The true are the two anterior, two lateral, and the
urachus. The false are five, and consist of folds of
Method of Urine Secretion. The urine contains
the waste products resultant from body metabolism
which are eliminated through the kidneys, ureter,
bladder, and urethra.
Several theories have been demonstrated in regard
to how these waste products pass from the blood to
the urine. However, the two accepted methods of
urine secretion or excretion are based on the principles
of filtration and secretion.
The uriniferous tubules as described above com-
mence as the capsule of Bowman, which surrounds
a collection of capillaries (glomerulus) . Bowman's
capsule is simply an indentation of the tubule. It
consists of two walls, an outer one covered with
flattened epithelium resting on a very thin basement
membrane, and an inner wall consisting of flattened
epithelium which is reflected over and encloses the
glomerulus. Thus the blood in the capillaries is
separated from the interior of Bowman's capsule
by the intervention of the capillary wall and the
inner layer of epithelium, lining the inner wall of the
capsule. The secretion of urine primarily takes
320 THE URINARY APPARATUS
place by a rise of blood pressure in the arterioles
(afferent vessels). The capsule of Bowman becomes
so distended that the two layers of cells approximate
and practically obliterate the cavity between them.
Then the water, salts, sugars, peptones, etc., pass
from the blood to the interior of the capsule of Bow-
man, by a process of filtration or transudation through
the capillary wall and the thin inner layer of Bow-
man's capsule, and pass along the tubules. However,
Heidenhain believes that the latter constituents of
the urine are passed through the glomerular epithe-
lium by the processes of cell selection and cell activity;
in other words, the entire constituents of the urine
obtained in the capsule of Bowman from the blood
is due to process of secretion, assisted or regulated by
the degrees of blood-pressure, blood-velocity, etc.
The blood of the glomerulus being emptied of a
portion of its water, salts, etc., as described above,
still possesses other waste products in the blood
which must be eliminated as urea, uric acid, etc. This
further elimination is based on a distinct and proved
function of the cells, lining the convoluted tubules of
the kidney, of selecting from the blood and secreting
the above-mentioned products as constituents of the
urine. The methods by which these products leave
the glomerulus and reach the cells of the convoluted
tubules is as follows: A small arteriole leaves each
glomerulus (efferent vessel) and divides and sub-
divides, forming a capillary net-work, which surrounds
the convoluted tubules, thus bringing the blood in
intimate relation with the lining cells of the tubules,
which, to repeat, select and secrete the urea, uric
acid, etc., from the blood, and eliminate them in the
The remaining quantity of blood which has given
off its waste product to be eliminated by the two
methods described above, is taken up by venules
which anastomose with the arterioles around the con-
THE URINARY ORGANS 321
voluted tubules and straight tubules, and is returned
through the renal vein to the venous system.
The Urine. The urine is the fluid by which the
end-products resulting from tissue metabolism are
excreted or, literally speaking, are secreted by the
kidneys from the body. The phenomena, however, is
essentially the same as takes place during secretion of
fluids by the body cells. It must be remembered that
to perform work, create energy, nourish, and develop
the body from birth to death, food is necessary. The
body receives its nourishment from the food we eat, and
the essential constituents of the same are used by the
tissues to perform the various and complex processes
necessary to carry on and maintain the normal physio-
logical functions of the human body. Were this
intake of food not used or eliminated, there would
be a general interference of the normal functions of
cell life, but as we have demonstrated in previous
chapters, it is used and then undergoes changes, the
residue forming products which must be eliminated,
and the urine is the fluid by means of which this
Normal urine is a pale yellow or amber-colored
fluid, with an aromatic odor and acid reaction. Its
specific gravity is 1.020, but varies between 1.015 to
1.025. It is usually transparent, except when mucus,
phosphates, urates, render it cloudy in appearance.
The color varies from a pale yellow to a reddish
brown, dependent upon the physiologic processes
occurring prior to elimination. Its color is due to
the presence of a pigment-urobilin, urochrome, uro-
erythrin, derived from the bile pigments absorbed
from the liver or alimentary canal. The acidity of
the urine is due to the presence of acid phosphates
of sodium and calcium. Urine is usually acid in the
morning, alkaline or neutral following digestion.
The quantity of urine passed in twenty-four hours
amounts to 40 to 50 ounces (2| to 3 pints 2 ounces).
322 THE URINARY APPARATUS
The odor is due to the presence of aromatic com-
Composition of Urine:
Water 1500.00 c.c.
Total solids 72.00 gm.
Uric acid (urates) 0.55 gm.
Hippuric acid (hippurates) 0.45 gm
Kreatinin, xanthin, hypoxanthin, guanin,
ammonium salts, pigments, etc. . . 11.21 gm.
Inorganic salts, sodium and potassium sul- ^
phates, phosphates, and chlorides; mag-
nesium and calcium phosphates. . . I 27.00 gm.
Organic salts: lactates, acetates, formates I
in small amounts
Sugar a trace.
Gases nitrogen and carbonic acid.
Urea, being the most abundant and important
organic compound of the urine, will be described.
It is present to the amount of 2 to 3 per cent. It is
found after analysis of the urine to consist of a
colorless, neutral substance, crystallizing in long,
silky needles. It is composed of carbon, oxygen,
nitrogen, and hydrogen (CON 2 H 4 ) . The daily quantity
excreted amounts to 30 to- 34 grams. It is the end-
product of the protein metabolism which has gone on
within the body, and the quantity excreted in the
urine is dependent upon the amount of protein food
consumed and upon the degree to which the protein
constituents of the tissues have undergone metabolic
The skin is the structure investing the entire outer
surface of the body, blending with the mucous mem-
branes which bound the cavities leading into the
body, as the mouth, etc. Its dimensions vary in
thickness in different parts of the body, from ^ to
THE SKIN 323
of an inch, total area 16 to 20 square feet in man, and
12 to 16 square feet in woman.
The skin secretes a clear, colorless fluid, the sweat;
it acts as a protection to the underlying structures, and
aids in the excretion of waste-products of metabolism,
possessing an accessory function in conjunction with
the lungs and kidneys of elimination of these products
from the body. It also assists in regulating the
temperature of the body by promoting heat dissi-
The skin must be studied under the microscope in
order to properly grasp its structure. There are two
principal layers, superficial and deep; the former is
termed the epidermis, the latter the derma or corium.
The Epidermis. This consists of epithelial cells
derived from the ectoderm. There are two layers
within the epidermis: superficial or horny layer, and
deep or Malpighian layer. The horny layer consists
of non-nucleated scaly cells composed of keratin.
The surface cells of this layer are being continually
rubbed off, and are replaced by cells from the Mal-
pighian layer underneath, which undergo a change
and are converted into keratin as they approach the
surface. The Malpighian or deep layer is divided into
four layers, named from without inward stratum
lucidum, stratum granulosum, stratum mucosum, and
.the stratum germinativum. The stratum mucosum
contains the prickle cells which contain the pigment
granules that give to, the skin its different individual
and racial characteristics in regard to color.
The Derma, Corium, or True Skin. This is com-
posed of the two layers: superficial or papillary layer,
and the reticular.
The superficial or papillary layer lies beneath the
epidermis. It contains numerous projections called
papillae, and i composed of a net-work of fine bundles
of fibrous tissue. The papillae are composed of fibrous
THE URINARY APPARATUS
and elastic tissue. They project from the true skin
or corium, and enter into depressions of the epidermis.
The reticular layer connects the skin with the under-
lying structures. It also supports the minute blood-
vessels, lymphatics, and nerves which are distributed
to the papillse.
The subcutaneous tissue is the layer beneath the
reticular layer of the true skin, which holds the skin
to the parts beneath. It is made up of thin connec-
FURROWS OF SKIN
RIDGES OF SKIN
f STRATUM CORN EUM/
MIS-j STRATUM LUCIDUM
( STRATUM PAPILLARE ("
STRATUM RETICULARE t
Vertical section through the skin of the finger tip. The layers of the epi-
dermis and of the corium. The subcutaneous areolar tissue. The sudoriferous
or sweat gland. (Toldt.)
tive tissue which crosses repeatedly and forms spaces.
The skin in certain parts is held firmly to the under-
lying structures by the subcutaneous tissue, as the
skin over the palms and soles of the feet; in others
it is loosely attached and is freely movable, as the
skin over the front of the arms and neck.
The skin is supplied by branches of the larger
THE SKIN 325
arteries coursing through the subcutaneous tissues.
These form minute capillary plexuses which send off
branches to form other plexuses in the corium and
papillary layer; from the latter branches pass to the
papilla, sweat glands, sebaceous glands, fat, and hair
The Appendages of the Skin. They are the nails,
hairs, the sudoriferous or sweat glands, and sebaceous
The Nails. These are flattened, elastic structures
of a horny texture, placed upon the back surface of
each distal extremity of each finger and toe. The
nail is implanted by means of a portion called the
root, within a groove in the skin. The rest of the con-
vex surface of the nail is called the body. Beneath the
root and body is a portion of the cutis called the
matrix. This is the part from which the nail grows.
The white, crescentic-shaped area of the nail seen
behind the matrix and above the root is called the
lunula. Its color is due to its being less vascular
compared to the remaining portion of the nail. The
nail can be injured, and if any cells of the Malpighian
layer remain, a new nail will develop from these
The Hairs. They are found in certain regions of
the body. They act as a protection to the part; pre-
vent friction; prevent foreign bodies from entering the
organs they protect, as the eyes, nose, etc. We speak
of hairs of the head, of the eyebrows, of the axilla, of
the eyelids, of the nose, of the pubes, and of the skin.
They vary much in length, thickness, and quality.
In some individuals the hair is straight, in others
curly. Hairs usually are oblique to the surface from
which they arise.
Hairs are modifications of the skin (epidermis) and
consist essentially of the same structure as it. Hair
consists of the root, the part implanted in the skin;
326 THE URINARY APPARATUS
the shaft, the portion extending from the surface; and
The root of the hair presents at its deep extremity a
bulb-like enlargement, the hair-bulb, which is lodged in
a follicular involution of the epidermis called the hair
follicle. The hair follicle commences in the surface
of the skin with a funnel-shaped opening, and passes
inward in an oblique direction, to become dilated at
its deep extremity or fundus, where it corresponds
with the bulbous shape of the hair which it contains.
Each hair follicle has at its base a small, conical,
vascular eminence or papilla, the hair papilla, similar
to the papilla? found upon the surface of the skin.
The latter are highly vascular and probably supplied
with nerve fibrils. Each hair follicle has an opening into
it near its free extremity, the openings or orifices of
the ducts of one or more sebaceous glands. Connected
with the hair follicles are minute bundles of involuntary
muscle fibers called arrectores pilonim. They originate,
from the superficial surface of the true skin, or corium,
and are inserted into the outer surface of the hair
follicle, below the orifice of the duct of the sebaceous
gland. They are located on the side toward which
the hair slopes, and when they contract elevate the
The Sebaceous Glands. These are simple and com-
pound racemose glands which open into the hair
follicle, and sometimes the skin surface, by means of
a duct. These glands are lodged in the surface of the
true skin or corium. They are very plentiful, and
are found in all parts of the body, especially in the
skin of the face and scalp; also numerous around the
openings of the mouth, anus, nose, and external ear,
but are not found in the skin covering the palms of
the hands and the soles of the feet. Their structure
consists of a delicate transparent membrane, enclosing
THE SKIN 327
Sebum is the oily fluid secreted by the sebaceous
glands. It contains, by analysis^ water, epithelium,
proteins, fats, cholesterin, and inorganic salts.
The pouring-out of seburn by the glands is not a
true secretion, but occurs as a result of multiplication
and breaking down of the gland epithelium. Sebum
when first secreted is oily and semiliquid, but soon
becomes hard and acquires a cheese-like consistency.
It lubricates the hair and skin and prevents dryness
Vemix caseosa is the whitish, oily substance seen
covering the body of the newborn child. It is supposed
to keep the skin in a normal condition by protecting
it from the effects of the long-continued action of the
amniotic fluid in which the fetus is suspended during
The Sweat Glands. The sweat glands are the glands
which when active promote perspiration and aid in
heat dissipation, at the same time eliminating waste
products as the result of body metabolism, brought to
them by the blood.
They are situated in the lower part of the corium,
derma, or true skin, and sometimes in the subcutaneous
tissue. The glands are tubular, and the lower or
inner extremity is coiled upon itself a number of
times, forming a rounded mass. Extending from
this coil to the epidermis is the duct which follows
a straight course in this situation, and after a few
spiral turns, opens onto the surface of the skin. The
glands consist of epithelial cells which rest upon a
very thin basement membrane. These glands are
very numerous; it has been estimated that they
average from 2,000,000 to 2,500,000. They are more
abundant in some localities than others. Each sweat
gland is richly supplied with bloodvessels and nerves
(vasomotor and secretor).
Perspiration. Perspiration or sweat is the fluid
secreted by the sweat glands of the skin. It is a
328 THE URINARY APPARATUS
clear, colorless liquid of a specific gravity varying
from 1.003 to 1.006; slightly acid in reaction and salty
to the taste. Except when collected from the soles
of the feet and palms of the hands, it is mixed with
epithelial cells and sebum secreted by the sebaceous
glands. The amount of sweat secreted in twenty-four
hours has been estimated at 700 to 1000 grams; however,
this is uncertain, owing to the difficulty of collection,
and the influence temperature, diet, drink, season of
the year, etc., exert upon its secretion.
The secretion of sweat, though essentially an ex-
cretion, is chiefly concerned in the regulation of the
body temperature in maintaining heat dissipation,
rather than the elimination of waste materials by
means of the sweat glands brought to them by the
blood and lymph vessels.
The Part Played by the Nerve System on the Produc-
tion of Sweat. The secretion of sweat is practically
the result of the activity of the epithelial cells of the
sweat glands and is regulated by the nerve system.
The fluid contained in the sweat is derived from
the materials in the lymph channels, furnished by
To produce sweat there must be a glandular activity,
and a regulation of the blood-supply. The former is
brought about by a set of nerves called the secretor,
which stimulate the cells to activity; the latter is
regulated by nerves called the vasomotor, that regu-
late the blood-pressure of the capillaries and increase
or decrease the blood-supply to the glands. Other
influences increase the production of sweat, by their
related nerve centres sending out impulses in two
ways: first, by nerve impulses from the central domin-
ating centre, supposed to be located in the medulla,
being stimulated by mental emotions, as shock, shame,
etc., venosity of the blood, hot drinks, violent muscular
exercise, etc.; second, by reflex impulses being con-
veyed to the centres in the spinal cord by the sensor
nerves in the skin, as a result of hot applications, high
external temperature, etc.
The nerve centres which regulate the secretion of
sweat are located in the spinal cord and reach the
glands of the skin by means of the sympathetic nerves
with which the spinal nerves communicate. The domi-
nating centre which is influenced to activity by emotional
states, etc., is situated in the medulla oblongata
and sends its impulses down the spinal cord and out
through the spinal nerves and 'the sympathetic system
to the cells of the glands. Sweat may be produced
by a general relaxation of the bloodvessels which
supply the sweat glands, resulting from a stimulation
of the vasomotor nerves. But it must be remembered
that a normal production of sweat is based on the
activity of both the nerves influencing the blood
supply to the glands, and the nerves which stimulate
the cells of the sweat glands to secrete.
1. What organs include the urinary apparatus?
2. Give the location of the kidneys.
3. Which is higher, the right or left?
4. Give dimensions and weight.
5. Are the kidneys behind the peritoneum?
6. How are the kidneys held in position?
7. What do you understand by the medulla and cortex of the
8. How many pyramids are there in the medulla?
9. What part of the pyramids drain the urine into the pelvis of
10. What structures form the medullary rays in the cortex of
the kidney? The labyrinth?
11. What structures form Bowman's capsule? The glomerulus?
12. What structures form the renal or Malpighian corpuscles in
13. Where do the urinifetous tubules commence in the substance
of the kidney? Where do they terminate?
14. What type of epithelium lines Bowman's capsule? The
convoluted portion of the uriniferous tubules? The loops of Henle?
15. How many ureters are there?
16. What is the function of the ureters? How long is each one?
17. Give the location, dimensions, and capacity of the bladder.
330 THE URINARY APPARATUS
18. Name the portions of the bladder.
19. Through what structure does the urine leave the bladder?
20. Describe how the waste products of the blood pass through
the capsule of Bowman during urine secretion.
21. What function do the cells of the uriniferous tubules play as
regards the elimination of urea, uric acid, etc., from the blood-
22. How does the venous blood from the capillaries of the kidney
reach the venous system?
23. What resulting products of metabolism does the urine repre-
24. How much urine should be passed daily by a healthy indi-
25. What is the normal color of urine?
26. What end-product does urea represent in the urine?
27. Will a diet rich in protein increase the amount of urea?
28. What are the functions of the skin?
29. Name the two principal layers of the skin.
30. What is the function of the subcutaneous tissue?
31. Name the appendages of the skin.
32. Name the parts of a nail.
33. Name the, functions of hairs.
34. Name the parts of a hair.
35. Describe a hair follicle.
36. What muscles cause hairs to stand erect?
37. Which layer of the skin lodges the sebaceous glands? When
do they empty? In what portions of the body are they most abun-
38. What is the secretion from the sebaceous glands called? Its
39. Describe vernix caseosa.
40. In which layer of the skin are the sweat glands located?
41. Do they possess ducts, and when do they pour out their
42. What are the functions of the sweat glands?
43. Is sweat acid or alk.aline in reaction?
44. Does the secretion of sweat aid heat dissipation?
45. Name the nerves which stimulate the. cells of the sweat glands
to secrete, also regulate the blood-supply to a sweat gland.
ANATOMY AND PHYSIOLOGY OF THE
THE nerve system is divided for the purpose of
description into the cerebrospinal and sympathetic
systems. The cerebrospinal system consists of the
central nerve axis (brain and spinal cord), and the
peripheral nerves (cranial and spinal).
THE STRUCTURE OF THE NERVE SYSTEM
Neurone, or Nerve Cell Element. The essential
structure from which all the functions of the human
body arise as a result of innervation, is the cell ele-
ment called the neurone. They differ from all the
other cells in the tissues, in that their protoplasm
is extended in the form of processes, and these
reach some distances from the nuclear portion of the
The neurones are the essential structures concerned
in all nerve reflex. However, the fact of a sensor
impulse reaching a neurone from a muscle, gland, or
other cell, does not say a motor impulse will be returned
from the neurone direct, as the neurones are connected
with other neurones by means of their extending
processes, which have the power of reacting and
sending out excitomotor impulses, and of checking
or reducing the impulse to the structure to be inner-
THE NERVE SYSTEM
The neurones form an aggregation of cells which
are the basis of the nerve system from which all
Showing some varieties of cell bodies of neurones (diagrammatic). A.
Unipolar (amacrine) cell from the retina. B. Bipolar cell from vestibular
ganglion. C. Multipolar cell, with long axone, from spinal cord. D. "Golgi
cell," with short axone breaking up into numerous temiinal twigs. E. Pyrami-
dal cell from cerebral cortex, a. Axone. clt. Collaterals, t. Telodendria.
THE STRUCTURE OF THE NERVE SYSTEM 333
nerve force originates, and which maintains the
specific functions of the body expressed in motion,
trophic changes, or stimuli of a chemic, mechanic
(touch, sound), thermal, or photic nature.
Neurones are so arranged to be receptive and
receive (afferent) impulses from other parts of the
body. These are termed sensor neurones. Others
are emissive and return (efferent) impulses; the latter
are called motor neurones; if connected with muscle
cells, excitomotor, and with gland cells, excito-
The neurones or nerve cells compose the cellular
element of the whole nerve system, and the balance
is the supporting white fibrous tissue and neuroglia
derived from the supporting membrane or from the
sheaths of vessels.
The Structure of a Neurone or Nerve Cell. It consists
of a cell mass or body containing a nucleus, and within
the latter a nucleolus. From this cell body are given
off protoplasmic processes of two different varieties:
(1) dendrites, and (2) axone, or axis-cylinder.
The Bodies of Nerve Cells. They vary in size,
they measure 4 to 135 microns or more in diameter,
and when it is considered that 1 micron is equal to
"2 5~ToT f an inch, their minute size may be appreciated.
Neurones are classified according to the number of
processes arising from the body, as unipolar, bipolar,
The Dendrites. - They are processes extending
from the body of the cell in large numbers. They
consist of the same structure as the cell, and thus
increase the functional surface or expression of the
cell. The dendrites never communicate with the
branches of the same process direct, or anastomose
with the terminals of dendrites from adjoining nerve
cells. The function of the dendrites is supposed to