CRANIAL NERVES AT EXIT FROM SKULL. 3t 



the ganglion petrosum, or ganglion of Andersch. The gan- 

 glion of Andersch gives off the tympanic, or Jacobson's 

 nerce ; this enters a small bony canal in the jugular fossa, 

 and is distributed to the tympanum, forming the tympanic 

 plexus, which communicates with the sympathetic and with 

 the fifth pair of nerves. One or two other minute branches 

 are also given off from the ganglion or its vicinity. The 

 glosso-pharyngeal nerve is distributed to the base of the 

 tongue, the fauces, and the pharynx. 



* The pneumogastric, or par vagum nerve, passes out of 

 the foramen lacerum posterius in a sheath common to it 

 and the spinal accessory nerve ; it is the longest of the 

 three nerves. In the foramen, it has a large ganglion called 

 the ganglion of the root, in contradistinction to the ganglion 

 of the trunk, which is formed after it has escaped from the 

 skull. 



* The spinal accessory nerve passes out of the foramen 

 lacerum posterius with the pneumogastric ; it has no gan- 

 glion. In the jugular fossa it divides into two branches, 

 one of which sends a few filaments to the upper ganglion 

 of the pneumogastric, with the trunk of which it becomes 

 continuous below the second ganglion, and the other de- 

 scends to the sterno-mastoid muscle, which it perforates, 

 and to which, as well as the trapezius muscle, it is distri- 

 buted. 



The NINTH, or HYPOGLOSSAL NERVE, consists of two 

 bundles, which pass out at the anterior condyloid foramen 

 by separate orifices of the dura mater. These unite after 

 emerging from the skull, and the nerve is distributed to the 

 muscles of the tongue. 



According to the arrangement which this book proposes, 

 the subject is now to be turned over for the dissection of 

 the back : if the student has kept up with his companions, 

 and accomplished the previous dissections, the turning- 

 may be done without inconvenience. The muscles of the 

 back of the neck are given with those of the back, in Part 

 Second, Dissection Y. 



