Clark, Comparative Anatomy of the Insula. 83 



volutions are exposed in the sheep and elephant." He also says 

 (44, 123) " It is well marked and rises high up the Sylvian fis- 

 sure in the Proboscidians." In 1879 Spitzka (52 ) said that the in- 

 sula in the elephant is completely covered. The largest branch of 

 the medicerebral artery lies in what I have called the transinsular 

 fissure but this artery does not reach the dorsal margin of this area. 

 At about one-half or two-thirds of the distance from the ven- 

 tral boundary of the insula, the artery leaves the area to pass 

 dorsad into the Sylvian fissure. This peculiar condition seems 

 to have been brought about by the very unusual growth of the 

 area dorsad of the insula, which fold has been projected ventrad 

 as a rudimentary subopercular fold. 



THE INSULA IN THE RODENTIA. 



None of the members of this order so far as examined by 

 the writer showed any evidence of a macroscopic insula. Tran- 

 sections of the Sylvian region prepared by the Weigert method 

 failed to show the presence either of an insula or a claustrum in 

 the woodchuck. 



THE INSULA IN THE UNGULATA. 



With the exception of the primates, members of this order 

 seem in general to have reached a higher state of insular devel- 

 opment than those of any other order, a significant fact when it 

 is considered that this order is usually placed so far down the list 

 on account of other characters. The specimen of the camel here 

 shown (Fig. 22) can hardly be taken to indicate much more 

 than the existence of an insula in this animal. The area is 

 nearly flat and presents no fissures other than the circuminsular. 

 The insula is proportionally very small and shows on the whole 

 a rudimentary state of development compared with the sur- 

 rounding lobes. It was completely concealed within the Sylvian 

 fissure, the ventral end scarcely reaching the rhinal fissure ; the 

 wider end of the insula is dorsal. It is concealed and rudimen- 

 tary in the bactrian camel {Camcllus bactj'ianus). 



The deer (No. 961) presents a well defined area and at the 

 same time one not indicating a high degree of development. 

 The insula (Fig. 23) was completely concealed and is situated 



