344 PHYSIOLOGICAL SERIES. 



D. 505. Two casts of the cranial cavity of u Yak (r<>e/>/i<i</</* 

 grunruent). 



The shape of this brain is very much like that of tin- 

 Elephant. 



ORDER SIBENIA. 



D. 506. The brain of a Manatee (Trichechus manatus), which had 

 been sliced in various planes by Mr. Garrod and partially 

 built up again. 



Amongst the whole series of placental mammals there i> 

 no other animal in which the brain presents feature- M 

 extraordinary and so bizarre as in the Sirenia. The only 

 parallel which can be found for the peculiar cases pre- 

 sented by the Manatee and the Dugong is that occasionally 



Fig. 198. (x|.) 



PSEUDO SYL.F. 



OLF. BULB 



-y \, PONS. 



SULC. ECTOSYL. OPT CHfASMA. * 



presented in the brains of idiots, in which the proces- of 

 elaboration has ceased in the earlier months of intra-utei -me 

 life, and the organ has simply grown in si/e without 

 l.--omiiig perfected in structure. 



In the two species of Manatee tin- *hape of the c'rcl>ral 

 hemispheres varies considerably, as Beddard ha- -hown 

 (Proc. Zool. Soc. 1897). 



The corc'nral betnisphere is a large thick- walled Madder 

 (figs. 198 & 200) with a very spacious ventricular cavity, 

 such ;i- i- Iniiud in In-tjil brains, but not usually in tho-e .f 

 animals. 



