680 Dynamic Theory. 



tire change in his intellectual character. It does not appear from this 

 report that all the sight memories were lost, but there is nothing to show, 

 as in the other case, which of the hemispheres was injured. Most 

 likely, however, it was only one, and the few saved memories were in 

 the other. 



' ' Such a loss of visual memories may be temporary, as is well illus- 

 trated by the case of a city district messenger-boy, who found on several 

 occasions that he suddenly lost his way, and could not recognize streets 

 with which he was usually familiar, so that he was obliged to ask a po- 

 liceman to take him to his home, where, however, in the course of a few 

 hours he recovered his memory of places and of faces, which he had 

 lost. In this case, which may be regarded as one form of epilepsy, the 

 loss of memory can be explained by the hypothesis that a spasm of the 

 arteries occurred in the posterior part of the brain, just as such a spasm 

 in those of the face gives rise to a sudden pallor." The contraction of 

 the blood vessels expels the blood, and deprives the cells of their essen- 

 tial supply. 



The law that the habit of use strengthens and improves an organ in 

 its function, applies to the brain as well as to muscles and sense organs. 

 The converse is likewise true, that is, that the disuse of the brain, or 

 any special part of it, leads to the loss or impairment of its functional 

 force, and to its anatomical degeneracy. See case of atrophy of an op- 

 tic nerve, no doubt accompanied by atrophy of the cortical center in 

 consequence of blindness, fig. 377. When any external organ or any 

 muscle is destroyed, or rendered through some accident, unable to per- 

 form its function, the brain cells with which such organ is connected, 

 will be left without anything to do. And this inactivity will, in course 

 of time, work the atrophy of such cells. ' ' If, from a new-born animal 

 you remove an eye, the nerve tract leading to the posterior part of the 

 brain, and that part of the brain, will never be brought into use, and 

 hence they never develop to a normal size. If a child is born blind, or 

 loses his eyesight in infancy, the same is true, so that when in old age 

 he dies, the posterior part of his brain will be found small and shrunken. " 

 (Dr. Star. ) It is inferred that the hearing and articulating cells of the 

 deaf and dumb are atrophied. It has been proved in hundreds of cases 

 that disease of the articulating cells destroys the function of articula- 

 tion ; so that the inference of a converse reciprocity is obviously well 

 taken. " It is known that if a limb be amputated, and the individual 

 live for twenty years or more, the part of the brain which formerly gov- 

 erned the movements of that limb, and which received sensation from 

 it, will be found shrunken and withered. " 



The fact that the protracted disuse of the brain cells finally involves 

 the loss of their plasticity, fully accounts for the circumstance that all 



