Page:Popular Science Monthly Volume 25.djvu/628

612 and their memories. The perception of sounds and sound-memories are destroyed when the lower lateral part of the brain (the temporal region) is injured, but are not affected as long as this region remains intact. When the anterior portion of this region is destroyed, the animal becomes deaf to sounds of a low pitch; when the posterior portion is injured, high notes are no longer heard. If the region is entirely extirpated, the animal is totally and permanently deaf. If it is only partly extirpated, the animal loses all memory of words or commands formerly recognized, attaches no meaning to the cry of its puppies, to the snap of the whip, or to its master's whistle. The perception of touch and its memories are destroyed when the upper lateral portion of the brain is injured (the parietal region). Voluntary motion is suspended when the antero-lateral portion is destroyed. If the destruction of this part is complete, the paralysis is permanent; if not, recovery is possible. In all these regions the distinction between actual and potential obtains: if the actual area only is cut out, the acquisitions already gained are lost; but, as long as some of the potential area remains, the power to acquire is present and recovery is possible.



A. Visual area; potential area of sight-memnories A1. Visual area; actual area of sight-memories before operation. B. Auditory area and potential area of sound-memories. B1. Actual sound-memories. C. Area governing motion and sensation in hind-leg of the opposite side. D. Area governing motion and sensation in fore-leg of the opposite side. E. Area governing motion and sensation in head or the opposite side. F, G. Area governing motion of the muscles of the eye and ear respectively of the opposite side. H, I. Area governing motion and sensation In neck and body of the opposite side.

Thus, by experiment, a number of regions are mapped out on the surface of the brain and the function of each is determined. When the results of the physiologists are compared with those of the anatomists, they are found to agree. The area of the brain which the physiologist has shown to govern sight has been shown by the anatomist