1 62 BRAINS OF RATS AND MEN 



tory function of this cortex in rodents by other evi- 

 dence, with entirely negative results. Having made 

 a minute examination of the cortex of area ^ in several 

 kinds of rodents, he arranged these species in the 

 order of their supposed acuteness of hearing, as fol- 

 lows: squirrel, guinea pig, rat, mouse, rabbit, waltz- 

 ing mouse (totally deaf). Neither this nor any other 

 order of arrangement of these species is found to cor- 

 relate in any significant way with the relative size of 

 area/), with the relative thickness of its supragranular 

 cortex, with the number of spiral turns in the cochlea, 

 or with the number of nerve fibers in the cochlear 

 nerve. This does not prove, as Fortuyn points out, 

 that area p is not auditory cortex, but it certainly 

 leaves the question open for further study. 



Area w of the rat is clearly comparable with the 

 area striata, or visual cortex (17 of Brodmann) of 

 other vertebrates. This is supported by its position, 

 by its internal structure, and by physiological experi- 

 ments to be cited later. 



If now we compare the preceding data on the 

 cerebral cortex of the rat with Gray's similar charts 

 of the opossum (Figs. 36-37), the patterns are seen 

 to be very unlike. Comparison of the detailed descrip- 

 tions of the internal structure of the cortex of these 

 two animals enables us to recognize some of the cor- 

 responding areas. 



Area w of the rat is evidently directly comparable 

 with the area striata of the opossum. In the rat the 



