78 ANATOMY OF A CHELONIAN. 



seventh, nerve, and turning around the cornu 

 may be traced into a muscle which passes 

 from that to the proximal end of the mandible 

 on the same side. 



195. Divide the hyoidean apparatus, the larynx, and 

 the ventral walls of the pharynx and gullet in the me- 

 dian line, and turn the halves outward so as to expose 

 the base of the skull, covered by the mucous mem- 

 brane of the roof of the mouth and pharynx. Then 

 proceed to trace the nerves described below, taking the 

 greatest care not to injure the rest while following one 

 of them. 



196. Find the pneumogastric in the neck (99), where 

 it has already been seen with the carotid artery and the 

 cervical sympathetic accompanying it. Trace all three 

 from that point to the base of the skull, where the ar- 

 tery (crossed on its course by several nerves, which 

 must not be cut) passes out of sight, entering the ca- 

 nal which opens just behind the proximal end of the 

 quadrate-bone (26, e). Then cut away the artery, dis- 

 entangling it from the nerves around. 



197. Next trace the pneumogastric nerve up to the 

 skull (for its peripheral distribution see section 100). 

 Jt will be seen to enter a ganglion (superior cervical 

 ganglion of the sympathetic) which lies on the base of 

 the skull, immediately posterior to the cartilaginous 

 floor of the tympanum. 



198. Next trace back the hypoglossal from the point 

 where it has already been seen (194, a) ; it crosses on 



