HuBER, Innervation of the Intracranial Vessels. 5 



are continued on the intracranial branches of the vertebral and 

 basilar arteries." 



Testus states that " in the course of the arteries of the cra- 

 nial pia-mater numerous nerves, arising probably from the carotid 

 plexus, may be found. Their branches have been found on 

 the small branches of the pial vessels, even such as penetrate 

 the convolutions. Nothing however is known about their 

 mode of ending." He asks the question, — " What is the ana- 

 tomical significance of the nerve plexus on the pial vessels? " 

 And answers, "It is very rational to think, they terminate in 

 the smooth muscle of the arteries, and that they become here, 

 as in other parts of the body, regulators of the circulation." He 

 further suggests the probability of there being nerves other 

 than vaso-motor on the vessels of the pia-mater, namely sensory 

 nerves, susceptible of being stimulated in the periphery and thus 

 becoming, both in normal and pathological conditions, points 

 of departure of reflexes. Kolliker refers to the nerves on 

 the cranial vessels in the following words. — "An der Hirn- 

 basis finden sich an den Arterien des Circulus Willisii viele 

 ahnliche Geflechte" [Reference is here made to nerve plexuses 

 on the vessels of the pia of the cord, first described by Purk- 

 inje] "welche mit Stammchen von hochtens 6^] fx mit den ver- 

 schiedenen Arterien, mit Ausnahme derer des Cerebellum, 

 immer dem Verlaufe desselben folgend, durch die ganze Pia 

 des Gehirnes sich ausbreiten, gedoch in ihren Enden nirgends 

 erkennen lassen ; doch verfolgte ich dieselben bis zu Arterien 

 von 90 /f und darunter in die Substanz des Gehirns hinein." 



' He further states that in the pia-mater of the brain, other than 

 sympathetic fibers (Plexus caroticus internus. Plexus vertebralis), 

 are to be found ; quoting Bochdalek to the effect that he had 

 traced numerous branches from the roots of four of the cranial 

 nerves to the perivascular plexuses on the vessels of the base of 

 the brain and the cerebellum. That there are nerve plexuses on 

 the larger vessels of the base of the brain, has long been known. 

 This is shown by the fact that Bourgery and Arnold described 

 very delicate nerve fibrils passing from the carotid plexus to the 

 anterior and middle cerebral and posterior communicating. In 



