242 COMPARATIVE ANATOMY 



mucous membrane of the lower jaw, and then gives off one or 

 more branches to the integument of the latter and of the lower 

 lip : in Mammals, a smaller branch passes upwards in front of the 

 ear to the temporal region, supplying the adjacent skin and the 

 pinna of the ear. Two ganglia, the submaxillary and the otic (Fig. 

 180), derived from the sympathetic, are connected with its sensory 

 portion, the former being situated close beneath the exit of the 

 nerve from the skull, the latter on the lingual nerve at the point 

 where it passes into the tongue. The otic ganglion is connected 

 with the glossopharyngeal nerve, but it is doubtful whether the 

 gustatory fibres in connection with the lingual ganglion are 

 derived from this nerve or from the facial. 



Facial Nerve. This, which is also a mixed nerve, presents 

 important differences in branchiate and pulmonate forms respec- 

 tively. In many Fishes (e.g. Cyclostomes, Elasmobranchs, many 

 Teleosts, Dipnoans) and in perennibranchiate Urodeles, it possesses 

 two distinct ganglia at its origin in connection with the sensory and 

 mixed portions respectively. In other Fishes (e.g. Chimrera, Polyp- 

 terus, Lepidosteus, certain Teleosts) and more especially in Anurans, 

 the facial nerve comes into such close connection with the trigeminal 

 that the ganglia in question are no longer distinguishable from the 

 Gasserian ganglion, and such complications arise that the original re- 

 lations of many of the components of the two nerves are no longer 

 traceable and cannot be analysed by dissection. Another (the gcnicu- 

 late) ganglion of the facial nerve is retained in all Vertebrates. 



In aquatic branchiate Vertebrates the facial nerve consists of 

 the following main branches (Fig. 179): 



I. A system of sensory branches for the supply of the in- 

 tegumentary sense-organs of the head (q.v.). These branches, 

 together with the auditory nerve and the lateral line branches of 

 the glossopharyngeal and vagus (p. 245), arise from the same centre 

 in the medulla oblongata (tuber acusticum), each originally possessing 

 its own ganglion, and together forming a primitive acustico-lateral 

 sensory nervous system, arising, like the sensory organs which they 

 supply, direct from the ectoderm. The following branches may be 

 distinguished : (a) a superficial ophthalmic, running parallel to the 

 like-named branch of the trigeminal and sometimes (e.g. in 

 Chimsera) becoming very closely connected with its deep portion : 

 (6) a buccal, close to the maxillary portion of the trigeminal, and, 

 giving off near its origin an otic branch ; and (c) an external 

 mandibular, in the region of the hyomandibular nerve, dividing 

 into an anterior and a posterior branch and frequently anastomos- 

 ing with the mandibular branch of the trigeminal. 



II. A sensory (a) palatine * which may anastomose with the 



1 There can be no doubt that the palatine branch of the facial in the Anamnia, 

 comparable to the visceral or pharyngeal branches of the glossopharyngeal and 

 vagus, corresponds to the greater superficial petrosal of Mammals, which is 

 a purely sensory nerve : the motor fibres which are said to arise from it probably 

 belong to the vagus. 



