82 K. S. LASHLEY AND S. I. FRANZ 



from the dorsal convexity through the fornix and internal cap- 

 sule and penetrating the thalamus in the region of the lateral 

 thalamic nucleus. Left hemisphere. First operation. The 

 lesion is similarly placed to that on the right but more super- 

 ficial, passing just under the cortex through the end of the for- 

 ceps to the base of the olfactory bulb. It narrows at the base 

 and does not involve the olfactory tracts. The entire pole 

 exclusive of the mesial cortex is destroyed, however. Second 

 operation. There is a transverse lesion extending down from the 

 dorsal convexity just in front of the hippocampus, cutting through 

 the fornix and penetrating the crux cerebri for one half its width. 



Experiment 11 (page 12). Perfect retention. Errors: learn- 

 ing 11, retention 1. 



Lesion (plate II, fig. 11). Right hemisphere. First operation. 

 There is a transverse section of the hemisphere just back of the 

 knee of the corpus callosum and extending diagonally laterad 

 to the cortex along the forceps of the callosum and ventrad to 

 the floor of the lateral ventricle. The ventricle is distended 

 until it occupies one-third of the width of the hemisphere. Sec- 

 ond operation. There is a superficial incision extending from above 

 the anterior end of the lateral ventricle to the posterior border of 

 the corpus callosum and laterad along the external capsule to 

 the level of the thalamus. There is a large cyst replacing the 

 fibers of the external capsule in the occipital lobe. Left hemis- 

 phere. First operation. There is a transverse lesion just behind 

 the knee of the corpus callosum extending downward to the level 

 of the fornix. Internally it extends deeper, pentrating the olfac- 

 tory fibers in the region of the anterior olfactory nucleus. Sec- 

 ond operation. There is an incision passing in from the cortex 

 to the external capsule near the posterior limit of the first lesion, 

 thence extending backward along the external capsule for an in- 

 determinate distance. The external capsule is largely replaced 

 by a cyst extending into the occipital pole. The frontal poles 

 of both hemispheres were completely severed from the rest of 

 the brain by the first operation. 



Experiment 12 (page 12). Retention perfect. Errors: learn- 

 ing 2, retention 0. 



