1904.] 



OF THE BRAINS OP MAMMALS. 



195 



the human arterial arrangement ajDpear to be the long distance 

 from the middle cerebral artery of the anterior communicating 

 artery, and the fact that the two callosals fuse together immedi- 

 ately after their origin from the anterior cerebrals. Suricata 

 tetradactyla and Arctictis have a cerebral arterial system which is 

 constructed upon the same plan. 



It will be remembered * that the cerebi'al arterial system of 

 Man diffei's from that of, at any rate, some Apes and Lemurs in 

 the fact that there is an anterior communicating artery and that, 

 apart from this connection, the two callosal arteries I'emain 

 separate. In the Apes and Lemurs, on the other hand, the two 

 callosal arteries are given off early and immediately fuse to form 

 a single callosal artery which, later, divides. This condition 

 seems to me to be simply an exaggeration of the anterior com- 

 municating artery. Now precisely the same thing occurs among 



Text-fig. 22. 

 0. 0. 



Anterior cerebral system of (A) Myopotamus coijpu, (B) Lagostoum s 

 tricJiodactylus, (C) Tamandua tetradactyla. 



For d andy see text, p. 196. Otlier letters as in text-fig. 21. 



the Carnivora. In the genei'a Ursits, Ictonyx, Galictis, and 

 Mustela the disposition of the callosal arteries is as in the Apes ; 

 while, as already mentioned, certain ^luroid genera agree with 

 Man. The classificatory significance of this cannot be passed 

 over ; and I would specially direct attention to the fact that the 



* See for example Beddard, supra, p. 161. 



13-^ 



