186 



MR. F, E. BEDDARD ON THE ARTERIES 



[Feb. 2, 



In Myopotcmius coypii I detected some charactei'istics of the 

 arteries not observable in the other rodents studied by me. The 

 carotids * appear to be absent and the ophthalmic arteries descend 

 (or rather, of covirse, ascend) to the circle of Willis in close contact 

 with, and bound by connective tissue to, the optic nerve. That 

 of the left side is, as is shown in the accompanying drawing 

 (text-fig. 17), much larger than that of the right side. Before 

 reaching the circle of Willis each artery gives off a strong branch 

 to the pituitary body, from which arise several small arteries 

 running forward to and over the tuber cinereum to the optic 



Text-fig. 17. 



Base of brain of Mi/ojootamus coi/pti. 



a., callosal avtery; ce., junction of anterior and middle cerebrals; 

 o., ophthalmic arteries. 



chiasma. The anterior cerebellar artery divides very soon on the 

 left side, and a little later on the right, into two equisized branches. 

 In front of this the posterior choroidal and the posterior cerebral 

 arise by a common stem. Nearly opposite to, but a little in front 

 of, the entrance of the carotid into the circle of Willis arises a 

 stout artery (quite as large as the posterior cerebral) which im- 

 mediately plunges beneath the pyriform lobe. I suppose that this 



* The same state of affairs exists, according to Tandler, in Cavia cohaya. 



