884 COMPARATIVE ANATOMY 



the motor fibers which innervate the muscles of the jaw as well as the 

 sensory fibers supplying the lips and teeth. In the mammals it also 

 supplies part of the face, and in some of the reptiles a branch called the 

 lingual nerve is sent into the tongue. In mammals the mandibular nerve 

 is connected with both an otic and a superior maxillary ganglion, while 

 fibers from the sympathetic system also connect. 



It is now thought that the ophthalmic branches of the trigeminal 

 really form a distinct nerve, and are not parts of the trigeminus at all. 

 The reason for this belief is that the trigeminal proper arises in the 

 medulla, while certain fibers of the ophthalmic seem to arise in the 

 midbrain. 



The trigeminus nerve may also send a twig backward. This is 

 called the recurrent, or lateralis, of the fifth nerve. This recurrent nerve 

 from the fifth is only found in teleosts and passes to the dorsal side of 

 the jaw near the dorsal fin, or, in a few fishes, it goes into the paired fins. 



VII. The Facial Nerve. This arises just in front of the ear, in the 

 medulla. In all higher forms than those which have lateral line organs, 

 there is a single geniculate ganglion which is closely associated with the 

 semilunar (Gasserian) ganglion of the fifth in the fishes and the amphib- 

 ians. The facial nerve gives off a palatine branch running to me root 

 of the mouth, where it divides into a pre-trematic nerve, as already 

 stated, which enters the lower jaw, and a post-trematic branch called 

 the hyoid nerve. The hyoid in man is called the facial nerve, and in all 

 the higher vertebrates a small twig Called the chorda tympani (Fig. 494) 

 leaves the hyoid and unites with the mandibular branch of the fifth 

 nerve, after which its fibers enter the lingual branch of the fifth nerve, 

 and go to the taste organs at the tip of the tongue. The remaining por- 

 tion of the facial nerve is almost entirely motor in function, its fibers 

 controlling the muscles of the neck and the muscles which open the 

 mouth. In mammals that have a large facial musculature the facial 

 nerve is distributed to more regions of the face. 



In animals having organs of the lateral line (Fig. 479), the seventh 

 nerve has an additional ganglion immediately beyond which it divi4es 

 into three branches, namely, the superficial ophthalmic, which usually 

 unites with the superficial ophthalmic of the fifth cranial nerve and then 

 supplies the lateral line organs and related structures on the top of the 

 head dorsal to the eyes. The buccal nerve, which supplies the organs 

 below the eye and along the line of the upper jaw, and the external 

 mandibular nerve, complete the three branches. The latter is connected 

 to the lateral line organs, of the operculum when this is present, or with 

 the lower jaw. 



The buccal nerve is usually quite closely associated with the maxil- 

 lary nerve, while the external mandibular is closely associated with the 

 mandibular ramus of the fifth nerve. 



In all higher vertebrates, where no lateral line organs appear, there 



