1932] Poliak: Afferent Fiber Systems, Primate Cerehral Cortex 149 



The operation proved to be a shock for the animal, thoug'h some- 

 what less than in the foreg'oin^ case, and was followed by irregular 

 respiration. One hour after the operation the monkey was found, 

 however, already hang-ing high up on the wall of the cage. Eleven days 

 after the operation no gross disturbance of the ^asion was apparent, 

 so far as could be determined by simple obserA^ation of the behavior. 

 It is doubtful, however, that the monkey saw anything that fell into 

 the right halves of his visual fields. Two days later the animal did not 

 seem to notice objects falling into the right halves of his visual fields, 

 or at least he did not notice these with the same speed with w'hich he 

 noticed objects on his left side. When exploring the fur of his com- 

 panion his visual behavior — the converging of both eyes in filing and 

 the visual control of fine movements of his fingers — appeared remark- 

 ably aecurate. The next day the monkey with his left hand picked up 

 the pieces of the apple and raisins falling into the left halves of his 

 visual fields as far as the median sagittal plane. One day later the 

 attempt was made in the company of Dr. H. Kliiver to ascertain the 

 presence or absence of a homonymous hemianopsia. The monkey was 

 held by the extremities and by the neck in a fixed position by one 

 person while the other person, standing behind, advanced the objects 

 from the right or from the left side in such a way that the picture 

 of these would fall upon either the right or the left halves of the reti- 

 nae. The animal invariably moved his eyelids and turned his eyes 

 toward the stimulus when it appeared on his left side, but the eyes 

 and even the eyelids remained perfectly still when the object 

 approached from the right side. There was a marked difference in the 

 size of the pupils independent of the direction of the light. Three 

 days later the monlvey appeared to have some difficulties in exploring 

 the heap of vegetables and fruit strewn over the floor of the cage : he 

 slowly descended to the floor and at first cautiously surveyed the heap 

 for a few seconds before choosing a morsel. In exploring he invariably 

 used his left hand ; he did not reach with his hand to the right over the 

 midline (as did, for example, the monkey in the preceding case) ; at 

 most he picked up the morsel that lay directly in front of him. A day 

 later the monkey appeared fully recovered as far as his general 

 behavior and condition were concerned ; he was almost as vigorous and 

 active as before the operation. Nevertheless, disturbance of the vision 

 was the saime, as before : ability to see only to the left, to grasp and 

 take the morsels with his left hand, though afterwards when bringing 

 the food to the mouth he could use well either of the hands separately 



