8 THE TONER LECTURES. 



tion of sight. The cases that can serve as proof are, therefore, 

 ]iot those alone in which we find that the disease exists, since 

 the loss of sight exists when there is a disease. The cases that 

 can serve positively must clearly bring us to a conclusion ; as 

 those, on the contrary, which establish that an injury in any 

 part or one-half of the brain — even in that part which receives 

 the optic track — can exist without producing any loss of siglit; 

 and that fact has been observed — more than five or six times to 

 my knowledge — and in those cases in the most decisive manner. 

 Therefore the conclusion I have drawn is estal)lished. Either 

 half of the brain may serve for the function of sight. 



Now, as regards the volitional movements, the voluntary 

 movements, if you like to call them so. Those movements, as 

 you well know, have been considered as depending on each half 

 of the brain for one-half of the body. Still, many physiologists 

 have ascertained that there are muscles in our system in the 

 neck, in the eye, in the throat, and in the back also, which 

 escape paralysis when there is disease in one-half of the brain ; 

 and for these cases a theory has been imagined to explain how 

 it was that the left half of the brain, for instance, is not the 

 regulator of the movements in the right side of the body. I 

 shall pass over that theory, and come to the point of importance 

 in the object which I have in view. 



As regards volitional movements, there are cases on record 

 which leave no doubt that either the anterior lobe of the brain, 

 the middle lobe, or the posterior lobe, the three essential parts 

 of the organ, can be destroyed and voluntary movements not 

 be interfered with at all. There are many cases — perhaps the 

 word " many" is too strong, but there are at least seven or eight 

 to my knowledge — of the destruction of the whole half of the 

 brain without any interference with the voluntary movement. 

 Therefore we are not to look upon one-half of the brain as being 

 necessarily the organ serving to the movement of the body on 

 the opposite side. And also another inference ; we are to look 



