Page:Popular Science Monthly Volume 35.djvu/763

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the right hand, and have to be learned by the left brain. The reverse is true of left-handed people.

At the extreme back is the visual area which receives impressions from the eye (Fig. 3, 2; Fig. 4, 2). In the lower part PSM V35 D763 Functional areas of the brain surface.jpgFig. 3.—The Functional Areas on the Brain Surface. The parallel lines show the situation of different areas: 1, area of motion; 2, area of sight; 3, area of hearing; 4, area of smell and taste; 5, area of touch. of the side the auditory area is situated, where impressions from the ear are received (Fig. 3, 3). On the under surface and in front of the auditory, the senses of taste and smell are located (Figs. 3 and 4, 4). Touch, which includes the senses of location and of movement, as well as those of temperature and pain, is assigned to the same area as that of motion, but extends a little farther back (Figs. 3 and 4, 5), and this overlapping of the two is not strange when we consider that our motions are guided by touch; think how differently you lift a heavy lamp or a fine bit of cotton-wool, and you will see how your grasp is guided by touch. These PSM V35 D763 Right half of the brain showing functional areas.jpgFig. 4.—The Median Surface of the Right Half of the Brain, showing Functional Areas. are the areas which are thus far discovered, but our knowledge of the brain is by no means complete, for there are large regions, on this African map, of undiscovered country. Fortunately, several Stanleys are on the way.

Let us now, accepting this theory of the localization or functions in the brain, go on to see how much it reveals to us regarding the process of thinking.

Although a part of our thinking is done by the aid of language, the greater part of it is carried on without the consciousness of actual words. Mental images are constantly passing