382 NERVOUS SYSTEM. 



by a sort of knot to the posterior fasciculi, or root of the first and 

 second cervical nerves; this knot, seems to be neither after the 

 fashion of ganglion or plexus, but is peculiar, and looks some- 

 what as if one nerve was wrapped around the other. 



This nerve varies in respect to the number of its roots, and 

 the mode of their origin. In all cases, the trunk, thus formed, 

 passes from the cranium through the foramen lacerum posterius, 

 traversing there the dura rflater, either in a sheath common to it 

 and to the pneumo-gastric nerve, or in its own particular open- 

 ing behind that of the latter. 



Its general distribution is to the muscles and to the integu- 

 ments of the neck. 



The Hypoglossal Nerve, (Nervus Hypoglossus, or Ninth Pair,) 

 arises from the medulla oblongata, by several fasciculi placed 

 one above the other. The roots of these fasciculi spring from 

 the fissure which separates the corpus pyramidale from the cor- 

 pus olivare, being traced to that surface of the corpus pyrami- 

 dale. The fasciculi are from four to eight in number, being sub- 

 ject to vary in different individuals. They unite into two or 

 three trunks, which coalesce into one, after penetrating the dura 

 mater by distinct openings; and then proceed through the ante- 

 rior condyloid foramen of the occipital bone. 



The general distribution of this nerve is to the muscles of the 

 tongue. 



SECT. VII. OF THE ARTERIES OF THE BRAIN. 



The arteries of the brain, or pia mater, are derived from the 

 two internal carotids, and from the two vertebrals. 



The Internal Carotid Artery (CarUis Interna) gets into the ca- 

 vity of the cranium through the carotid canal of the temporal 

 bone, conforming itself of course to the curvature of this canal, 

 and is brought by it to the posterior part of the body of the 

 sphenoidal bone, In escaping from the petrous bone it has to 

 ascend, and also to advance somewhat, by which it is brought 

 to the posterior part of the sella turcica. From this point it 

 goes horizontally forwards through the cavernous sinus; and, 

 reaching its fore part, it then ascends again, and towards the fis- 



