NERVOUS SYSTEM. VERTEBRATA. 243 



Aard-vark, and many Rodents, but in many Ungulates and 

 Rodents there is no such lateral expansion in a feather-like 

 pattern, but a simple transverse arrangement of the folia. 



In the Primates this region of the cerebellum becomes 

 so enormously expanded that it forms the great mass of 

 the organ. 



The third lobule consists of an extremely narrow mesial 

 bridge connecting two large vertical worm-like masses, 

 which extend downward on the caudal surface and separate 

 the posterior lobe from the paraflocculus. 



The fourth lobule consists of the pyramid, which is 

 laterally joined to the dorsal paraflocculus by a narrow 

 band, which has become so compressed by the downward 

 growth of the third lobule as to be recognised with difficulty 

 in the Cat's brain. It is, however, clearly shown in such 

 brains as that of Lepus and Cabassous. 



Burt G. Wilder, Proc. Arner. Phil. Soc. 1881, p. 524. 



D. 291. The brain of a Oat (Felis domesticd), in which the corpus 

 callosum has been cut through in a sagittal direction and 

 the cerebral hemispheres widely divaricated. 



The caudate nuclei lying in the lateral ventricles have 

 been thus exposed. The optic thalami have been drawn 

 asunder and the soft commissure partially torn through, so 

 that the slit-like third ventricle has been converted into a 

 widely open space the limits of which are indicated by the 

 taenise thalami, which together form a semicircle. The 

 corpora quadrigemina are exposed, and external to the 

 anterior quadrigeminal body the large mesial geniculate 

 body may be seen immediately behind the optic thalamus. 

 This mesial geniculate body may also be well seen upon 

 the left side of the base of the brain, the natiform portion 

 of the pyriform lobe having been removed in order to 

 expose it. 0. C. 1325 D. 



D. 292. The brain of a Cat (Felis domestica) presenting an 

 anomalous arrangement of the cerebral sulci. 



On the right hemisphere the pseudosylvian sulcus is 

 very short, and on the^ left is reduced to a mere notch in 



R2 





