A Practical Physiology
by
Albert F. Blaisdell
Part 2 out of 9
not think of anything else. It would take all our time to attend to
living. Hence the care of such delicate and important machinery has wisely
been put beyond our control.
Thus, too, these muscles act instinctively without training; but the
voluntary need long and careful education. A babe can use the muscles of
swallowing on the first day of its life as well as it ever can. But as it
grows up, long and patient education of its voluntary muscles is needed to
achieve walking, writing, use of musical instruments, and many other acts
of daily life.
[Illustration: Fig. 32.--A Spindle Cell of Involuntary Muscle. (Highly
magnified.)]
Experiment 18. _To show the general appearance of the muscles._
Obtain the lower part of a sheep's or calf's leg, with the most of the
lean meat and the hoof left on. One or more of the muscles with their
bundles of fibers, fascia, and tendons; are readily made out with a
little careful dissection. The dissection should be made a few days
before it is wanted and the parts allowed to harden somewhat in dilute
alcohol.
68. Properties of Muscular Tissue. The peculiar property of living
muscular tissue is irritability, or the capacity of responding to a
stimulus. When a muscle is irritated it responds by contracting. By this
act the muscle does not diminish its bulk to any extent; it simply changes
its form. The ends of the muscle are drawn nearer each other and the
middle is thicker.
Muscles do not shorten themselves all at once, but the contraction passes
quickly over them in the form of a wave. They are usually stimulated by
nervous action. The delicate nerve fibrils which end in the fibers
communicate with the brain, the center of the will power. Hence, when the
brain commands, a nervous impulse, sent along the nerve fibers, becomes
the exciting stimulus which acts upon the muscles and makes them shorter,
harder, and more rigid.[10]
Muscles, however, will respond to other than this usual stimulus. Thus an
electrical current may have a similar effect. Heat, also, may produce
muscular contraction. Mechanical means, such as a sharp blow or pinching,
may irritate a muscle and cause it to contract.
We must remember that this property of contraction is inherent and belongs
to the muscle itself. This power of contraction is often independent of
the brain. Thus, on pricking the heart of a fish an hour after removal
from its body, obvious contraction will occur. In this case it is not the
nerve force from the brain that supplies the energy for contraction. The
power of contraction is inherent in the muscle substance, and the stimulus
by irritating the nerve ganglia of the heart simply affords the
opportunity for its exercise.
Contraction is not, however, the natural state of a muscle. In time it is
tired, and begins to relax. Even the heart, the hardest-working muscle,
has short periods of rest between its beats. Muscles are highly elastic as
well as contractile. By this property muscle yields to a stretching force,
and returns to its original length if the stretching has not been
excessive.
[Illustration: Fig. 33.--Principal Muscles of the Body. (Anterior view.)]
69. The Object of Contraction. The object of contraction is obvious.
Like rubber bands, if one end of a muscle be fixed and the other attached
to some object which is free to move, the contraction of the muscle will
bring the movable body nearer to the fixed point. A weight fastened to the
free end of a muscle may be lifted when the muscle contracts. Thus by
their contraction muscles are able to do their work. They even
contract more vigorously when resistance is opposed to them than when it
is not. With increased weight there is an increased amount of work to be
done. The greater resistance calls forth a greater action of the muscle.
This is true up to a certain point, but when the limit has been passed,
the muscle quickly fails to respond.
Again, muscles work best with a certain degree of rapidity provided the
irritations do not follow each other too rapidly. If, however, the
contractions are too rapid, the muscles become exhausted and fatigue
results. When the feeling of fatigue passes away with rest, the muscle
recovers its power. While we are resting, the blood is pouring in fresh
supplies of building material.
Experiment 19. _To show how muscles relax and contract_. Lay your
left forearm on a table; grasp with the right hand the mass of flesh on
the front of the upper arm. Now gradually raise the forearm, keeping the
elbow on the table. Note that the muscle thickens as the hand rises.
This illustrates the contraction of the biceps, and is popularly called
"trying your muscle" Reverse the act. Keep the elbow in position, bring
the forearm slowly to the table, and the biceps appears to become softer
and smaller,--it relaxes.
Experiment 20. Repeat the same experiment with other muscles. With
the right hand grasp firmly the extended left forearm. Extend and flex
the fingers vigorously. Note the effect on the muscles and tendons of
the forearm. Grasp with the right hand the calf of the extended right
leg, and vigorously flex the leg, bringing it near to the body. Note the
contractions and relaxations of the muscles.
70. Arrangement of Muscles. Muscles are not connected directly with
bones. The mass of flesh tapers off towards the ends, where the fibers
pass into white, glistening cords known as tendons. The place at
which a muscle is attached to a bone, generally by means of a tendon, is
called its origin; the end connected with the movable bone is its
insertion.
There are about 400 muscles in the human body, all necessary for its
various movements. They vary greatly in shape and size, according to their
position and use. Some are from one to two feet long, others only a
fraction of an inch. Some are long and spindle-shaped, others thin and
broad, while still others form rings. Thus some of the muscles of the arm
and thigh are long and tapering, while the abdominal muscles are thin and
broad because they help form walls for cavities. Again, the muscular
fibers which surround and by their contraction close certain orifices, as
those of the eyelids and lips, often radiate like the spokes of a wheel.
Muscles are named according to their shape, position, division of origin
or insertion, and their function. Thus we have the _recti_ (straight), and
the _deltoid_ (Δ, delta), the _brachial_ (arm), _pectoral_
(breast), and the _intercostals_ (between the ribs), so named from their
position. Again, we have the _biceps_ (two-headed), _triceps_
(three-headed), and many others with similar names, so called from the
points of origin and insertion. We find other groups named after their
special use. The muscles which bend the limbs are called _flexors_ while
those which straighten them are known as _extensors_.
After a bone has been moved by the contraction of a muscle, it is brought
back to its position by the contraction of another muscle on the opposite
side, the former muscle meanwhile being relaxed. Muscles thus acting in
opposition to each other are called antagonistic. Thus the biceps serves
as one of the antagonists to the triceps, and the various flexors and
extensors of the limbs are antagonistic to one another.
71. The Tendons. The muscles which move the bones by their
contraction taper for the most part, as before mentioned, into
tendons. These are commonly very strong cords, like belts or straps,
made up of white, fibrous tissue.
Tendons are most numerous about the larger joints, where they permit free
action and yet occupy but little space. Large and prominent muscles in
these places would be clumsy and inconvenient. If we bend the arm or leg
forcibly, and grasp the inside of the elbow or knee joint, we can feel the
tendons beneath the skin. The numerous tendons in the palm or on the back
of the hand contribute to its marvelous dexterity and flexibility. The
thickest and strongest tendon in the body is the tendon of Achilles,
which connects the great muscles in the calf of the leg with the heel bone
(sec. 49).
When muscles contract forcibly, they pull upon the tendons which transmit
the movement to the bones to which they are attached. Tendons may be
compared to ropes or cords which, when pulled, are made to act upon
distant objects to which one end is fastened. Sometimes the tendon runs
down the middle of a muscle, and the fibers run obliquely into it, the
tendon resembling the quill in a feather. Again, tendons are spread out in
a flat layer on the surface of muscles, in which case they are called
aponeuroses. Sometimes a tendon is found in the middle of a muscle as well
as at each end of it.
[Illustration: Fig. 34.--The Biceps Muscle dissected to show its Tendons.]
72. Synovial Sheaths and Sacs. The rapid movement of the tendons
over bony surfaces and prominences would soon produce an undue amount of
heat and friction unless some means existed to make the motion as easy as
possible. This is supplied by sheaths which form a double lining around
the tendons. The opposed surfaces are lined with synovial
membrane,[11] the secretion from which oils the sheaths in which the
tendons move.
Little closed sacs, called synovial sacs or bursæ, similarly lined
and containing fluid, are also found in special places between two
surfaces where much motion is required. There are two of these bursæ near
the patella, one superficial, just under the skin; the other deep beneath
the bone (Fig. 29). Without these, the constant motion of the knee-pan and
its tendons in walking would produce undue friction and heat and
consequent inflammation. Similar, though smaller, sacs are found over the
point of the elbow, over the knuckles, the ankle bones, and various other
prominent points. These sacs answer a very important purpose, and are
liable to various forms of inflammation.
Experiment 21. Examine carefully the tendons in the parts dissected
in Experiment 18. Pull on the muscles and the tendons, and note how they
act to move the parts. This may be also admirably shown on the leg of a
fowl or turkey from a kitchen or obtained at the market.
Obtain the hoof of a calf or sheep with one end of the tendon of
Achilles still attached. Dissect it and test its strength.
73. Mechanism of Movement. The active agents of bodily movements, as
we have seen, are the muscles, which by their contraction cause the bones
to move one on the other. All these movements, both of motion and of
locomotion, occur according to certain fixed laws of mechanics. The bones,
to which a great proportion of the muscles in the body are attached, act
as distinct levers. The muscles supply the power for moving the
bones, and the joints act as fulcrums or points of support. The weight of
the limb, the weight to be lifted, or the force to overcome, is the
resistance.
74. Levers in the Body. In mechanics three classes of levers are
described, according to the relative position of the power, the fulcrum,
and the resistance. All the movements of the bones can be referred to one
or another of these three classes.
Levers of the first class are those in which the fulcrum is between
the power and the weight. The crowbar, when used to lift a weight at one
end by the application of power at the other, with a block as a fulcrum,
is a familiar example of this class. There are several examples of this in
the human body. The head supported on the atlas is one. The joint between
the atlas and the skull is the fulcrum, the weight of the head is the
resistance. The power is behind, where the muscles from the neck are
attached to the back of the skull. The object of this arrangement is to
keep the head steady and balanced on the spinal column, and to move it
backward and forward.
[Illustration: Fig. 35.--Showing how the Bones of the Arm serve as Levers.
P, power;
W, weight;
F, fulcrum.
]
Levers of the second class are those in which the weight is between
the fulcrum and the power. A familiar example is the crowbar when used for
lifting a weight while one end rests on the ground. This class of levers
is not common in the body. Standing on tiptoe is, however, an example.
Here the toes in contact with the ground are the fulcrum, the power is the
action of the muscles of the calf, and between these is the weight of the
body transmitted down the bones of the leg to the foot.
Levers of the third class are those in which the power is applied at
a point between the fulcrum and weight. A familiar example is where a
workman raises a ladder against a wall. This class of levers is common in
the body. In bending the forearm on the arm, familiarly known as "trying
your muscle," the power is supplied by the biceps muscle attached to the
radius, the fulcrum is the elbow joint at one end of the lever, and the
resistance is the weight of the forearm at the other end.
Experiment 22. _To illustrate how the muscles use the bones as
levers._ First, practice with a ruler, blackboard pointer, or any other
convenient object, illustrating the different kinds of levers until the
principles are familiar. Next, illustrate these principles on the
person, by making use of convenient muscles. Thus, lift a book on the
toes, by the fingers, on the back of the hand, by the mouth, and in
other ways.
These experiments, showing how the bones serve as levers, may be
multiplied and varied as circumstances may require.
75. The Erect Position. The erect position is peculiar to man. No
other animal naturally assumes it or is able to keep it long. It is the
result of a somewhat complex arrangement of muscles which balance each
other, some pulling backwards and some forwards. Although the whole
skeleton is formed with reference to the erect position, yet this attitude
is slowly learned in infancy.
In the erect position the center of gravity lies in the joint between the
sacrum and the last lumbar vertebra. A line dropped from this point would
fall between the feet, just in front of the ankle joints. We rarely stand
with the feet close together, because that basis of support is too small
for a firm position. Hence, in all efforts requiring vigorous muscular
movements the feet are kept more or less apart to enlarge the basis of
support.
Now, on account of the large number and flexibility of the joints, the
body could not be kept in an upright position without the cooperation of
certain groups of muscles. The muscles of the calf of the leg, acting on
the thigh bone, above the knee, keep the body from falling forward, while
another set in front of the thigh helps hold the leg straight. These thigh
muscles also tend to pull the trunk forward, but in turn are balanced by
the powerful muscles of the lower back, which help keep the body straight
and braced.
The head is kept balanced on the neck partly by the central position of
the joint between the atlas and axis, and partly by means of strong
muscles. Thus, the combined action of these and other muscles serves to
balance the body and keep it erect. A blow on the head, or a sudden shock
to the nervous system, causes the body to fall in a heap, because the
brain has for the time lost its power over the muscles, and they cease to
contract.
[Illustration: Fig. 36.--Diagram showing the Action of the Chief Muscles
which keep the Body Erect. (The arrows indicate the direction in which
these muscles act, the feet serving as a fixed basis.) [After Huxley.]
_Muscles which tend to keep the body from falling forward._
A, muscles of the calf;
B, of the back of the thigh;
C, of the spinal column.
_Muscles which tend to keep the body from falling backward._
D, muscles of the front of the leg;
E, of the front of the thigh;
F, of the front of the abdomen;
G, of the front of the neck.
]
76. Important Muscles. There are scores of tiny muscles about the
head, face, and eyes, which, by their alternate contractions and
relaxations, impart to the countenance those expressions which reflect the
feelings and passions of the individual. Two important muscles, the
temporal, near the temples, and the masseter, or chewing muscle,
are the chief agents in moving the lower jaw. They are very large in the
lion, tiger, and other flesh-eating animals. On the inner side of each
cheek is the buccinator, or trumpeter's muscle, which is largely
developed in those who play on wind instruments. Easily seen and felt
under the skin in thin persons, on turning the head to one side, is the
sterno-cleido-mastoid muscle, which passes obliquely down on each
side of the neck to the collar bone--prominent in sculpture and painting.
The chest is supplied with numerous muscles which move the ribs up and
down in the act of breathing. A great, fan-shaped muscle, called the
pectoralis major, lies on the chest. It extends from the chest to the
arm and helps draw the arm inward and forward. The arm is raised from the
side by a large triangular muscle on the shoulder, the deltoid, so
called from its resemblance to the Greek letter delta, Δ. The
biceps, or two-headed muscle, forms a large part of the fleshy mass
in front of the arm. Its use is to bend the forearm on the arm, an act
familiarly known as "trying your muscle." Its direct antagonist is the
three-headed muscle called the triceps. It forms the fleshy mass on
the back of the arm, its use being to draw the flexed forearm into a right
line.
On the back and outside of the forearm are the extensors, which
straighten the wrist, the hand, and the fingers. On the front and inside
of the forearm are the flexors, which bend the hand, the wrist, and
the fingers. If these muscles are worked vigorously, their tendons can be
readily seen and felt under the skin. At the back of the shoulder a large,
spread-out muscle passes upward from the back to the humerus. From its
wide expanse on the back it is known as the latissimus dorsi
(broadest of the back). When in action it draws the arm downward and
backward, or, if one hangs by the hands, it helps to raise the body. It is
familiarly known as the "climbing muscle."
[Illustration: Fig. 37.--A Few of the Important Muscles of the Back.]
Passing to the lower extremity, the thigh muscles are the largest and the
most powerful in the body. In front a great, four-headed muscle,
quadriceps extensor, unites into a single tendon in which the
knee-cap is set, and serves to straighten the knee, or when rising from a
sitting posture helps elevate the body. On the back of the thigh are
several large muscles which bend the knee, and whose tendons, known as the
"hamstrings," are readily felt just behind the knee. On the back of the
leg the most important muscles, forming what is known as the calf, are the
gastrocnemius and the soleus. The first forms the largest part
of the calf. The soleus, so named from resembling a sole-fish, is a muscle
of broad, flattened shape, lying beneath the gastrocnemius. The tendons of
these two muscles unite to form the tendon of Achilles, as that hero
is said to have been invulnerable except at this point. The muscles of the
calf have great power, and are constantly called into use in walking,
cycling, dancing, and leaping.
77. The Effect of Alcoholic Drinks upon the Muscles. It is found that
a man can do more work without alcohol than with it. After taking it there
may be a momentary increase of activity, but this lasts only ten or
fifteen minutes at the most. It is followed by a rapid reduction of power
that more than outweighs the momentary gain, while the quality of the work
is decidedly impaired from the time the alcohol is taken.
Even in the case of hard work that must be speedily done, alcohol does not
help, but hinders its execution. The tired man who does not understand the
effects of alcohol often supposes that it increases his strength, when in
fact it only deadens his sense of fatigue by paralyzing his nerves. When
put to the test he is surprised at his self-deception.
Full intoxication produces, by its peculiar depression of the brain and
nervous system, an artificial and temporary paralysis of the muscles, as
is obvious in the pitifully helpless condition of a man fully intoxicated.
But even partial approach to intoxication involves its proportionate
impairment of nervous integrity, and therefore just so much diminution of
muscular force. All athletes recognize this fact, as while training for a
contest, rigid abstinence is the rule, both from liquors and tobacco. This
muscular weakness is shown also in the unsteady hand, the trembling limbs
of the inebriate, his thick speech, wandering eye, and lolling head.
78. Destructive Effect of Alcoholic Liquors upon Muscular Tissue.
Alcoholic liquors retard the natural chemical changes so essential to good
health, by which is meant the oxidation of the nutritious elements of
food. Careful demonstration has proved also that the amount of carbon
dioxide escaping from the lungs of intoxicated persons is from thirty to
fifty per cent less than normal. This shut-in carbon stifles the nervous
energy, and cuts off the power that controls muscular force. This lost
force is in close ratio to the retained carbon: so much perverted chemical
change, so much loss of muscular power. Not only the strength but the fine
delicacy of muscular action is lost, the power of nice control of the hand
and fingers, as in neat penmanship, or the use of musical instruments.
To this perverted chemical action is also due the fatty degeneration so
common in inebriates, affecting the muscles, the heart, and the liver.
These organs are encroached upon by globules of fat (a hydrocarbon),
which, while very good in their proper place and quantity, become a
source of disorder and even of death when they abnormally invade vital
structures. Other poisons, as phosphorus, produce this fatty decay more
rapidly; but alcohol causes it in a much more general way.
This is proved by the microscope, which plainly shows the condition
mentioned, and the difference between the healthy tissues and those thus
diseased.
[Illustration: Fig. 38.--Principal Muscles on the Left Side of Neck.
A, buccinator;
B, masseter;
C, depressor anguli oris;
D, anterior portion of the digastric;
E, mylo-hyoid;
F, tendon of the digastric;
G, sterno-hyoid;
H, sterno-thyroid;
K, omo-hyoid;
L, sternal origin of sterno-cleido-mastoid muscle;
M, superior fibers of deltoid;
N, posterior scalenus;
O, clavicular origin of sterno-cleido-mastoid;
P, sterno-cleido-mastoid;
R, trapezius;
S, anterior constrictor;
T, splenius capitis;
V, stylo-hyoid;
W, posterior portion of the digastric;
X, fasciculi of ear muscles;
Z, occipital.
]
[NOTE. It was proposed during the Civil War to give each soldier in a
certain army one gill of whiskey a day, because of great hardship and
exposure. The eminent surgeon, Dr. Frank H. Hamilton of New York, thus
expressed his views of the question: "It is earnestly desired that no
such experiment will ever be repeated in the armies of the United
States. In our own mind, the conviction is established, by the
experience and observation of a life, that the regular routine
employment of alcoholic stimulants by man in health is never, under
any circumstances, useful. We make no exceptions in favor of cold or
heat or rain."
"It seems to me to follow from these Arctic experiences that the
regular use of spirits, even in moderation, under conditions of great
physical hardship, continued and exhausting labor, or exposure to
severe cold cannot be too strongly deprecated."
A. W. Greely, retired Brigadier General, U.S.A., and formerly leader
of the Greely Expedition.]
79. Effect of Tobacco on the Muscles. That other prominent narcotic,
tobacco, impairs the energy of the muscles somewhat as alcohol does, by
its paralyzing effect upon the nervous system. As all muscular action
depends on the integrity of the nervous system, whatever lays its
deadening hand upon that, saps the vigor and growth of the entire frame,
dwarfs the body, and retards mental development. This applies especially
to the young, in the growing age between twelve or fourteen and twenty,
the very time when the healthy body is being well knit and compacted.
Hence many public schools, as well as our national naval and military
academies, rigidly prohibit the use of tobacco by their pupils. So also
young men in athletic training are strictly forbidden to use it.[12] This
loss of muscular vigor is shown by the unsteady condition of the muscles,
the trembling hand, and the inability to do with precision and accuracy
any fine work, as in drawing or nice penmanship.
Additional Experiments.
Experiment 23. _ To examine the minute structure of voluntary
muscular fiber._ Tease, with two needles set in small handles, a bit of
raw, lean meat, on a slip of glass, in a little water. Continue until
the pieces are almost invisible to the naked eye.
Experiment 24. Place a clean, dry cover-glass of about the width of
the slip, over the water containing the torn fragments. Absorb the
excess of moisture at the edge of the cover, by pressing a bit of
blotting-paper against it for a moment. Place it on the stage of a
microscope and examine with highest obtainable power, by light reflected
upward from the mirror beneath the stage. Note the apparent size of the
finest fibers; the striation of the fibers, or their markings,
consisting of alternate dim and bright cross bands. Note the arrangement
of the fibers in bundles, each thread running parallel with its
neighbor.
Experiment 25. _To examine the minute structure of involuntary
muscular fiber, a tendon, or a ligament._ Obtain a very small portion of
the muscular coat of a cow's or a pig's stomach. Put it to soak in a
solution of one dram of bichromate of potash in a pint of water. Take
out a morsel on the slip of glass, and tease as directed for the
voluntary muscle. Examine with a high power of the microscope and note:
(1) the isolated cells, long and spindle-shaped, that they are much
flattened; (2) the arrangement of the cells, or fibers, in sheets, or
layers, from the torn ends of which they project like palisades.
Experiment 26. Tease out a small portion of the tendon or ligament
in water, and examine with a glass of high power. Note the large fibers
in the ligament, which branch and interlace.
Experiment 27. With the head slightly bent forwards, grasp between
the fingers of the right hand the edge of the left
sterno-cleido-mastoid, just above the collar bone. Raise the head and
turn it from left to right, and the action of this important muscle is
readily seen and felt. In some persons it stands out in bold relief.
Experiment 28. The tendons which bound the space (popliteal) behind
the knee can be distinctly felt when the muscles which bend the knee are
in action. On the outer side note the tendons of the biceps of the leg,
running down to the head of the fibula. On the inside we feel three
tendons of important muscles on the back of the thigh which flex the leg
upon the thigh.
Experiment 29. _To show the ligamentous action of the muscles._
Standing with the back fixed against a wall to steady the pelvis, the
knee can be flexed so as to almost touch the abdomen. Take the same
position and keep the knee rigid. When the heel has been but slightly
raised a sharp pain in the back of the thigh follows any effort to carry
it higher. Flexion of the leg to a right angle, increases the distance
from the lines of insertion on the pelvic bones to the tuberosities of
the tibia by two or three inches--an amount of stretching these muscle
cannot undergo. Hence the knee must be flexed in flexion of the hip.
Experiment 30. A similar experiment may be tried at the wrist. Flex
the wrist with the fingers extended, and again with the fingers in the
fist. The first movement can be carried to 90°, the second only to 30°,
or in some persons up to 60°. Making a fist had already stretched the
extensor muscles of the arm, and they can be stretched but little
farther. Hence, needless pain will be avoided by working a stiff wrist
with the parts loose, or the fingers extended, and not with a clenched
fist.
Review Analysis: Important Muscles.
Location.
Name. Chief Function.
Head and Neck.
Occipito-frontalis. moves scalp and raises eye brow.
Orbicularis palpebrarum. shuts the eyes.
Levator palpebrarum. opens the eyes.
Temporal. raise the lower jaw.
Masseter. " " " "
Sterno-cleido-mastoid. depresses head upon neck and neck upon chest.
Platysma myoides. depresses lower jaw and lower lip.
Trunk.
Pectoralis major. draws arm across front of chest.
Pectoralis minor. depresses point of shoulder,
Latissimus dorsi. draws arm downwards and backwards.
Serratus magnus. assists in raising ribs.
Trapezius. Rhomboideus. backward movements of head and shoulder,
Intercostals. raise and depress the ribs.
External oblique. /various forward movements
Internal oblique. \ of trunk
Rectus abdominis. compresses abdominal viscera and acts upon
pelvis.
Upper Limbs.
Deltoid. carries arm outwards and upwards.
Biceps. flexes elbow and raises arm.
Triceps. extends the forearm.
Brachialis anticus. flexor of elbow.
Supinator longus. flexes the forearm.
Flexor carpi radialis. flexors of wrist.
Flexor carpi ulnaris. " " "
Lower Limbs.
Gluteus maximus. adducts the thigh.
Adductors of thigh. draw the leg inwards.
Sartorius. crosses the legs.
Rectus femoris. flexes the thigh.
Vastus externus. extensor of leg.
Vastus internus. extensor of leg upon thigh.
Biceps femoris. flexes leg upon thigh.
Gracilis. flexes the leg and adducts thigh.
Tibialis anticus. draws up inner border of foot.
Peroneus longus. raises outer edge of foot,
Gastrocnemius. keep the body erect, and
Soleus. aid in walking and running.
Chapter IV.
Physical Exercise.
80. Importance of Bodily Exercise. Nothing is so essential to success
in life as sound physical health. It enables us to work with energy and
comfort, and better to endure unusual physical and mental strains. While
others suffer the penalties of feebleness, a lower standard of functional
activities, and premature decay, the fortunate possessor of a sound mind
in a sound body is better prepared, with proper application, to endure the
hardships and win the triumphs of life[13].
This element of physical capacity is as necessary to a useful and
energetic life, as are mental endowment and intellectual acquirement.
Instinct impels us to seek health and pleasure in muscular exercise. A
healthy and vigorous child is never still except during sleep. The
restless limbs and muscles of school children pent up for several hours,
feel the need of movement, as a hungry man craves food. This natural
desire for exercise, although too often overlooked, is really one of the
necessities of life. One must be in ill health or of an imperfect nature,
when he ceases to feel this impulse. Indeed, motion within proper bounds
is essential to the full development and perfect maintenance of the bodily
health. Unlike other machines, the human body becomes within reasonable
limits, stronger and more capable the more it is used.
As our tenure of life at best is short, it is our duty to strive to live
as free as possible from bodily ills. It is, therefore, of paramount
importance to rightly exercise every part of the body, and this without
undue effort or injurious strain.
Strictly speaking, physical exercise refers to the functional
activity of each and every tissue, and properly includes the regulation of
the functions and movements of the entire body. The word exercise,
however, is used usually in a narrower sense as applied to those movements
that are effected by the contraction of the voluntary muscles.
Brief reference will be made in this chapter only to such natural and
systematic physical training as should enter into the life of every
healthy person.
81. Muscular Activity. The body, as we have learned, is built up of
certain elementary tissues which are combined to make bones, muscles,
nerves, and other structures. The tissues, in turn, are made up of
countless minute cells, each of which has its birth, lives its brief
moment to do its work in the animal economy, is separated from the tissue
of which it was a part, and is in due time eliminated by the organs of
excretion,--the lungs, the skin, or the kidneys. Thus there is a
continuous process of growth, of decay, and removal, among the individual
cells of each tissue.
[NOTE. The Incessant Changes in Muscular Tissue. "In every tiny
block of muscle there is a part which is really alive, there are parts
which are becoming alive, there are parts which have been alive, and
are now dying or dead; there is an upward rush from the lifeless to
the living, a downward rush from the living to the dead. This is
always going on, whether the muscle be quiet and at rest, or whether
it be active and moving,--some of the capital of living material is
being spent, changed into dead waste; some of the new food is always
being raised into living capital. But when the muscle is called upon
to do work, when it is put into movement, the expenditure is
quickened, there is a run upon the living capital, the greater, the
more urgent the call for action."--Professor Michael Foster.]
These ceaseless processes are greatly modified by the activity of the
bodily functions. Every movement of a muscle, for instance, involves
change in its component cells. And since the loss of every atom of the
body is in direct relation to its activity, a second process is necessary
to repair this constant waste; else the body would rapidly diminish in
size and strength, and life itself would soon end. This process of repair
is accomplished, as we shall learn in Chapters VI. and VII., by the organs
of nutrition, which convert the food into blood.
[Illustration: Fig. 39.--Showing how the Muscles of the Back may be
developed by a Moderate Amount of Dumb-Bell Exercise at Home. (From a
photograph.)]
82. Effect of Exercise upon the Muscles. Systematic exercise
influences the growth and structure of the muscles of the body in a manner
somewhat remarkable. Muscular exercise makes muscular tissue; from the
lack of it, muscles become soft and wasted. Muscles properly exercised not
only increase in size, both as a whole and in their individual structure,
but are better enabled to get rid of material which tends to hamper their
movements. Thus muscular exercise helps to remove any needless
accumulation of fat, as well as useless waste matters, which may exist in
the tissues. As fat forms no permanent structural part of the organism,
its removal is, within limits, effected with no inconvenience.
Muscular strength provides the joints with more powerful ligaments and
better developed bony parts. After long confinement to the bed from
disease, the joints have wasted ligaments, thin cartilages, and the bones
are of smaller proportions. Duly exercised muscles influence the size of
the bones upon which they act. Thus the bones of a well-developed man are
stronger, firmer, and larger than those of a feeble person.
He who has been physically well trained, has both a more complete and a
more intelligent use of his muscles. He has acquired the art of causing
his muscles to act in concert. Movements once difficult are now carried on
with ease. The power of coördination is increased, so that a desired end
is attained with the least amount of physical force and nervous energy. In
learning to row, play baseball, ride the bicycle, or in any other
exercises, the beginner makes his movements in a stiff and awkward manner.
He will use and waste more muscular force in playing one game of ball, or
in riding a mile on his wheel, than an expert would in doing ten times the
work. He has not yet learned to balance one set of muscles against their
antagonists.
[Illustration: Fig. 40.--The Standard Special Chest Weight.
A convenient machine by means of which all the muscles of the body may be
easily and pleasantly exercised with sufficient variations in the
movements to relieve it of monotony.
A space 6 ft wide, 6 ft deep, and 7 ft high nearly in front of the machine
is required for exercise.]
In time, however, acts which were first done only with effort and by a
conscious will, become automatic. The will ceases to concern itself. By
what is called reflex action, memory is developed in the spinal cord and
the muscular centers (sec. 273). There is thus a great saving of actual
brain work, and one important cause of fatigue is removed.
83. Effect of Exercise on Important Organs. The importance of
regular exercise is best understood by noting its effects upon the
principal organs of the body. As the action of the heart is increased both
in force and frequency during exercise, the flow of blood throughout the
body is augmented. This results from the force of the muscular
contractions which play their part in pressing the blood in the veins
onward towards the heart. Exercise also induces a more vigorous
respiration, and under increased breathing efforts the lung capacity is
increased and the size of the chest is enlarged. The amount of air
inspired and expired in a given time is much larger than if the body were
at rest. The blood is thus supplied with a much larger amount of oxygen
from the air inhaled, and gives off to the air a corresponding excess of
carbon dioxid and water.
Again, exercise stimulates and strengthens the organs of digestion. The
appetite is improved, as is especially noted after exercise in the open
air. The digestion is more complete, absorption becomes more rapid, the
peristaltic movements of the bowels are promoted, and the circulation
through the liver is more vigorous. More food is taken to supply the force
necessary for the maintenance of the mechanical movements. Ample exercise
also checks the tendency towards a torpid circulation in the larger
digestive organs, as the stomach and the liver, so common with those who
eat heartily, but lead sedentary lives. In short, exercise may be regarded
as a great regulator of nutrition.
Exercise increases the flow of blood through the small vessels of the
skin, and thus increases the radiation of heat from the surface. If the
exercise be vigorous and the weather hot, a profuse sweat ensues, the
rapid evaporation of which cools the body. The skin is thus a most
important regulator of the bodily temperature, and prevents any rise above
the normal which would otherwise result from vigorous exercise. (See secs.
226 and 241).
84. Effect of Exercise upon the Personal Appearance. Judicious and
systematic exercise, if moderately employed, soon gives a more upright and
symmetrical figure, and an easier and more graceful carriage. Rounded
shoulders become square, the awkward gait disappears, and there is seen a
graceful poise to the head and a bearing of the body which mark those
whose muscles have been well trained. A perfectly formed skeleton and
well-developed muscles give the graceful contour and perfect outline to
the human body. The lean, soft limbs of those who have never had any
physical education, often look as if they belonged to persons recovering
from sickness. The effects of sound physical exercise are well exhibited
in the aspect of the neck, shoulders, and chest of one who has been well
trained. This is noticeable in gymnasts and others who practice upon the
horizontal bar, with chest weights, dumb-bells, and other apparatus which
develop more especially the muscles of the upper half of the trunk.
[Illustration: Fig. 41.--Young Woman practicing at Home with the "Whitely
Exerciser." (From a photograph)]
Exercise improves the condition of the tissues generally. They become more
elastic, and in all respects sounder. The skin becomes firm, clear, and
wholesome. Hence, every part of the surface of the body rapidly takes on a
change in contour, and soon assumes that appearance of vigor and soundness
which marks those of firm physical condition. The delicate, ruddy aspect
of the complexion, the swing about the body and the bearing of the head
and shoulders, of young women whose physical training has been efficient,
are in marked contrast with those characteristics in persons whose
education in this respect has been neglected.
85. Effect of Unsuitable or Excessive Exercise. But exercise, like
everything else which contributes to our welfare, may be carried to
excess. The words excessive and unsuitable, when applied to muscular
exertion, are relative terms, and apply to the individual rather than to
amount of work done. Thus what may be excessive for one person, might be
suitable and beneficial to another. Then the condition of the individual,
rather than the character of the muscular work, is always a most important
factor.
Breathlessness is, perhaps, the most common effect of undue exertion. Let
a middle-aged person, who is out of practice, run a certain distance, and
he is soon troubled with his breathing. The respirations become irregular,
and there is a sense of oppression in his chest. He pants, and his
strength gives out. His chest, and not his legs, has failed him. He is
said to be "out of breath." He might have practiced dumb-bells or rowed
for some time without inconvenience.
The heart is often overstrained, and at times has been ruptured during
violent exertion, as in lifting an immense weight. The various forms of
heart-disease are common with those whose occupations involve severe
muscular effort, as professional athletes and oarsmen. Hæmorrhages of
various kinds, especially from the lungs, or rupture of blood-vessels in
the brain, are not uncommon results of over-exertion.
Excessive repetition of muscular movements may lead to permanent
contractions of the parts involved. Thus sailors, mechanics, and others
frequently develop a rigidity of the tendons of the hand which prevents
the full extension of the fingers. So stenographers, telegraphers and
writers occasionally suffer from permanent contractions of certain muscles
of the arm, known as writer's cramp, due to their excessive use. But the
accidents which now and then may result from severe physical exertion,
should discourage no one from securing the benefits which accrue from
moderate and reasonable exercise.
86. Muscular Fatigue. We all know how tiresome it is to hold the arm
outstretched horizontally even for a few moments. A single muscle, the
deltoid, in this case does most of the work. Even in a vigorous man, this
muscle can act no longer than four to six minutes before the arm drops
helpless. We may prolong the period by a strong effort of the will, but a
time soon comes when by no possible effort are we able to hold out the
arm. The muscle is said to be fatigued. It has by no means lost its
contractile power, for if we apply a strong electric stimulus to it, the
fatigue seems to disappear. Thus we see the functional power of a muscle
has a definite limit, and in fatigue that limit is reached.
[Illustration: Fig. 42.--A Well-Equipped Gymnasium. (From a photograph.)]
The strength of the muscle, its physical condition, the work it has done,
and the mental condition of the individual, all modify the state of
fatigue. In those difficult acts which involve a special effort of the
will, the matter of nerve exhaustion is largely concerned. Thus, the
incessant movements in St. Vitus' dance result in comparatively little
fatigue, because there is no association of the brain with the muscular
action. If a strong man should attempt to perform voluntarily the same
movements, he would soon have to rest. None of the movements which are
performed independently of the will, as the heart-beats and breathing
movements, ever involve the sensation of fatigue. As a result of fatigue
the normal irritability of muscular tissue becomes weakened, and its force
of contraction is lessened. There is, also, often noticed in fatigue a
peculiar tremor of the muscles, rendering their movements uncertain. The
stiffness of the muscles which comes on during severe exercise, or the day
after, are familiar results of fatigue.
This sense of fatigue should put us on guard against danger. It is a kind
of regulator which serves in the ordinary actions of life to warn us not
to exceed the limits of useful exercise. Fatigue summons us to rest long
before all the force of the motor organs has been expended, just as the
sensation of hunger warns us that we need food, long before the body has
become weak from the lack of nourishment.
We should never forget that it is highly essential to maintain an unused
reserve of power, just as a cautious merchant always keeps at the bank an
unexpended balance of money. If he overspends his money he is bankrupt,
and the person who overspends his strength is for the time physically
bankrupt. In each case the process of recovery is slow and painful.
87. Rest for the Muscles. Rest is necessary for the tissues, that
they may repair the losses sustained by work; that is, a period of rest
must alternate with a period of activity. Even the heart, beating
ceaselessly, has its periods of absolute rest to alternate with those of
work. A steam-engine is always slowly, but surely, losing its fitness for
work. At last it stops from the need of repair. Unlike the engine, the
body is constantly renewing itself and undergoing continual repair. Were
it not for this power to repair and renew its various tissues, the body
would soon be worn out.
This repair is really a renovation of the structure. Rest and work are
relative terms, directly opposed to each other. Work quickens the pulse
and the respiration, while rest slows both. During sleep the voluntary
muscles are relaxed, and those of organic life work with less energy. The
pulse and the respiration are less frequent, and the temperature lower
than when awake. Hence sleep, "tired Nature's sweet restorer," may be
regarded as a complete rest.
The periods of rest should vary with the kind of exercise. Thus exercise
which produces breathlessness requires frequent but short rests. The
trained runner, finding his respiration embarrassed, stops a moment to
regain his breath. Exercises of endurance cause fatigue less quickly than
those of speed, but require longer rest. Thus a man not used to long
distances may walk a number of hours without stopping, but while fatigue
is slow to result, it is also slow to disappear. Hence a lengthy period of
rest is necessary before he is able to renew his journey.
88. Amount of Physical Exercise Required. The amount of physical
exercise that can be safely performed by each person, is a most important
and practical question. No rule can be laid down, for what one person
bears well, may prove very injurious to another. To a certain extent, each
must be guided by his own judgment. If, after taking exercise, we feel
fatigued and irritable, are subject to headache and sleeplessness, or find
it difficult to apply the mind to its work, it is plain that we have been
taxing our strength unduly, and the warnings should be heeded.
Age is an important factor in the problem, as a young man may do with
ease and safety, what might be injurious to an older person. In youth,
when the body is making its most active development, the judicious use of
games, sports, and gymnastics is most beneficial. In advanced life, both
the power and the inclination for exercise fail, but even then effort
should be made to take a certain reasonable amount of exercise.
Abundant evidence shows that physical development is most active from
thirteen to seventeen years of age; this manifests itself clearly by
increase in weight. Hence this period of life is of great consequence. If
at this age a boy or girl is subjected to undue physical strain, the
development may suffer, the growth be retarded, and the foundation laid
for future ill health.
[Illustration: Fig. 43.--Student exercising in the School Gymnasium on the
Rowing Machine. (From a photograph.)]
The proper amount of exercise must vary greatly with circumstances. It may
be laid down as a fairly safe rule, that a person of average height and
weight, engaged in study or in any indoor or sedentary occupation, should
take an amount of exercise equivalent to walking five or six miles a day.
Growing children, as a rule, take more exercise than this, while most men
working indoors take far less, and many women take less exercise than men.
Exercise may be varied in many ways, the more the better; but for the most
part it should always be taken in the open air.
89. Time for Exercise. It is not prudent to do hard work or take
severe exercise, just before or just after a full meal. The best time is
one or two hours after a meal. Vigorous exercise while the stomach is
busily digesting food, may prove injurious, and is apt to result sooner or
later in dyspepsia. On the other hand, severe exercise should not be taken
on an empty stomach. Those who do much work or study before breakfast,
should first take a light lunch, just enough to prevent any faint feeling.
With this precaution, there is no better time for moderate exercise than
the early morning.
In the case of children, physical exercises should not be undertaken when
they are overtired or hungry. Neither is it judicious for adults to take
vigorous exercise in the evening, after a long and arduous day's work.
90. Walking, Running, and Jumping. Walking is generally regarded as
the simplest and most convenient mode of taking exercise. Man is
essentially a walking animal. When taken with a special object in view, it
is the best and most pleasant of all physical activities. It is suited for
individuals of all ages and occupations, and for residents of every
climate. The child, the athlete, and the aged are all able to indulge in
this simple and effective means of keeping the body in health.
In walking, the muscles of the entire body are brought into action,
and the movements of breathing and the circulation of the blood are
increased. The body should be erect, the chest thrown out, the head and
shoulders held back, and the stride long and elastic. It is an excellent
custom to add to the usefulness of this fine exercise, by deep, voluntary
inhalations of pure air.
Running is an excellent exercise for children and young people, but
should be sparingly indulged in after the age of thirty-five. If it be
accompanied with a feeling of faintness, breathlessness, and palpitation
of the heart, the exercise is too severe, and its continuance may do
serious harm. Running as an exercise is beneficial to those who have kept
themselves in practice and in sound condition. It brings into play nearly
every muscle of the body, and thus serves to develop the power of
endurance, as well as strength and capacity for rapid movement.
Jumping may well be left to boys and young men under twenty, but
skipping with a rope, allied to jumping, is an admirable and beneficial
form of exercise. It brings into action many muscles without putting undue
strain upon any particular group.
91. Skating, Swimming, and Rowing. Skating is a delightful and
invigorating exercise. It calls into play a great variety of muscles, and
is admirably adapted for almost all ages. It strengthens the ankles and
helps give an easy and graceful carriage to the body. Skating is
especially valuable, as it can be enjoyed when other out-door exercises
are not convenient.
Every child above ten years of age should be taught to swim. The art,
once mastered, is never forgotten. It calls into use a wide combination of
muscles. This accomplishment, so easily learned, should be a part of our
education, as well as baseball or bicycling, as it may chance to any one
to save his own life or that of a companion.
In many respects rowing is one of the most perfect exercises at our
command. It expands the chest, strengthens the body, and gives tone to the
muscles of the abdomen. It is very suitable for girls and women, as no
other exercise is so well adapted to remedy the muscular defects so marked
in their sex. Even elderly persons can row day after day without
difficulty. The degree of muscular effort required, can be regulated so
that those with weak hearts and weak lungs can adjust themselves to the
exercise.
92. Bicycling as an Exercise. The bicycle as a means of taking
exercise has come into popular use with remarkable rapidity. Sharp
competition bids fair to make the wheel more popular and less expensive
than ever. Its phenomenal use by persons of all ages and in all stations
of life, is proof of the enthusiasm with which this athletic exercise is
employed by women as well as by men.
Mechanical skill has removed most of the risks to health and person which
once existed. A good machine, used by its owner with judgment, is the most
convenient, the safest, and the least expensive means of traveling for
pleasure or exercise. It is doing more than any other form of exercise to
improve the bodily condition of thousands whose occupations confine them
all day to sedentary work. Dependent upon no one but himself, the cyclist
has his means of exercise always at hand. No preparation is necessary to
take a spin of ten miles or so on the road, during a summer evening or
before breakfast.
Bicycling brings into active use the muscles of the legs as well as those
of the trunk and arms. It seems to benefit those who suffer from
dyspepsia, constipation, and functional disorders of the liver.
A special caution must be used against overdoing in cycling, for the
temptation by rivalry, making a record, by social competition on the road,
is stronger in this form of exercise than in any other, especially for
young folks. Many cases have occurred of permanent injury, and even loss
of life, from collapse simply by excessive exertion and exhaustion.
93. Outdoor Games and Physical Education. While outdoor games
are not necessary to maintain health, yet we can scarcely overestimate the
part that the great games of baseball, football, tennis, golf, and
croquet, play in the physical development of young people. When played in
moderation and under suitable conditions, they are most useful and
beneficial exercises. They are played in the open air, and demand a great
variety of vigorous muscular movement, with a considerable amount of skill
and adroitness of action. These games not only involve healthful exercise,
but develop all those manly and wholesome qualities so essential to
success in life.
A vigorous body is well-nigh essential to success, but equally important
are readiness of action, sound judgment, good temper, personal courage, a
sense of fair play, and above all, a spirit of honor. Outdoor games, when
played in a reasonable and honorable manner, are most efficient and
practical means to develop these qualities in young people.
94. The School and Physical Education. The advantages to be derived,
during the school period, from the proper care and development of the
body, should be understood and appreciated by school officials, teachers,
and parents. The school period is the best time to shape the lives of
pupils, not mentally or morally alone, but physically as well. This is the
time, by the use of a few daily exercises at school, to draw back the
rounding shoulders, to form the habit of sitting and standing erect, to
build up strong and comely arms and chests, and otherwise to train pupils
to those methods which will serve to ripen them into vigorous and
well-knit men and women.
Teachers can by a little effort gain the knowledge requisite properly to
instruct their pupils in a few systematic exercises. Gratifying results
will follow just as the teacher and pupils evince interest and judgment in
the work. It is found by experience that pupils are not only quick to
learn, but look forward eagerly to the physical exercises as an
interesting change from the routine of school life.
There should be a stated time for these school exercises, as for any other
duty. There can be practiced in the schoolroom a great variety of
interesting and useful exercises, which call for little or no expense for
apparatus. Such exercises should no more interfere with the children's
usual games than any other study does. Under no circumstances should the
play hours be curtailed.
95. Physical Exercises in School. Physical exercises of some sort,
then, should be provided for pupils in our schools, especially in large
towns and cities, where there is little opportunity for outdoor games, and
they should form a part of the regular course of study. The object should
be the promotion of sound health rather than the development of muscle, or
performing feats of agility or strength. Exercises with dumb-bells and
wands, or even without any apparatus, practiced a few times a day, for
five minutes at a time, do a great deal of good. They relax the tension of
body and mind, and introduce an element of pleasure into the routine of
school life. They increase the breathing power and quicken the action of
the heart.
[Illustration: Fig. 44.--Physical Exercises as carried on in Schools.
(From photographs.)]
[NOTE. "In early boyhood and youth nothing can replace the active
sports so much enjoyed at this period; and while no needless
restrictions should be placed upon them, consideration should be paid
to the amount, and especially to the character, of the games pursued
by delicate youth. For these it would be better to develop the
weakened parts by means of systematic physical exercises and by
lighter sports."--Dr. John M. Keating on "Physical Development" in
Pepper's _Cyclopædia of the Diseases of Children_.]
If vigorously and systematically carried out, these exercises invigorate
all the tissues and organs of the body, and stimulate them to renewed
activity. They serve to offset the lack of proper ventilation, faulty
positions at the desks, and the prolonged inaction of the muscles. To
secure the greatest benefit from physical training in school, it is
important that the pupils be interested in these exercises, and consider
them a recreation, and not a task[14].
96. Practical Points about Physical Exercise. The main object in
undertaking systematic and graduated physical exercises is not to learn to
do mere feats of strength and skill, but the better to fit the individual
for the duties and the work of life. Exercises should be considered with
reference to their availability from the learner's standpoint. The most
beneficial exercises ordinarily are the gentle ones, in which no strain is
put upon the heart and the respiration. The special aim is to secure the
equal use of all the muscles, not the development of a few. The
performance of feats of strength should never come within the scope of any
educational scheme. Exercises which call for sustained effort, violent
exertion, or sudden strain are best avoided by those who have had no
preparation or training.
Regular exercise, not sudden and occasional prolonged exertion, is
necessary for health. The man or woman who works in an office or store all
the week, and on Sunday or a holiday indulges in a long spin on the
bicycle, often receives more harm than good from the exertion. Exercise
should be taken, so far as is convenient, in the open air, or in a large
and well-ventilated room.[15]
After the more violent exercises, as baseball, football, a long ride on
the bicycle, or even after a prolonged walk, a warm bath should be taken
at the first convenient opportunity. Care should be taken to rub down
thoroughly, and to change a part or all of the clothing. Exercise is
comparatively valueless until the idea of taking it for health is quite
forgotten in the interest and pleasure excited by the occasion. No
exercise should be carried to such a degree as to cause fatigue or
exhaustion. Keep warmly clad after exercise, avoid chills, and always stop
exercising as soon as fatigue is felt.
Wear clothing which allows free play to all the muscles of the body. The
clothing should be light, loose, and made of wool. Care should be taken
not to take cold by standing about in clothes which are damp with
perspiration. In brisk walking and climbing hills keep the mouth shut,
especially in cold weather, and breathe through the nose, regulating the
pace so that it can be done without discomfort.
97. Effect of Alcoholic Liquors and Tobacco upon Physical Culture. As
a result of the unusual attention given to physical culture in the last
few years, hundreds of special instructors are now employed in training
young people in the theory and practice of physical exercise. These expert
teachers, to do their work with thoroughness and discipline, recognize the
necessity of looking after the daily living of their students. The time of
rising and retiring, the hours of sleep, the dress, the care of the diet,
and many other details of personal health become an important part of the
training.
Recognizing the fact that alcoholic drink and tobacco are so disastrous to
efficiency in any system of physical training, these instructors rigidly
forbid the use of these drugs under all circumstances. While this
principle is perhaps more rigorously enforced in training for athletic
contests, it applies equally to those who have in view only the
maintenance of health.
Books on Physical Education. There are many excellent books on
physical education, which are easily obtained for reading or for
reference. Among these one of the most useful and suggestive is Blackie's
well-known book, "How to Get Strong and how to Stay so." This little book
is full of kindly advice and practical suggestions to those who may wish
to begin to practice health exercises at home with inexpensive apparatus.
For more advanced work, Lagrange's "Physiology of Bodily Exercise" and the
Introduction to Maclaren's "Physical Education" may be consulted. A
notable article on "Physical Training" by Joseph H. Sears, an Ex-Captain
of the Harvard Football Team, may be found in Roosevelt's "In Sickness and
in Health."
Price lists and catalogues of all kinds of gymnastic apparatus are easily
obtained on application to firms handling such goods.
Various Systems of Physical Exercises. The recent revival of popular
interest in physical education has done much to call the attention of the
public to the usefulness and importance of a more thorough and systematic
use of physical exercises, both at home and in the schools. It is not
within the scope of this book to describe the various systems of gymnastic
and calisthenic exercises now in common use in this country. For the most
part they have been modified and rearranged from other sources, notably
from the two great systems, i.e., Swedish and German.
For a most comprehensive work on the Swedish system, the teacher is
referred to the "Swedish System of Educational Gymnastics," with 264
illustrations, by Baron Nils Posse. There is also a small manual for
teachers, called "Handbook of School Gymnastics of the Swedish Systems,"
by the same author.
Chapter V.
Food and Drink.
98. Why we need Food. The body is often compared to a steam-engine in
good working order. An engine uses up fuel and water to obtain from them
the energy necessary to do its work. So, we consume within our bodies
certain nutritious substances to obtain from them the energy necessary for
our activities. Just as the energy for the working of the engine is
obtained from steam by the combustion of fuel, so the energy possessed by
our bodies results from the combustion or oxidation within us of the food
we eat. Unless this energy is provided for the body it will have but
little power of doing work, and like an engine without steam, must soon
become motionless.
99. Waste and Repair. A steam-engine from the first stroke of its
piston-rod begins to wear out, and before long needs repair. All work
involves waste. The engine, unless kept in thorough repair, would soon
stop. So with our bodies. In their living cells chemical changes are
constantly going on; energy, on the whole, is running down; complex
substances are being broken up into simpler combinations. So long as life
lasts, food must be brought to the tissues, and waste products carried
away from them. It is impossible to move a single muscle, or even to think
for one moment, without some minute part of the muscular or brain tissue
becoming of no further use in the body. The transformation of dead matter
into living tissue is the ever-present miracle which life presents even in
its lowest forms.
In childhood the waste is small, and the amount of food taken is more
than sufficient to repair the loss. Some of the extra food is used in
building up the body, especially the muscles. As we shall learn in Chapter
VIII., food is also required to maintain the bodily heat. Food, then,
is necessary for the production of energy, for the repair of the body, for
the building up of the tissues, and for the maintenance of bodily heat.
100. Nature of the Waste Material. An ordinarily healthy person
passes daily, on an average, by the kidneys about 50 ounces of waste
material, of which 96 per cent is water, and from the intestines, on an
average, 5½ ounces, a large proportion of which is water. By the skin,
in the shape of sweat and insensible perspiration, there is cast out about
23 ounces, of which 99 per cent is water; and by the lungs about 34
ounces, 10 of which are water and the remainder carbon dioxid.
Now if we omit an estimate of the undigestible remains of the food, we
find that the main bulk of what daily leaves the body consists of water,
carbon dioxid, and certain solid matters contained in solution in
the renal secretion and the sweat. The chief of these solid matters is
urea, a complex product made up of four elements,--carbon, hydrogen,
oxygen, and nitrogen. Water contains only two elements, hydrogen and
oxygen; and carbon dioxid also has only two, carbon and oxygen. Hence,
what we daily cast out of our bodies consists essentially of these four
elements in the form mainly of water, carbon dioxid, and urea.
These waste products represent the oxidation that has taken place in
the tissues in producing the energy necessary for the bodily activities,
just as the smoke, ashes, clinkers, and steam represent the consumption of
fuel and water in the engine. Plainly, therefore, if we could restore to
the body a supply of these four elements equivalent to that cast out, we
could make up for the waste. The object of food, then, is to restore to
the body an amount of the four elements equal to that consumed. In other
words, and briefly: The purpose of food is to supply the waste of the
tissues and to maintain the normal composition of the blood.
101. Classification of Foods. Foods may be conveniently divided into
four great classes, to which the name food-stuffs or alimentary
principles has been given. They correspond to the chief "proximate
principles" of which the body consists. To one or the other of these
classes all available foods belong[16]. The classification of food-stuffs
usually given is as follows:
I. Proteids, or Nitrogenous Foods.
II. Starches and Sugars, or Carbohydrates.
III. Fats and Oils.
IV. Inorganic or Mineral Foods,--Water, Salt.
102. Proteids; or Nitrogenous Foods. The proteids, frequently
spoken of as the nitrogenous foods, are rich in one or more of the
following organic substances: albumen, casein, fibrin, gelatine, myosin,
gluten, and legumin.
The type of this class of foods is albumen, well known as the white of an
egg. The serum of the blood is very rich in albumen, as is lean meat. The
curd of milk consists mainly of casein. Fibrin exists largely in blood and
flesh foods. Gelatine is obtained from the animal parts of bones and
connective tissue by prolonged boiling. One of the chief constituents of
muscular fiber is myosin. Gluten exists largely in the cereals wheat,
barley, oats, and rye. The proteid principle of peas and beans is legumin,
a substance resembling casein.
As the name implies, the proteids, or nitrogenous foods, contain nitrogen;
carbohydrates and fats, on the contrary, do not contain nitrogen. The
principal proteid food-stuffs are milk, eggs, flesh foods of all kinds,
fish, and the cereals among vegetable foods. Peas and beans are rich in
proteids. The essential use of the proteids to the tissues is to supply
the material from which the new proteid tissue is made or the old proteid
tissue is repaired. They are also valuable as sources of energy to the
body. Now, as the proteid part of its molecule is the most important
constituent of living matter, it is evident that proteid food is an
absolute necessity. If our diet contained no proteids, the tissues of
the body would gradually waste away, and death from starvation would
result. All the food-stuffs are necessary in one way or another to the
preservation of perfect health, but proteids, together with a certain
proportion of water and inorganic salts, are absolutely necessary for the
bare maintenance of animal life--that is, for the formation and
preservation of living protoplasm.
103. Starches and Sugars. The starches, sugars, and gums, also known
as carbohydrates, enter largely into the composition of foods of
vegetable origin. They contain no nitrogen, but the three elements,
carbon, hydrogen, and oxygen, the last two in the same proportion as in
water. The starches are widely distributed throughout the vegetable
kingdom. They are abundant in potatoes and the cereals, and in arrowroot,
rice, sago, and tapioca. Starch probably stands first in importance among
the various vegetable foods.
The sugars are also widely distributed substances, and include the
cane, grape, malt, maple, and milk sugars. Here also belong the gums and
cellulose found in fruit, cereals, and all vegetables which form the
basis of the plant cells and fibers. Honey, molasses, and manna are
included in this class.
The physiological value of the starches and sugars lies in the fact that
they are oxidized in the body, and a certain amount of energy is thereby
liberated. The energy of muscular work and of the heat of the body comes
largely from the oxidation, or destruction, of this class of foods. Now,
inasmuch as we are continually giving off energy from the body, chiefly in
the form of muscular work and heat, it is evident that material for the
production of this energy must be taken in the food. The carbohydrates
constitute the bulk of our ordinary food.
104. Fats and Oils. These include not only the ordinary fats of
meat, but many animal and vegetable oils. They are alike in
chemical composition, consisting of carbon and hydrogen, with a little
oxygen and no nitrogen. The principal kinds of fat used as food are the
fat of meat, butter, suet, and lard; but in many parts of the world
various vegetable oils are largely used, as the olive, palm, cotton seed,
cocoanut, and almond.
The use of the fats in the body is essentially the same as that of the
starches and sugars. Weight for weight they are more valuable than the
carbohydrates as sources of energy, but the latter are more easily
digested, and more easily oxidized in the body. An important use of fatty
foods is for the maintenance of the bodily heat. The inhabitants of Arctic
regions are thus enabled, by large use of the fat and oil from the animals
they devour, to endure safely the severe cold. Then there is reason to
believe that fat helps the digestion of other foods, for it is found that
the body is better nourished when the fats are used as food. When more fat
is consumed than is required to keep up the bodily heat and to yield
working power, the excess is stored up in various parts of the body,
making a sort of reserve fuel, which may be drawn upon at any future time.
105. Saline or Mineral Foods. All food contains, besides the
substances having potential energy, as described, certain saline
matters. Water and salts are not usually considered foods, but the results
of scientific research, as well as the experience of life, show that these
substances are absolutely necessary to the body. The principal mineral
foods are salt, lime, iron, magnesia, phosphorus, potash, and water.
Except common salt and water, these substances are usually taken only in
combination with other foods.
These saline matters are essential to health, and when not present in due
proportion nutrition is disturbed. If a dog be fed on food freed from all
salines, but otherwise containing proper nutrients, he soon suffers from
weakness, after a time amounting to paralysis, and often dies in
convulsions.
About 200 grains of common salt are required daily by an adult, but a
large proportion of this is in our food. Phosphate of lime is obtained
from milk and meats, and carbonate of lime from the hard water we drink.
Both are required for the bones and teeth. The salts of potash, which
assist in purifying the blood, are obtained from vegetables and fruits. An
iron salt is found in most foods, and sulphur in the yolk of eggs.
106. Water. Water is of use chiefly as a solvent, and while not
strictly a food, is necessary to life. It enters into the construction of
every tissue and is constantly being removed from the body by every
channel of waste[17].
As a solvent water aids digestion, and as it forms about 80 per cent
of the blood, it serves as a carrier of nutrient material to all the
tissues of the body.
Important Articles of Diet.
107. Milk. The value of milk as a food cannot be overestimated.
It affords nourishment in a very simple, convenient, and perfect form. It
is the sole food provided for the young of all animals which nourish their
young. It is an ideal food containing, in excellent proportions, all the
four elements necessary for growth and health in earlier youth.
[Table: Composition of Food Materials. Careful analyses have been
made of the different articles of food, mostly of the raw, or uncooked
foods. As might be expected, the analyses on record differ more or less in
the percentages assigned to the various constituents, but the following
table will give a fair idea of the fundamental nutritive value of the more
common foods:
In 100 parts Water Proteid Fat Carbohydrate Ash
Digestible Cellulose
Meat 76.7 20.8 1.5 0.3 -- 1.3
Eggs 73.7 12.6 12.1 -- -- 1.1
Cheese 36-60 25-33 7-30 3-7 -- 3.4
Cow's Milk 87.7 3.4 3.2 4.8 -- 0.7
Wheat Flour 13.3 10.2 0.9 74.8 0.3 0.5
Wheat Bread 35.6 7.1 0.2 55.5 0.3 1.1
Rye Flour 13.7 11.5 2.1 69.7 1.6 1.4
Rye bread 42.3 6.1 0.4 49.2 0.5 1.5
Rice 13.1 7.0 0.9 77.4 0.6 1.0
Corn 13.1 9.9 4.6 68.4 2.5 1.5
Macaroni 10.1 9.0 0.3 79.0 0.3 0.5
Peas and Beans 12-15 23-26 1½-2 49-54 4.7 2-3
Potatoes 75.5 2.0 0.2 20.6 0.7 1.0
Carrots 87.1 1.0 0.2 9.3 1.4 0.9
Cabbage 90 2.3 0.5 4-6 1-2 1.3
Fruit 84 0.5 -- 10 4 0.5
]
Cheese is the nitrogenous part of milk, which has been coagulated by the
use of rennet. The curd is then carefully dried, salted, and pressed.
Cheese is sometimes difficult of digestion, as on account of its solid
form it is not easily acted upon by the digestive fluids.
108. Meats. The flesh of animals is one of our main sources of food.
Containing a large amount of proteid, it is admirably adapted for building
up and repairing the tissues of the body. The proportion of water is also
high, varying from 50 to 75 per cent. The most common meats used in
this country are beef, mutton, veal, pork, poultry, and game.
Beef contains less fat and is more nutritious than either mutton or pork.
Mutton has a fine flavor and is easily digested. Veal and lamb, though
more tender, are less easily digested. Pork contains much fat, and its
fiber is hard, so that it is the most difficult to digest of all the
meats. Poultry and game have usually a small proportion of fat, but are
rich in phosphates and are valued for their flavor.
109. Eggs. Consisting of about two-thirds water and the rest albumen
and fat, eggs are often spoken of as typical natural food. The white
of an egg is chiefly albumen, with traces of fat and salt; the yolk is
largely fat and salts. The yellow color is due partly to sulphur. It is
this which blackens a silver spoon. Eggs furnish a convenient and
concentrated food, and if properly cooked are readily digested.
110. Fish. Fish forms an important and a most nutritious article of
diet, as it contains almost as much nourishment as butcher's meat. The
fish-eating races and classes are remarkably strong and healthy. Fish
is less stimulating than meat, and is thus valuable as a food for invalids
and dyspeptics. To be at its best, fish should be eaten in its season. As
a rule shell-fish, except oysters, are not very digestible. Some persons
are unable to eat certain kinds of fish, especially shell-fish, without
eruptions on the skin and other symptoms of mild poisoning.
111. Vegetable Foods. This is a large and important group of foods,
and embraces a remarkable number of different kinds of diet. Vegetable
foods include the cereals, garden vegetables, the fruits, and other less
important articles. These foods supply a certain quantity of albumen and
fat, but their chief use is to furnish starches, sugars, acids, and salts.
The vegetable foods indirectly supply the body with a large amount of
water, which they absorb in cooking.
112. Proteid Vegetable Foods. The most important proteid vegetable
foods are those derived from the grains of cereals and certain
leguminous seeds, as peas and beans. The grains when ground make the
various flours or meals. They contain a large quantity of starch, a
proteid substance peculiar to them called gluten, and mineral salts,
especially phosphate of lime. Peas and beans contain a smaller proportion
of starch, but more proteid matter, called legumin, or vegetable casein.
Of the cereal foods, wheat is that most generally useful. Wheat, and corn
and oatmeal form most important articles of diet. Wheat flour has starch,
sugar, and gluten--nearly everything to support life except fat.
Oatmeal is rich in proteids. In some countries, as Scotland, it forms an
important article of diet, in the form of porridge or oatmeal cakes.
Corn meal is not only rich in nitrogen, but the proportion of fat is also
large; hence it is a most important and nutritious article of food. Rice,
on the other hand, contains less proteids than any other cereal grain, and
is the least nutritious. Where used as a staple article of food, as in
India, it is commonly mixed with milk, cheese, or other nutritious
substances. Peas and beans, distinguished from all other vegetables by
their large amount of proteids--excel in this respect even beef, mutton,
and fish. They take the place of meats with those who believe in a
vegetable diet.
113. Non-proteid Vegetable Foods. The common potato is the best type
of non-proteid vegetable food. When properly cooked it is easily
digested and makes an excellent food. It contains about 75 per cent of
water, about 20 per cent of carbohydrates, chiefly starch, 2 per cent of
proteids, and a little fat and saline matters. But being deficient in
flesh-forming materials, it is unfit for an exclusive food, but is best
used with milk, meat, and other foods richer in proteid substances. Sweet
potatoes, of late years extensively used as food, are rich in starch and
sugar. Arrowroot, sago, tapioca, and similar foods are nutritious, and
easily digested, and with milk furnish excellent articles of diet,
especially for invalids and children.
Explanation of the Graphic Chart. The graphic chart, on the next
page, presents in a succinct and easily understood form the composition of
food materials as they are bought in the market, including the edible and
non-edible portions. It has been condensed from Dr. W. O. Atwater's
valuable monograph on "Foods and Diet." This work is known as the Yearbook
of the U.S. Department of Agriculture for 1894.
KEY: 1, percentage of nutrients; 2, fuel value of 1 pound in calories. The
unit of heat, called a _calorie_, or gramme-degree, is the amount of heat
which is necessary to raise one gramme (15.43 grains) of water one degree
centigrade (1.8° Fahr.). A, round beef; B, sirloin beef; C, rib beef; D,
leg of mutton; E, spare rib of pork; F, salt pork; G, smoked ham; H, fresh
codfish; I, oysters; J, milk; K, butter; L, cheese; M, eggs; N, wheat
bread; O, corn meal; P, oatmeal; Q, dried beans; R, rice; S, potatoes; T,
sugar.
This table, among other things, shows that the flesh of fish contains more
water than that of warm-blooded animals. It may also be seen that animal
foods contain the most water; and vegetable foods, except potatoes, the
most nutrients. Proteids and fats exist only in small proportions in most
vegetables, except beans and oatmeal. Vegetable foods are rich in
carbohydrates while meats contain none. The fatter the meat the less the
amount of water. Thus very lean meat may be almost four-fifths water, and
fat pork almost one-tenth water.
[Illustration: Fig. 45.--Graphic Chart of the Composition of Food
Materials. Composition of Food Materials. Nutritive ingredients, refuse,
and fuel value. ]
114. Non-proteid Animal Foods. Butter is one of the most digestible
of animal fats, agreeable and delicate in flavor, and is on this account
much used as a wholesome food. Various substitutes have recently come into
use. These are all made from animal fat, chiefly that of beef, and are
known as butterine, oleomargarine, and by other trade names. These
preparations, if properly made, are wholesome, and may be useful
substitutes for butter, from which they differ but little in composition.
115. Garden Vegetables. Various green, fresh, and succulent
vegetables form an essential part of our diet. They are of importance
not so much on account of their nutritious elements, which are usually
small, as for the salts they supply, especially the salts of potash. It is
a well-known fact that the continued use of a diet from which fresh
vegetables are excluded leads to a disease known as scurvy. They are also
used for the agreeable flavor possessed by many, and the pleasant variety
and relish they give to the food. The undigested residue left by all green
vegetables affords a useful stimulus to intestinal contraction, and tends
to promote the regular action of the bowels.
116. Fruits. A great variety of fruits, both fresh and dry, is
used as food, or as luxuries. They are of little nutritive value,
containing, as they do, much water and only a small amount of proteid, but
are of use chiefly for the sugar, vegetable acids, and salts they contain.
In moderate quantity, fruits are a useful addition to our regular diet.
They are cooling and refreshing, of agreeable flavor, and tend to prevent
constipation. Their flavor and juiciness serve to stimulate a weak
appetite and to give variety to an otherwise heavy diet. If eaten in
excess, especially in an unripe or an overripe state, fruits may occasion
a disturbance of the stomach and bowels, often of a severe form.
117. Condiments. The refinements of cookery as well as the craving
of the appetite, demand many articles which cannot be classed strictly as
foods. They are called condiments, and as such may be used in
moderation. They give flavor and relish to food, excite appetite and
promote digestion. Condiments increase the pleasure of eating, and by
their stimulating properties promote secretions of the digestive fluids
and excite the muscular contractions of the alimentary canal.
The well-known condiments are salt, vinegar, pepper, ginger, nutmeg,
cloves, and various substances containing ethereal oils and aromatics.
Their excessive use is calculated to excite irritation and disorder of the
digestive organs.
118. Salt The most important and extensively used of the condiments
is common salt. It exists in all ordinary articles of diet, but in
quantities not sufficient to meet the wants of the bodily tissues. Hence
it is added to many articles of food. It improves their flavor, promotes
certain digestive secretions, and meets the nutritive demands of the body.
The use of salt seems based upon an instinctive demand of the system for
something necessary for the full performance of its functions. Food
without salt, however nutritious in other respects, is taken with
reluctance and digested with difficulty.
Salt has always played an important and picturesque part in the history of
dietetics. Reference to its worth and necessity abounds in sacred and
profane history. In ancient times, salt was the first thing placed on the
table and the last removed. The place at the long table, above or below
the salt, indicated rank. It was everywhere the emblem of hospitality. In
parts of Africa it is so scarce that it is worth its weight in gold, and
is actually used as money. Torture was inflicted upon prisoners of state
in olden times by limiting the food to water and bread, without salt. So
intense may this craving for salt become, that men have often risked their
liberty and even their lives to obtain it.
119. Water. The most important natural beverage is pure water; in
fact it is the only one required. Man has, however, from the earliest
times preferred and daily used a variety of artificial drinks, among which
are tea, coffee, and cocoa.
All beverages except certain strong alcoholic liquors, consist almost
entirely of water. It is a large element of solid foods, and our
bodies are made up to a great extent of water. Everything taken into the
circulating fluids of the body, or eliminated from them, is done through
the agency of water. As a solvent it is indispensable in all the
activities of the body.
It has been estimated that an average-sized adult loses by means of the
lungs, skin, and kidneys about eighty ounces of water every twenty-four
hours. To restore this loss about four pints must be taken daily. About
one pint of this is obtained from the food we eat, the remaining three
pints being taken as drink. One of the best ways of supplying water to the
body is by drinking it in its pure state, when its solvent properties can
be completely utilized. The amount of water consumed depends largely upon
the amount of work performed by the body, and upon the temperature.
Being one of the essential elements of the body, it is highly important
that water should be free from harmful impurities. If it contain the germs
of disease, sickness may follow its use. Without doubt the most important
factor in the spread of disease is, with the exception of impure air,
impure water. The chief agent in the spread of typhoid fever is
impure water. So with cholera, the evidence is overwhelming that filthy
water is an all-powerful agent in the spread of this terrible disease.
120. Tea, Coffee, and Cocoa. The active principle of tea is called
theine; that of coffee, caffeine, and of cocoa, theobromine. They also
contain an aromatic, volatile oil, to which they owe their distinctive
flavor. Tea and coffee also contain an astringent called tannin, which
gives the peculiar bitter taste to the infusions when steeped too long. In
cocoa, the fat known as cocoa butter amounts to fifty per cent.
121. Tea. It has been estimated that one-half of the human race now
use tea, either habitually or occasionally. Its use is a prolific source
of indigestion, palpitation of the heart, persistent wakefulness, and of
other disorders. When used at all it should be only in moderation. Persons
who cannot use it without feeling its hurtful effects, should leave it
alone. It should not be taken on an empty stomach, nor sipped after every
mouthful of food.
122. Coffee. Coffee often disturbs the rhythm of the heart and causes
palpitation. Taken at night, coffee often causes wakefulness. This effect
is so well known that it is often employed to prevent sleep. Immoderate
use of strong coffee may produce other toxic effects, such as muscular
tremors, nervous anxiety, sick-headache, palpitation, and various
uncomfortable feelings in the cardiac region. Some persons cannot drink
even a small amount of tea or coffee without these unpleasant effects.
These favorite beverages are unsuitable for young people.
123. Cocoa. The beverage known as cocoa comes from the seeds of the
cocoa-tree, which are roasted like the coffee berries to develop the
aroma. Chocolate is manufactured cocoa,--sugar and flavors being added to
the prepared seeds. Chocolate is a convenient and palatable form of highly
nutritious food. For those with whom tea and coffee disagree, it may be an
agreeable beverage. The large quantity of fat which it contains, however,
often causes it to be somewhat indigestible.
124. Alcoholic Beverages. There is a class of liquids which are
certainly not properly food or drink, but being so commonly used as
beverages, they seem to require special notice in this chapter. In view
of the great variety of alcoholic beverages, the prevalence of their
use, and the very remarkable deleterious effects they produce upon the
bodily organism, they imperatively demand our most careful attention, both
from a physiological and an hygienic point of view.
125. Nature of Alcohol. The ceaseless action of minute forms of plant
life, in bringing about the decomposition of the elaborated products of
organized plant or animal structures, will be described in more detail
(secs. 394-398).
All such work of vegetable organisms, whether going on in the moulding
cheese, in the souring of milk, in putrefying meat, in rotting fruit, or
in decomposing fruit juice, is essentially one of fermentation,
caused by these minute forms of plant life. There are many kinds of
fermentation, each with its own special form of minute plant life or
micro-organism.
In this section we are more especially concerned about that fermentation
which results from the decomposition of sweet fruit, plant, or other
vegetable, juices which are composed largely of water containing sugar and
flavoring matters.
This special form of fermentation is known as alcoholic or vinous
fermentation, and the micro-organisms that cause it are familiarly termed
alcoholic ferments. The botanist classes them as _Saccharomycetes_, of
which there are several varieties. Germs of _Saccharomycetes_ are found on
the surfaces and stems of fruit as it is ripening. While the fruit remains
whole these germs have no power to invade the juice, and even when the
skins are broken the conditions are less favorable for their work than for
that of the moulds,[18] which are the cause of the rotting of fruit.
But when fruit is crushed and its juice pressed out, the
_Saccharomycetes_ are carried into it where they cannot get the oxygen
they need from the air. They are then able to obtain oxygen by taking it
from the sugar of the juice. By so doing they cause a breaking up of the
sugar and a rearrangement of its elements. Two new substances are formed
in this decomposition of sugar, viz., carbon dioxid, which arises
from the liquid in tiny bubbles, and alcohol, a poison which
remains in the fermenting fluid.
Now we must remember that fermentation entirely changes the nature of the
substance fermented. For all forms of decomposition this one law holds
good. Before alcoholic fermentation, the fruit juice was wholesome and
beneficial; after fermentation, it becomes, by the action of the minute
germs, a poisonous liquid known as alcohol, and which forms an essential
part of all intoxicating beverages.
Taking advantage of this great law of fermentation which dominates the
realm of nature, man has devised means to manufacture various alcoholic
beverages from a great variety of plant structures, as ripe grapes, pears,
apples, and other fruits, cane juices, corn, the malt of barley, rye,
wheat, and other cereals.
The process differs according to the substance used and the manner in
which it is treated, but the ultimate outcome is always the same,
viz., the manufacture of a beverage containing a greater or less
proportion of alcoholic poison. By the process of _distillation_, new and
stronger liquor is made. Beverages thus distilled are known as ardent
spirits. Brandy is distilled from wine, rum from fermented molasses, and
commercial alcohol mostly from whiskey.
The poisonous element in all forms of intoxicating drinks, and the one so
fraught with danger to the bodily tissues, is the alcohol they
contain. The proportion of the alcoholic ingredient varies, being about 50
per cent in brandy, whiskey, and rum, about 20 to 15 per cent in wines,
down to 5 per cent, or less, in the various beers and cider; but whether
the proportion of alcohol be more or less, the same element of danger is
always present.
126. Effects of Alcoholic Beverages upon the Human System. One of the
most common alcoholic beverages is wine, made from the juice of grapes. As
the juice flows from the crushed fruit the ferments are washed from the
skins and stems into the vat. Here they bud and multiply rapidly,
producing alcohol. In a few hours the juice that was sweet and wholesome
while in the grape is changed to a poisonous liquid, capable of injuring
whoever drinks it. One of the gravest dangers of wine-drinking is the
power which the alcohol in it has to create a thirst which demands more
alcohol. The spread of alcoholism in wine-making countries is an
illustration of this fact.
Another alcoholic beverage, common in apple-growing districts, is cider.
Until the microscope revealed the ferment germ on the "bloom" of the
apple-skin, very little was known of the changes produced in cider during
the mysterious process of "working." Now, when we see the bubbles of gas
in the glass of cider we know what has produced them, and we know too that
a poison which we do not see is there also in corresponding amounts. We
have learned, too, to trace the wrecked hopes of many a farmer's family to
the alcohol in the cider which he provided so freely, supposing it
harmless.
Beer and other malt liquors are made from grain. By sprouting the grain,
which changes its starch to sugar, and then dissolving out the sugar with
water, a sweet liquid is obtained which is fermented with yeast, one kind
of alcoholic ferment. Some kinds of beer contain only a small percentage
of alcohol, but these are usually drunk in proportionately large amounts.
The life insurance company finds the beer drinker a precarious risk; the
surgeon finds him an unpromising subject; the criminal court finds him
conspicuous in its proceedings. The united testimony from all these
sources is that beer is demoralizing, mentally, morally, and physically.
127. Cooking. The process through which nearly all food used by
civilized man has to pass before it is eaten is known as cooking.
Very few articles indeed are consumed in their natural state, the
exceptions being eggs, milk, oysters, fruit and a few vegetables. Man is
the only animal that cooks his food. Although there are savage races that
have no knowledge of cooking, civilized man invariably cooks most of his
food. It seems to be true that as nations advance in civilization they
make a proportionate advance in the art of cooking.
Cooking answers most important purposes in connection with our food,
especially from its influence upon health. It enables food to be more
readily chewed, and more easily digested. Thus, a piece of meat when raw
is tough and tenacious, but if cooked the fibers lose much of their
toughness, while the connective tissues are changed into a soft and
jelly-like mass. Besides, the meat is much more readily masticated and
acted upon by the digestive fluids. So cooking makes vegetables and grains
softer, loosens their structure, and enables the digestive juices readily
to penetrate their substance.
Cooking also improves or develops flavors in food, especially in animal
foods, and thus makes them attractive and pleasant to the palate. The
appearance of uncooked meat, for example, is repulsive to our taste, but
by the process of cooking, agreeable flavors are developed which stimulate
the appetite and the flow of digestive fluids.
Another important use of cooking is that it kills any minute parasites or
germs in the raw food. The safeguard of cooking thus effectually removes
some important causes of disease. The warmth that cooking imparts to food
is a matter of no slight importance; for warm food is more readily
digested, and therefore nourishes the body more quickly.
The art of cooking plays a very important part in the matter of health,
and thus of comfort and happiness. Badly cooked and ill-assorted foods are
often the cause of serious disorders. Mere cooking is not enough, but good
cooking is essential.
Experiments.
Experiments with the Proteids.
Experiment 31. As a type of the group of proteids we take the white
of egg, egg-white or egg-albumen. Break an egg carefully, so as not to mix
the white with the yolk. Drop about half a teaspoonful of the raw white of
egg into half a pint of distilled water. Beat the mixture vigorously with
a glass rod until it froths freely. Filter through several folds of muslin
until a fairly clear solution is obtained.
Experiment 32. To a small quantity of this solution in a test tube
add strong nitric acid, and boil. Note the formation of a white
precipitate, which turns yellow. After cooling, add ammonia, and note that
the precipitate becomes orange.
Experiment 33. Add to the solution of egg-albumen, excess of strong
solution of caustic soda (or potash), and then a drop or two of very
dilute solution (one per cent) of copper sulphate. A violet color is
obtained which deepens on boiling.
Experiment 34. Boil a small portion of the albumen solution in a test
tube, adding drop by drop dilute acetic acid (two per cent) until a flaky
coagulum of insoluble albumen separates.
Experiments with Starch.
Experiment 35. Wash a potato and peel it. Grate it on a nutmeg grater
into a tall cylindrical glass full of water. Allow the suspended particles
to subside, and after a time note the deposit. The lowest layer consists
of a white powder, or starch, and above it lie coarser fragments of
cellulose and other matters.
Experiment 36. Examine under the microscope a bit of the above white
deposit. Note that each starch granule shows an eccentric hilum with
concentric markings. Add a few drops of very dilute solution of iodine.
Each granule becomes blue, while the markings become more distinct.
Experiment 37. Examine a few of the many varieties of other kinds of
starch granules, as in rice, arrowroot, etc. Press some dry starch powder
between the thumb and forefinger, and note the peculiar crepitation.
Experiment 38. Rub a few bits of starch in a little cold water. Put a
little of the mixture in a large test tube, and then fill with boiling
water. Boil until an imperfect opalescent solution is obtained.
Experiment 39. Add powdered dry starch to cold water. It is
insoluble. Filter and test the filtrate with iodine. It gives no blue
color.
Experiment 40. Boil a little starch with water; if there is enough
starch it sets on cooling and a paste results.
Experiment 41. Moisten some flour with water until it forms a tough,
tenacious dough; tie it in a piece of cotton cloth, and knead it in a
vessel containing water until all the starch is separated. There remains
on the cloth a grayish white, sticky, elastic "gluten," made up of
albumen, some of the ash, and fats. Draw out some of the gluten into
threads, and observe its tenacious character.
Experiment 42. Shake up a little flour with ether in a test tube,
with a tight-fitting cork. Allow the mixture to stand for an hour, shaking
it from time to time. Filter off the ether, and place some of it on a
perfectly clean watch glass. Allow the ether to evaporate, when a greasy
stain will be left, thus showing the presence of fats in the flour.
Experiment 43. Secure a specimen of the various kinds of flour, and
meal, peas, beans, rice, tapioca, potato, etc. Boil a small quantity of
each in a test tube for some minutes. Put a bit of each thus cooked on a
white plate, and pour on it two or three drops of the tincture of iodine.
Note the various changes of color,--blue, greenish, orange, or yellowish.
Experiments with Milk.
Experiment 44. Use fresh cow's milk. Examine the naked-eye character
of the milk. Test its reaction with litmus paper. It is usually neutral or
slightly alkaline.
Experiment 45. Examine with the microscope a drop of milk, noting
numerous small, highly refractive oil globules floating in a fluid.
Experiment 46. Dilute one ounce of milk with ten times its volume of
water. Add cautiously dilute acetic acid until there is a copious,
granular-looking precipitate of the chief proteid of milk (caseinogen),
formerly regarded as a derived albumen. This action is hastened by
heating.
Experiment 47. Saturate milk with Epsom salts, or common salt. The
proteid and fat separate, rise to the surface, and leave a clear fluid
beneath.
Experiment 48. Place some milk in a basin; heat it to about 100° F.,
and add a few drops of acetic acid. The mass curdles and separates into a
solid curd (proteid and fat) and a clear fluid (the whey), which contains
the lactose.
Experiment 49. Take one or two teaspoonfuls of fresh milk in a test
tube; heat it, and add a small quantity of extract of rennet. Note that
the whole mass curdles in a few minutes, so that the tube can be inverted
without the curd falling out. Soon the curd shrinks, and squeezes out a
clear, slightly yellowish fluid, the whey.
Experiment 50. Boil the milk as before, and allow it to cool; then
add rennet. No coagulation will probably take place. It is more difficult
to coagulate boiled milk with rennet than unboiled milk.
Experiment 51. Test fresh milk with red litmus paper; it should turn
the paper pale blue, showing that it is slightly alkaline. Place aside for
a day or two, and then test with blue litmus paper; it will be found to be
acid. This is due to the fact that lactose undergoes the lactic acid
fermentation. The lactose is converted into lactic acid by means of a
special ferment.
Experiment 52. Evaporate a small quantity of milk to dryness in an
open dish. After the dry residue is obtained, continue to apply heat;
observe that it chars and gives off pungent gases. Raise the temperature
until it is red hot; allow the dish then to cool; a fine white ash will be
left behind. This represents the _inorganic matter_ of the milk.
Experiments with the Sugars.
Experiment 53. Cane sugar is familiar as cooking and table sugar. The
little white grains found with raisins are grape sugar, or glucose. Milk
sugar is readily obtained of the druggist. Prepare a solution of the
various sugars by dissolving a small quantity of each in water. Heat each
solution with sulphuric acid, and it is seen to darken or char slowly.
Experiment 54. Place some Fehling solution (which can be readily
obtained at the drug store as a solution, or tablets may be bought which
answer the same purpose) in a test tube, and boil. If no yellow
discoloration takes place, it is in good condition. Add a few drops of the
grape sugar solution and boil, when the mixture suddenly turns to an
opaque yellow or red color.
Experiment 55. Repeat same experiment with milk sugar.
Chapter VI.
Digestion.
128. The Purpose of Digestion. As we have learned, our bodies are
subject to continual waste, due both to the wear and tear of their
substance, and to the consumption of material for the production of their
heat and energy. The waste occurs in no one part alone, but in all the
tissues.
Now, the blood comes into direct contact with every one of these tissues.
The ultimate cells which form the tissues are constantly being bathed by
the myriads of minute blood-vessels which bring to the cells the raw
material needed for their continued renewal. These cells are able to
select from the nutritive fluid whatever they require to repair their
waste, and to provide for their renewed activity. At the same time, the
blood, as it bathes the tissues, sweeps into its current and bears away
the products of waste.
Thus the waste occurs in the tissues and the means of repair are obtained
from the blood. The blood is thus continually being impoverished by having
its nourishment drained away. How, then, is the efficiency of the blood
maintained? The answer is that while the ultimate purpose of the food is
for the repair of the waste, its immediate destination is the blood.[19]
129. Absorption of Food by the Blood. How does the food pass from the
cavity of the stomach and intestinal canal into the blood-vessels? There
are no visible openings which permit communication. It is done by what in
physics is known as _endosmotic_ and _exosmotic_ action. That is, whenever
there are two solutions of different densities, separated only by an
animal membrane, an interchange will take place between them through the
membrane.
To illustrate: in the walls of the stomach and intestines there is a
network of minute vessels filled with blood,--a liquid containing many
substances in solution. The stomach and intestinal canal also contain
liquid food, holding many substances in solution. A membrane, made up of
the extremely thin walls of the blood-vessels and intestines, separates
the liquids. An exchange takes place between the blood and the contents of
the stomach and bowels, by which the dissolved substances of food pass
through the separating membranes into the blood.
[Illustration: Fig. 46.--Cavities of the Mouth, Pharynx, etc. (Section in
the middle line designed to show the mouth in its relations to the nasal
fossæ, the pharynx, and the larynx.)
A, sphenoidal sinus;
B, internal orifice of Eustachian tube;
C, velum palati;
D, anterior pillar of soft palate;
E, posterior pillar of soft palate;
F, tonsil;
H, lingual portion of the pharynx;
K, lower portion of the pharynx;
L, larynx;
M, section of hyoid bone;
N, epiglottis;
O, palatine arch
]
This change, by which food is made ready to pass into the blood,
constitutes food-digestion, and the organs concerned in bringing
about this change in the food are the digestive organs.
130. The General Plan of Digestion. It is evident that the digestive
organs will be simple or complex, according to the amount of change which
is necessary to prepare the food to be taken up by the blood. If the
requisite change is slight, the digestive organs will be few, and their
structure simple. But if the food is varied and complex in composition,
the digestive apparatus will be complex. This condition applies to the
food and the digestion of man.
[Illustration: Fig. 47.--Diagram of the Structure of Secreting Glands.
A, simple tubular gland;
B, gland with mouth shut and sac formed;
C, gland with a coiled tube;
D, plan of part of a racemose gland
]
The digestive apparatus of the human body consists of the alimentary canal
and tributary organs which, although outside of this canal, communicate
with it by ducts. The alimentary canal consists of the mouth, the pharynx,
the œsophagus, the stomach, and the intestines. Other digestive organs
which are tributary to this canal, and discharge their secretions into it,
are the salivary glands,[20] the liver, and the pancreas.
The digestive process is subdivided into three steps, which take place in
the mouth, in the stomach, and in the intestines.
131. The Mouth. The mouth is the cavity formed by the lips, the
cheeks, the palate, and the tongue. Its bony roof is made up of the upper
jawbone on each side, and the palate bones behind. This is the _hard
palate_, and forms only the front portion of the roof. The continuation of
the roof is called the _soft palate_, and is made up of muscular tissue
covered with mucous membrane.
The mouth continues behind into the throat, the separation between the two
Back to Full Books
|