BLOOD-VESSELS OP THE BRAIN. 425 



place of distribution the glosso pharyngeal to the tongue 

 and pharynx, the pneumogastric to the lungs and stomach, 

 and the spinal accessory to the muscles on the side of the neck. 



The several portions of the eighth pair, at the foramen 

 lacerum posterius, have each a distinct sheath of dura ma- 

 ter; though the par vagum and spinal accessory, having heen 

 seen occupying the same canal, have been compared to a 

 spinal nerve, the latter representing the anterior or motor 

 root, the former the posterior or sentient. 



Ninth Pair, Lingual or Hypoglossal, (Figs. 118, 9 1.) These 

 belong to the tongue, and are motor nerves. They arise by 

 a number of filaments, which vary from four to ten, from 

 between the corpus pyramidaleand olivare. These filaments 

 unite into a single trunk, one for each side, and receiving 

 a sheath of the dura mater, pass through the anterior con- 

 dyloid foramen of the occipital bone, to be distributed prin- 

 cipally to the tongue. 



BLOOD-VESSELS OF THE BRAIN. 



The internal carotid and vertebral arteries are the great 

 sources of supply of blood to the brain. Each internal caro- 

 tid gets into the cavity of the cranium, by a tortuous course 

 through the carotid canal of the temporal bone. On leav- 

 ing this canal it ascends through the cavernous sinus, and 

 at the anterior clinoid process it gives off the ophthalmic 

 artery which goes to the eye and its appendages. At this 

 point the carotid gives off, in its course, small branches to 

 the cavernous sinus and dura mater. The remainder of its 

 branches supply the brain, and consist of the anterior, 

 middle, and posterior cerebral. 



The anterior branch, anterior cerebri, called also the artery 

 of the corpus callosum, proceeds forward and inward, and 

 after uniting with its fellow by a transverse branch, (the 

 anterior communicating artery ,) ascends upon the upper sur- 

 face of the corpus callosum, supplying this body and the 

 inner surface of the hemispheres. The middle artery is the 

 largest, and goes outward to the fissure of Sylvius, supplying 

 the anterior and middle lobes of the cerebrum, and accend- 



