mind, since only that can feel. When any nerve brings news to the brain of
an injury, the mind refers the pain to the end of the nerve. A familiar
illustration is seen in the "funny bone" behind the elbow. Here the nerve
(_ulnar_) gives sensation to the third and fourth fingers, in which,
if this bone be struck, the pain will seem to be. Long after a limb has
been amputated, pain will be felt in it, as if it still formed a part of
the body--any injury in the stump being referred to the point to which the
nerve formerly led. [Footnote: Only about five per cent. of those who
suffer amputation lose the feeling of the part taken away. There is
something tragical, almost ghastly, in the idea of a spirit limb haunting
a man through his life, and betraying him in unguarded moments into some
effort, the failure of which suddenly reminds him of his loss. A gallant
fellow, who had left an arm at Shiloh, once, when riding, attempted to use
his lost hand to grasp the reins while with the other he struck his horse.
A terrible fall was the result of his mistake. When the current of a
battery is applied to the nerves of an arm stump, the irritation is
carried to the brain, and referred to all the regions of the lost limb. On
one occasion a man's shoulder was thus electrized three inches above the
point where the limb was cut off. For two years he had ceased to be
conscious of his limb. As the electric current passed through, the man,
who had been profoundly ignorant of its possible effects, started up,
crying, "Oh, the hand! the hand!" and tried to seize it with the living
grasp of the sound fingers. No resurrection of the dead could have been
more startling.--DR. MITCHELL _on "Phantom Limbs" in Lippincott's
Magazine_.]
The nerves are divided into three general classes--the _spinal_, the
_cranial_, and the _sympathetic_.
FIG. 54.
[Illustration: P, _posterior root of a spinal nerve;_ G,
_ganglion;_ A, _anterior root;_ S, _spinal nerve. The white
portions of the figure represent the white fibers; and the dark, the
gray._]
THE SPINAL NERVES, of which there are thirty-one pairs, issue from the
spinal cord through apertures provided for them in the backbone. Each
nerve arises by two roots; the anterior is the motory, and the posterior
the sensory one. The posterior alone connects directly with the gray
matter of the cord, and has a small ganglion of gray matter of its own at
a little distance from its origin. These roots soon unite, _i. e_.,
are bound up in one sheath, though they preserve their special functions.
When the posterior root of a nerve is cut, the animal loses the power of
feeling, and when the anterior root is cut, that of motion.
THE CRANIAL NERVES, twelve pairs in number, spring from the lower part of
the brain and the medulla oblongata.
1. The _olfactory_, or first pair of nerves, ramify through the
nostrils, and are the nerves of smell.
2. The _optic_, or second pair of nerves, pass to the eyeballs, and
are the nerves of vision.
3, 4, 6. The _motores oculi_ (eye movers) are three pairs of nerves
used to move the eyes.
5. The _trifacial_, or fifth pair of nerves, divide each into three
branches--hence the name--the first to the upper part of the face, eyes,
and nose; the second to the upper jaw and teeth; the third to the lower
jaw and the mouth, where it forms the nerve of taste. These nerves are
implicated when we have the toothache or neuralgia.
7. The _facial_, or seventh pair of nerves, are distributed over the
face, and give it expression. [Footnote: If it is palsied, on one side
there will be a blank, while the other side will laugh or cry, and the
whole face will look funny indeed. There were some cruel people in the
middle ages who used to cut the nerve and deform children's faces in this
way, for the purpose of making money of them at shows. When this nerve was
wrongly supposed to be the seat of neuralgia, or tic douloureux, it was
often cut by surgeons. The patient suffered many dangers, and no relief of
pain was gained.--MAPOTHER.]
FIG. 55.
[Illustration: _The Brain and the origin of the twelve pairs of Cranial
Nerves._ F, E, _the cerebrum;_ D, _the cerebellum, showing the
arbor vitæ;_ G, _the eye;_ H, _the medulla oblongata;_ A,
_the spinal cord;_ C and B, _the first two pairs of spinal
nerves._]
8. The _auditory_, or eighth pair of nerves, go to the ears, and are
the nerves of hearing.
9. The _glos-so-pha-ryn'-ge-al_, or ninth pair of nerves, are
distributed over the mucous membrane of the pharynx, tonsils, etc.
10. The _pneu-mo-gas'-tric_, or tenth pair of nerves, preside over
the larynx, lungs, liver, stomach, and one branch extends to the heart.
This is the only nerve which goes so far from the head.
11. The _accessory_, or eleventh pair of nerves, rise from the spinal
cord, run up to the medulla oblongata, and thence leave the skull at the
same opening with the ninth and tenth pairs. They regulate the vocal
movements of the larynx.
12. The _hyp-o-glos'-sal_, or twelfth pair of nerves, give motion to
the tongue.
FIG. 56.
[Illustration: _Spinal Nerve, Sympathetic Cord, and the Network of
Sympathetic Nerves around the Internal Organs_. K, _aorta;_ A,
_ophagus;_ B, _diaphragm;_ C, _stomach._]
THE SYMPATHETIC SYSTEM contains the nerves of organic life. It consists of
a double chain of ganglia on either side of the backbone, extending into
the chest and abdomen. From, these, delicate nerves, generally soft and of
a grayish color, run to the organs on which life depends--the heart,
lungs, stomach, etc.--to the blood vessels, and to the spinal and cranial
nerves over the body. Thus the entire system is bound together with cords
of sympathy, so that, "if one member suffers, all the members suffer with
it."
Here lies the secret of the control exercised by the brain over all the
vital operations. Every organ responds to its changing moods, especially
those of respiration, circulation, digestion, and secretion,--processes
intimately linked with this system, and controlled by it. (See p. 330.)
CROSSING OF CORDS.--Each half of the body is presided over, not by its own
half of the brain, but that of the opposite side. The motory nerves, as
they descend from the brain, in the medulla oblongata, cross each other to
the opposite side of the spinal cord. So the motor nerves of the right
side of the body are connected with the left side of the brain, and
_vice versa_. Thus a derangement in one half of the brain may
paralyze the opposite half of the body. The nerves going to the face do
not thus cross, and therefore the face may be motionless on one side, and
the limbs on the other. Each of the sensory fibers of the spinal nerves
crosses over to the opposite side of the spinal cord, and so ascends to
the brain; an injury to the spinal cord may, therefore, cause a loss of
motion in one leg and of feeling in the other.
REFLEX ACTION.--Since the gray matter generates the nervous force, a
ganglion is capable of receiving an impression, and of sending back or
_reflecting_ it so as to excite the muscles to action. This is done
without the consciousness of the mind. [Footnote: Instances of an
unconscious working of the mind are abundant. An illustration, often
quoted, is given, as follows, by Dr. Abercrombie, in his _Intellectual
Powers_:
"A lawyer had been excessively perplexed about a very complicated
question. An opinion was required from him, but the question was one of
such difficulty that he felt very uncertain how he should render it. The
decision had to be given at a certain time, and he awoke in the morning of
that day with a feeling of great distress. He said to his wife, 'I had a
dream, and the whole thing was clearly arranged before my mind, and I
would give anything to recover the train of thought.' His wife said to
him, 'Go and look on your table.' She had seen him get up in the night and
go to his table and sit down and write. He did so, and found there the
opinion which he had been most earnestly endeavoring to recover, lying in
his own handwriting. There was no doubt about it whatever."
In this case the action of the brain was clearly automatic, _i. e._,
reflex. The lawyer had worried his brain by his anxiety, and thus
prevented his mind from doing its best. But it had received an impulse in
a certain direction, and when left to itself, worked out the result. (See
Appendix for other illustrations.)] Thus we wink involuntarily at a flash
of light or a threatened blow. [Footnote: A very eminent chemist a few
years ago was making an experiment upon some extremely explosive compound
which he had discovered. He had a small quantity of this compound in a
bottle, and was holding it up to the light, looking at it intently; and
whether it was a shake of the bottle or the warmth of his hand, I do not
know, but it exploded in his hand, and the bottle was shivered into a
million of minute fragments, which were driven in every direction. His
first impression was that they had penetrated his eyes, but to his intense
relief he found presently that they had only struck the outside of his
eyelids. You may conceive how infinitesimally short the interval was
between the explosion of the bottle and the particles reaching his eyes;
and yet in that interval the impression had been made upon his sight, the
mandate of the reflex action, so to speak, had gone forth, the muscles of
his eyelids had been called into action, and he had closed his eyelids
before the particles had reached them, and in this manner his eyes were
saved. You see what a wonderful proof this is of the way in which the
automatic action of our nervous apparatus enters into the sustenance of
our lives, and the protection of our most important organs from injury.--
DR. CARPENTER.] We start at a sudden sound. We jump back from a precipice
before the mind has time to reason upon the danger. The spinal cord
conducts certain impressions to the brain, but responds to others without
troubling that organ. [Footnote: There is a story told of a man, who,
having injured his spinal cord, had lost feeling and motion in his lower
extremities. Dr. John Hunter experimented upon him. Tickling his feet, he
asked him if he felt it; the man, pointing to his limbs, which were
kicking vigorously about, answered, "No, but you see my legs do."
Illustrations of this independent action of the spinal cord are common in
animals. A headless wasp will ply its sting energetically. A fowl, after
its head is cut off, will flap its wings and jump about as if in pain,
although, of course, all sensation has ceased. "A water beetle, having had
its head removed, remained motionless as long as it rested on a dry
surface, but when cast into water, it executed the usual swimming motions
with great energy and rapidity, striking all its comrades to one side by
its violence, and persisting in these for more than half an hour."] The
medulla oblongata carries on the process of respiration. The great
sympathetic system binds together all the organs of the body.
USES OF REFLEX ACTION.--We breathe eighteen times every minute; we stand
erect without a consciousness of effort; [Footnote: In this way we account
for the perilous feats performed by the somnambulist. He is not conscious,
as his operations are not directed by the cerebrum, but by the other
nervous centers. Were he to attempt their repetition when awake, the
emotion of fear might render it impossible.] we walk, eat, digest, and at
the same time carry on a train of thought. Our brain is thus emancipated
from the petty detail of life. If we were obliged to attend to every
breath, every pulsation of the heart, every wink of the eye, our time
would be wasted in keeping alive. Mere standing would require our entire
attention. Besides, an act which at first demands all our thought soon
requires less, and at last becomes mechanical, [Footnote: "As every one
knows," says Huxley, "it takes a soldier a long time to learn his drill--
for instance, to put himself into the attitude of 'attention' at the
instant the word of command is heard. But, after a time, the sound of the
word gives rise to the act, whether the soldier be thinking of it or not.
There is a story, which is credible enough, though it may not be true, of
a practical joker, who, seeing a discharged veteran carrying home his
dinner, suddenly called out 'Attention!' whereupon the man instantly
brought his hands down and lost his mutton and potatoes in the gutter. The
drill had been thorough, and its effects had become embodied in the man's
nervous structure."] as we say, _i. e._, reflex. Thus we play a
familiar tune upon an instrument and carry on a conversation at the same
time. All the possibilities of an education and the power of forming
habits are based upon this principle. No act we perform ends with itself.
It leaves behind it in the nervous centers a tendency to do the same thing
again. Our physical being thus conspires to fix upon us the habits of a
good or an evil life. Our very thoughts are written in our muscles, so
that the expression of our face and even our features grow into harmony
with the life we live.
BRAIN EXERCISE.--The nervous system demands its life and activity. The
mind grows by what it feeds on. One who reads mainly light literature, who
lolls on the sofa or worries through the platitudes of an idle or
fashionable life, decays mentally; his system loses tone, and physical
weakness follows mental poverty. On the other hand, an excessive use of
the mind withdraws force from the body, whose weakness, reacting on the
brain, produces gradual decay and serious diseases. (See p. 331.)
The brain grows by the growth of the body. The body grows through good
food, fresh air, and work and rest in suitable proportion. For the full
development and perfect use of a strong mind, a strong body is essential.
Hence, in seeking to expand and store the intellect, we should be equally
thoughtful of the growth and health of the body.
SLEEP [Footnote: Sleep procured by medicine is rarely as beneficial as
that secured naturally. The disturbance to the nervous system is often
sufficient to counterbalance all the good results. The habit of seeking
sleep in this way, without the advice of a physician, is to be most
earnestly deprecated. The dose must be constantly increased to produce the
effect, and thus great injury may be caused. Often, too, where laudanum or
morphine is used, the person unconsciously comes into a terrible and fatal
bondage. (See p. 342.) Especially should infants never be dosed with
cordials, as is a common family practice. The damage done to helpless
childhood by the ignorant and reckless use of soothing syrups is frightful
to contemplate. All the ordinary sleeping draughts have life-destroying
properties, as is proved by the fatal effects of an overdose. At the best,
they paralyze the nerve centers, disorder the digestion, and poison the
blood. Their promiscuous use is therefore full of danger.] is as essential
as food. During the day, the process of tearing down goes on; during the
night, the work of building up should make good the loss. In youth more
sleep is needed than in old age, when nature makes few permanent repairs,
and is content with temporary expedients. The number of hours required for
sleep must be decided by each person. Napoleon took only five hours, but
most people need from six to eight hours,--brain workers even more. In
general, one should sleep until he naturally wakes. If one's rest be
broken, it should be made up as soon as possible. (See p. 334.)
SUNLIGHT.--The influence of the sun's rays upon the nervous system is very
marked. [Footnote: The necessity of light for young children is not half
appreciated. Many of their diseases, and nearly all the cadaverous looks
of those brought up in great cities, are ascribable to the deficiency of
light and air. When we see the glass room of the photographers in every
street, in the topmost story, we grudge them their application to what is
often a mere personal vanity. Why should not a nursery be constructed in
the same manner? If parents knew the value of light to the skin,
especially to children of a scrofulous tendency, we should have plenty of
these glass house nurseries, where children might run about in a proper
temperature, free from much of that clothing which at present seals up the
skin--that great supplementary lung--against sunlight and oxygen. They
would save many a weakly child who now perishes from lack of these
necessaries of infant life.--DR. WINTER.] It is said also to have the
effect of developing red disks in the blood. All vigor and activity come
from the sun. Vegetables grown in subdued light have a bleached and faded
look. An infant kept in absolute darkness would grow into a shapeless
idiot. That room is the healthiest to which the sun has the freest access.
Epidemics frequently attack the inhabitants of the shady side of a street,
and exempt those on the sunny side. If, on a slight indisposition, we
should go out into the open air and bright sunlight, instead of shutting
ourselves up in a close, dark chamber, we might often avoid a serious
illness. The sun bath is doubtless a most efficient remedy for many
diseases. Our window blinds and curtains should be thrown back and open,
and we should let the blessed air and sun stream in to invigorate and
cheer. No house buried in shade, and no room with darkened windows, is fit
for human habitation. In damp and darkness, lies in wait almost every
disease to which flesh is heir. The sun is their only successful foe. (See
p. 336.)
WONDERS OF THE BRAIN.--After having seen the beautiful contrivances and
the exquisite delicacy of the lower organs, it is natural to suppose that
when we come to the brain we should find the most elaborate machinery. How
surprising, then, it is to have revealed to us only cells and fibers! The
brain is the least solid and most unsubstantial looking organ in the body.
Eighty per cent of water, seven of albumen, some fat, and a few minor
substances constitute the instrument which rules the world. Strangest of
all, the brain, which is the seat of sensation, is itself without
sensation. Every nerve, every part of the spinal cord, is keenly alive to
the slightest touch, yet "the brain may be cut, burned, or electrified
without producing pain."
ALCOHOLIC DRINKS AND NARCOTICS.
ALCOHOL (Continued from p. 187).
EFFECT UPON THE NERVOUS SYSTEM.--In the progressive influence of alcohol
upon the nervous system, there are, according to the researches of Dr.
Richardson, four successive stages.
1. THE STAGE OF EXCITEMENT. [Footnote: The pupil should be careful to note
here that alcohol does not act upon the heart directly, and cause it to
contract with more force. The idea that alcohol gives energy and activity
to the muscles is entirely false. It really, as we have seen (p. 183),
weakens muscular contraction. The enfeeblement begins in the first stage,
and continues in the other stages with increased effect. The heart beats
quickly merely because the resistance of the minute controlling vessels is
taken off, and it works without being under proper regulation. _What is
called a stimulation or excitement is, in absolute fact, a relaxation, a
partial paralysis_ of one of the most important mechanisms in the
animal body. Alcohol should be ranked among the narcotics.--RICHARDSON.]--
The first effect of alcohol, as we have already described on page 144, is
to paralyze the nerves that lead to the extreme and minute blood vessels,
and so regulate the passage of the blood through the capillary system. The
vital force, thus drawn into the nervous centers, drives the machinery of
life with tremendous energy. The heart jumps like the mainspring of a
watch when the resistance of the wheels is removed. The blood surges
through the body with increased force. Every capillary tube in the system
is swollen and flushed, like the reddened nose and cheek.
In all this there is exhilaration, but no nourishment; there is animation,
but no permanent power conferred on brain or muscle. Alcohol may cheer for
the moment. It may set the sluggish blood in motion, start the flow of
thought, and excite a temporary gayety. "It may enable a wearied or feeble
organism to do brisk work for a short time. It may make the brain briefly
brilliant. It may excite muscle to quick action, but it does nothing at
its own cost, fills up nothing it has destroyed, and itself leads to
destruction." Even the mental activity it has excited is an unsafe state
of mind, for that just poise of the faculties so essential to good
judgment is disturbed by the presence of the intruder. Johnson well
remarked, "Wine improves conversation by taking the edge off the
understanding."
2. THE STAGE OF MUSCULAR WEAKNESS.--If the action of the alcohol be still
continued, the spinal cord is next affected by this powerful narcotic. The
control of some of the muscles is lost. Those of the lower lip usually
fail first, then those of the lower limbs, and the staggering, uncertain
steps betray the result. The muscles themselves, also, become feebler as
the power of contraction diminishes. The temperature, which, for a time,
was slightly increased, soon begins to fall as the heat is radiated; the
body is cooled, and the well-known "alcoholic chill" is felt.
3. THE STAGE OF MENTAL WEAKNESS.--The cerebrum is now implicated. The
ideal and emotional faculties are quickened, while the will is weakened.
The center of thought being overpowered, the mind is a chaos. Ideas flock
in thick and fast. The tongue is loosened. The judgment loses its hold on
the acts. The reason giving way, the animal instincts generally assume the
mastery of the man. The hidden nature comes to the surface. All the gloss
of education and social restraint falls off, and the lower nature stands
revealed. The coward shows himself more craven, the braggart more
boastful, the bold more daring, and the cruel more brutal. The inebriate
is liable to become the perpetrator of any outrage that the slightest
provocation may suggest.
4. THE STAGE OF UNCONSCIOUSNESS.--At last, prostration ensues, and the
wild, mad revel of the drunkard ends with utter senselessness. In common
speech, the man is "dead drunk." Brain and spinal cord are both benumbed.
Fortunately, the two nervous centers which supply the heart and the
diaphragm are the slowest to be influenced. So, even in this final stage,
the breathing and the circulation still go on, though the other organs
have stopped. Were it not for this, every person thoroughly intoxicated
would die. [Footnote: Cold has a wonderful influence in hastening this
stage, so that a person, previously only in the first stage of excitement,
on going outdoors on a winter night, may rapidly sink into a lethargy
(become _comatose_), fall, and die. He is then commonly said to have
perished with cold. The signs of this coma are of great practical
importance, since so many persons die in police stations and elsewhere who
are really comatose, when they are supposed to be only sound asleep. The
pulse is slow, and almost imperceptible. The face is pale, and the skin
cold. "If the arm be pinched, it is not moved; if the eyeballs are
touched, the lids will not sink." The respiration becomes slower and
slower, and, if the person dies, it is because liquid collects in the
bronchial tubes, and stops the passage of the air. The man then actually
drowns in his own secretions.]
EFFECT UPON THE BRAIN.--Alcohol seems to have a special affinity for the
brain. This organ absorbs more than any other, and its delicate structure
is correspondingly affected. The "Vascular enlargement" here reaches its
height. The tiny vessels become clogged with blood that is unfitted to
nourish, because loaded with carbonic acid, and deprived of the usual
quantity of the life-giving oxygen.--HINTON. The brain is, in the language
of the physiologist, malfunctioned. The mind but slowly rallies from the
stupor of the fourth stage, and a sense of dullness and depression remains
to show with what difficulty the fatigued organ recovers its normal
condition. So marked is the effect of the narcotic poison, that some
authorities hold that "a once thoroughly intoxicated brain never fully
becomes what it was before."
In time, the free use of liquor hardens and thickens the membrane
enveloping the nervous matter; the nerve corpuscles undergo a "Fatty
degeneration"; the blood vessels lose their elasticity; and the vital
fluid, flowing less freely through the obstructed channels, fails to
afford the old-time nourishment. The consequent deterioration of the
nervous substance--the organ of thought--shows itself in the weakened mind
[Footnote: The habitual use of fermented liquors, even to an extent far
short of what is necessary to produce intoxication, injures the body, and
diminishes the mental power.--Sir Henry Thompson.] that we so often notice
in a person accustomed to drink, and at last lays the foundation of
various nervous disorders--epilepsy, paralysis, and insanity. [Footnote:
Casper, the great statistician of Berlin, says: "So far as that city is
concerned, one third of the insane coming from the poorer classes, were
made so by spirit drinking."] The law of heredity here again asserts
itself, and the inebriate's children often inherit the disease which he
has escaped.