122 



PHYSIOLOGICAL SERIES. 



cerebellum, in open communication respectively with the 

 aqueduct of Sylvius and the fourth ventricle. The limits of 

 the va>eular and non-vascular portions 'of the membranous 

 roof of the fourth ventricle are also very clearly shown. 



D 144. The left cerebral hemisphere of the previous specimen 

 divided lv a longitudinal vertical section and with the two 

 halves mounted to show the internal surface. 



Fig. 32. 



The lateral wall. The mesial 



Chelone my das, left hemisphere. 



Tin- corpu- -triatum (which is seen in the lower part of 

 the lateml mid ventral walls of the ventricle) is relatively 

 very small. It consists of a narrow and thin hand of 

 matter that extend-, in the floor of the ventricle, from the 

 olfactory prdimele in front to the anterior end of the optic 

 thalamu- behind, and I'n-.- \\itli the latter l.ody hcneath 

 the foramen of Monro. In its slenderness and "eneral 

 relation^ it re-eniMe- the rorpn- .-triatum of Amphihia and 

 Splif" nd diflers in these respects markedly from 



that of Ophidia, Lacertilia, and Mammalia. 



