108 K. S. LASHLEY 



right eye was closed. On the first day he seemed to discriminate 

 correctly whenever, in starting, his left eye was directed toward the 

 illuminated alley. There was a marked tendency to circus movements 

 towards the functional eye. On the second day he was not tested. 

 On the third and later days he made no errors and there was unmistak- 

 able secondary evidence of discrimination. 



Postoperative retention tests, per cent error 20 



After first day 



Lesion: Plate III, figure 8. The lesion is almost identical with 

 that of number 7, but more complete in the mesial region. 



After destruction of the greater part of the parietal and orbital 

 regions these animals gave good evidence of the retention of the 

 discrimination habit. If we disregard the records of the first day 

 (24 hours after operation) when both animals were in an abnormal 

 condition, we find that they showed perfect retention. Like the 

 frontal pole, the parietal and orbital regions are not functional 

 in the visual habit. 



Group 8. Occipital control. To determine whether or not the 

 shock of operation in the occipital region would produce loss of 

 the habit, irrespective of injury to the brain, I trephined the skull 

 in one animal in the region through which the occipital operations 

 were to be performed. 



Number 9. Small male (castrated), 115 days old. Trained in 

 brightness discrimination. 



Number of trials required for learning 60 



Preliminary retention tests, per cent error 2.5 



Two openings were made in the skull about two millimeters in front 

 of the parieto-occipital suture, similar to those through which opera- 

 tions on the occipital lobes were performed in other animals. The 

 brain was left with no other injury than that occasioned by opening 

 the skull. Retention was tested on the following day. Reactions 

 were prompt and without error. His behavior was quite uninfluenced 

 by the operation. 



Postoperative retention tests, per cent error 



Lesions: Plate III, figure 9. Except for adhesions in the area of 

 the trephine holes the brain was uninjured. 



