HuBER, Innei'Vatmi of the Intracranial Vessels. g 



sufficient number of observations have been made on the dog 

 and rabbit to enable me to say that the endings described for the 

 cat hold good for these animals also. 



The most successful preparation obtained, showing the 

 mode of termination of the medullated fibers accompanying the 

 pial vessels is reproduced in Fig. 2, which gives the ending of 

 a single medullated nerve fiber as seen under the 1-12 in. oil im- 

 mersion. The preparation was unusually fortunate, as owing to 

 the caprice of the methylen blue method, in the region of the 

 vessel — posterior cerebral — from which the drawing was made, 

 beside the branches of this one nerve, only a few coarse medul- 

 lated branches with some few non-medullated fibers were 

 stained. As may be seen from this figure, the medullated fiber, 

 after reaching the vessel, gives off a number of relatively large 

 medullated branches which leave the parent fiber at nodes of 

 Ranvier ; these primary branches divide further into medullated 

 fibers of a second order, and of somewhat smaller size, some 

 of which divide still further into still smaller medullated branches. 

 The medullated branches terminate at a longer or shorter dis- 

 tance from the parent fiber in fine, varicose, non-medullated, 

 terminal fibrils, which may often be traced for relatively long 

 distances before they end, and this usually in a small granule or 

 nodule. Similar non-medullated fibrils proceed from the med- 

 ullated fibers, at nodes of Ranvier. These terminal, varicose 

 fibrils have, as the figure may serve to show, a course which 

 may be parallel or oblique to the long axis of the vessel, and 

 therefore not parallel to the long axis of the non-striated muscle 

 cells of the vessel wall, a fact to which I draw attention at this 

 time, for reasons which will appear later. Complete, or even 

 nearly complete endings such as shown here I have not often 

 met. In well stained preparations, varicose fibrils such as above 

 described and having a similar course, are met with in connect- 

 ion with the pial vessels in all parts of the pia-mater of the 

 cerebral hemisphere, even on vessels with a musculature con- 

 sisting at most of two or three layers of non-striated muscle 

 cells. It is often somewhat difficult, however, and again impos- 

 sible, to trace them for distances long enough to ascertain their 



