ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 



699 



way. Irritation of the auditory centers produces movements of the 

 ears, rotation and inclination of the head as in hearing sounds. 



Visual Center. In man, the visual center is in relation with the 

 corresponding half of each retina. The destruction of one of these 

 centers produces a bilateral hemianopsia, and not a total loss of 

 vision in the opposite half of the eye. The seat of the visual center 

 is in the cuneus. The anterior part of the visual center is in rela- 

 tion with the superior part of the retina ; the posterior portion of the 

 same center is in relation with the inferior part of the retina. 



Fig. 282. Areas and Centers of the Mesial Aspect of the Human 

 Hemicerebrum. ( MILLS. ) 



Irritation of the occipital lobes produces extensive movements 

 of the eyes. Excitation of the occipital lobe always produces move- 

 ments of the eyes, which are directed to the opposite side: to the 

 left when the right occipital lobe is irritated. It is evident that the 

 occipital lobes, whilst concerned in vision, also have efferent fibers 

 to centers beneath the cortex. The center for the memories of 

 objects seen is located in the right gyrus angularis. Ablation of 

 this area produces in man mind-blindness; that is, the person fails 

 to recall to mind the visual image of the appearance of an object, 

 although fully seen. This condition must not be confounded with 

 word-blindness, which is located in the left angular gyrus. 



