482 BRAIN MECHANISMS AND LEARNING 



retinal fibres at the optic chiasnia. This altered the rctino-ceutral relations 

 such that excitations from each eye were conducted in an afferent sense 

 only to the brain-half on the same side, as illustrated in Fig. i. Thereafter, 



Fig. 2 

 Chiasma-sectioned cat with one eye masked. A shifting of tlie nia^k troiu one 

 eye to the other results in a shift of retinal afferent stimulation from one brain- 

 half to the other. 



by occluding one or the other eye it was possible in these cats to determine 

 which of the two brain-halves was to receive afferent visual stimulation 

 during any given visual experience. A simple rubber mask was used as 

 shown in Fig. 2 to be applied only during periods ot training or testing. 



