CEREBRAL FUNCTION IN LEARNING 113 



animals could see perfectly well after the occipital destruction. 

 Vision in the rat is difficult to detect without prolonged training, 

 but some indication of vision is given by the following observa- 

 tions. The animals would jump up and grasp the edges of 

 training box accurately although the depth of the box was so 

 great that they could not reach the top of it with their vibrissae, 

 even when they stood on tip toe. They would also leap across 

 a space too broad to be spanned by their vibrissae but showed 

 greater hesitation in this than do normal animals. Finally they 

 relearned the problem in no greater time than the average of 

 normal animals, which could scarcely have occurred had they 

 been handicapped by cortical blindness. The operation which 

 destroyed the visual habit did not destroy the ability to see. 



The destruction of the occipital pole did not result in a loss of 

 all habits, but only in the loss of the visual one. The accurate 

 running of the discrimination box requires not only the formation 

 of the sensory habit but also a great many adjustments to the 

 box. The animal learns to go directly through the alleys to the 

 food, to turn back and pass through the discrimination compart- 

 ment and second alley without a pause in case the wrong alley 

 was chosen first, to claw at the door of the starting compartment 

 in case the experimenter is slow in releasing him, and to grab a 

 double handfull of food as the experimenter transfers him to the 

 starting compartment. All these activities appeared in the rats 

 with occipital lesions. The tactile and kinaesthetic motor habits ^- 

 were retained, only the visual habit was lost. Von Monakow 

 ('14) has criticized Franz's experiments on the ground that they 

 merely produced a 'protracted clouding of the sensorium' similar 

 to that following skull-fracture in man and that the loss of 

 habitual reactions after injury to the frontal lobes was merely a 

 diaschesis effect (shockartige Stoning). The complete elimina- 

 tion of one habit with the perfect retention of other probably no 

 less complicated ones after occipital lesions speaks very strongly 

 against Von Monakow's view and in favor of the one advanced 

 above, that the loss is due to the interruption of specific reflex 

 arcs. 



P8TCHOBIOLOGT, VOL. II, NO. 1 



