THE CEREBRAL HEMISPHERES i6i 



structure, as in position, it seems to correspond fairly 

 well with the somesthetic area (postcentral area, 1-3 

 of Brodmann) of higher brains. Both the anatomical 

 and the physiological evidence suggest that som- 

 esthetic and motor projection areas of the rat over- 

 lap and are largely coextensive, and that neither of 

 these cortical types has attained to more than incipi- 

 ent differentiation. 



Area/) occupies the position of the supposed audi- 

 tory projection cortex of lower mammals (20-22 of 

 Brodmann), and to this Fortuyn has devoted very 

 especial attention. We have no direct proof that this 

 cortex of the rat does serve the auditory functions, or 

 that auditory projection fibers do enter it from the 

 auditory area of the thalamus (medial geniculate 

 body). The latter point, however, has been estab- 

 lished for the rabbit by several workers, the most re- 

 cent of whom is Yoshida (1924). In these experiments 

 the supposed auditory cortex (area temporalis su- 

 perior et medialis) was destroyed on one hemisphere 

 and two weeks later the brain was prepared by Nissl's 

 method. On the operated side the cells of the ventral 

 part of the medial geniculate body were in pro- 

 nounced chromatolytic degeneration, and the author 

 concludes that fibers of the auditory sensory radia- 

 tions arise from these degenerated cells for distribu- 

 tion in the temporal cortical field. Presumably the 

 same anatomical connections are present in all ro- 

 dents, and Fortuyn endeavored to confirm the audi- 



