CEREBRAL FUNCTION IN THE RAT .81 



Lesion (plate II, fig. 6). The operation was by a single 

 median opening. There is an extensive destruction of cortex at 

 the opening in the skull and a transverse cut extending ventrad 

 from it past the knee of the corpus callosum, destroying all the 

 cortex lying between and in front of the forceps of the callosum. 



Experiment 7 (page 11). Retention nearly perfect. Errors: 

 learning 11, retention 1. 



Lesion (plate II, fig. 7). Right hemisphere. There is a 

 transverse cut extending forward from over the knee of the cor- 

 pus callosum, through the forceps to the fibers of the peduncle. 

 There is a large cyst in the mesial cortex of the frontal pole. 

 The destruction is probably limited to the dorso-medial surfaces 

 of the lobe. Left hemisphere. The lesion extends from the tip 

 of the frontal pole along the course of the fibers to the end of 

 the forceps, then turns laterad along the external capsule for a 

 short distance and finally out along the course of the radial 

 fibers to the cortex. 



Experiment 8 (page 11). Partial retention. Errors: learn- 

 ing 7, retention 3. The brain was so damaged in sectioning that 

 nothing could be made of the extent of the lesion. 



Experiment 9 (page 12). Nearly perfect retention. Errors: 

 learning 23, retention 2. 



Lesion (plate II, fig. 9). Right hemisphere. There is a sec- 

 tion of the hemisphere from above the knee of the corpus cal- 

 losum diagonally forward to the base of the olfactory bulb. 

 The lesion is superficial, destroying chiefly the mesial cortex in 

 front of the callosum and above the olfactory tracts. Left 

 hemisphere. There is a complete transverse section similar to 

 that on the right but extending around onto the orbital surface. 



Experiment 10. (page 12). Nearly perfect retention. Errors: 

 learning 33, retention 2. 



Lesion (plate II, fig. 10). Right hemisphere. First operation. 

 There is a transverse incision extending ventrad in a plane pass- 

 ing through the end of the forceps of the corpus callosum to the 

 base of the olfactory bulb, destroying all the frontal pole, which 

 is filled by a large cyst, and cutting a part of the olfactory tract. 

 Second operation. There is a small incision extending down 



PSYCHOBIOLOQY, VOL. I, NO. 2 



