1904.] 



OF THE BRAINS OF MAMMALS, 



191 



this artery is that it arises in front of the sixth nerve as in Man, 

 and not behind it as in at least many other mammals. The 

 anterior cerebellar artery has also a somewhat anomalous position 

 and character. It arises fi'om the basilar artery before — but only 

 just before — the latter divides to form the circle of Willis. On 

 the i"ight side the anterior cerebellar artery divides soon into two 

 equisized branches. On the left side there are also two branches, 

 but they arise separately from the basilar artery. Another 

 remarkable fact is that a strong branch arises on the left side 

 from the middle cerebral and joins the anterior cerebral after a 

 near-ly straight course. This branch lies to. the ovitside of the 

 third nesrve. On the right side is a corresponding, but more 

 slender and perhaps even slightly imperfect anastomosis. 



Text-fig. 20. 



■ ce. 



Base of brain of Tragiilus meminna. 

 ce., middle cerebral artery ; mc, middle cerebellar arterj' ; o., oplithalmic artery. 



The posterior cerebral artery divides, as in other mammals, 

 and at once, into two main branches. The anterior (which on 

 the left side of the brain arises separately from the circle of 

 Willis) immediately buries itself below the lobus pyriformLs. The 

 posterior branch divides again into several others, which run at 



