184 



MR. F. E. BEDDARD ON THE ARTERIES 



[Feb. % 



§ Circle of Willis and Basilar Artery. 



Chinchilla lanigera. — Of this Rodent I have examined two brains. 

 One is so perfectly injected that it appears to me to be worth 

 figuring (text-fig. 16) and describing in detail, as a contribution 

 to the knowledge of the cerebral cii'culatory system in mammals. 

 Commencing at the posterior end, the two vertebral arteries unite 

 to form the basilar artery. Close to their jiinction two arteries on 

 the left and three on the right are given ofi', which appear to be 

 collectively the equivalents of the inferior cerebellar arteries of Man. 



Text-fiff. 16. 



Base of brain of Chinchilla lanigera. 



a.sp., anterior spinal artery; ce., junction of middle and anterior cerebral arteries ; 

 op., oplitlialmic arteries; v., vertebral arteries. 



They are, however, mainly arteries for the supply of the meduUa 

 and adjacent parts, and if they reach the cerebellum at all it is 

 only their most feeble twigs that do so. Close up to the junction 

 of the vertebrals rises by a root from each the minute and back- 

 wardly running anterior spinal artery. Further up the basilar 

 artery, but well behind the origin of the sixth nerves, arises 



