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THE POPULAR SCIENCE MONTHLY. 



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 en- 

 tirely extirpated, the animal is totally and permanently deaf. If it is 

 only partly extirpated, the animal loses all memory of words or com- 

 mands formerly recognized, attaches no meaning to the cry of its pup- 

 pies, to the snap of the whip, or to its master's whistle. The percep- 

 tion of touch and its memories are destroyed when the upper lateral 

 portion of the brain is injured (the parietal region). Voluntary mo- 

 tion 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. 



FlQ. 1. 



Brain of a Dog. Diagbam or Munk. 



A. Visual area ; potential area of siffht-memories. 



A-y. Visual area ; actual area of sight-memories before operation. 



B. Auditory area and potential area of sound-memories. 5,. Actual sound-memones. 



C. Area governing motion and sensation in liind-leg of the opposite side. 

 r>. Area governing motion and sensation in fore-leg of the opposite side. 



E. Area governing motion and sensation in head of the opposite side. 



F, O. Area governing motion of the muscles of the eye and ear respectively of the opposite Side. 

 H, I. Area governing motion and sensation in ueck 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 anato- 

 mists, they are found to agree. The area of the brain which the physi- 

 ologist has shown to govern sight has been shown by the anatomist 



