CEREBRAL FUNCTION IN THE RAT 103 



slowly about the floor of the restraining cage but made no at- 

 tempt to climb up to the plane in more than an hour. On the 

 following day he was more active but gave marked fear reac- 

 tions, squeaking and jumping blindly against the sides of the 

 cage when touched and biting at the experimenter's hands or 

 at his own feet when he was picked up. This behavior persisted 

 for four days, then he became more normal and on the eighth 

 day after the operation he solved the problem box five times. 

 On the following day he was spastic and on the tenth day after 

 the operation died. His average time per trial on the five suc- 

 cessful trials was: to plane, 138 seconds; to door, 50 seconds. 

 At no time in the retention tests did the plane seem to have any 

 more intense stimulating value than other parts of the problem 

 situation. The only evidence for retention is the short time 

 required for solving the problem, and this may be merely a 

 chance variation. 



Lesion (plate III, fig. 25). Right hemisphere. There is a 

 lesion over the dorsal surface of the gyrus hippocampus, extend- 

 ing cephalad along the roof of the lateral ventricle, then ventrad 

 through the knee of the corpus callosum, transsecting the corpus 

 striatum and extending to the base of the hemisphere. A large 

 cyst has been formed filling the greater part of the frontal pole 

 and the anterior half of the corpus striatum is degenerated. 



Left hemisphere. There is a large pit on the dorsal con- 

 vexity, extending down around the gyrus hippocampus and a 

 transverse incision extending from this through the anterior 

 horn of the lateral ventricle to the base of the olfactory bulb, 

 completely severing the anterior pole. 



After practically complete destruction of the anterior third of 

 both hemispheres this animal succeeded in solving the inclined- 

 plane problem in considerably less time than that usually required 

 by normal individuals and in kss than one fourth of the time which 

 he took for an equal number of trials in the initial training. 



Experiment 26. The frontal poles of both hemispheres of a 

 small male rat, 143 days old, were incised through large open- 

 ings in the parietal bones. He had been trained on the inclined- 

 plane box for 40 trials. The average time required per trial 



