HuBER, Innervatio7i of the Intracranial Vessels. ii 



majority of the slender, varicose fibrils, terminal branches of 

 the medullated nerves, end in the adventitia of the vessel or in 

 the surrounding connective tissue. When such varicose fibrils 

 are seen by the side of the vessel, their termination in the con- 

 nective tissue seems often easy to make out. When on the 

 surface of the vessel presented to the observer, careful focusing 

 will usually enable one to determine that, for the greater por- 

 tion of their course, at least, they are not in the muscular layer 

 of the vessel, although they are often in focus at the same time 

 as is the superficial part of the muscular coat. This statement 

 has reference especially to the larger vessels. In sections, pre- 

 pared as above mentioned, I have now and again found rela- 

 tively long segments of varicose nerve fibres in the adventitia, 

 having a course parallel to the long axis of the vessels. Sec- 

 tions are however not so serviceable as surface preparations in 

 the elucidation of this point, as it is impossible to obtain in a 

 section segments of nerve long enough to form an idea concern- 

 ing their course and relation to other nerve fibers. 



So far as I may judge from my own observations, I believe I 

 am warranted in making the statement that many at least of the 

 non-medullated, terminal branches of the medullated fibers ac- 

 companying the vessels of the pia, end in the adventitia of the 

 vessels or the fibrous tissue surrounding them ; whether all do 

 or whether some of them terminate in the muscular coat or 

 even under the endothelium, I must leave as an open question. 



In a number of preparations, medullated nerve fibers and 

 their terminal branches were seen in the pia-mater some dis- 

 tance removed from vessels. This I have seen more frequently 

 in the pia of the base of the brain and especially that portion 

 enclosed in the circle of Willis. In the pia covering the lateral 

 surfaces of the cerebral hemispheres such medullated nerve 

 fibers have not been found frequently, but often enough to war- 

 rant the statement that here also the medullated nerves term- 

 inate in the pia in regions free from vessels. No medullated 

 nerve fibers were found accompanying the veins of the pia. 

 These veins, as is well known, have no muscular coat, and are 

 therefore easily distinguished from the arteries in which the 



