CEREBRAL FUNCTION IN THE RAT 83 



Lesion (plate II, fig. 12). Right hemisphere. First opera- 

 tion. There is a transverse incision just in front of the forceps 

 of the corpus callosum severing all of the anterior pole, except the 

 mesial cortex, down to the olfactory tracts. Second operation. 

 There is a lesion over the dorsal and orbital surfaces with com- 

 pletely degnerated cortex in the regions indicated in the figure. 

 Left hemisphere. First operation. There is a lesion extending 

 from the end of the forceps of the corpus callosum to the mesial 

 cortex and ventrad into the olfactory fiber tracts. All of the 

 mesial co/tex anterior to the knee of the callosum is destroyed 

 but little injury has been done to that of the lateral face of the 

 anterior pole. Second operation. There is a lesion over the 

 dorsal and orbital surfaces of the hemisphere extending along 

 the fibers of the external capsule over the area indicated, with 

 complete degeneration of the overlying cortex. 



Experiment 13 (page 12). Retention nearly perfect. Errors: 

 learning 3, retention 0. 



Lesion (plate II, fig. 13). Right hemisphere. First opera- 

 tion. There is a complete transverse section of the anterior 

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

 the level of the olfactory tracts. Second operation. There is a 

 lesion extending from the first backward along the external 

 capsule to the posterior border of the hippocampus, narrowing 

 forward below at the level of the lateral ventricle. All the cor- 

 tex overlying the lesion is completely degenerated. Left hemi- 

 sphere. First operation. Transverse section of the anterior 

 pole extending downward to just above the level of the olfac- 

 tory tracts. Second operation. There is a longitudinal incision 

 extending backward in the external capsule from the first lesion 

 to the posterior edge of the hippocampus, covering the entire 

 orbital surface down to the olfactory cortical funiculus. All the 

 overlying cortex is degenerated. 



Experiment 14 (page 13). No retention. The animal de- 

 veloped hemiparesis and was stupor ous. 



Lesion. An invasion of the thalamus by an extensive clot was 

 determined by gross dissection. 



Of the fourteen animals described in this series thirteen gave 



