196 ox THE ARTERIES OF THE BRAINS OF MAMMALS. [Feb. 2, 



Binturong agrees with other ^luroids, and that its alleged 

 resemblances to the Arctoidea are not boiiie out by the facts put 

 forward in the pi-esent papei'. 



As to the XJngulata, my observations refer only to Tragidus 

 meminna, Gazella riififrons, and Hyrax cajyensis. The general 

 plan appears 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 oft* to the right side of the 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 fi'om details — there is a real coi-respondence in these 

 points between Gazella and Tragulus. 



I may finally call attention to the anteiior cerebral artery in 

 Tamandua. Whether the branch lettered "/'" in the drawing 

 (text-fig. 22, C, p. 195) is really the equivalent of that similarly 

 lettered in drawings of othei- brains or not, I am unable to say, 

 since it was broken oft". The arteries " d," again, may have theii' 

 counterpart in that similarly lettered in the figure of the brain of 

 Myopotatwas (text-fig. 22, A, p. 195). 



It is plain from the foregoing series of facts that the callosal 

 artery in those mammals which I have had the opportunity of 

 studying may have one or two sources of origin. In Man and 

 the Primates and in the Carnivoi'a, the callosal artery or artei'ies 

 ai*ise from the anterior cerebral by one branch on each side, which 

 is sometimes more 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 anterioi- 

 cerebral does not seem to be of importance. In the Mai'supials 

 and Rodents there is this more anteriorly situated origin ; but it 

 is reinforced by a branch or bi-anches (that is one on each side), 

 which arise from the cerebral artery furthei' 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 conti-asted with Man and the Pidmates. 



(2) The laig-e size of the anteiior 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 ai'teries, forming thus a continuous 

 vessel of rhomboidal shape and of approximately equal diameter 

 throughout. In Ungulates thei-e is not always such a connection, 

 but the anterior spinal is generally simply continuous with the 

 basilar, and the vertebrals are small. The existence of the i-hom- 

 boidal area, of course, is not peculiar to Carnivoi'a ; l^ut the equality 

 in calibre of its several component tubes is characteristic. 



(3) In Man the middle cerebellar artery arises in front of the 

 sixth nerve. In other mammals the general rule is for this 



