

CEREBRAL NERVES 185 



orbit, supplying the lachrymal and Harderian glands, when present, 

 as well as the roof of the mouth ; it then passes to the upper jaw, 

 supplying the teeth; and finally, as the infraorbital branch, per- 

 forates the skull to reach the integument in the region of the 

 upper jaw, snout, and upper lip. 



The third division of the trigeminal is of a mixed nature; it 

 supplies on the one hand the masticatory muscles and several 

 muscles on the floor of the mouth, and also gives rise, from 

 Amphibians onwards, to the great sensory nerve of the tongue 

 (lingual or gustatory nerve) ; while another branch, passing 

 through the inferior dental canal, supplies the teeth of the lower 

 jaw, and then gives off one or more branches to the integument of 

 the latter and of the lower lip. Two ganglia, the submaxillary and 

 the otic (Fig. 149), derived from the sympathetic, are connected 

 with its mandibular division (sensory portion). 



Facial nerve. This, which is also a mixed nerve, originally 

 possesses two distinct ganglia in connection with its sensory and 

 mixed portion (Fig. 148) : these can be recognised up to Urodeles, 

 but in the course of development one of them gradually comes into 

 connection with the ganglion of the trigeminal, and in Anura is 

 indistinguishable from it. The other known as the geniculate 

 ganglion is retained in all Vertebrates, in connection with its 

 mixed root (Fig. 149). 



The facial nerve consists primarily (in aquatic Vertebrates) of 

 the following main branches (Fig. 148) : 



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

 mentary sense-organs of the head (p. 190), 1 as follows : (a) a super- 

 ficial ophthalmic, running- parallel to and usually accompanying the 

 corresponding branch of the trigeminal; (b) a buccal, which gives 

 off an otic branch ; and (c) an external mandibular ( = part of the 

 hyomandibular, see below). 



II. A sensory (a) palatine, anastomosing with the maxillary 

 branch of the trigeminal, and (b) internal mandibular or chorda 

 tympani. 



III. A main trunk, largely motor ( = hyomandibular less the 

 elements which give rise to the sensory external mandibular), 

 which passes behind the spiracle, all the other branches passing 

 in front of it. 



In adult terrestrial Vertebrates (Caducibranchiate Urodeles. 

 Anura, and Amniota) the integumentary sense-organs become re- 

 duced, and the corresponding branches of the facial nerve undergo 

 corresponding reduction (Fig. 149); the parts of this nerve which per- 

 sist are the pharyngeal section (palatine and chorda tympani) and 



1 These branches, together with the lateral line branches of the glosso- 

 pharyngeal and vagus (p. 187) appear to form an independent and distinct 

 system of lateral line nerves, having a common internal origin in the brain, for the 

 innervation of the special sensory organs of the integument in Fishes, Dipiioans 

 and Amphibians. The auditory nerve arises from the same centre. 



