ur, 



PHYSIOLOGICAL SERIES. 



The auditory nerves are indeed large, bat the mesial 



Vulate body, which it is customary to regard as an 



integral part of the cortical acoustic path, cannot even be 



_iuised as a projection behind the optic thalamus [see 



specimen I). 1*J3] ; so that it is unlikely that the cortical 



auditory tract is sufficiently largely developed to explain 



the large neopaUiom. Nor is the extent of the surface of 



the bodv, the tactile acuteness of which can hardly be 



heightened by its covering of spines, sufficient to explain a 



large tactile area in the cortex. Yet these are the factors 



which in lowly organised mammals are supposed to be the 



chief determinants of the extent of the neopallium. 



Fig. 38. (Nat. size.) 



OLF. BULB 



Dnboifl has clearly demonstrated that, among the more 

 lowly organised Mammalia the size of the cerebral corie\ 

 varies with the extent of the various sensory surfaces of 

 the hod y, and that the lowlier the position of the creature 

 in the Mammalian phylum the smaller this cortical repre- 

 sentation become-. I'ut in the Spiny Anteater all ihesn 

 generalisations are upset: for this small animal, with no 

 >p.-ci:iHy acute sense except that of smell and a high 

 degree of macrosiiiatism is usually associated \\itha small 

 neopallinm occupies the lowliest status in ihe Mammalian 

 hierarchy, and hence should have the feeblest cortical 

 ntation for its sense-organs. 



The cen-hral hemispheres are short and broad (fig. 38). 

 Th''ir growth in the antero-po-terior direction ajipears to 



