144 THE SALAMANDER 



passes anteriorly in the alveolar canal of the lower jaw, latero-dorsal 

 to Meckel's cartilage. It gives fine twigs to the teeth, while its ter- 

 minal branches pass out laterally through foramina in the dentary 

 to supply the skin covering the anterior part of the lower jaw, and 

 may thus be called RR. mentales. It is important to notice that this 

 branch throughout the whole of its course remains lateral to the 

 primitive jaw. Stadtmuller (1924) describes a rather complicated 

 anastomosing system between it and the R. alveolaris VII, which, 

 however, is only traceable by means of sections. 



(^)The main branch (n.m.e.) which passes right through the jaw 

 and then turns anteriorly along its ventral side. It is a mixed nerve 

 and supplies cutaneous branches to the skin between the rami of the 

 mandible, and motor branches to the M. intermandibularis, while 

 very occasionally its most posterior twigs may encroach on the region 

 belonging to the Vllth nerve and enter the most anterior portion 

 of the M. interhyoideus (cf. Driiner, 1901, p. 542). From its distri- 

 bution it is known as R. intermandibularis. 



VII. N. Facialis (n.7) (mixed, communis, visceral motor). In 

 the Salamander the facial nerve leaves the brain in company with 

 the auditory nerve and shares a common ganglion — the acustico- 

 facialis ganglion (g. 7 + 8) — ^with it. The combined nerve leaves the 

 lateral border of the medulla about f mm. posterior to the trigeminus, 

 and passes into a recess in the petrosal bone near the anterior end of 

 the otic capsule, and ventral to the auditory organ. Within this recess 

 the ganglion is situated. The fine R. communicans passing to the 

 Gasserian ganglion has already been mentioned (p. 139). In the 

 larva, where it is much larger, it arises independently from the me- 

 dulla — according to Druner — but in the adult it appears to leave the 

 combined acustico-facialis nerve, or the ganglion itself. It is not 

 always demonstrable. 



The facial nerve separates from the ganglion and passes directly 

 outwards through a canal in the petrosal bone — the facialis canal — 

 beneath the auditory organ, and finally enters the antrum petrosum 

 laterale (cf. p. 26). 



(i) R. Palatinus (n.pal.) (communis). The palatine nerve is 

 given off immediately distal to the ganglion, while the nerve is 

 still in the facialis canal, and passes obliquely antero-ventrally 

 through a special foramen in the floor of the petrosal bone 

 (fo.pal. fig. 2), emerging from the foramen just lateral to the 

 origin of the M. retractor bulbi. The nerve then turns antero-mesi- 

 ally and crosses the M. retractor bulbi, passing between the muscle 

 and the epithelium of the roof of the mouth. At the postero-mesial 



