HuBER, Innervation of the Intfacranial Vessels. 7 



removed from the base of a cat's brain, was reflected by camera 

 lucida. From the same preparation the nerve bundles are 

 sketched in semi-diagrammatically, only a sufficient number of 

 nerve fibers being sketched to give the general course of the 

 larger bundles of meduUated nerves. In the preparation a rela- 

 tively large bundle of meduUated nerves divides into two 

 branches, the one, a, accompanying the posterior commu- 

 nicating branch. This bundle and its branches could be fol- 

 lowed along this artery on to the posterior cerebral of the 

 side on which the nerves are sketched and on to the posterior 

 cerebral of the opposite side. In this bundle, I was able to 

 count, at its origin, some twenty relatively large meduUated 

 fibers. The other branch, b, containing ten large meduUated 

 fibers, accompanies the middle cerebral. The nerve bundle, c, 

 I regarded as a continuation of b, although the connection is not 

 apparent, as the nerves on the intervening portion of the vessels 

 were practically unstained. The bundle of meduUated nerves 

 on the basilar artery, in which I was able to count 1 5 large 

 nerve fibers, divides into branches which follow the right and 

 left posterior cerebral. The branch on the left side was traced 

 to the middle of the posterior communicating artery. There 

 are then, and this may be emphasized, no distinct areas of dis- 

 tribution for the meduUated nerve fibers, accompanying the pial 

 vessels and coming from the two sources above mentioned. The 

 bundles of meduUated nerve fibers on the vessels forming the 

 anterior part of the circle of Willis, are distributed to half of the 

 circle of Willis and from this to the arteries arising from it, and 

 to some extent to the opposite side of the circle of Willis ; the 

 meduUated nerves entering with the basilar artery are distribut- 

 ed, in part, at least, to the anterior portion of the circle of 

 Willis. 



The meduUated nerve fibers here under discussion undergo 

 repeated division, such division taking place at the nodes of 

 Ranvier; the resulting branches now and then seem to run parallel 

 for a distance, again diverging at acute or obtuse angles. Such 

 branching is repeatedly observed at places where the artery 

 divides, one branch of a dividing meduUated nerve accompany- 



