NUTRITION.
438. NUTRITION is the vital act by which the different parts of the
body renew the materials of which they are composed. Digestion,
circulation, absorption, and respiration, are but separate links in
the chain of nutrition, which would be destroyed by the absence of any
one of them.
439. The nutritive process is also a kind of secretion, by which
particles of matter are separated from the blood and conveyed with
wonderful accuracy to the appropriate textures. The function of the
nutrient vessels antagonizes those of absorption: while one system is
constructing, with beautiful precision, the animal frame, the other is
diligently employed in pulling down this complicated structure.
440. This ever-changing state of the body is shown by giving animals
colored matter, mixed with their food, which in a short time tinges
their bones with the same color as the matter introduced. Let it be
withdrawn, and in a few days the bones will assume their former
color--evidently from the effects of absorption. The changeful state
of the body is further shown by the losses to which it is subjected;
by the necessity of aliment; by the emaciation which follows
abstinence from food.
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438-454. _What remarks respecting nutrition?_ 438. What is nutrition?
439. What is said of the nutritive process? The function of the
nutrient vessels? 440. Give a proof of the ever-changing state of the
body. Give other instances illustrative of the changeful state of the
body.
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441. Every part of the body is subject to this continual change of
material, yet it is effected with such regularity, that the size,
shape, and appearance, of every organ is preserved; and after an
interval of a few years, there may not remain a particle of matter
which existed in the system at a former period. Notwithstanding this
entire change, the personal identity is never lost.
442. Many calculations have been made to determine in what length of
time the whole body is renewed. Some have supposed that it is
accomplished in four years; others have fixed the period at seven
years; but the time of the change is not definite, as was supposed by
a genuine son of the Emerald Isle, who had been in America _seven
years and three months_, and consequently maintained that he was a
native American.
_Observation._ India ink, when introduced into the skin, is not
removed; hence some assert that this tissue is an exception to the
alternate deposition and removal of its atoms. The ink remains because
its particles are too large to be absorbed, and when in the skin it is
insoluble.
443. "Those animals which are most complicated in their structure, and
are distinguished by the greatest variety of vital manifestations, are
subject to the most rapid changes of matter. Such animals require more
frequent and more abundant supplies of food; and, in proportion as
they are exposed to the greater number of external impressions, will
be the rapidity of this change of matter."
444. "Animals may be situated so that they lose nothing by secretion;
consequently, they will require no nutriment. Frogs have been taken
from fissures in solid lime rock, which were imbedded many feet below
the surface of the earth, and, on being exposed to the air, exhibited
signs of life."
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441. Why is the personal identity never lost in the change of
materials, which is unceasing in the system? 442. Give the opinion of
physiologists respecting the time required for the renewal of the
whole body. What exception to the changing state Of the different
textures? 443. What animals are subject to the most rapid changes of
material? 444. May animals be situated so that they require no
nutriment? What is related of frogs?
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445. The renovation of the bone, muscle, ligament, tendon, cartilage,
fat, nerve, hair, &c., is not perfected merely by the general
circulation of the fluid which is expelled from the left side of the
heart, but through the agency of a system of minute vessels, which,
under ordinary circumstances, cannot be seen by the eye, even when
aided by the microscope; still, minute as they are, the function of
these agents is necessary to the continuance of life. They are the
smallest capillary vessels.
446. "As the blood goes the round of the circulation, the nutrient
capillary vessels select and secrete those parts which are similar to
the nature of the structure, and the other portions pass on; so that
every tissue imbibes and converts to its own use the very principles
which it requires for its growth; or, in other words, as the vital
current approaches each organ, the particles appropriate to it feel
its attractive force,--obey it,--quit the stream,--mingle with the
substance of its tissue,--and are changed into its own true and proper
nature."
447. Thus, if a bone is broken, a muscle or a nerve wounded, and, if
the system is in a proper state of health, the vital economy
immediately sets about healing the rupture. The blood, which flows
from the wounded vessels, coagulates in the incision, for the double
purpose of stanching the wound, and of forming a matrix for the
regeneration of the parts. Very soon, minute vessels shoot out from
the living parts into the coagulum of the blood, and immediately
commence their operations, and deposit bony matter, where it is
required to unite fractured bones, and nervous substance to heal the
wounded nerve, &c.
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445. Show how the renovation of the bones, muscles, &c., is perfected.
446. What is said of the office of the nutrient capillary vessels?
447. When a bone is fractured, by what process is it healed?
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448. But the vital economy seems not to possess the power of
reproducing the muscles and true skin, and therefore, when these parts
are wounded, the rupture is repaired by a gelatinous substance, which
gradually becomes hard, and sometimes assumes something of a fibrous
appearance. It so perfectly unites the divided muscle, however, as to
restore its functional power. When the cuticle is removed, it is
reproduced and no scar remains; but, when the true skin is destroyed,
a scar is formed.
449. It is not uncommon that the nutrient arteries have their action
so much increased in some parts, as to produce preternatural growth.
Sometimes the vessels whose function it is to deposit fat, are
increased in action, and wens of no inferior size are formed. Again,
there may be a deposition of substances unlike any known to exist in
the body. Occasionally, these nutrient arteries of a part take on a
new action, and not only deposit their ordinary substance, but others,
which they have not heretofore secreted, but which are formed by
vessels of other parts of the body. It is in this way that we account
for the bony matter deposited in the valves of the heart and brain,
also the chalky deposits around the finger-joints.
450. In infancy and childhood, the function of nutrition is very
active; a large amount of food is taken, to supply the place of what
is lost by the action of the absorbents, and also to contribute to the
growth of the body. In middle age, nutrition and absorption are more
equal; but in old age, the absorbents are more active than the
nutrient vessels. The size, consequently, diminishes, the parts become
weaker, the bones more brittle, the body bends forward, and every
function exhibits marks of decay and dissolution.
451. A striking instance of active absorption in middle age was
exhibited in the person of Calvin Edson, of Vermont, who was exhibited
in the large towns of New England, as the "living skeleton." In early
manhood he was athletic, and weighed one hundred and sixty pounds; but
the excessive action of the absorbents over the nutrient vessels,
reduced his weight, in the interval of eighteen years, to sixty
pounds.
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448. What occurs when a muscle is divided? 449. State some of the
results of an increased action of the nutrient arteries. 450. When is
nutrition most active? How in middle age? How in old age? 451. Relate
a striking instance of active absorption in middle age.
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452. Instances, on the other hand, have occurred, of the action of the
nutrient vessels exceeding, in an extreme degree, those of absorption;
as in the person of a colored girl, thirteen years of age, who was
exhibited in New York in the summer of 1840. She was of the height of
misses at that age, but weighed five hundred pounds. Several cases are
on record of persons weighing eight hundred pounds.
453. As already mentioned, the blood is the nutritive fluid of
animals. When this fluid is coagulated, a thick, jelly-like mass
floats in the serum, called coagulum. This coagulated mass is composed
of fibrin, and red globulated matter. The color of the red globules is
owing to the presence of iron, though some physiologists think it
depends on an animal substance of a gelatinous character.
_Observation._ That portion of the serum which remains fluid after
coagulation by heat has taken place, is called _se-ros'i-ty_. It is
more abundant in the blood of old, than in that of young animals; and
it forms the "red gravy" in roasted meats.
454. The blood is not necessarily red. It may be white, as in most
fish. There is no animal in which the blood is equally red in all
parts of the body. The ligaments, tendons, and other white tissues in
man are supplied but sparingly with red blood. The fluid that supplies
these tissues is whitish.
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452. Of excessive nutrition in early life. 453. Describe the parts
that enter into the composition of the blood. What part of the blood
forms the red gravy in roasted meats? 454. Is the blood necessarily
red? Of what color is the blood of the fish? What part of the human
system has white blood?
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HYGIENE OF NUTRITION.
455. _Healthy nutrition requires pure blood._ If the nutrient arteries
of the bones are supplied with impure blood, they will become soft or
brittle, their vitality will be impaired, and disease will be the
ultimate result. The five hundred muscles receive another portion of
the blood. These organs are attached to, and act upon the bones. Upon
the health and contractile energy of the muscles depends the ability
to labor. Give these organs of motion impure blood, which is an
unhealthy stimulus, and they will become enfeebled, the step will lose
its elasticity, the movement of the arm will be inefficient, and every
muscle will be incapacitated to perform its usual amount of labor.
456. When the stomach, liver, and other organs subservient to the
digestion of food, are supplied with impure blood, the digestive
process is impaired, causing faintness and loss of appetite, also a
deranged state of the intestines, and, in general, all the symptoms of
dyspepsia.
457. The delicate structure of the lungs, in which the blood is or
should be purified, needs the requisite amount of pure blood to give
them vigor and health. When the blood is not of this character, the
lungs themselves lose their tone, and, even if permitted to expand
freely, have not power fully to change the impure quality of this
circulating fluid.
458. The health and beauty of the skin require that the blood should
be well purified; but, if the arteries of the skin receive vitiated
blood, pimples and blotches appear, and the individual suffers from
"humors." Drinks, made of various kinds of herbs, as well as pills
and powders, are taken for this affection. These will never have the
desired effect, while the causes of impure blood exist.
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455-462. _Give the hygiene of nutrition._ 455. What is the effect of
impure blood upon the bones? On the muscles? 456. On the digestive
organs? 457. On the lungs? 458. What is the effect if the vessels of
the skin are supplied with vitiated blood?
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459. If the nutrient arteries convey impure material to the brain, the
nervous and bilious headache, confusion of ideas, loss of memory,
impaired intellect, dimness of vision, and dulness of hearing, will be
experienced; and in process of time, the brain becomes disorganized,
and the brittle thread of life is broken.
_Observations._ 1st. An exertion of any organ beyond its powers,
induces weakness that will disturb the nutrition of the part that is
called into action; and it recovers its energy more slowly in
proportion to the excess of the exertion. The function of the organ
may be totally and permanently destroyed, if the exertion is extremely
violent. We sometimes see palsy produced in a muscle simply by the
effort to raise too great a weight. The sight is impaired, and total
blindness may be produced, by exposure to light too strong or too
constant. The mind may be deranged, or idiocy may follow the excess of
study or the over-tasking of the brain.
2d. When the function of an organ is permanently impaired or destroyed
by over-exertion, the nutrition of the part is rendered insufficient,
or is entirely arrested; and then the absorbents remove it wholly or
partially, as they do every thing that is no longer useful. Thus, in
palsied patients, a few years after the attack, we often find scarce
any trace of the palsied muscles remaining; they are reduced almost to
simple cellular tissue. The condition of the calf of the leg, in a
person having a club-foot, is a familiar proof of this.
460. _The blood may be made impure, by the chyle being deficient in
quantity or defective in quality._ This state of the chyle may be
produced by the food being improper in quantity or quality, or by its
being taken in an improper manner, at an improper time, and when the
system is not prepared for it. The remedy for impure blood produced in
any of these ways is to correct the injudicious method of using food.
(See Chapters XV. and XVI.)
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459. How does impure blood affect the brain? What is the effect when
any organ is exerted beyond its powers? What is the effect when an
organ is permanently impaired? 460. How may the blood become impure?
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461. _The blood may also be rendered impure, by not supplying it with
oxygen in the lungs, and by the carbon not being eliminated from the
system through this channel._ The remedy for "impurities of the
blood," produced in this manner, would be, to carefully reduce to
practice the directions in the chapters on the hygiene of the
respiratory organs, relative to the free movements of the ribs and
diaphragm, and the proper ventilation of rooms.
462. _A retention of the waste products of the skin produces impure
blood._ When the vessels of the skin, by which the waste, useless
material is eliminated from the system, have become inactive by
improper and inadequate clothing, or by a want of cleanliness, the
dead, injurious atoms of matter are retained in the circulatory
vessels. The only successful method of purifying the blood and
restoring health when this condition exists, is to observe the
directions given relative to clothing and bathing. (See Chapters
XXXIII. and XXXIV.)
_Observation._ If the blood has become "impure," or "loaded with
humors," (an idea generally prevalent,) it is not and cannot be
"purified" by taking patent pills, powders, drops, &c. But, on the
contrary, by observing the suggestions in the preceding paragraphs,
the blood can be freed of its impurities, and, what is of greater
importance, such "injurious humors" will be prevented.
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461. Mention another means by which the blood may be made impure. How
remedied? 462. What is the effect of want of cleanliness upon the
blood? What is said respecting "humors" in the blood?
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[Illustration: Fig. 88. A front view of the organs within the chest and
abdomen. 1, 1, 1, 1, The muscles of the chest. 2, 2, 2, 2, The ribs. 3,
3, 3, The upper, middle, and lower lobes of the right lung. 4, 4, The
lobes of the left lung. 5, The right ventricle of the heart. 6, The left
ventricle. 7, The right auricle of the heart. 8, The left auricle. 9, The
pulmonary artery. 10, The aorta. 11, The vena cava descendens. 12, The
trachea. 13, The oesophagus. 14, 14, 14, 14, The pleura. 15, 15, 15, The
diaphragm. 16, 16, The right and left lobe of the liver. 17, The
gall-cyst. 18, The stomach. 26, The spleen. 19, 19, The duodenum. 20, The
ascending colon. 21, The transverse colon. 25, The descending colon. 22,
22, 22, 22, The small intestine. 23, 23, The abdominal walls turned down.
24, The thoracic duct, opening into the left subclavian vein, (27.)]