onion on the tongue. 
Do certain areas of the tongue taste certain bodies ? 
Yes. The sulphate of quinine is scarcely noticed at the tip, at 
the back it is very well perceived. Sugar, on the other hand, is 
best tasted on the tip of the tongue. 
The Sense of Smell. 
How is the sense of smell excited ? 
By fine bodies floating in the atmosphere. 
What effect on smelling has drying of the nasal mucous 
membrane ? 
It impairs the power of perceiving odors very greatly. 
What is the object of sniffing? 
In order to draw over the nerve endings a current of air con- 
taining the odor. 
In what way are the olfactory nerves arranged ? 
Most of these nerves are distributed to the mucous membrane of 
the middle and upper meatus of the nose. The mucous membrane 
1 For the muscular movements of the tongue, see Mastication. THE SENSE OF SIGHT. 
131 
in this area is not covered by motile cilia such as are found in the 
rest of the nasal cavity; it is less vascular and of a peculiar 
yellow hue. The extreme delicacy of smell can best be understood 
when we remember that Valentin has estimated that two-millionths 
of a milligram of musk is sufficient to excite the olfactory nerves 
of man. In other animals this sense is even more acute. 
The Sense of Sight. 
What is the function of the eyelids ? 
To protect the eyeballs, and to distribute moisture over them 
constantly, thereby preventing drying. 
How are they formed ? 
They are movable folds of skin, each of which is kept in shape 
by a thin plate of yellow elastic tissue. 
What is the function of the eyelashes ? 
To prevent the entrance of foreign bodies, especially when the 
lids are half closed. 
In what way do they differ from ordinary hairy growths ? 
They possess tactile sensibility, which causes, reflexly, the lids 
to close tightly when a foreign body touches them. 
What is the purpose of the Meibomian glands along- the edges 
of the lids? 
To lubricate them, and prevent irritation from the tears. 
In what portion of the orbit is the lachrymal gland placed ? 
In the upper and outer angle. 
What is the use of the lachrymal gland ? 
To secrete liquid, which will lubricate and keep the eye moist. 
When an excessive secretion takes place it runs over the lower 
lids, in the form of tears. 
On what side of the orbit does the lachrymal secretion escape? 
On the inner side, through the puncta lachrymalia, one of which 
The Eye and. its Coverings 132 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
exists in each lid; thence it passes into the lachrymal sac, and 
from there through the nasal ducts into the nose. 
What function has the lower eyelid which is not possessed 
by the upper lid? 
It acts as a gutter along which an excess of the tears may flow; 
when one cries the gutter overflows. 
What is the function of the orbicularis palpebrarum muscle, 
and what is its nerve supply ? 
It closes the eye, and is supplied by the facial nerve. 
What muscle opens the eye ? 
The upper lid is raised by the levator palpebrarum superior, 
which is supplied by the oculo-motor nerve. 
In what way does the ending of the optic nerve differ from 
any other sensory nerve ? 
It is enclosed in a specially arranged organ, the eyeball. 
What is the*object of the eyeball? 
For the purpose of so directing the rays of light that they strike 
in a certain way upon the peripheral optic filaments. It also pro- 
tects the nerve filaments from all contact with external conditions, 
except light. 
What is the only stimulus which ordinarily excites the optic 
nerve ? 
Light. 
What is the purpose of the movements of the eyeball ? 
In order that objects may be brought within the range of vision 
without movements of the head. 
If electrical, mechanical, or other stimuli be applied to the 
optic nerve, what sensations will they produce ? 
Light is the only thing appreciated. 
What is the function of the sclerotic coat of the eye ? 
It gives shape and protection to the organ. 
Is the sclerotic coat continuous all over the eyeball? 
No, it is not; for at the anterior portion is a window-like open- 
ing, known as the cornea, through which the rays of light pass. THE SENSE OF SIGHT. 
133 
What is the function of the cornea? 
It permits light to enter the eye in much the same manner as a 
window-pane lets light into a room, and it also effects very mark- 
edly refraction of the rays of light. 
What peculiar bodies have we in the cornea which move 
about ? 
The corneal corpuscles, which resemble amoebae in their move- 
ments. 
Does the cornea possess nerves and bloodvessels ? 
Only nerves, which are partly sensory in function. 
In what way, then, is it nourished ? 
By absorption from the bloodvessels at the corneal margin. 
What is the function of the choroid root ? 
Owing to its black, pigmented connective tissue cells, it prevents 
the transmission of all light from the exterior, save by the corneal 
opening, and prevents reflections from side to side. It is this coat 
which lacks pigment in albinoes and nocturnal animals, and its 
absence prevents good vision in the daytime. 
What are the ciliary processes ? 
They are highly vascular folds of the choroid, occurring near 
the edge of the cornea. 
What is the function of the ciliary muscle ? 
It attaches the choroid to the sclerotic coat, and governs the 
diameter and shape of the crystalline lens. 
What is the function of the iris ? 
It is a circular membranous diaphragm provided with a central 
aperture, the pupil, and regulates the amount of light entering 
the eye. It contains two sets of muscular fibres, circular and 
radiating. 
What are the functions of these two sets of muscular 
fibres ? 
The radiating fibres dilate the pupil, the circular fibres contract it. 134 
ESSENTIALS OF HUMAN PHYSIOLOGY 
What is the object of this pupillary movement? 
The regulation of the amount of light entering the eye. 
What arrangement have we on the posterior surface of the 
iris to prevent the transmission of light through it ? 
A layer of dark pigment. 
What is the nerve supply of the circular fibres of the iris ? 
The oculo motor. 
What is the nerve supply of radiating or dilating fibres ? 
The trifacial and sympathetic. 
Why does the pupil contract when we are looking at near 
objects, but dilate for objects which are far away? 
When an object is near the rays of light are so near together 
that they enter through a small opening; when it is far off the 
pupil dilates, in order to let all the rays in that it can to make the 
image more distinct. 
What is the function of the retina ? 
Lying next to the choroid coat the retina is formed by the expan- 
sion of the optic nerve, and it is this membrane which receives the 
impression of light. 
In what way do the nerve filaments end in the retina ? 
In the rods and cones. 
Which of these is most highly developed in man ? 
The rods. 
What do you mean by the blind spot? 
A small point in the retina on which, when light falls, no 
impulse is produced ; it is the point of entrance of the optic nerve. 
What do you mean by the macula lutea ? 
The point at which rays of light produce the greatest visual 
impression. It is exactly in the centre of the retina. THE SENSE OF SIGHT. 
135 
Are the rods or the cones in greater number here ? 
The cones. 
What is the visual purple ? 
A certain purple substance on the retina, which is destroyed by 
contact with light. It has been supposed that it aids vision, but 
this is apparently contradicted by the fact that it is absent from 
the cones and the macula lutea, where vision is best. It can only 
be seen by opening an eye in a dark room, and flashing a light 
upon it. If the operation be quickly done the image falling on 
the retinal pigment may be made permanent by dipping it quickly 
in a strong solution of alum. 
Does every part of the retina receive all the rays of light ? 
No. Each portion receives different colored rays. The periph- 
eral portion sees the red rays, etc. 
What is the function of the aqueous humor of the eye ? 
It affords a medium in which the iris can move. It also supports 
the posterior surface of the cornea, and influences the refraction of 
light. 
What is the function of the vitreous humor ? 
It fills out the eyeball and keeps it tense, and aids very largely 
in the refraction of the rays of light transmitted to it through the 
crystalline lens. 
What is the function of the crystalline lens ? 
It acts like a strong, magnifying glass, and is biconvex. It is 
the most important refracting portion of the eye, and, aided by 
other portions of the optical apparatus, directs the rays of light in 
such a manner that they fall properly on the retina. It also sepa- 
rates the aqueous from the vitreous humor. 
In what way are images thrown on the retina ? 
They are inverted by the lens, which is biconvex. 
Why do we not see objects, therefore, upside down? 
Because the brain interprets the inverted image for one in the 
proper position. , 136 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What variation is there in the power of refraction of the 
various parts of the lens ? 
It increases in power of refraction from without inward. 
Give the essential portions of the eye for the carrying out 
of its functions, namely, sight. 
1. A retina or nervous mass to receive and transmit impulses. 
2. Certain refracting media so arranged as to throw the rays of 
light in proper form. 
3. A contractile diaphragm, the iris, which governs quantity of 
light admitted. 
4. A contractile muscle, the ciliary muscle, to regulate the shape 
of the lens and to 11 accommodate ” the eye to distances. 
What would be the effect if the retina was exposed to the 
light with no refracting media in front of it ? 
The perception of light from darkness, but no objects could be 
seen. 
What do you mean by the term “accommodation of the 
eye ?” 
The function of the eye by which we are enabled to see objects 
at various distances. 
The rays of light for good sight must be transmitted from an 
object and focussed at a given point on the retina. If the focus 
occurs in front or behind the retina instead of on it, the vision 
is indistinct. The lens,.however, in the normal eye varies in its 
biconvexity to such an extent that it collects the rays, be they far 
apart or near together, and in every instance focusses them directly 
on the retina. 
What do you mean by the “near point ?” 
The “ near point ” is the nearest point at which the eye can 
clearly perceive an object held before it, as, for example, printed 
matter held close to the face. 
The “ far point ” is the same thing reversed, save that the far 
point in the human eye is an infinite distance. 
By what means do we judge of distance? 
This is largely a matter of education and is unconsciously ob- THE SENSE OF SIGHT. 
137 
tained, in the same way as the judgment of size, a mere matter of 
practice. 
What is chromatic aberration ? 
It is the breaking up of ordinary white light into colored rays, 
owing to the different colored lights of which ordinary light is 
made up. It is due to a defect in the optical apparatus, but in the 
normal eye it is diminished by the iris, which cuts off the marginal 
rays. 
What is spherical aberration ? 
It depends upon the fact that luminous rays passing through a 
convex lens strike the various parts of the surface at different 
angles, and, hence, are differently refracted, the rays striking the 
margin of the lens being more bent than those passing through 
the centre. Spherical aberration does not, however, cause in- 
convenience, since the iris allows only the central rays to pass. 
What is astigmatism ? 
It consists in an inability to see clearly lines running at certain 
angles. 
It depends either upon some irregularity in the shape of the 
cornea, or in the shape of the lens. 
What are entopic images ? 
Those which depend on the presence of some opacity in the 
transparent media of the eye itself. They occur in all eyes to a 
a certain extent, and are frequently noticed when one uses the 
microscope. 
What is the cause of color-blindness ? 
The inability of certain areas of the retina to perceive those 
rays of light which normally fall on them, owing to the imperfect 
development of these areas. The common forms of blindness are 
for the red, green, and yellow rays. 
What is diplopia ? 
Double vision, due to the fact that each eye receives the impulse 
at a different time from the other. 138 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is hemianopsia ? 
Blindness of one-half of the eye so that objects are split down 
the middle and only half of the body perceived. Since the rays 
of light cross in the eye, the part of the retina which is blind is 
always opposite the object, which cannot be seen. Thus, when the 
eye sees no objects to the left of it, it is the right side of the eye 
which is blind. 
What is myopia ? 
“Short sightedness.” A condition of the eye in which objects 
are focussed at a point in front of the retina. 
What is hypermetropia ? 
“ Far sightedness.” A condition of the eye in which objects are 
focussed behind the retina. 
What do you mean by presbyopia ? 
A state common to old age, due to loss of the power of accom- 
modation. 
What is an emmetropic eye ? 
A normal eye. 
Does such an eye as an absolutely normal eye exist? 
Probably not, or in very rare instances. 
By what form of glass would you remedy myopia? 
By a concave glass. 
By what form of glass would you relieve hypermetropia? 
By a convex glass. 
Why do you do this ? 
Because in the myopic eye the lens is too convex, while in the 
hypermetropic eye it is not convex enough. 
What do you mean by dioptric media ? 
Transparent bodies which so refract the light that images come 
to a focus on the retina. HEARING. 
139 
Hearing. 
In the same way that all impulses travelling along the optic 
nerve are interpreted as light, so are all the impulses travelling 
along the auditory nerve interpreted as sound. 
Through how many divisions of the ear does the sound pass? 
Three, the external ear and auditory canal, the middle ear, 
which is shut off from the auditory canal by the tympanic mem- 
brane, and the labyrinth. 
What is the purpose of the external ear? 
To collect sound. 
What is the function of the auditory canal ? 
By circumscribing the air it increases its vibrations. 
What is the function of the cerumen of the external ear ? 
To catch foreign bodies which might otherwise enter. 
What is the function of the tympanic membrane ? 
It receives the vibrations of the air in the auditory canal, trans- 
mitting them to the bones of the middle ear. 
For what purpose is the tympanic membrane sloped from 
outward inward ? 
If it were directly across the canal it would not be of great 
enough extent. 
By what means are the vibrations of sound transmitted 
after leaving the tympanic membrane ? 
Three small bones known as the malleus, incus, and stapes join 
together, and reach from the membrane to a secondary membrane 
which covers the oval window leading into the vestibule of the 
internal ear; the malleus is attached to the tympanic membrane, 
while the stapes is in contact with the oval window. 
What is the function of the stapedius muscle ? 
It is attached to the stapes, and when it contracts pulls that 
bone away from the oval window, otherwise a loud sound might 
jam the bone into the oval window and produce deafness. 140 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the function of the tensor tympani muscle? 
By drawing the handle of the malleus internally it increases 
the intensity of the tympanic membrane and prevents it from 
vibrating too much to sounds of great intensity. 
What is the function of the laxator tympani muscle ? 
It draws the handle of the malleus outward, and relaxes the 
tympanic membrane. 
What is the function of the Eustachian tube ? 
It communicates with the pharynx and opens into the middle 
ear back of the tympanic membrane, affording vent by which, 
when the drum is driven in, some of the air may escape. It 
equalizes the pressure within and without. 
Is the Eustachian tube constantly open? 
No, it is not; if it were, the various sounds in the mouth would 
produce sounds in the ear. 
In what way is sound transmitted, after passing- through 
the ossicles, to the terminal filaments of the audi- 
tory nerve ? 
Through the semicircular canals and the spiral staircase. 
What fills the semicircular canals? 
A liquid known as the endolymph. 
In what manner does the endolymph receive impulses from 
the exterior ? 
The endolymph is in direct contact with the membrane which 
covers the oval window, and when the stapes strikes against this 
membrane it produces vibrations which are taken up by the endo- 
lymph. 
In what way do the nerves end in the semicircular canals? 
In peculiar epithelioid cells, to which are attached fine hair-like 
processes. 
What are the functions of the otoliths? 
These small calcareous masses are set in motion by the vibra- THE VOICE AND SPEECH. 
141 
tions of the endolymph and come in contact with the endings of 
the nerves, producing impulses. The function of those nerve fibres 
which run to the cochlea is not clearly understood. 
What function have the semicircular canals other than 
hearing ? 
They appear to govern equilibrium, for if injured the animal 
immediately loses its balance. When the horizontal canal is divided 
the animal rolls its head from side to side. When one of the ver- 
tical canals is cut the head moves up and down. 
What is the function of the organ of Corti? 
It is not distinctly known, but it was supposed to be especially 
developed in persons with musical tendencies, till it was found 
that the pig possessed them in a highly developed state. As 
nerve filaments end in these rods, it has been supposed that each 
set of rods responds to a certain set of notes. 
What differences in sound can the ear distinguish ? 
Loudness, pitch, and quality. The judging of the distance from 
which a sound is transmitted is purely a matter of training. 
The Voice and Speech. 
With scarcely any exception all air-breathing vertebrates possess 
some arrangement for the production of sound in some part of 
the respiratory apparatus. In some animals various modifications 
of this sound are produced. In man its modifications are so great 
as to permit of speech. 
In what way is the voice or sound produced ? 
By an expiratory blast of air being forced through the narrow 
opening at the top of the windpipe, called the glottis. The glottis, 
it will be remembered, lies in the lower part of the larynx and is 
bounded on each side by thin membranous bands, which, extend- 
ing from side to side, vibrate as the air rushes over them. For 
this reason, opening of the trachea prevents speech, since* all the 
air rushes out of the opening rather than over the cords. 142 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What are the chief organs of the voice? 
The vocal cords. These are governed by the muscles of the 
larynx.1 
What is the function of the larynx ? 
It acts as a cavity in which the vocal cords may produce the 
voice. 
What is the function of the thyroid and cricoid cartilages? 
The function of these two cartilages is chiefly for the purpose of 
affording stiff walls around the vocal apparatus for the sake of 
protection and attachment. The thyroid cartilage forms an in- 
complete ring around the larynx, and covers only the front portion 
and sides. The cricoid cartilage, on the other hand, is a complete 
ring, the back part of the ring being broader than the front. 
What is the function of the arytenoid cartilages ? 
They are situated on the top of the back portion of the cricoid 
cartilage and are movable upon it, forming a place for the inser- 
tion of certain muscles concerned in speech. 
What are the intrinsic muscles of the larynx ? 
They are those which have a direct action on the vocal (jord, 
and are nine in number—four pairs and a single muscle: two 
crico-thyroids, two thyro-arytenoids, two posterior crico-arytenoids, 
two lateral crico-arytenoids, and one arytenoid muscle. 
What are the functions of these muscles ? 
When the crico-thyroids contract they rotate the cricoid on the 
thyroid cartilage in such a manner that the upper and back part 
of the former, and of necessity the arytenoid cartilages on the top 
of the cricoid cartilage, are tipped backward, while the thyroid is 
inclined forward. The result of this is that the vocal cords being 
attached in front to the thyroid cartilage and posteriorly to the 
cricoid cartilage are put on the stretch. The thyro-arytenoid 
muscles have an opposite action, for they pull the thyroid back- 
ward and the arytenoid and the upper and back part of the cricoid 
1 For the anatomy of the larynx and those portions of the body concerned in speech, 
see an anatomical text-book. THE VOICE AND SPEECH. 
143 
cartilages forward, thus relaxing the vocal cords. The posterior 
crico-arytenoids dilate the glottis and separate the vocal cords by 
an action on the arytenoid cartilage. When they contract they 
pull together the outer angles of the arytenoid cartilages in such 
a manner as to rotate the latter at their joint with the cricoid, and 
to throw asunder their anterior angles to which the vocal cords 
are attached. 
What muscles oppose these posterior crico-arytenoid 
muscles ? 
The lateral crico-arytenoids, which, pulling in the opposite 
direction from the other side of the axis of rotation, have, of 
course, exactly the opposite effect, and enclose the glottis. The 
arytenoid muscle may also close the glottis almost completely, by 
pulling together the upper parts of the arytenoid cartilages, 
between which it extends. 
What is the nervous mechanism of the voice ? 
The sensory filaments in the pneumogastric give the glottis that 
acute sensibility which prevents the ingress of foreign bodies or 
noxious gases into the air-passages. The superior laryngeal 
branch of the vagus and the inferior laryngeal branch, or the re- 
current nerve, cooperate not only with the pneumogastric in the 
closure of the glottis which excludes foreign bodies, but also in 
the protection and regulation of the voice. The inferior laryn- 
geal nerve governs the contraction of the muscles that vary the 
tension of the vocal cords, while the superior laryngeal conveys to 
the mind the sensations of the state of these muscles, which is 
absolutely necessary for their intelligent guidance. 
What three properties are possessed by the human voice ? 
Quality, pitch, and intensity. 
Over how wide a musical range does the human voice 
extend ? 
Including all forms of voice, about three and one-half octaves; 
but of this wide range a single individual can rarely sing more 
than two octaves. 144 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What difference exists between the notes of the female 
voice and those of the male ? 
The lowest note of the female voice is about an octave higher 
than the lowest note of the male voice. The highest note of the 
female voice is about an octave higher than the highest note of 
the male. 
In what portion of the vocal apparatus is the variation in 
sound produced which results in speech ? 
Not in the larynx, but in the mouth and nose, by means of the 
teeth, tongue, and lips. 
What sound do we have when speech is not accompanied 
by the action of the vocal cords ? 
Only a whisper. 
What effect upon sound has approximation of the vocal 
cords f 
The sound emitted is high pitched in character, while non- 
approximation of the cords produces sound of greater volume, but 
of lower pitch. The pitch does not depend, however, absolutely 
on the approximation or non-approximation of the cords, but 
more upon the tensity of the cords themselves. 
What is the function of the epiglottis in regard to sound? 
When pressed down so as to cover the cavity of the larynx it 
serves to render the notes deeper in tone, and, at the same time, 
somewhat fuller in quality. 
The Sympathetic Nerve. 
It will be remembered that the sympathetic system contains a 
very large number of non-medullated nerve fibres, and consists of 
a double gangliated prevertebral cord, one on each side of the 
vertebral column. 
What are the rami communicantes ? 
The nerves given off by the spinal nerves to the sympathetic 
cord. Each spinal nerve does this. 145 
THE SYMPATHETIC NERVE. 
What do you mean by the cephalic, dorsal, and abdominal 
portions of the sympathetic? 
Those portions which govern these areas. In the head the 
cephalic portion anastomoses with the cranial nerves to a great 
extent. The abdominal portion supplies the abdominal organs. 
What are the functions of the sympathetic? 
First, the independent functions as represented by the automatic 
cardiac ganglia, the mesenteric plexus of the intestine, and the 
plexuses of the uterus, Fallopian tubes, ureters, and lymph and 
bloodvessels. They are independent in that they are capable of 
acting without any impulses from higher centres, but they may 
also be governed by the spinal centres under some circumstances. 
Second, the dependent functions which are governed by centres, as, 
for example, the sensory fibres of the splanchnics. 
What is the function of the cervical sympathetic ? 
It contains (1) pupil-dilating fibres which, according to Budge, 
arise from the spinal cord and run through the upper two dorsal 
and lowest cervical nerves into the cervical sympathetic, which 
conveys them to the head. 
What does the cervical sympathetic also supply ? 
(2) Motor fibres for Muller’s smooth muscle of the orbit, and 
partly for the external rectus muscle of the eye. It also supplies 
(3) vaso-motor branches for the outer ear and the side of the face, 
tympanum, iris, choroid, retina in part, the oesophagus, larynx, 
thyroid gland, and fibres for the vessels of the brain and its mem- 
branes ; (4) secretory and vaso-motor fibres for the salivary glands. 
(5) Sweat secretory fibres are given off, as are also secretory fibres 
to the (6) lachrymal glands, according to Wolferz and Demtschenko. 
What are the functions of the thoracic and abdominal 
sympathetic ? 
(1) The sympathetic portion of the cardiac plexus, which receives 
accelerating fibres for the heart from the lower cervical and first 
thoracic ganglion. (2) The cervical sympathetic and the splanch- 
nics contain fibres which, when their central ends are stimulated, 
excite the cardio-inhibitory centre in the medulla. 146 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Give an example of this. 
If an animal be struck sharply on the belly, over the solar 
plexus, death may result from cardiac stoppage due to reflex 
inhibition. 
What is the splanchnic ? 
The splanchnic is a division of the sympathetic, and contains 
vaso-motor filaments. All the vaso-motor nerves do not run 
through the cord, but some of them leave the cord high up and 
pass into the sympathetic. These nerve filaments in the splanch- 
nics govern the bloodvessels of the abdomen very largely. The 
splanchnic also contains vaso-motor fibres which supply the 
kidneys. 
What effect has section of the cervical sympathetic, or its 
rami communicantes, on the pupil ? 
It causes contraction of the pupil. 
What other effect has section of the cervical sympathetic ? 
It causes increased fulness of the bloodvessels on that side, the 
eyelids are not held well apart, while the eyeball is sunken and 
retracted. Sometimes unilateral atrophy of the face comes on. If 
this section be performed in young growing animals, hypertrophy 
of that ear and side of face occurs, owing to the increased blood 
supply and other trophic changes. 
What is the effect of stimulation of the cervical sympa- 
thetic ? 
It causes dilatation of the pupil, and occasionally hyperidrosis 
or profuse sweating of that side of the head. There is also pro- 
trusion of the eyeball, and the.eyelids are held wide open. The 
eyeball, instead of being sunken, as after section, is in a condition 
of exophthalmos. 
GENERATION AND DEVELOPMENT. 
What do you mean by generation and development ? 
The first term signifies the original cause of growth, while the 
second term signifies the manner of growth after it is once begun. GENERATIVE ORGANS OF THE FEMALE 
147 
Generative Organs of the Female. 
They consist of two ovaries, two Fallopian tubes or oviducts, the 
uterus, and a canal known as the vagina. 
What is the function of the ovaries ? 
The formation of the ova or eggs. 
What is the function of the Fallopian tubes or oviducts? 
The conduction of the ova from the ovaries to the uterus. 
What is the function of the uterus ? 
It is a cavity in which, if impregnated, the ovum is retained 
until it is fully developed and capable of maintaining its life inde- 
pendent of the parent. 
What is the function of the vagina? 
It is the canal which receives the male generative organ, the 
penis, in the act of copulation, and is the passage through which 
the foetus is discharged. 
Describe the ovaries. 
They are two oval bodies situated in the cavity of the pelvis, one 
on each side, inclosed in the folds of the broad ligaments. Each 
ovary measures about an inch and a half in length and three- 
quarters of an inch in width. They are about half an inch in 
thickness, and are attached to the uterus by a narrow fibrous cord, 
the ligament of the ovary, and move slightly to one of the fimbriae 
of the Fallopian tubes. They are enveloped by a dense fibrous 
tissue. They are covered on the exterior by the germ epithelium. 
The inner substance, or stroma, is a soft fibrous tissue containing, 
imbedded in it, a number of vesicles in various stages of develop- 
ment. 
What are these vesicles called ? 
Graafian vesicles. 148 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
In what way do the Fallopian tubes grasp the ovule when 
it is expelled from the ovary? 
By means of their fimbriated extremities, which are in constant 
ciliary movement. 
Describe the formation of the ovule in the ovary. 
The vesicles in the stroma gradually approach the surface until 
they project above it. Each follicle or vesicle is covered by an 
external membranous envelope lined with a layer of nucleated 
cells, the membrana granulosa. This follicle contains liquid full of 
small microscopic bodies, with the ovule nearly in its centre, unless 
the follicle is fully matured when it comes in contact with the 
membrana granulosa. 
What is the discus proligerus ? 
A granular zone of the nucleated cells of the membrana granu- 
losa, which is heaped around about the ovule. 
What is the size of the human ovule? 
About rztfth of an inch. 
What is the zona pellucida or vitelline membrane ? 
The investment of the ovule, and it adheres closely to the discus 
proligerus. 
What lies within the zona pellucida ? 
The yelk or vitellus, which is composed of granules and globules 
of various sizes. 
What arrangement have these globules? 
The largest are at the periphery, the smallest are at the centre. 
What does the yelk or vitellus contain? 
The germinal vesicle or the vesicula germinativa. 
What does this germinal vesicle contain? 
At its periphery, at the point nearest the yelk, it contains the 
germinal spot or the macula germinativa. 
These are all the parts of the Graafian follicle. GENERATIVE ORGANS OF THE FEMALE 
149 
Does the formation of Graafian follicles go on constantly 
during the child-bearing part of life ? 
Yes. 
What do you mean by the discharge of the ovule ? 
When the follicle is ripe and has reached the surface of the 
ovary, the follicular wall becomes thinner and finally bursts. The 
ovule and its fluid surroundings escape on the surface of the ovary, 
which is grasped by the Fallopian tube, down which the ovule 
travels. 
Is there any difference in the periodicity of the maturity of 
the ovule in the different varieties of animals ? 
Yes; in human beings it is once in every twenty-eight days, 
while in the common fowl it is constant. 
What is the difference between the ovule and the ovum ? 
The term ovule is ordinarily applied to the egg previous to 
impregnation, while the ovum is the fecundated ovule. 
What is menstruation ? 
It is regarded by most physiologists as the flow of blood accom- 
panying the discharge of a ripened ovule. The rupture of a 
follicle is not necessarily accompanied by menstruation, neither is 
menstruation necessarily followed by ovulation. 
Does rupture of the follicle take place before or after the 
flow ? 
In most cases before or at the beginning; more rarely at the 
middle or end of menstruation. 
Describe the menstrual discharge. 
It is a thin, sanguinolent fluid having a peculiar odor, and 
consists of blood, epithelium, the mucus of the uterus and vagina, 
and the remains of the mucous membrane lining the uterus. 
What is this mucous membrane called? 
The decidua menstrualis, which is developed to perfection just 
before the menstrual flow and then thrown off. 150 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
Can menstruation be regarded as a hemorrhage ? 
No; it can not. It is merely a destructive process whereby the 
membrane which was prepared for receiving a fecundated ovule is 
thrown off. 
At what time of life does menstruation begin and end in 
the temperate zone ? 
It begins at twelve or fourteen years of age, and ceases at a period 
between forty and fifty. 
Does menstruation ever occur during pregnancy, or in 
nursing women? 
Rarely; but such cases are on record. 
What is the corpus luteum ? 
At the time of rupture of the Graafian vesicle, a yellowish mass, 
the corpus luteum, develops itself. It is a round, solid body whose 
walls, after the rupture, become covered by small buds of flesh- 
like matter, resembling a granulating wound, and these granula- 
tions extend above the ovarian surface. Ultimately they become 
covered, but still go on growing inside the ovary. As pregnancy 
goes on, the red granulations change to yellow and its consistence 
becomes firmer. 
Does the corpus luteum depend for its formation on the 
effusion of blood which takes place when the 
follicle ruptures ? 
Not in the least. Remember this. The corpus luteum is, in 
reality, a growth of cells from the membrana granulosa. 
What difference is there in the growth of the corpus 
luteum of pregnancy and in that of ordinary men- 
struation? 
In pregnancy it remains till gestation is nearly ended. When 
impregnation does not occur it shortly disappears. 
The Male Sexual Organs. 
What is the function of the testicles? 
They are the organs which secrete portions of the semen. THE MALE SEXUAL ORGANS. 
151 
What other tissues aid in this secretion? 
The vesiculae seminales, the prostate gland, and Cowper’s glands. 
What does the semen consist of? 
Of the secretion of all these tissues. 
In what way is the secreting portion of the testicle 
arranged ? 
Into two parts, one of which is the body of th£ testicle inclosed 
within a tough, fibrous membrane, the tunica albuginea, which is 
covered externally by a serous membrane, the tunica vaginalis. 
The second part is the epididymis and vas deferens. 
What is the vas deferens, and what is its function ? 
It is the duct of the testicle, about two feet in length. It passes 
to the lower part of the epididymis, with which it is continuous, 
where it becomes exceedingly tortuous in its course. 
Of what does the epididymis consist? 
Of a single tube about twenty feet long. 
What are the tubuli seminiferi ? 
They make up the parenchyma of the organ. 
In what way, and from what are the spermatozoids formed? 
The seminal tubule is limited by an elastic membrane, the mem- 
brana propria, inside of which are several layers of cells, known as 
the seminal cells. 
How many kinds of seminal cells have we ? 
Two. Those resting quietly, others in a state of active division. 
The active cells are called the mother cells; and the smaller cells, 
resulting from their division, the daughter cells or spermatoblasts. 
The spermatozoids are formed from the spermatoblasts. 
What is the appearance of the spermatozoid? 
It consists of a small body or head, to which is attached a cilium, 
or rapidly moving tail. 152 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the function of the spermatozoids ? 
They are absolutely needful for impregnation, and it is the sper- 
matozoids which fecundate the ovule. 
How does the semen reach the exterior of the body ? 
It is secreted in the tubules of the testicles, then passes along 
the vasa deferentia into the vesiculse seminales, and from there into 
the urethra. 
What is the function of the seminal vesicles other than the 
carrying oif of the semen? 
They secrete some of the liquid in which the spermatozoids float 
or swim. This is probably their chief function, at least in some 
animals. 
What is the function of the prostate and Cowper’s glands? 
To add the proper liquid to the semen. 
Of what, therefore, does semen consist? 
The liquor seminis and the spermatozoids, with detached epi- 
thelial cells. 
Development. 
In what part of the female genital organs does the ovule 
become fecundated? 
Most commonly in the upper part of the Fallopian tube. 
What changes take place in the ovum or the fecundated 
ovule ? 
The visible change is a slight amoeboid movement of the proto- 
plasm of the ovum, which is shortly followed by segmentation, 
which consists in the repeated subdivision of the cells present. 
How long does this segmentation last ? 
It is finished by the time the ovum reaches the uterus. 
What is seen in the centre of each segment ? 
A central vesicle, which is the result of the repeated division of 
another central vesicle, just as the segments themselves are the 
result of the division of the yelk itself. DEVELOPMENT. 
153 
What appearance has the ovum as it enters the uterus ? 
Owing to the many segmentations, it is granular, and resembles 
a mulberry. 
How long1 a time does the passage of the ovum from the 
ovary to the uterus take? 
Probably eight or ten days. 
What is the germinal or blastodermic membrane ? 
It is a membrane which is formed by the accumulation at the 
periphery of the yelk of a number of the segments or cells. Owing 
to their number they are pressed against one another, and become 
polyhedral in shape. 
What are the layers of the blastoderm? 
The epiblast, mesoblast, and hypoblast. 
What is the function of the epiblast ? 
From the epiblast are eventually developed the epidermis and 
its various appendages, the cerebro-spinal nerve centres, the sensory 
epithelium of the mouth, and the salivary glands. 
What are developed from the hypoblast ? 
The epithelum of the whole digestive canal, and the lining of all 
the ducts which open into it; the parenchyma of the liver and 
pancreas, and the epithelium of the respiratory tract. 
What are developed from the mesoblast ? 
All the organs not so far mentioned, all the connective tissues, 
the muscles, the vascular and genito-urinary apparatus, and the 
entire digestive tract, save its lining epithelium. 
What is the germinal area ? 
The position at which the embryo is about to appear. It is at 
first circular, then pyriform. 
What is the area pellucida ? 
A clear, transparent spot, which develops in the centre of the 
germinal area. 154 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the area opaca? 
That portion of the germinal area surrounding the area pellucida. 
What is the primitive groove ? 
A shallow longitudinal groove which is the first trace of the 
embryo. It appears near the back part of the area pellucida. 
What is the medullary groove ? 
A more permanent groove which soon replaces the primitive 
groove. It begins at the anterior part of the area pellucida, and 
gradually displaces the primitive groove. 
What are the laminae dorsales ? 
Two longitudinal elevations which bound the medullary canal. 
They are folds of the epiblast which grow up and extend over and 
join each other over the medullary canal, forming it into a closed 
canal or tube. 
What is this tube now called? 
The primitive cerebro-spinal axis. 
At what portion of the embryo do the laminae dorsales 
first unite ? 
About the neck, then the head, and down to the lower ex- 
tremity. 
What is the notochord or chorda dosalis ? 
It is an aggregation of cells from the mesoblast immediately 
underneath or back of the medullary canal. It extends nearly the 
whole length of the canal, and occupies the future position of the 
vertebrae. 
What are the protovertebrae ? 
Square segments composed of cells from the mesoblast which 
appear on each side of the medullary canal along its whole length. 
What is the “splitting of the mesoblast”? 
Outside of the protovertebrae the mesoblastic cells are split up 
into two laminae, known as the parietal and visceral. These laminae 
form the origin for the walls of the trunk. The parietal lamina is 
closely connected with the epiblast which adheres closely to the DEVELOPMENT. 
155 
hypoblast, and forms the serous and muscular walls of the alimen- 
tary canal and other parts. 
What is the somatopleure ? 
The united parietal lamina and the epiblast. 
What is the splanchnopleure ? 
The united visceral layer and the hypoblast. 
What eventually becomes of the space between the soma- 
topleure and the splanchnopleure ? 
It forms the pericardium, pleurae, and peritoueum. 
What are the head and tail folds ? 
Those folds of the blastoderm which limit the embryo at the 
head and caudal extremities. Similar folds or depressions mark 
off the lateral margins of the embryo, which now finds itself entirely 
separate from the yelk and surrounded by a clear space. 
What is the last portion of the embryo to become com- 
pletely separated from the yelk ? 
The head and caudal extremity are first separated, but the an- 
terior wall of the belly is not closed by the folds till later. Indeed 
it is never closed in foetal life, for the umbilicus is the remains of 
this connection with the yelk. 
What is the neural cavity ? 
That cavity formed by the upward growth of the laminae dor- 
sales. 
What is the body cavity ? 
That cavity formed by the downwardly folded blastoderm. 
What are the visceral plates ? 
The downwardly folded portions of the blastoderm are known as 
the visceral plates. 
What forms the rudiment of the alimentary canal ? 
The folding in of the splanchnopleure lined by hypoblast pinches 
off a portion of the yelk-sac inclosing it in the body cavity. 156 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the condition of this rudimentary alimentary canal? 
It is blind or closed at both ends at this time, while its centre 
communicates freely with the cavity of the yelk-sac. 
What is the canal called which permits of this communi- 
cation ? 
The vitelline or omphalo-mesenteric duct. This condition 
divides the yelk-sac into two portions. 
What is the portion of the yelk-sac outside the body cavity 
called ? 
The umbilical vesicle. 
What is the purpose of the umbilical vesicle ? 
It affords nutriment for the embryo. 
In what way does the nutriment reach the embryo ? 
Through the omphalo-mesenteric vessels which ramify in the 
walls of the yelk-sac. 
Does this yelk-sac or umbilical vesicle afford food all 
through pregnancy for the embryo ? 
In mammalia it lasts only for a short time, the nourishment 
being derived from the mother. 
What is the amnion ? 
Beyond the head and tail folds the somatopleure, coated by epi- 
blast, rises in folds which grow up and arch over the embryo, 
anteriorly, posteriorly, and laterally, all directed toward one point 
over the dorsal surface of the embryo. 
What is the true amnion ? 
The inner of the two layers of the somatopleure forms the true 
amnion. 
What is the false amnion? 
The outer layer of the somatopleure. 
What is the chorion ? 
It is formed by the coalescing of the inner surface of the original 
vitelline membrane with the false amnion. DEVELOPMENT. 
157 
How is the amniotic cavity formed ? 
The cavity between the true amnion and the external surface of 
the embryo becomes a closed space, which is called the amniotic 
cavity. 
Does the amnion adhere closely to the embryo ? 
No, it gradually is distended with fluid which separates it from 
the embryo. 
What is this fluid called, and what is its function ? 
The liquor amnii, which increases as pregnancy goes on. This 
forms a.yielding cushion-like support for the embryo, protecting 
it from injury and gradually distends the neck of the uterus in 
parturition. 
What is the allantois ? 
It is a highly vascular growth, arising from the hinder portion 
of the peritoneal cavity, which gradually pushes its way out 
through the amniotic folds, attaching itself to the outer layer of 
the amnion (false amnion). In other words, it becomes attached to 
the chorion, in mammals in one spot, in birds all over the chorion. 
What is formed at this point? 
By the interlacing of these vessels with those of the mother the 
placenta is developed. 
Of what does the chorion now consist ? 
Three layers : 1st, the vitelline membrane; 2d, the outer layer 
of the amniotic fold; 3d, the allantois. 
What are the villi of the chorion ? 
Small processes on its surface which soon become vascular, 
particularly so in the region of the future placenta, so as to dip 
between the maternal vessels. 
What changes take place in the uterine mucous membrane 
during this time ? 
The follicles become tortuous and enlarged, while the epithe- 
lial layers increase in amount. 158 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is the result of this increase in the uterine mucous 
membrane ? 
It makes up the membrana decidua. 
Into how many divisions are the portions of the membrana 
decidua divided? 
Three: The decidua vera, decidua reflexa, and the decidua serotina. 
What is the function of these three divisions ? 
The vera lines the cavity of the uterus; the reflexa grows up 
around the ovum and forms an investment for it; while the sero- 
tina becomes especially developed in connection with the villi of 
the chorion. Remember, by the third month the vera and reflexa 
come in contact, and can no longer be distinguished one from the 
other. 
What is the function of the placenta ? 
It is an organ by which the gaseous and nutritive changes take 
place between the maternal tissues and the embryo. 
The placenta has, therefore, a foetal part and a maternal part. 
THE DEVELOPMENT OF ORGANS. 
How are the vertebral column and cranium developed? 
The notochord or chorda dorsalis consists primarily of soft cellu- 
lar cartilage which is gradually inclosed in a membranous sheath, 
which after a time becomes fibrous and has transverse annular 
fibres. The protovertebrae (see page 154) send processes downward 
and inward to surround the notochord, and also upward between 
the medullary canal and the epiblast covering it. In the former 
situation the cartilaginous bodies of the vertebrae make their ap- 
pearance, in the latter their arches which inclose the neural canal. 
The vertebrae do not exactly correspond in their position with the 
protovertebrae, but each permanent vertebra is developed from the 
contiguous halves of the protovertebrae. 
The cranium is developed from a prolongation of the vertebral 
Vertebral Column and Cranium. HEART AND BLOODVESSELS. 
159 
column, and is formed long before the facial bones. It is formed 
of one mass, the cerebral capsule, the chorda dorsalis being con- 
tinued into its base and ending there with a tapering point. 
In what way is the dorsal portion of the body formed ? 
The muscles and integument of the back, with the exception of 
the epiderm, which is developed from the epiblast, are developed 
from the musculo-cutaneous plate which is formed by the dorsal 
portion of the protovertebrae. 
What is developed from the ventral portion of the proto- 
vertebrae ? 
They give rise to the vertebrae and the heads of the ribs, but the 
outer part of each protovertebra gives rise to a spinal ganglion and 
nerve-root. 
What is the condition at this time of the chorda ? 
It is inclosed in a case, formed by the bodies of the vertebrae, and 
gradually wastes and disappears. 
How are the body cavities formed? 
The dorsal laminae, coalesce at the back and complete, by their 
union, the spinal canal, and the visceral laminae coalesce anteriorly 
and thus form the thoracic and abdominal cavities. An analogous 
process occurs in the facial and cervical regions, but the inclosing 
laminae are cleft. When these clefts fail to unite in the median 
line cleft-palate or harelip results. 
Extremities. 
In what way are the extremities developed ? 
They appear in the form of leaf-like elevations from the parietes 
of the trunk at points where more or less of an arch will be pro- 
duced for them within. 
Heart and Bloodvessels 
How is the heart developed ? 
It makes its first appearance as a solid mass of cells of the 
splanchnopleure. A cavity is hollowed out of the centre, and 160 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
those detached cells float about in a liquid which soon begins to 
move about under the pulsations of the embryonic heart. 
How are the bloodvessels developed ? 
In the formation of the large vessels masses of embryonic cells 
are arranged in longitudinal form and hollowed out in much the 
same manner as the heart, the cells of the heart cavity and blood- 
vessel cavities forming corpuscles. The capillaries seem to be 
formed of cells arranged end to end in single line and hollowed 
like a pipe-stem. 
Nervous System. 
How is the nervous system developed ? 
All the spinal nerves are derived from the mesoblast, as are also 
the cranial nerves, except the optic and olfactory, which are out- 
growths of the anterior cerebral vesicles. The sympathetic system 
is also developed from the same mesoblastic layer. 
Have the spinal cord and brain the same origin as the 
* spinal nerves ? 
Yes. They arise from the epiblast for the gray matter, and for 
the white matter. 
From what is the spinal cord developed ? 
Out of the primitive medullary tube, which results from the 
folding in of the dorsal laminae. 
How is the gray matter formed ? 
The tube is narrowed in one diameter so that the canal becomes 
narrow and oval in shape, and finally the two opposite sides unite 
in the centre of the slit, while the attachments of the two sides at 
the top and bottom of the canal decrease in thickness, and finally 
separate. The white matter is derived from the surrounding meso- 
blast and grows up around the gray columns. The fissures are 
formed by the separating at the top and bottom of the tube already 
described. 
What do you mean by the cerebral vesicles ? 
A widening out of the medullary canal very early in embryonic 
life. EYE. 
161 
Mow many cerebral vesicles have wet 
Three. 
What is the purpose of each ? 
From the first anterior vesicle are budded off the two primary 
optic vesicles, and the rudiments of the hemispheres appear in the 
form of two outgrowths at a higher level. The middle vesicle 
gives off the rudiments of the corpora quadrigemina, the crura 
cerebri, and the aqueduct of Sylvius. The posterior vesicle gives 
off the rudiments of the cerebellum, pons Varolii, the medulla 
oblongata, and auditory nerve. 
Eye. 
From what is the eye developed ? 
The anterior cerebral vesicle, which sends out a smaller vesicle 
on each side, the primary optic vesicles, which are hollow. The 
stalks which attach the vesicles to the original vesicle form the 
optic nerves. After this the formation of the lens and optic cups, or 
secondary optic vesicles, begins. 
How is the lens formed ? 
By a thickening of the epiblast, which indents the extremity of 
the primary optic vesicle and pushes it back till the front wall of 
the vesicle is in contact with the posterior wall, and the optic cup 
is thereby obliterated. 
What does this front wall, which has been pushed back, 
form ? 
The retina. 
What does the back wall form ? 
The pigment layer of the choroid. 
The margins of the cups grow up around the lens everywhere 
except at the lower part, by the optic nerve, where a fissure 
remains. 
What is this fissure called ? 
The choroidal fissure. 162 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
What is its purpose ? 
Through it the mesoblast, which forms the connective tissue of 
the eye, finds an entrance into the cavity of the eye. 
Ear. 
How is the ear developed ? 
Early in embryonic life a depression occurs on each side of the 
surface of the head, which is covered by a membrane, the primary 
otic vesicle. 
What is the purpose of this vesicle? 
It develops the membranous labyrinth of the internal ear. The 
surrounding mesoblast gives rise to the various bony and carti- 
laginous parts inclosing the membranous labyrinth, the bony 
semicircular canals, etc. The mesoblast also develops the auditory 
nerve. 
Nose. 
How is the nose developed ? 
It originates, like the eyes and ears, in a depression of the 
superficial epiblast at each side of the fronto-nasal process, and 
these cavities gradually grow back till they reach the cavity of the 
mouth. 
Alimentary Canal and Organs. 
In what way is the alimentary canal developed ? 
It results from the folding in of the splanchnopleure, and is at 
first straight and parallel to the vertebral column. It is connected 
with the omphalo-mesaraic duct, a point which corresponds with 
the lower segment of the ileum, but the duct atrophies and usually 
disappears about the fourth month. The attachment is at first 
very broad, and only a thin stratum of mesoblast separates the 
hypoblast of the canal from the notochord and proto vertebrae; but 
it subsequently attenuates and becomes the mesentery. In the 
fourth month the part connected with the umbilical vesicle loops 
forward. The part above the umbilical opening becomes the FCETAL CIRCULATION. 
163 
small intestine, and the part below almost wholly the large in- 
testine. The limit between the two is soon indicated by a 
projection, the caecum. The intestine separates from the abdominal 
wall, the remains of the attachment appearing at the third month, 
and sometimes later, as a thread-like appendage to the lower part 
of the ileum. Convolutions then begin to form, and an enlarge- 
ment in the region of the liver, which is the stomach. 
In what way is the posterior opening1 in the intestine 
formed ? 
By the establishment of a communication between the cloaca, or 
tube common to the gut and allantois, and a depression outside of 
the body at about the sixth or seventh week. At the same time a 
septum, which is the future perineum, separates the intestine from 
the organs forming the allantois. The mouth is formed in the 
same manner. 
In what way are the salivary glands, the pancreas, and 
the liver developed? 
The liver commences as a projection formed by two primitive 
hepatic ducts, which divide and subdivide. At the periphery of 
the ducts are solid masses of cells which proceed from the hypo- 
blast. The mass of the gland is developed from the mesoblast. 
The liver secretes as early as the third month. The pancreas is 
also formed from the mesoblast, as are also the salivary glands. 
The lining of their ducts is, however, derived from the hypoblast. 
The Foetal Circulation. 
Describe the foetal circulation ? 
The blood in the placenta, aerated and well nourished, passes 
up the umbilical vein to the navel, where it enters the body of the 
foetus, and, after a short course, reaches the liver, where it is split up 
into two streams, one of which supplies the lobes of the liver, while 
the other passes through the ductus venosus, which lies in the longi- 
tudinal fissure of the liver, into the inferior vena cava and right 
auricle of the heart, but instead of passing into the right ventricle 
it is directed by the Eustachian valve along the back of the auricle 164 
ESSENTIALS OF HUMAN PHYSIOLOGY. 
to the foramen ovale, and immediately enters the left auricle; the 
left auricle, contracting, propels it into the left ventricle, which 
drives it into the general circulation. 
What is the difference in the circulation of blood in the 
inferior vena cava from that of the superior vena 
cava? 
The blood returning from the head, or superior vena cava, passes 
into the right auricle and enters the right ventricle (which the 
blood from the inferior vena cava does not). When the right 
ventricle contracts the blood is driven into the pulmonary artery, 
but instead of being distributed through the lungs it is directed 
through a channel given off by the left pulmonary artery, known 
as the ductus arteriosus, into the aorta just beyond the point where 
the left subclavian is given off from that vessel. The right ventricle 
and the left ventricle may, therefore, be said to drive the blood 
through the general circulation in foetal life. As the result of this, 
however, it will be seen that in the aorta we have blood, half of 
which is aerated and half of which is not. 
In what way does the blood return to the placenta to be 
nourished and oxygenated ? 
It passes through the descending aorta, the common iliacs, and 
the umbilical artery, by which it reaches the placenta. 
What changes take place in the circulation at birth ? 
Respiration is commenced, the lungs become expanded, and, in 
consequence of this, the pulmonary vessels permit the blood to 
traverse them freely. The ductus arteriosus being no longer 
required, contracts and shrivels up, but remains as a fibrous cord. 
At the same time the detachment of the placenta leads to the im- 
mediate arrest of the flow of blood from the umbilical arteries, and 
no flow passes along the umbilical vein. The ductus venosus 
contracts, the currents of the superior and inferior vena cava mix 
in the right side of the heart, and the Eustachian valve and the 
foramen ovale become useless. INDEX. 
Bladder, 80 
Blastoderm, 153 
Blind spot, 134 
Blood, the, 21 
coagulation of, 28 
pressure, 39 
Bloodvessels, 37 
development of, 159 
Body cavity, 155 
Boundary zone of kidney, 73 
Buffy coat, 30 
Burdach’s column, 110 
flALCIUM phosphate in milk, 93 
V Calix of kidney, 75 
Capacity of the parts of the vascular 
system, 39 
Capillaries, 37 
Carbohydrates, 20 
Carbonic dioxide, 48 
Cardiac nerves, 36 
Casein, 20 
Cavities of the heart, 31 
Centre for deglutition, 120 
for respiration, 120 
for urination, 81 
for vomiting, 120 
vasomotor, 120 
inhibitory, 120 
Centrifugal nerves, 104 
Centripetal nerves, 104 
Cerebellar tract, 110, 119 
Cerebellum, 021 
Cerebral localization, 122 
Cerebrum, 122 
Cerumen, 139 
Cervical sympathetic, 146 
Chemical basis of the body, 17 
changes in muscles, 101 
composition of the liver, 64 
Chiasm, optic, 123 
Cholesterin, 65 
Choluria, 86 
Abducent nerve, 125 
Aberration, chromatic, 137 
Absorption, 67 
Accelerator ganglion of the heart, 35 
nerves, 36 
Accommodation of eye, 136 
Acid-albumin, 20 
Action of muscles, 96 
Afferent nerves, 104 
Albumen, 19 
Albuminous foods, 94 
Alimentary canal, development of, 
160 
Alkali-albumin, 20 
Allantois, 157 
Amnion, 156 
Amylolopsin, 61 
Anaemia, 30 
Anelectrotonus, 106 
Animal heat, 68 
source of, 69 
Anterior columns, 110 
Aphasia, 122 
Apnoea, 50 
Appendages of the skin, 87 
Aqueous humor, 135 
Area opaca, 154 
pellucida, 153 
Arteries, 37 
Arterioles, 43 
Arytenoid cartilages, 142 
Asphyxia, influence of, on blood- 
pressure, 41 
Astigmatism, 137 
Auditory canal, 139 
nerve, 125 
Auricles of the heart, 31 
Automatism, 115 
Bile, 65 
acids, 65 
pigments, 65 
Bizzozero, blood plaque of, 24 166 
INDEX. 
Chorda dorsalis, 154 
tympani nerve, 53 
Chord® tendine®, 33 
Chorion, 156 
Choroid coat, 133 
Chromatic aberration, 137 
Chyluria, 86 
Chyme, 58 
Ciliary muscle, 133 
processes, 133 
Cilio-spinal centre, 120 
Circulation, 42 
Classification of proteids, 19 
Coagulation of the blood, 28 
Coats of the arteries, 37 
of the eye, 133 
Color-blindness, 134 
Color of the bile, 66 
of the blood, 22 
of the urine, 83 
Colostrum, 93 
Column® carne®, 33 
Columns of the spinal cord, 111 
Complemental air, 47 
Course of the medullary fibres, 118 
Cones of the eye, 134 
Consciousness, 122 
Consistency of muscle, 97 
Constituents of the blood, 23 
of milk, 91 
Contraction of muscles, 99 
Cornea, 133 
Corpora quadrigemina, 121 
striata, 121 
Corpus luteum, 150 
Corpuscles, nerve, 107 
red blood, 22 
Cortex of kidney, 73 
Corti, organ of, 141 
Coughing, 51 
Coverings of eye, 131 
Cranium, development of, 158 
Cricoid cricoid, 142 
Crossed pyramidal tracts, 110, 118 
Crura cerebri, 120 
Crystalline lens, 135 
DECIDUA menstrualis, 149 
reflexa, 158 
• serotina, 158 
vera, 158 
Decussation, 118 
Defibrinated blood, 29 
Deglutition, 55,120 
Depressor nerves, 37 
Development, 146 
of organs, 158 
Diabetes insipidus, 86 
mellitus, 86 
Diapedesis, 24 
Diastatic action of saliva, 54 
Diffusion, 67 
Digestion, 51 
Dioptric media, 138 
Diplopia, 137 
Direct cerebellar tract, 119 
pyramidal tracts, 110,118 
Discus proligerus, 148 
Ductus arteriosus, 164 
venosus, 164 
Dysperistalsis, 60 
Dyspnoea, 50 
EAR, development of, 160 
Efferent nerves, 104 
Eggs, 94 
Elasticity of muscles, 98 
Electrical phenomena of muscle, 99 
Electrotonus, 105 
Endolymph, 140 
Endosmosis, 67 
Eutopic images, 137 
Epiblast, 153 
Epididymis, 151 
Epiglottis, 144 
Euperistalsis, 60 
Eupnoea, 50 
Eustachian tube, 140 
Excretion, 89 
Expiration, 46 
External ear, 139 
Extremities, development of, 159 
Eye, 131 
development of, 160 
Eyeball, 132 
Eyelashes, 131 
FRACTAL nerve, 125 
Falling energy, 102 
Fallopian tubes, 147 
Far point, 136 
Fats, 21,94 
Feces, amount of, 66 
Fecundation, 152 
Fibrin, 20, 28 INDEX. 
167 
Fibrin-ferments, 28 
Fibrinogen, 19 
Fibrinoplastin, 28 
Flesh, 94 
Foetal circulation, 163 
Fourth ventricle, 118 
Functions of the bladder, 80 
of the blood, 21 
of the coats of the arteries, 38 
of the gray matter of cord, 111 
of the heart, 31 
of the kidneys, 73 
of the liver, 65 
' of the skin, 88 
of tracts of cord, 111-113 
of the white matter of cord, 111 
Ganglion of the heart, 35 
Gases of the blood, 27 
of the stomach, 58 
Gastric digestion, 51 
juice, 57 
Gelatinous substance of Rolando, 110 
Generation, 146 
Generative organs of female, 147 
Germinal area, 153 
Globulins, 19 
Glomerulus, 75 . 
Glosso-pharyngeal nerve, 125 
Glycogen, 64 
Glycosuria, 86 
Goll’s column, 110 
Graafian vesicles, 147 
Gray matter of cord, 109 
HHEMATIN, 27 
Haemoglobin, 27 
Haemoglobinuria, 86 
Hair, 89 
Head folds, 155 
Hearing, 139 
Heart, the, 31 
development of, 159 
Heat, animal, 68 
dissipation, 70 
production, 70 
Heintz’s test, 65 
Hemianopsia, 138 
Hiccough, 51 
Hippuric acid, 85 
Humors of the eye, 135 
Hypermetropia, 138 
I Hypoblast, 153 
I Hypoglossal nerve, 126 
INDIFFERENT point, 106 
Indol, 61 
| Inhibitory centre, 120 
ganglion of the heart, 35 
| Injuries of optic nerve, 123 
Intestinal digestion, 51 
Inverson of images, 135 
Iris, 133 
Irritability of muscle, 99 
KATELECTROTONUS, 106 
Kidneys, 73 
Kinetic energy, 91 
Kreatin and kreatinin, 85 
I ABYRINTH of kidney, 74 
lj Lachrymal glands, 131 
Lacteals, 67 
Lactic acid, 57 
Lactiferous ducts, 90 
Laminae dorsalis, 154 
Large intestine, function of, 66 
Larynx, 142 
muscles of, 142 
Latent period, 102 
Lateral columns of spinal cord, 111 
Laughing, 51 
Laws of contraction, 107 
Laxator tympani muscle, 140 
Lens, 135 
Lesions of spinal cord, 116 
Leucin, 61 
Leucocytheemia, 30 
Liquor amnii, 157 
Liver, 62 
Locus niger, 120 
Macula lutea, 134 
Male sexual organs, 150 
Malpighian body, 75 
Mammary glands, 90 
Mastication, 55 
Maximum stimulation, 102 
contraction, 103 
Medulla of kidney, 73 
oblongata, 117 168 
INDEX. 
Medullary groove, 154 
Meibomian glands, 131 
Meissner’s plexus, 60 
Membrana decidua, 168 
Membranes of brain and cord, 108 - 
Menstruation, 149 
Mesoblast, 153 
Metabolism, 90 
Microcytes, 24 
Milk, 91 
Milk-curdling ferment, 62 
’ Milk globules, 91 
plasma, 91 
Millon’s reagent, 20 
Motor ganglion of the heart, 35 
nerves, 104 
Movements of the heart, 34 
of respiration, 46 
of the stomach, 56 
Muscle, ciliary, 133 
laxator tympani, 140 
plasma, 97 
tensor tympani, 140 
Muscles, 96 
of larynx, 142 
Musculi papillares, 33 
Myopia, 138 
Myosin, 19, 97 
Nails, 89 
Near point, 136 
Negative variation, 99, 105 
Nerval cavity, 155 
Nerve, abducent, 125 
auditory, 125 
corpuscles, 107 
facial, 125 
glosso-pharyngeal, 125 
hypoglossal, 126 
oculo-motor, 123 
olfactory, 123 
pathetic, 124 
pneumogastric, 126 
sublingual, 126 
spinal accessory, 126 
sympathetic, 144 
vagus, 126 
Nerves of the kidney, 79 
of special sense, 127 
of the stomach, 57 
of taste, 130 
Nervous mechanism of deglutition, 56 
of the heart, 35 
Nervous mechanism of heat, 70 
of respiration, 50 
of speech, 143 
of urination, 81 
Nervous system, 103 
development of, 160 
Neuroglia, 109 
Nose, development of, 160 
Notochord, 154 
OBJECT of respiration, 45 
Oculo-motor nerve, 123 
Odor of the blood, 22 
Olfactory nerve, 123 
Olivary body, 118 
Optic chiasm, 123 
nerve, 123 
Organ of Corti, 141 
Organs of generation, 147 
Otoliths, 140 
Ovaries, 147 
Ovule, 148 
Ovum, 149 
Oxyhaemoglobin, 22 
PANCREATIC digestion, 61 
ferments, 61 
Papillae of the skin, 87 
Paraglobulin, 19 
Parotid, 52 
Parts of the kidney, 73 
Pathetic nerve, 124 
Pepsin, 57 
Peptones, 19 
Peristalsis, 59 
Perspiration, 88 
function of, 71 
Pettenkofer’s test, 65 
Physical forces of the circulation, 42 
Physiology of the spinal nerves, 17 
Placenta, 157,158 
Plasma, blood, 23 
milk, 97 
muscle, 97 
Plethora, 30 
Pneumogastric nerve, 36, 126 
Pons Varolii, 120 
Posterior columns of spinal cord, 111 
Pressor fibres, 37 
Primitive groove, 154 
Processes, ciliary, 133 
I Prostate gland, 152 INDEX. 
169 
Proto vertebrae, 154 
Proteids, 18 
Ptyalin, 54 
Pulse, 44 
Pupil, 124 
Pupillary movement, 134 
Pyramids of kidney, 75 
of medulla oblongata, 117 
Quadrigeminal bodies, 121 
Quantity of bile, 66 
Quantity of the blood, 28 
RAMI communicantes, 144 
Rate of the heart, 35 
Rate of respirations, 48 
Reaction of the blood, 22 
of muscles, 98 
of the urine, 83 
Recurrent sensibility, 108 
Reflex action, 114 
inhibiting centre, 115 
Refraction, 136 
Reserve air, 47 
Residual air, 47 
Respiration, 45 
Respiratory centre, 50, 119 
Restiform bodies, 117 
Retina, 134 
Rising energy, 102 
Rods of eye, 134 
Rolando, gelatinous substance of, 110 
Roots of trifacial nerve, 124 
Rouleaux, 25 
0 ALIVA, 52 
kJ Salivary centre, 120 
digestion, 51 
glands, 51 
Salts, 94 
of urine, 85 
Sclerotic coat, 132 
Sebaceous glands, 89 
Secretion, 89 
Segmentation of ovum, 152 
Semicircular canals, 140 
Sense of sight, 131 
of smell, 130 
of taste, 129 
Sensibility, 128 
Sensory nerves, 104 
Serum, blood, 23 
Setschenow’s centre, 115 
Sighing, 51 
Sight, 131 
Size of the kidneys, 73 
Skatol, 61 
Skin, 87 
Smell, sense of, 130 
Sneezing, 51 
Sobbing, 51 
Somatopleure, 155 
Sounds of the heart, 34 
Source of animal heat, 69 
Special centres, 119 
, senses, 127 
I Specific gravity of the blood, 23 
of milk, 91 
of urine, 82 
Speech, 141 
centre, 122 
Speed of the circulation, 45 
Spermatozoids, 151 
Spherical aberration, 137 
Spinal accessory nerve, 126 
nerves, 107 
Splanchnic, 146 
Splanchnics, or peristalsis, 60 
Splanchnopleure, 155 
Stapedius muscle, 139 
Starch, 20 
Starches, 94 
Starvation, 95 
Steapsin, 62 
Stomach, 56 
Sublingual nerve, 126 
saliva, 52 
Submaxillary saliva, 52 
Sudoriferous glands, 88 
Sugar, 20 
Summation, 103 
Sweat, 88 
Sympathetic, 53 
nerve, 144 
Tactile sensibility, 128 
Tail folds, 155 
Taste, 129 
buds, 129 
goblets, 129 
nerves of, 130 
of the blood, 23 
Temperature of the blood, 23 
1 Tensor tympani muscle, 140 170 
INDEX. 
Testicles, 150 
Tests for proteids, 20 
Tetanus, 103 
Thyroid cartilage, 142 
Tidal air, 47 
Transference, 114 
Trifacial nerve, 124 
Trommer’s test, 21 
Trypsin, 61 
’Tubes, Fallopian, 147 
Tubuli seminiferi, 151 
uriniferi, 75 
Tympanic membrane, 139 
Tyrosin, 61 
UMBILICAL veins, 164 
vesicle, 156 
Urea, 84 
Ureters, 79 
Uric acid, 85 
Urinse potus, cibi, and sanguinis, 83 
Urination, 81 
Urine, 82 
Uterus, 144 
VAGINA, 147 
Vagus nerve, 126 
Valves of the heart, 31 
of the veins, 39 
Variations in the blood, 23 
Vasa recta, 78 
Vas deferens, 151 
Vasomotor centre, 40 
nerves, 40 
Vegetable foods, 94 
Veins, 37 
Ventricles of the heart, 31 
Vernix caseosa, 89 
Vertebrae, development of, 158 
Vesiculae seminales, 151 
Vesicular columns of Clark, 110 
Visceral plates, 155 
Visual purple, 135 
Vital capacity, 47 
Villi of chorion, 157 
Vitellin, 19 
Vitelline membrane, 148 
Vitreous humor, 135 
Voice, 141 
Vomiting, 59 
centre, 120 
WATER, 91, 94 
White blood-corpuscles, 24 
matter of the spinal cord, 
109 
ANTHO-PROTEIC reaction, 20 
ONA pellucida, 148