Disease and Its Causes by William Thomas Councilman

W >> William Thomas Councilman >> Disease and Its Causes

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14

In no way is the individuality of living matter more strongly
expressed than in the resistance to disease. The variation in the
degree of resistance to an unfavorable environment is seen in every
tale of shipwreck and exposure. In the most extensive epidemics
certain individuals are spared; but here care must be exercised in
interpreting the immunity, for there must be differences in the degree
of exposure to the cause of the epidemic. It would not do to interpret
the immunity to bullets in battle as due to any individual
peculiarity, save possibly a tendency in certain individuals to remove
the body from the vicinity of the bullets; in battle and in epidemics
the factors of chance and of prudence enter. No other living organism
is so resistant to changes in environment as is man, and to this
resistance he owes his supremacy. By means of his intelligence he can
change the environment. He is able to resist the action of cold by
means of houses, fire and clothing; without such power of intelligent
creation of the immediate environment the climatic area in which man
could live would be very narrow. Just as disease can be acquired by an
unfavorable environment, man can so adjust his environment to an
injury that harmony will result in spite of the injury. The
environment which is necessary to compensate for an injury may become
very narrow. For an individual with a badly working heart more and
more restriction of the free life is necessary, until finally the only
environment in which life is even tolerably harmonious is between
blankets and within the walls of a room.

The various conditions which may act on an organism producing the
changes which are necessary for disease are manifold. Lack of
resistance to injury, incapacity for adaptation, whether it be due to
a congenital defect or to an acquired condition, is not in itself a
disease, but the disease is produced by the action on such an
individual of external conditions which may be nothing more than those
to which the individuals of the species are constantly subject and
which produce no harm.

[Illustration: FIG. 3.--A SECTION OF THE SKIN. 1. A hair. Notice there
is a deep depression of the surface to form a small bulb from which
the hair grows. 2. The superficial or horny layer of the skin; the
cells here are joined to form a dense, smooth, compact layer
impervious to moisture. 3. The lower layer of cells. In this layer new
cells are continually being formed to supply those which as thin
scales are cast off from the surface. 4. Section of a small vein. 9.
Section of an artery. 8. Section of a lymphatic. The magnification is
too low to show the smaller blood vessels. 5. One of the glands
alongside of the hair which furnishes an oily secretion. 6. A sweat
gland. 7. The fat of the skin. Notice that hair, hair glands and sweat
glands are continuous with the surface and represent a downward
extension of this. All the tissue below 2 and 3 is the corium from
which leather is made.]

[Illustration: FIG. 4.--DIAGRAMMATIC SECTION OF A SURFACE SHOWING THE
RELATION OF GLANDS TO THE SURFACE. (_a_) Simple or tubular gland,
(_b_) compound or racemose gland.]

All of the causes of disease act on the body from without, and it is
important to understand the relations which the body of a highly
developed organism such as man has with the world external to him.
This relation is effected by means of the various surfaces of the
body. On the outside is the skin [Fig. 3], which surface is many times
increased by the existence of glands and such appendages to the skin
as the hair and nails. A gland, however complicated its structure, is
nothing more than an extension of the surface into the tissue beneath
[Fig. 4]. In the course of embryonic development all glands are formed
by an ingrowth of the surface. The cells which line the gland surface
undergo a differentiation in structure which enables them to perform
certain definite functions, to take up substances from the same source
of supply and transform them. The largest gland on the external
surface of the body is the mammary gland [Fig. 5] in which milk is
produced; there are two million small, tubular glands, the sweat
glands, which produce a watery fluid which serves the purpose of
cooling the body by evaporation; there are glands at the openings of
the hairs which produce a fatty secretion which lubricates the hair
and prevents drying, and many others.

[Illustration: FIG. 5.--A SECTION OF THE MAMMARY GLAND. (_a_) The
ducts of the gland, by which the milk secreted by the cells which line
all the small openings, is conveyed to the nipple. All these openings
are continuous with the surface of the skin. On each side of the large
ducts is a vein filled with blood corpuscles.]

[Illustration: FIG. 6.--PHOTOGRAPH OF A SECTION OF THE LUNG OF A MOUSE.
_x x_ are the air tubes or bronchi which communicate with all of
the small spaces. On the walls of the partitions there is a close
network of blood vessels which are separated from the air in the
spaces by a thin membrane.]

The external surface passes into the interior of the body forming two
surfaces, one of which, the intestinal canal, communicates in two
places, at the mouth and anus, with the external surface; and the
other, the genito-urinary surface, which communicates with the
external surface at one place only. The surface of the intestinal
canal is much greater in extent than the surface on the exterior, and
finds enormous extensions in the lungs and in the great glands such as
the liver and pancreas, which communicate with it by means of their
ducts. The extent of surface within the lungs is estimated at
ninety-eight square yards, which is due to the extensive infoldings of
the surface [Fig 6], just as a large surface of thin cloth can, by
folding, be compressed into a small space. The intestinal canal from
the mouth to the anus is thirty feet long, the circumference varies
greatly, but an average circumference of three inches may safely be
assumed, which would give between seven and eight square feet of
surface, this being many times multiplied by adding the surfaces of
the glands which are connected with it. A diagram of the microscopic
structure of the intestinal wall shows how little appreciation of the
extent of surface the examination with the naked eye gives [Fig. 7].
By means of the intestinal canal food or substances necessary to
provide the energy which the living tissue transforms are introduced.
This food is liquefied and so altered by the action of the various
fluids formed in the glands of the intestine and poured out on the
surface, that it can pass into the interior of the body and become
available for the living cells. Various food residues representing
either excess of material or material incapable of digestion remain in
the intestine, and after undergoing various changes, putrefactive in
character, pass from the anus as feces.

[Illustration: FIG. 7.--A SECTION OF THE SMALL INTESTINE TO SHOW THE
LARGE EXTENT OF SURFACE. (_a_) Internal surface. The small finger-like
projections are the villi, and between these are small depressions
forming tubular glands.]

By means of the lungs, which represent a part of the surface, the
oxygen of the air, which is indispensable for the life of the cells,
is taken into the body and carbonic acid removed. The interchange of
gases is effected by the blood, which, enclosed in innumerable, small,
thin-walled tubes, almost covers the surface, and comes in contact
with the air within the lungs, taking from it oxygen and giving to it
carbonic acid.

The genito-urinary surface is the smallest of the surfaces. In the
male (Fig. 8,--27, 28, 30) this communicates with the general external
surface by the small opening at the extremity of the penis, and in the
female by the opening into the vagina. In its entirety it consists in
a surface of wide extent, comprising in the male the urethra, a long
canal which opens into the bladder, and is continuous with ducts that
lead into the genital glands or testicles. The internal surface of the
bladder is extended by means of two long tubes, the ureters, into the
kidneys, and receives the fluid formed in these organs. In the female
(Fig 9) there is a shallow external orifice which is continued into
the bladder by a short canal, the urethra, the remaining urinary
surface being the same as in the male; the external opening also is
extended into the short, wide tube of the vagina, which is continuous
with the canal of the uterus. This canal is continued on both sides
into the Fallopian tubes or oviducts. There is thus in the female a
more complete separation of the urinary and the genital surfaces than
in the male. Practically all of the waste material of the body which
results from cell activity and is passed from the cells into the fluid
about them is brought by the blood to the kidneys, and removed by
these from the blood, leaving the body as urine.

[Illustration: FIG. 8.--A LONGITUDINAL SECTION THROUGH THE MIDDLE OF
THE BODY SHOWING THE EXTERNAL AND INTERNAL SURFACES AND THE ORGANS.

1. The skull.
2. The brain, showing the convolutions of the gray exterior in which
the nerve cells are most numerous.
3. The white matter in the interior of the brain formed of nerve
fibres which connect the various parts of this.
4. The small brain or cerebellum.
5. The interior of the nose. Notice the nearness of the upper part of
this cavity to the brain.
6. The hard or bony palate forming the roof of the mouth.
7. The soft palate which hangs as a curtain between the mouth and the
pharynx.
8. The mouth cavity.
9. The tongue.
10. The beginning of the gullet or oesophagus.
11. The larynx.
12. The windpipe or trachea.
13. The oesophagus.
14. The thyroid gland.
15. The thymus gland or sweetbread.
16. The large vein, vena cava, which conveys the blood from the brain
and upper body into the heart.
17-25. Lymph nodes; 17, of the neck; 25, of the abdomen.
18. Cross section of the arch of the aorta or main artery of the body
after it leaves the heart.
19. The sternum or breast bone.
20. The cavity of the heart.
21. The liver.
22. The descending aorta at the back of the abdominal cavity.
23. The pancreas.
24. The stomach.
26. Cross section of the intestines.
27. The urinary bladder.
28. The entrance into this of the ureter or canal from the kidney.
29. Cross sections of the pubic bone.
30. The canal of the urethra leading into the bladder.
31. The penis.
32. The spinal cord.
33. The bones composing the spinal column.
34. The sacrum. The space between this and No. 29 is the pelvis.
35. The coccyx or extremity of the back bone.
36. The rectum.
37. The testicles.]

Between these various surfaces is the real interior of the body, in
which there are many sorts of living tissues,[2] each, of which, in
addition to maintaining itself, has some function necessary for the
maintenance of the body as a whole. Many of these tissues have for
their main purpose the adjustment and cooerdination of the activities
of the different organs to the needs of the organism as a whole. The
activity of certain of the organs is essential for the maintenance of
life; without others life can exist for a time only; and others, such
as the genital glands, while essential for the preservation of the
life of the species, are not essential for the individual. There is a
large amount of reciprocity among the tissues; in the case of paired
organs the loss of one can be made good by increased activity of the
remaining, and certain of the organs are so nearly alike in function
that a loss can be compensated for by an increase or modification of
the function of a nearly related organ. The various internal parts are
connected by means of a close meshwork of interlacing fibrils, the
connective tissue, support and strength being given by the various
bones. Everywhere enclosing all living cells and penetrating into the
densest of the tissues there is fluid. We may even consider the body
between the surfaces as a bag filled with fluid into which the various
cells and structures are packed.

[Illustration: FIG. 9.--A LONGITUDINAL SECTION THROUGH THE FEMALE
PELVIS.

1. The Fallopian tube which forms the connection between
the ovary and the uterus.
2. The ovary.
3. The body of the uterus.
4. The uterine canal.
5. The urinary bladder represented as empty.
6. The entrance of the ureter.
7. The pubic bone.
8. The urethra.
9. The vagina.
10. The common external opening or vulva.
11. The rectum and anus.]

[Illustration: FIG. 10.--THE LUNGS AND WINDPIPE. Parts of the lungs
have been removed to show the branching of the air tubes or bronchi
which pass into them. All the tubes and the surfaces of the lungs
communicate with the inner surface of the body through the larynx.]

The nervous system (Fig. 8) represents one of the most important of
the enclosed organs. It serves an important function, not only in
regulating and cooerdinating all functions, but by means of the special
senses which are a part of it, the relations of the organism as a
whole with the environment are adjusted. It consists of a large
central mass, the brain and spinal cord, which is formed in the embryo
by an infolding of the external surface, much in the same way that a
gland is formed; but the connection with the surface is lost in
further development and it becomes completely enclosed. Connected with
the central nervous mass, forming really a part of it and developing
from it, are the nerves, which appear as white fibrous cords and after
dividing and subdividing, are as extremely fine microscopic filaments
distributed to all parts of the body. By means of the nerves all
impressions are conveyed to the brain and spinal cord; all impulses
from this, whether conscious or unconscious, are conveyed to the
muscles and other parts. The brain is the sole organ of psychical
life; by means of its activity the impressions of the external world
conveyed to it through the sense organs are converted into
consciousness. Whatever consciousness is, and on this much has been
written, it proceeds from or is associated with the activity of the
brain cells just as truly as the secretion of gastric juice is due to
the activity of the cells of the stomach. The activity of the nervous
system is essential for extra-uterine life; life ceases by the
cessation of circulation and respiration when either the whole or
certain small areas of its tissue are destroyed. In intra-uterine
life, with the narrow and unchanging environment of the fluid within
the uterine cavity which encloses the foetus, life is compatible with
the absence or rudimentary development of the nervous system. The
foetus in this condition may be otherwise well developed, and it would
be not a misuse of words to say that it was healthy, since it is
adjusted to and in harmony with its narrow environment, but it would
not be normal. The intra-uterine life of the unborn child, it must be
remembered, is carried out by the transmission of energy from the
mother to the foetus by means of the close relation between the
maternal and foetal circulation. It is only when the free existence
demands activities not necessary in intra-uterine life that existence
without a central nervous system becomes impossible.

It is essential in so complicated a structure as the body that some
apparatus should exist to provide for the interchange of material. The
innumerable cell units of the body must have material to provide
energy, and useless material which results from their activity must be
removed. A household might be almost as much embarrassed by the
accumulation of garbage and ashes as by the absence of food and coal.
The food, which is taken into the alimentary canal and converted by
the digestive fluids into material more directly adapted to the uses
of cells, must be conveyed to them. A supply of oxygen is essential
for the life of the cells, and the supply which is given by
respiration must be carried from the lungs to every cell of the body.
All this is effected by the circulation of the blood, which takes
place in the system of branching closed tubes in which the blood
remains (Fig. 11). Certain of these tubes, the arteries, have strong
and elastic walls and serve to convey and distribute the blood to the
different organs and tissues. From the ultimate branches of the
arteries the blood passes into a close network of tubes, the
capillaries, which in enormous numbers are distributed in the tissues
and have walls so thin that they allow fluid and gaseous interchange
between their contents and the fluid around them to take place. The
blood from the capillaries is then collected into a series of tubes,
the veins, by which it is returned to the heart. This circulation is
maintained by means of a pumping organ or heart, which receives the
blood from the veins and by the contraction of its powerful walls
forces this into the arteries, the direction of flow being determined
as in a pump, by a system of valves. The waste products of cell life
pass from the cells into the fluid about them, and are in part
directly returned into the blood, but for the greater part pass into
it indirectly through another set of vessels, the lymphatics. These
are thin-walled tubes which originate in the tissues, and in which
there is a constant flow towards the heart, maintained by the constant
but varying pressure of the tissue around them, the direction of flow
being maintained by numerous valves. The colorless fluid within these
vessels is termed "lymph." At intervals along these tubes are small
structures termed the lymph nodes, which essentially are filters, and
strain out from the fluid substances which might work great injury if
they passed into the blood. Between the capillary vessels and the
lymphatics is the tissue fluid, in which all the exchange takes place.
It is constantly added to by the blood, and returns fluid to the blood
and lymph; it gives material to the cells and receives material from
them.

[Illustration: FIG. 11.--A DIAGRAMMATIC VIEW OF THE BLOOD VESSELS. An
artery (_a_) opens into a system of capillaries, (_c_) and
after passing through these collects into a vein (_b_). Notice
that the capillaries connect with other vascular territories at
numerous points (_d_). If the artery (_a_) became closed the
capillaries which it supplies could be filled by blood coming from
other sources.]

In addition to the strength and elasticity of the wall of the
arteries, which enables them to resist the pressure of the blood, they
have the power of varying their calibre by the contraction or
expansion of their muscular walls. Many of the organs of the body
function discontinuously, periods of activity alternating with
comparative repose; during the period of activity a greater blood
supply is demanded, and is furnished by relaxation of the muscle
fibres which allows the calibre to increase, and with this the blood
flow becomes greater in amount. Each part of the body regulates its
supply of blood, the regulation being effected by means of nerves
which control the tension of the muscle fibres. The circulation may be
compared with an irrigation system in which the water supply of each
particular field is regulated not by the engineer, but by an automatic
device connected with the growing crop and responding to its demands.

[Illustration: FIG. 12.--THE VARIOUS CELLS IN THE BLOOD. (_a_) The red
blood cells, single and forming a roll by adhering to one another;
(_b_) different forms of the white blood cells; those marked "1" are
the most numerous and are phagocytic for bacteria.]

The blood consists of a fluid, the blood plasma, in which numerous
cells are contained. The most numerous of these are small cup-shaped
cells which contain a substance called _haemoglobin_, to which the
red color of the blood is due. There are five million of these cells
in a cubic millimeter (a millimeter is .03937 of an inch), giving a
total number for the average adult of twenty-five trillion. The
surface area of all these, each being one thirty-three hundredth of an
inch in diameter, is about thirty-three hundred square yards. The
haemoglobin which they contain combines in the lungs with the oxygen in
the inspired air, and they give up this indispensable substance to the
cells everywhere in the body. There are also eight thousand leucocytes
or colorless cells in a cubic millimeter of blood, this giving a total
number of four billion in the average adult, and these vary in
character and in relative numbers (Fig. 12). The most numerous of
these are round and slightly larger than the red cells; they have a
nucleus of peculiar shape and contain granules of a definite
character. These cells serve an important part in infectious diseases
in devouring and destroying parasites. They have power of active
independent motion and somewhat resemble certain of the free living
unicellular organisms. The blood plasma, when taken from the vessels,
clots or passes from a fluid into a gelatinous or semi-solid
condition, which is due to the formation within it of a network of
fine threads termed fibrin. It is by means of the clotting of the
blood that the escape of blood from ruptured vessels is arrested.

Several of the organs of the body, in addition to the formation of
secretions which are discharged on the surfaces by means of their
ducts, produce also substances which pass directly into the blood or
lymph, and have an influence in stimulating or otherwise regulating
the activity of other organs. There are also certain organs of
glandular structure which are called the _ductless glands_; these
are not connected with the surface and all their secretion passes into
the blood. It is a part of recent knowledge that the substances
produced in these glands are of great importance for the body, some of
them even essential for the maintenance of life. In front of the neck
is such an organ, the thyroid gland (Fig. 8, 14). Imperfect
development or absence of this organ, or an inactive condition of it,
produces in the child arrested growth and deficient mental development
known as cretinism, and in the adult the same condition gives rise to
mental deterioration, swelling of the skin, due to a greater content
of water, and loss of hair. This deficiency in the production of
thyroid secretion can be made good and the symptoms removed by feeding
the patient with similar glands removed from animals. The very complex
disease known as exophthalmic goitre, and shown by irregular and rapid
action of the heart, protruding eyeballs and a variety of mental
symptoms, is also associated with this gland, and occasioned not by a
deficiency but by an excess or perversion of its secretion.

Adjoining the thyroid there are four small glands, the parathyroids,
each about the size of a split pea. The removal of these glands in
animals produces a condition resembling acute poisoning accompanied by
spasmodic contraction of the muscles. A small glandular organ at the
base of the brain, the pituitary body, produces a secretion, one of
the most marked properties of which is a control of growth,
particularly that of the bones. Most cases of giantism, combined as
they are with imperfect mentality, are due to disease of this gland.
There are glands near the kidney which regulate the pressure of the
blood in the arteries by causing contraction of their muscular walls.
The sexual characteristics in the male and female are due to an
internal secretion produced by the respective sexual glands which
affects growth, body development and mentality.

So is the body constituted. A series of surfaces, all connected, of
enormous size, which enclose a large number of organs and tissues, the
activities of which differ, but all are cooerdinated to serve the
purposes of the organism as a whole. We should think of the body not
as an assemblage of more or less independent entities, but as a single
organism in which all parts are firmly knit together both in structure
and in function, as are the components of a single cell.

FOOTNOTES:
[1] They do, however, take place, since within comparatively
few years whole species have completely disappeared; for example, the
great auk and the passenger pigeon. In these cases it is not known
what part disease played in the destruction.

[2] A tissue represents an aggregate of similar cells with
the intercellular substances in relation with these as connective
tissue, muscular tissue, etc. Where such cell aggregates are localized
and where the cells are arranged in structures having definite form
and size and performing a definite function, it is customary to
designate such structures as organs, as the brain, liver, etc.

CHAPTER II

NO SHARP LINE OF DEMARKATION BETWEEN HEALTH AND DISEASE.--THE
FUNCTIONAL NUTRITIVE AND FORMATIVE ACTIVITIES OF CELLS.--DESTRUCTION
AND REPAIR CONSTANT PROCESSES IN LIVING MATTER.--INJURIES TO THE
BODY.--THE EFFECT OF HEAT.--THE ACTION OF POISONS.--THE LESIONS OF
DISEASE.--REPAIR.--THE LAWS GOVERNING REPAIR.--RELATION OF REPAIR TO
COMPLEXITY OF STRUCTURE AND AGE.--THE RESERVE FORCE OF THE BODY.--
COMPENSATORY PROCESSES IN THE BODY.--OLD AGE.--THE DIMINUTION OF
RESISTANCE TO THE EFFECT OF THE ENVIRONMENT A PROMINENT FACTOR IN OLD
AGE.--DEATH.--HOW BROUGHT ABOUT.--CHANGES IN THE BODY AFTER DEATH.--
THE RECOGNITION OF DEATH.

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14