Page:Popular Science Monthly Volume 42.djvu/781

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STRUCTURE, ACTION, AND THOUGHT.

they have been found by Horsley and Schäfer exactly in the place where, according to our idea, they ought to be, at the marginal convolution connecting the first and last centers of which we have just spoken and thus completing the circle of action.

Here I would like to draw your attention to the fact that great painters like great poets often appear to see more than ordinary mortals, and in his lovely picture, The Fall of Man, which is painted on the walls of the Loggia of the Vatican in Rome, Raphael seems to have almost forestalled the results of physiological experiment. In the mental picture of the scene which most of us must have formed for ourselves it is probable that it did not occur to many of us to pay any attention whatever to the movements of the great toe, and yet in Horsley's diagram of the cortical centers that for the hallux comes forward most prominently, and, as you will see from Raphael's picture (Fig. 15), Eve's foot is raised, and the great toe both in her foot and that of Adam is brought into what one would think rather too violent action. In the action of plucking and eating the fruit there is no break between the eyes, head, and arm, and that of the mouth and tongue, and in the usual process of eating the actions go on which are necessary simply to repeat the process of plucking and eating. Again, too, in the dog the arrangement is quite different (Fig. 11), and yet it is exactly what one would expect from the different necessities of the animal. In the frugivorous animal the motions are pluck and eat, pluck and eat; but in the carnivorous animal a long chase after the prey is necessary before thePSM V42 D781 Diagram of the nerve connections inner capsule.jpgFig. 12.—Diagram of the Internal Capsule. animal can bring the jaws into action, and in the dog accordingly we find that the movements of mastication, instead of being arranged in linear series with those of the limbs, are represented at a spot which is somewhat removed from them. In the cortex the centers are so far apart as to be distinguishable from one another; but as the nerve fibers which pass downward from them to the base of the brain become closely crowded together in the internal capsule, localization is more difficult (Fig. 12), although Horsley and Beevor have found generally that the arrangement of the fibers from before backward corresponds to the arrangement of the centers just described. But