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Page:Popular Science Monthly Volume 35.djvu/762

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THE POPULAR SCIENCE MONTHLY.

to look carefully at the paintings? You both see them with your eyes alike. Is it not because behind the eye there is something that is mental which enhances your enjoyment, and the lack of which prevents him from appreciating the beauties of art?

Go to a concert, and, as you come away, listen to the comments of people about you. One says that he was occupied chiefly in watching the gyrations of the man who plays the kettle-drums. Another is indulging in raptures over the intricate counterpoint displayed in the orchestration of the symphony. You have enjoyed the music without perhaps having noticed the counterpoint at all. And yet you and the other two have heard equally well, so far as the actual hearing goes. But how differently you have really heard! It has been the reception of the sounds in the brain, rather than in the ear, the appreciation of their meaning, the ideas awakened by the sensations there, which has determined this difference. You see and hear with the brain, and not with the eye or ear.

Or take another function of the brain, that of voluntary movement. You may be fairly skillful and graceful; you may have learned to write a good hand, or to play on the piano; you may even have succeeded in acquiring the power to pronounce foreign languages with the ease and fluency of your own. But this is not the limit to the knowledge of movement. There are many new motions which you might acquire; for example, the steps of new dances, the peculiar fingering of the violin or cornet or other musical instruments, or some one of the innumerable fine adjustments of motion which you see made with such rapidity by any one of fifty different operatives in every factory in the land. All these are movements of adaptation and adjustment, first studied by the aid of sight and then imitated by the aid of muscular sense, or the sense of movement, and finally acquired by practice till they can be executed with dexterity. It is not the fingers or the muscles which have learned the movements. It is the brain which, in its motor area, has received the sensation of movement, has retained a memory, and then combined the memories into new forms of motion so as to direct and guide the hand which carries them out. And so, though we all have hands and arms, there are some who use them deftly and are skillful, and there are others who will always be hopelessly clumsy and awkward. And the difference lies in the brain in the part called the motor area.

Where are the various areas? They can be shown by the aid of diagrams representing the brain surface (Figs. 3 and 4). In the middle lies the motor area (Fig. 3, 1), and it is interesting to know that on the left half of the brain, which guides the right hand, it is larger in extent than on the other side which controls the left hand; because the majority of fine movements are performed by