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Show 184 MR. F. E. BEDDARD ON THE ARTERIES [Feb. 2, § 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 m e to be wox-th figuring (text-fig. 16) and describing in detail, as a contribution to tlxe knowledge of tlxe cerebx-al circulatory system in mammals. Commencing at tlxe posterior end, tlxe two vertebral arteries unite to form the basilar artery. Close to their junction two arteries on tlxe left and three on tlxe right are given off, which appear to be collectively tlxe equivalents of the inferior-cerebellar arteries of Marx. Text-fig. 16. Base of brain of Chinchilla lanigera. a.sp., anterior spinal artery; ce., junction of middle and anterior cerebral arteries ; op., ophthalmic arteries; v., vertebral arteries. They are, however, mainly arteries for the supply of the medulla and adjacent parts, and if they reach the cerebellum at all it is only their- most feeble twigs that do so. Close up to tlxe junction of the vex-tebrals rises by a root from each the minute axxd back-wardly running anterior spinal artery. Further up tlxe basilar artery, but well behind the origin of the sixth nerves, arises |