of the ear, and is passed on from this through the chain of bones to the fluid that surrounds the fibres of the nerve of hearing.

23. In the sense of taste, the particles of the substance tasted are commonly applied in a coarser way to the nerve than in the sense of smell. In the sense of touch, the substances do not, as in smell and taste, come into actual contact with the nerves. They are felt through the cuticle; for this, as I have told you in § 28, Chapter VI., is not sensitive at all; that is, it has no nerves, but is only a soft delicate covering to the very sensitive true-skin.

24. In regard to the sense of sight, we know not what it is that enters the eye and pictures the images of things on the retina. Light is now generally supposed to be a vibration of an exceedingly fine substance, finer than air, which is thought to exist everywhere. The vibration of this substance, which is called ether, is thought to be like the vibration of air in sound. Like that, it goes in waves, in all directions, from where it begins. If light and sound are thus only motions, they are in some respects different motions. They never interfere with each other, though they are continually mingled together, and cross each other in all directions. They differ in one respect very much. Light is a much faster vibration than sound. If you look at a cannon fired at a distance, the flash comes to your eye much sooner than the sound comes to your ear. The same is true also of the flash of lightning and its sound, the thunder.

What is said of the sense of taste? What of the sense of touch? What is light supposed to be? What is said of the vibrations of light and sound?

CHAPTER XII.

CONNECTION OF THE MIND AND BODY.

I HAVE already said much of the connection of the mind and the body. I showed you in the chapter on the Nervous System that this connection is maintained by means of the brain and the nerves. You there learned, that all the knowledge which the mind gets of the world around it comes from the senses by means of the nerves; and also that the only way in which the mind communicates its knowledge to others is by means of the nerves that excite the muscles to action. In the chapters following that on the Nervous System, we considered the instruments by which the brain and nerves operate in thus connecting the mind with the world around it. These instruments are the muscles and bones, and the organs of the senses, the eye, the ear, the nose, the mouth, and the skin. In this chapter I wish to carry you on a little farther, and show you more than I have yet done in regard to the manner in which the mind uses these instruments by means of the nerves.

2. The mind is connected with every part of the body. It therefore feels what is done to any part, and it can move the muscles everywhere by willing to have them moved. But the mind, though it is connected with every part, is not in every part. If you pinch your finger the mind feels it as readily as if it.

Give the summary, in §1, of what has been already said in regard to the connection of the mind and the body. How do you know that the mind is connected with every part of the body?

were itself in the finger. So, also, it can move the finger as easily as if it were really there among the muscles. But if the hand be palsied, feeling and motion are gone in the part; and yet the mind may be active, and move other parts that are not palsied, and feel what is done to them.

3. The mind, then, is not, as life is, all over the body. It is in the brain. This is its central office, the nerves being its communicating wires. We seem to know very early in life that the mind is in the brain. The child is conscious that he does his thinking in his head. But besides this consciousness, we know some facts that prove that the mind resides in the brain. Thus, if a man be knocked down senseless by a blow on his head, the mind feels nothing, and can move no part, because the mind's organ, the brain, is so much affected by the blow. He breathes still, and his heart beats, because the mind, as you saw in $33 in the chapter on the Muscles, does not control. these operations. If the blow break the skull, and the broken part be pressed in upon the brain, the man will not think, and feel, and move, until the surgeon remove the pressure by raising the broken piece.

4. The brain is shown to be the organ of the mind by the manner in which the mind is affected by disease in the brain. Fever causes delirium by disordering the brain, and a violent inflammation of the brain produces fierce delirium. We sometimes see the mind. blotted out, step by step, by slow disease in the brain,

How do you know that the mind is not in every part? What is said of the consciousness that the mind has its seat in the brain? What fact can you cite that proves that it has its seat there?

so that the strong-minded man becomes gradually like an idiot.

5. You see, then, that the mind or soul, so long as it remains in the body, is dependent upon the brain. It can act only by means of this organ. If the brain be disordered in any way, the mind acts in a disordered manner. If the brain be much pressed upon, the mind cannot think, nor feel, nor move any part of the body. The mind is still there, but it is torpid. When the pressure is taken off, it comes out of this torpid

state.

6. As the brain is the organ with which the thinking is done, we find that those animals that think much have larger brains than those that think but little. A frog thinks very little, and he has a small brain. An oyster thinks still less, and it would be hard to make out where his brain is. But such animals as the canary-bird, the dog, and the horse, that know so much, have brains of considerable size. Man has a larger brain in proportion to his body than any other animal, because he has to think so much more than other animals do. And men that think much have larger brains than the stupid and ignorant.

7. The mind in the infant is feeble, just like its body. It knows but little. But as the body grows, the mind grows also, and continually adds to its knowledge. I wish to show you now how it does this.

8. If you look at a very young infant, you will see that it does not know as yet how to use its muscles at all well. It moves its hands about awkwardly.

How does disease sometimes show that the mind resides in the brain? What is said of the size of the brain in different animals and in man? What is said of the mind of the infant ?

It cannot even hold any thing in them. It does not use its eyes well. It cannot turn them so as to look directly at any thing, but they roll about in their sockets irregularly. It does not see any thing clearly.

9. The mind, you see, then, has to learn to use its instruments, the senses and the muscles. And the more it learns how to use them, the more knowledge it gets of the world around it. It learns, for example, to use the muscles and the nerves of touch, so as to know hard things from soft, rough from smooth, &c. In these ways it is continually learning more and more about the world of things with which it is surrounded.

10. In learning to use the senses, the mind makes one sense help another. Thus, the child sees a thing held before it, but as he reaches out his hands to touch it, it is plain that he does not know at first how far off it is. But after a while, by touching it again and again, he knows where it is. That is, by his sense of touch he corrects the report which the sense of sight makes to his mind. He makes many such corrections every day, and after awhile becomes able generally to estimate at what distance objects are the moment he looks at them. Just so the infant has to learn to use its ears as well as its eyes. It knows nothing at first of the direction of sound, or of the distance from which it comes.

What is said of the use which the infant makes of the muscles and the senses? What is said of its learning to use them? Illustrate the fact that the mind makes one sense help another in learning to use the senses?