I cannot at present tell you anything about the muscles, except that it is
by their means that we move arms, legs, head, eyes--every part of the body,
for bones cannot move of themselves, but are acted on by the muscles.
Nor can we learn much about the nerves, because the subject is very
difficult to understand. They come from the brain in the head, and from
that part of it which runs all down the backbone, through the little bony
rings of the vertebrae; and they are protected, because they are so very
delicate, and so precious to us, by a strong bony sheath. At first these
nerves are like coarse twine, but they divide and divide until they become
as fine as threads of white silk--almost as fine as the stronger part of a
spider's web--and they go all over the body, reaching to the very tips of
the fingers.
The first pair of nerves goes to the nose, for smell; the second to the
eye, for sight; and so on for hearing and taste. These are the nerves
called "sensory," which carry to the brain sensations from outside the
body. The "motor" nerves are those which take orders from the brain, to be
instantly obeyed by the muscles.
In the hand, which has twenty-seven bones--one more than the foot--and is
a more wonderful "tool" than any which God has given to the lower animals,
wonderful as _their_ tools are, the sense of touch is stronger than in any
other part of the body.
Suppose you put your fingers upon something very hot or very cold.
Pages:
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384