Page:Popular Science Monthly Volume 46.djvu/171

This page has been proofread, but needs to be validated.

ences of this kind, the impression produced by the pain being so much stronger than that produced by seeing the candle flame, the attempt to seize it is inhibited, and it finally comes about by means of these association fibers that the sight of flame immediately excites this inhibitory center. The cells and processes concerned transmit the impressions more readily by each repetition until the result becomes uniform; the child has learned something, and finally the desire diminishes. By the process of induction

PSM V46 D171 Communications between the brain and the body through sensory cells.jpg

Fig. 5.—a, skin on the surface of the body; 17, a sensory cell in the medulla oblongata; b, sensory cell in the cortex of the brain; c, motor cell in the cortex of the brain; D, cell in the cerebellum where muscular movements are coordinated; 3, motor cell in the spinal cord; m, muscle. The course of a stimulus at "a" can readily be followed to the cortex of the brain and back again to the muscle, resulting in a muscular movement.

from simple examples like this, those which are more complex may be explained. Here Nature inflicted the penalty in the form of bodily pain, which resulted in the establishment of a permanent inhibitory center. In a similar way society attempts, by