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Show 196 ON THE ARTERIES OF THE BRAINS OF MAMMALS. [Feb. 2, Binturong agrees with other JEluroids, and that its alleged resemblances to the Arctoidea are not borne out by the facts put forward in the present paper. As to the Ungulata, m y observations refer only to Tragidus meminna, Gazella rufifrons, and Hyrctx capensis. Tlxe gexxexal plan appeax-s to be that of the Carnivora ; but, as will be seen in the drawing (text-fig. 21, p. 194), the two former agree in that the callosal gives off to the right side of tlxe brain a supplementary artery which forms a communication or communications with the olfactory artery. It will be seen from the figures referred to that-apart fx-onx details-thex-e is a real correspondence in these points between Gazella and Tragidus. I may finally call attention to tlxe antex-iox- cex-ebx-al artery in Tamandua. Whether the branch lettered "f" in the drawing (text-fig. 22. C, p. 195) is really the equivalent of that similarly lettex'ed in drawings of other brains or not, I a m unable to say, since it was broken off. Tlxe arteries " d," again, m a y have their counterpart in that similarly lettered in the figure of the brain of Myopotamus (text-fig. 22, A, p. 195). It is plain from the foregoing series of facts that tlxe callosal ax-tery in those mammals which I have had the opportunity of studying may have one or two soux-ces of origin. Ixx M a n and the Primates and in the Carnivora, the callosal artery or arteries arise from the anterior cerebx-al by one branch on each side, which is sometimes xxxox-e anterior in position, e. g. Viverra civetta, Tiger, or more posterior in position, e. g. Man, Apes, and Ursus syriacus. The point at which the callosal artery splits off from the anterior cerebral does not seem to be of impox-tance. Ixx tlxe Marsupials and Rodents there is this more anteriorly situated origin ; but it is reinforced by a branch or branches (that is one on each side), which arise from the cerebral artery further back, and join the callosal anteriorly. § Conclusions. I may briefly state the main conclusions to which the above facts appear to lead. (1) The much greater proportionate length of the basilar artery in all lower mammals as contrasted with M a n and the Primates. (2) The large size of the anterior spinal artery in Carnivora and in at least some Ungulates as compared with Rodents and Primates. In Carnivora the anterior- spinal arises by two trunks- one from each of the vertebral arteries, forming thus a continuous vessel of rhomboidal shape and of approximately equal diameter throughout. In Ungulates thex-e is not always such a connection, but the antex-iox- spinal is generally simply continuous with the basilar, and tlxe vertebrals are small. Tlxe existence of the rhomboidal area, of course, is not peculiar to Carnivora ; but the equality ixx calibre of its several component tubes is characteristic. (3) In M a n the middle cerebellar artery arises in front of the sixth nerve. In other mammals the general rule is for this |
