THE CRANIAL OR ENCEPHALIC NERVES. 



roots soon unite in a single cord, which issues from the cranium by a particular 

 orifice in the posterior part of the foramen lacerum, and at this point it exhibits 

 a grey oval-shaped enlargement — the ganglion petrosum or ganglion of Andersch, 

 in which it is somewhat difficult to distinguish the motor filaments of the nerve 

 from those which arise between the lateral and superior columns of the medulla 

 (Fig. 456, 2). 



Course a?id Termination. — Scarcely has the glosso-pharyngeal nerve escaped 

 from the cranium, than it descends, in describing a curve with concavity 

 forward, behind the large branch of the os hyoides, included at first between 

 a fold of the guttural pouch, then between the latter and the internal pterygoid 

 muscle. Lying beside the ex- 

 ternal carotid artery in the F'S- "^55. 

 latter part of its course, it x'-*"''**\ ^^^ ^ 

 passes with it along the pos- "^^^ ^ ^ \f ^ V^' 

 terior border of the great cornu ^/^Vpys>^-^^<lX^->^^^^7^^^^^ 

 of the hyoid bone, and gains 

 the base of the tongue with 

 the lingual artery, by coursing 

 beneath the hyo-glossus brevis 

 muscle. The papillae on the 

 posterior portion of the lingual 

 mucous membrane receive the 

 terminal ramuscules of this 

 nerve. (See the Sense of Taste. ) 



Collateral Branches. — On 

 its course it furnishes — 



1. Jacobson's nerve {tym- 

 fanic hranch), a very thin fila- 

 ment springing from An- 

 dersch's ganghon, proceeding 

 upwards, and entering a par- 

 ticular foramen in the petrous 

 portion of the temporal bone, to 

 be distributed more especially 

 to the tympanum ; sending 



also to the superficial petrosal nerves two branches, which are designated the 

 great and deep small petrosal nerves. 



2. Filaments of communication with the superior cervical ganglion, two or three 

 in number, though sometimes replaced by a single ramuscule. 



3. A brafich to the carotid plexus, which passes back on the guttural pouch 

 to reach the terminal extremity of the common carotid, whence its filaments 

 are sent, with those of the sympathetic nerve, either to the external carotid, 

 occipital, or even to the common carotid artery itself. This branch communi- 

 cates, by several anastomoses, with the numerous sympathetic branches which 

 pass from the superior cervical ganglion to the surface of the guttural pouch, 

 and which are either expended in that membrane, or join the posterior border of 

 the great hypoglossal nerve. 



4. A pharyngeal branch (Fig. 459, 11), which is generally detached close 

 to the pharyngeal artery, and forms — along with the pharyngeal filaments of 

 the pneumogastric nerve — a remarkable intricate plexus {^pharyngeal) on the 



Aft 



DIAGRAM OF A SECTION OF THE MIDDLE PORTION OF THE 

 MEDULLA OBLONGATA OF MAN. 



PP, Pyramids ; CC, floor of the fourth ventricle : H, radicular 

 fibres of the great hypoglossal nerve ; nh, classical 

 nucleus of ditto; n'h', accessory nucleus of ditto; S, 

 accessory (motor) nucleus of the mixed nerves ; pn, 

 sensitive nucleus of the mixed nerves (glosso-pharyngeal, 

 pneumogastric, spinal accessory) ; nr, nucleus of the 

 restiform bodies; GP, gelatinous substance of Rolando 

 (head of the posterior cornu) ; T, ascending root of the 

 trigeminus ; M, radicular fibres of the pneumogastric ; 

 01, grey layer of the olivary body ; R, internal juxta- 

 olivary nucleus ; T, external ditto ; xx, raphe. 



