« PreviousContinue »
vey no impression of hearing, nor of smelling, nor of tasting; nor can it convey any impression of pain. If the eye be injured, a nerve of ordinary sensation is required to convey the intelligence to the mind. So in the nose; the nerve that takes notice of odors is a different one from that by which irritation on the same membrane is felt. The snuff-taker smells the snuff with one nerve, and feels its tingling with another.
8. Thus we have briefly explained the leading parts and principles of action of the Nervous System. In one part of this system we have found one set of nerves—
—the nerves of feeling, as they are called, whose office is to convey to the mind impressions of ordinary sensation from the surrounding world ; and a still different set, called nerves of motion, to convey the commands of the mind to the numerous voluntary muscles. In another part of this system we have also found two sets of nerves, but different from the former, running to and from the involuntary muscles, and regulating their motions. And we have also found still different nerves, sometimes called nerves of special sense, conveying to the mind those impressions which give us a knowledge of the objects of taste and of sounds, of shades and colors, and of odors. Some mysterious power presides over all of them, and keeps them in harmonious action, until accident, or disease, or age seriously mars the beautiful mechanism, and then we die. No, not WE! It is only the body—the machine that is broken or that is worn out, while we, the spirit-mind, shall exist forever.
LESSON V.-SPIRIT, THE MOTIVE POWER OF THE BODY.
1. A machine is a combination of parts composed of material substances, solid or fluid, or both, as the case may be; it possesses not its own principle of motion; it can not urge its own levers,' or stretch its own cords, or turn its own wheels, or put its own fluids into circulation. The efficient cause of its motion, which is altogether distinct from the machine itself, is called the prime mover. 2. The point on which I desire now to fix your
attention is, that this prime mover is altogether distinct from the machine, and independent of it; that it possesses, or at least may possess, no property in common with it; and that its existence or non-existence is not decided by the existence or non-existence of the machine.
3. The machine may be broken, destroyed, worn by age, or otherwise disabled, and yet the prime mover may still retain its original energy. Thus a steam-engine is moved by fire, a mill by wind or water; the steam-engine may be worn ont, and the mill be broken by accident; and yet the fire, and the wind, and the water will still preserve their powers.
4. These observations, which correctly describe a machine, may with propriety be applied to the human body. This body is also a combination of parts, composed of material substances, solid and fluid, having certain definite forms and arrangements, possessing certain capabilities of motion and force, destined and admirably adapted to obey the dictation of its prime mover, the living principle, the immaterial spirit.
5. So long as it pleases the Great Engineer who constructed this body to permit its connection with that intellectual spirit, so long will it obey the impulses which it receives; nor does the decay in this bodily machine infer any corresponding decay of the moving spirit any more than the wear and tear of a steam-engine proves the destruction of the principle of heat which gives it motion.
6. Neither are we to infer, because this bodily machine, in its obedience to the vital spirit, acts mechanically, and is adapted to all the ordinary properties and laws of matter, that therefore the spirit which moves it partakes of the nature of matter, or is answerable to its laws, any more than we should infer that the levers, wheels, pumps, chains, cords, and valves of a steam-engine are regulated by the laws which govern heat. On the contrary, I submit it to the candor of the most skeptical materialist3 whether the whole tendency of anal'ogy4 does not directly overthrow the hypoth'esiss that the principle of life is organic.6
7. We are assured in the Scriptures that in the first instance “God formed man of the dust of the ground;" that is to say, He created that curious and beautiful machine, the organized human body; but that body was still an inert? structure, without the principle of self-motion. A more noble work remained to be performed; the immaterial spirit, the divine essence, the prime mover of this machine, was to be applied; and, accordingly, we learn that God “breathed into his nostrils the breath of life;" and then, and not till then,“man became a living soul.”—LARDNER.
“Is, then, the being who such rule maintains
Naught but a bunch of fibres, bones, and veins' ?
Is all that acts, contrives, obeys, commands,
Moulder in kindred dust, and move no more' ? 9. “No': powers sublimer far that frame inspire,
And warm with energy of nobler fire,
Fill all the vast capacity of mind.”
6 OR-GĂN'-16. Organic bodies are such as SKĚP'-TIC-AL, doubting.
possess organs, on the action of which de3 MA-TE'-RI-AL-IST, one who denies any spir-. pend their growth and perfection. itual existence apart from matter.
power to move. 4 A-NĂL'-0-GY, remote likeness or similarity
between different objects.
LES. VI.–VARIOUS PHENOMENA THE NERVOUS SYSTEM.
(Adapted from Hooker and other writers.)
1. WHAT IS NECESSARY TO SENSATION AND VOLUNTARY
MOTION. 1. The nerves, branching out to all parts of the body, do not terminate in sharp points, but usually in loops, where impressions from external things are first received'; and it is found that if the organ on which the nerve is thus expanded is seriously injured, the nerve will not receive the impression. If the eye be so injured in its textures that the impression of light can not be made on the optic nerve, there can be no vision. So, too, of the other senses. Taste and smell are often impaired, sometimes even destroyed for a time, by an inflammation of the mucous membrane,2 on which the nerves devoted to these senses are expanded. This is sometimes the case in a common cold. The trunk of a nerve must also be in a proper condition. If the nerve of vision be pressed upon by a tumor,3 no impression will be transmitted from the images formed in the eye. So, too, if the nerve going to any part of the body be cut off, there can be no transmission of impressions to the brain from that part.
2. Again, it is necessary to sensation that the brain should be in a state to communicate the impression to the mind. If the brain be pressed upon strongly by a depression of the skull from violence, or by effusion of blood by the ruptures of an artery, as sometimes occurs in apoplexy, there can be no sensation. Excitement of mind, too, sometimes prevents the occurrence of sensation by its action upon the connection between the mind and the brain. The pain of a wound received in battle is often unfelt until the excitement of the battle is over, and the aching of a tooth is often stopped by the excitement consequent upon going to the dentist to have it extracted.
3. In these cases the cause of the pain is acting all the time upon the nervous extremity, the trunk of the nerve is capable of transmitting the impression, and the brain is doubtless capable of receiving it, but the mind is so intensely occupied with other things that it takes no notice of the messages sent up from the nerves. Thus the mind may at times rise superior to physical suffering, and withdraw itself, to a certain extent, from bodily influences. We witness this in the exultation with which the savage at the stake sings his deathsongs, and the Christian heroism6 with which martyrs have met death amid the direst tortures of the body. It is on the same principle that the man of stubborn and resolute will is often enabled to resist pain, while the feeble-minded and the irresolute are overcome by it.
II. NERVOUS PARALYSIS. 1. Sometimes the nerves of expression which extend over the face are paralyzed? on one side only. The result is, that while the individual can masticate8 equally well on both sides, he can laugh, and cry, and frown only on one side, and he can not close the eye on the side affected. Thus, if the nerve of expression covering the left side of the face be paralyzed, the left eye can not be closed by any effort, and the left side of the face will be wholly devoid of expression. This nerve of expression is often paralyzed by itself, the other nerves in the neighborhood, both nerves of sensation and of motion, being entirely unaffected. This nerve has been called the respiratory nerve of the face, because it controls motions which are connected with the movements of respiration.
2. If we observe how the various passions and emotions are expressed, we shall see that there is a natural association between the muscles of the face and those of the chest in this expression. This is very obvious in laughing and in weeping. But this association can be effected only through nervous connections, and these connections in this case are very extensive and intimate. When the nerve of expression, or the facial respiratory nerve, is paralyzed, all the motions of the face connected with the respiration are absent. Though the individual may sob in weeping, or send forth the rapid and excessive expirations of laughter, yet the face on the side where the nerve is paralyzed will be perfectly quiescent.10 So, too, those movements of the nostrils which are sometimes used in expression can not be performed. Sneezing can not be done on the affected side, nor can the individual whistle, because a branch of this nerve goes to the muscles at the corner of the mouth, which are therefore disabled. Sir Charles Bell, in cutting a tumor from before the ear of a coachman, divided this branch of the nerve. Shortly after, the man thanked him for curing him of a formidable disease, but complained that he could no longer whistle to his horses.
3. Another singular case of paralysis narrated by Sir Charles Bell is that of a mother who was seized with a paralysis, in which there was a loss of muscular power on one side, and a loss of sensibility on the other. She could hold her child with the arm of the side which retained its power of motion, but had lost its sensibility. But she could do it only when she was looking at it. She could not feel her child on the arm, and therefore, when her attention was drawn to any thing else, and she ceased to have her eyes fixed on the child, the muscles, having no overseer, as we may say, to keep them at work, were relaxed at once, and the child would fall from her
III. NO FEELING IN THE NERVES OF MOTION, IN THE
BRAIN, OR IN THE HEART. 1. It was formerly supposed that a nerve must, of course, have an exquisiteli sensibility.12 But there is no sensibility in nerves devoted to motion, as we have already seen. Neither is there any in the brain itself, but only in its enveloping membranes. Portions of the brain may be cut off without producing any pain. The heart, too, is insensible to touch. A case proving this fell under the observation of Harvey, the discoverer of the circulation of the blood. A
nobleman, from an injury received in a fall, had a large abscess13 on the chest, which occasioned such a destruction of the parts as to leave the lungs and heart exposed. Charles the first; on hearing of the case, desired Harvey to see it.
2. When,” says Harvey, “I had paid my respects to this young nobleman, and conveyed to him the king's request, he made no concealment, but exposed the left side of his breast, when I saw a cavity into which I could introduce my fingers and thumb. Astonished with the novelty, again and again