THE NERVOUS SYSTEM 151 



nerve as well as connexions between it and the sympathetic system. 

 It is associated with the pharyngeal branches of the succeeding 

 nerves in the formation of a pharyngeal plexus. All these nerves 

 are exceedingly fine and very difficult to dissect. 



The main portion of the R. pre-trematicus IX is distributed to 

 the epithelium of the mouth-floor directly dorsal to the cerato-hyal 

 cartilage. 



(iii) R. -post-trematicu (n.po.t.9) (general cutaneous, visceral motor, 

 and communis). After the R. pre-trematicus has been given off, the 

 post-trematic branch — constituting the major portion of the nerve — 

 passes ventrally, parallel with the internal carotid artery, to the 

 dorsal end of the posterior cornu (cerato-branchial I) of the hyo- 

 branchial apparatus. Just before leaving the artery it gives off: — 



{a) One or two RR, cutanei jugulares (n.cut.j.) (Driiner) which pass 

 to the skin overlying that region. They are exceedingly fine. 



{h) RR. pharyngei dorsales (Driiner), also very fine nerves dis- 

 tributed to the dorsal wall of the pharynx and, according to Driiner, 

 associated with sympathetic fibres around the internal carotid 

 artery. 



In its course from the arterial arch to the cerato-branchial cartilage 

 the nerve passes round the dorsal side of the large jugular lymph 

 sinus, thus producing a loose loop which allows for the stretching of 

 the nerve on the extrusion of the tongue. It then passes along the 

 dorso-mesial side of the third visceral arch to the copula, giving off 

 numerous twigs. 



{c) RR. musculares^ to the M. subarcualis rectus I. The remainder 

 of the nerve now becomes: 



{d) R. UnguaUs^ and passes between the radials of the copula where 

 it swells into a small ganglion — Ganglion copulare (Driiner) — from 

 which emerge two or more branches passing directly into, and rami- 

 fying through the tongue. The nerve is the sensory nerve to the 

 tongue. 



Belonging perhaps to both IXth and Xth nerves are the NN. 

 Cutanei occipitales^ anterior and posterior (nn.cut.oc.) (Driiner) arising 

 from the dorsal side of the IX+X ganglion. These nerves, carrying 

 general cutaneous components, pass through the overlying muscles 

 — usually somewhat lateral to the M. intertransversarius capitis 

 superior — to the skin covering the occipital region. In the larva they 

 are associated with a lateralis component which atrophies during 

 metamorphosis. 



X. N. Vagus +Accessorius Willisii (mixed communis, visceral 

 motor, general cutaneous fibres). The Xth nerve of Salamandra is an 



