Part 28

37. How may the digestive organs be strengthened?

38. Is the old rule, "after dinner sit awhile," a good one?

39. What would you do if you had taken laudanum by mistake? Paris Green? Sugar of lead? Oxalic acid? Phosphorus from matches? Ammonia? Corrosive sublimate? (See p. 265.)

40. What is the simplest way to produce vomiting, so essential in case of accidental poisoning?

41. In what way does alcohol interfere with the digestion?

42. Is alcohol assimilated?

43. What is the effect of alcohol on the albuminous substances?

44. Is there any nourishment in beer?

45. Show how the excessive use of alcohol may first increase, and, afterward, decrease, the size of the liver.

46. Will liquor help one to endure cold and exposure?

47. What is a fatty degeneration of the kidneys?

48. Contrast the action of alcohol and water in the body.

49. Is alcohol, in any proper sense of the term, a food?

50. Does liquor strengthen the muscles of a working man?

51. Is liquor a wholesome "tonic"?

52. Is it a good plan to take a glass of liquor before dinner?

VII.

THE NERVOUS SYSTEM.

"Mark then the cloven sphere that holds All thoughts in its mysterious folds, That feels sensation's faintest thrill, And flashes forth the sovereign will; Think on the stormy world that dwells Lock'd in its dim and clustering cells; The lightning gleams of power it sheds Along its hollow, glassy threads!"

"As a king sits high above his subjects upon his throne, and from it speaks behests that all obey, so from the throne of the brain cells is all the kingdom of a man directed, controlled, and influenced. For this occupant, the eyes watch, the ears hear, the tongue tastes, the nostrils smell, the skin feels. For it, language is exhausted of its treasures, and life of its experience; locomotion is accomplished, and quiet insured. When it wills, body and spirit are goaded like overdriven horses. When it allows, rest and sleep may come for recuperation. In short, the slightest penetration may not fail to perceive that all other parts obey this part, and are but ministers to its necessities."--Odd Hours of a Physician. ANALYSIS OF THE NERVOUS SYSTEM.

| 1. THE STRUCTURE | | | 1. Description. | | 1. The Brain........| 2. The Cerebrum. | | |3. The Cerebellum. | | | | 2. The Spinal Cord..| 1. Its Composition. | | |2. Medulla Oblongata. | | | 2. ORGANS OF | | 1. Description. | THE NERV- | | 2. Motory and Sensory. | OUS SYSTEM..| | 3. Transfer of Pain. | | | 4. The Spinal Nerves-- | | | 31 Pairs. | |3. The Nerves.......| 5. The Cranial Nerves-- | | 12 Pairs. | | 6. Sympathetic System. | | 7. Crossing of Cords. | | 8. Reflex Action. | | 9. Uses of Reflex | | Action | | | 1. Brain Exercise. | | 2. Connection between Brain Growth and Body Growth. | 3. HYGIENE.....| 3. Sleep. | | 4. Effect of Sleeping Draughts. | |5. Sunlight. | | 4. WONDERS OF THE BRAIN. | | | 1. Alcohol (Con'd.) | | | 1. Stage of Excitement. | || | 2. Stage of Muscular | || | Weakness. | || 1. Effect of Alco- | 3. Stage of Mental | || hol upon the | Weakness. | || Nervous System | 4. Stage of Unconscious- | || | ness. | || | || 2. Effect upon the Brain | ||3. Effect upon the Mental and Moral Powers. | | | | 2. Tobacco. | | | || 1. Constituents of Tobacco. | 5. ALCOHOLIC || 2. Physiological Effects. | DRINKS AND|| 3. Possible Disturbances produced by Smoking. | NARCOTICS.|| 4. Influence upon the Nervous System. || 5. Is Tobacco a Food? ||6. Influence of Tobacco on Youth. | | | 1. Description. | 3. Opium............| 2. Physiological | | Effects. | 4. Chloral Hydrate. | 5. Chloroform. |_6. Cocaine.

THE NERVOUS SYSTEM. [Footnote: The organs of circulation, respiration, and digestion, of which we have already spoken, are often called the vegetative functions, because they belong also to the vegetable kingdom. Plants have a circulation of sap through their cells corresponding to that of the blood through the capillaries. They breathe the air through their leaves, which act the part of lungs, and they take in food which they change into their own structure by a process which answers to that of digestion. The plant, however, is a mere collection of parts incapable of any combined action. On the other hand, the animal has a nervous system which binds all the organs together.]

STRUCTURE.--The nervous system includes the brain, the spinal cord, and the nerves. It is composed of two kinds of matter-- the white, and the gray. The former consists of minute, milk-white, glistening fibers, sometimes as small as 1/25000 of an inch in diameter; the latter is made up of small, ashen-colored cells, forming a pulp-like substance of the consistency of blancmange. [Footnote: In addition to the cells, the gray substance contains also nerve fibers continuous with the white fibers, but generally much smaller. These form half the bulk of the gray substance of the spinal cord, and a large part of the deeper layer of the gray matter in the brain.--LEIDY'S Anatomy, p. 507.] This is often gathered in little masses, termed ganglions (ganglion, a knot), because, when a nerve passes through a group of the cells, they give it the appearance of a knot. The nerve fibers are conductors, while the gray cells are generators, of nervous force. [Footnote: What this force is we do not know. In some respects it is like electricity, but, in others, it differs materially. Its velocity is about thirty three meters per second.--Popular Physics, p. 244, Note.] The ganglia, or nervous centers, answer to the stations along a telegraphic line, where messages are received and transmitted, and the fibers correspond to the wires that communicate between different parts.

FIG. 50.

The BRAIN is the seat of the mind. [Footnote: In proportion to the rest of the nervous matter in the body, it is larger in man than in any of the lower animals. It is the function which the brain performs that distinguishes man from all other animals, and it is by the action of his brain that he becomes a conscious, intelligent, and responsible being. The brain is the seat of that knowledge which we express when we say I. I know it, I feel it, I saw it, are expressions of our individual consciousness, the seat of which is the brain. It is when the brain is at rest in sleep that there is least consciousness. The brain may be put under the influence of poisons, such as alcohol and chloroform, and then the body is without consciousness. From these and other facts the brain is regarded as the seat of consciousness.--LANKESTER.] Its average weight is about fifty ounces. [Footnote: Cuvier's brain weighed 64 1/2 ounces; Webster's, 53 1/2 ounces; James Fisk's, 58 ounces; Ruloff's, 59 ounces; an idiot's, 19 ounces. See Table in FLINT'S Nervous System.] It is egg-shaped, and, soft and yielding, fills closely the cavity of the skull. It reposes securely on a water bed, being surrounded by a double membrane (arachnoid), delicate as a spider's web, which forms a closed sac filled, like the spaces in the brain itself, with a liquid resembling water. Within this, and closely investing the brain, is a fine tissue (pia mater), with a mesh of blood vessels which dips down into the hollows, and bathes them so copiously that it uses one fifth of the entire circulation of the body. Around the whole is wrapped a tough membrane (dura mater), which lines the bony box of the skull, and separates the various parts of the organ by strong partitions. The brain consists of two parts--the cerebrum, and the cerebellum.

The CEREBRUM fills the front and upper part of the skull, and comprises about seven eighths of the entire weight of the brain. As animals rise in the scale of life, this higher part makes its appearance. It is a mass of white fibers, with cells of gray matter sprinkled on the outside, or lodged here and there in ganglia. It is so curiously wrinkled and folded as strikingly to resemble the meat of an English walnut. This structure gives a large surface for the gray matter,--sometimes as much as six hundred and seventy square inches. The convolutions are not noticeable in an infant, but increase with the growth of the mind, their depth and intricacy being characteristic of high mental power.

FIG. 51.

The cerebrum is divided into two hemispheres, connected beneath by fibers of white matter. Thus we have two brains, [Footnote: This doubleness has given rise to some curious speculations. In the case of the hand, eye, etc, we know that the sensation is made more sure. Thus we can see with one eye, but not so well as with both. It is perhaps the same with the brain. We may sometimes carry on a train of thought, "build an air castle" with one half of our brain, while the other half looks on and watches the operation; or, we may read and at the same time think of something else. So in delirium, a patient often imagines himself two persons, thus showing a want of harmony between the two halves.--DRAPER, Human Physiology, p. 320.] as well as two hands and two eyes. This provides us with a surplus of brains, as it were, which can be drawn upon in an emergency. A large part of one hemisphere has been destroyed without particularly injuring the mental powers, [Footnote: A pointed iron bar, three and a half feet long and one inch and a quarter in diameter, was driven by the premature blasting of a rock completely through the side of the head of a man who was present. It entered below the temple, and made its exit at the top of the forehead, just about the middle line. The man was at first stunned, and lay in a delirious, semistupefied state for about three weeks. At the end of sixteen months, however, he was in perfect health, with wounds healed and mental and bodily functions unimpaired, except that sight was lost in the eye of the injured side.-- DALTON. It is noticeable, however, that the man became changed in disposition, fickle, impatient of restraint, and profane, which he was not before. He died epileptic, nearly thirteen years after the injury. The tamping iron and the skull are preserved in the Warren Anatomical Museum, Boston.]--just as a person has been blind in one eye for a long time without having discovered his loss. The cerebrum is the center of intelligence and thought. [Footnote: In man, the cerebrum presents an immense preponderance in weight over other portions of the brain; in some of the lower animals, the cerebrum is even less in weight than the cerebellum. Another interesting point is the development of cerebral convolutions in certain animals, by which the relative amount of gray matter is increased. In fishes, reptiles, and birds, the surface of the hemispheres is smooth; but, in many mammalia, especially in those remarkable for intelligence, the cerebrum presents a greater or less number of convolutions, as it does in the human subject.--FLINT. The average weight of the human brain in proportion to the entire body is about 1 to 36. The average of mammalia is 1 to 186; of birds, 1 to 212; of reptiles, 1 to 1,321; and of fishes, 1 to 5,668. There are some animals in which the weight of the brain bears a higher proportion to the body than it does in man; thus in the blue-headed tit, the proportion is as 1 to 12; in the goldfinch, as 1 to 24; and in the field mouse, as 1 to 31. "It does not hence follow, however, that the cerebrum is larger in proportion; in fact, it is probably not nearly so large; for in birds and rodent animals the sensory ganglia form a very considerable portion of the entire brain. M. Baillarger has shown that the surface and the bulk of the cerebral hemispheres are so far from bearing any constant proportion to each other in different animals that, notwithstanding the depth of the convolutions in the human cerebrum, its bulk is two and a half times as great in proportion to its surface as it is in the rabbit, the surface of whose cerebrum is smooth. The size of the cerebrum, considered alone, is not, however, a fair test of its intellectual power. This depends upon the quantity of vesicular matter which it contains, as evinced not only by superficial area, but by the number and depth of the convolutions and by the thickness of the cortical layer."--CARPENTER.] Persons in whom it is seriously injured or diseased often become unable to converse intelligently, both from inability to remember words and from loss of power to articulate them.