270 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



provided its left eye be closed. Munk assumes that 

 the image of memory of the whip or the burning 

 match had been deposited in the region A, and was 

 lost with the loss of this place. It can be shown that 

 Munk is as much mistaken concerning the psychic 

 character of the visual disturbance following the de- 

 struction of a small region in the occipital lobes, as 

 Hitzig was in regard to the psychic character of the 

 motor disturbances following the destruction of a 

 centre of the fore-leg. In the majority of cases the 

 removal of the region A t in one hemisphere produces 

 no visual disturbance. In the cases where a visual 

 disturbance is produced it is only temporary. I 

 noticed indeed that such dogs may no longer recog- 

 nise objects in the opposite eye, but the reason for 

 this is altogether different from that assumed by 

 Munk. 



It is known that in man the destruction of the 

 visual sphere in one hemisphere causes the same dis- 

 turbance as the destruction of the optic tract of the 

 same side namely, a hemianopia of the opposite half 

 of the visual field. This disturbance is not psychic 

 but purely physiological, inasmuch as it results in 

 a loss of irritability on one side of each retina, but not 

 in a loss in the processes of association. The same 

 occurs in a dog whose visual sphere has been injured 

 in one spot, with this difference, however, that the 

 loss of irritability is not complete. Thus if the left 

 occipital region be injured in a man, a hemianopia of 

 the left sides of both retinae follows, and the patient 



