CRANIAL NERVES. 171 



from the anterio-lateral angle of the myencephalon, and its fibres pass 

 almost immediately into the semilunar (Gasserian) ganglion, 

 which may lie either within or without the skull. In the higher verte- 

 brates the nerve divides beyond the ganglion into three main trunks 

 ophthalmic, maxillary, and mandibular whence the name. In 

 the lower vertebrates the maxillary and mandibular pursue a common 

 course for some distance before separating. 



In the fishes the ophthalmic is represented by two branches, an 

 ophthalmicus superficialis (not to be confused with the similarly 

 named branch of the seventh with which it is closely associated) and 

 an ophthalmicus profundus, which passes between the eye muscles 

 on its way to the tip of the head. Both are purely sensory-, in most 

 vertebrates general cutaneous, but in the teleosts they, together with 

 the maxillary, supply also the taste organs (visceral sensory) of the 

 surface of the head. The superficialis innervates the skin above and 

 in front of the eye; the profundus goes to the eyelids, conjunctiva, 

 snout and the mucous membrane of the nose, passing through the 

 ciliary ganglion in its course. In the urodeles, where the maxillaris 

 is reduced, the profundus supplies its region. 



The maxillaris, with components similar to those of the ophthalmic, 

 runs beneath the eye, passing the sphenopalatine ganglion (p. 165) 

 in its course, supplying much the same territory as the ophthalmic and, 

 in addition, the roof of the palate and the teeth of the upper jaw. 



The mandibularis ramus is a mixed nerve. The motor components 

 (visceral) innervate the muscles of the jaws, some muscles of the floor 

 of the mouth and in mammals the tensor tympani muscle. The sensory 

 component (general cutaneous) divides into two parts, the lingualis 

 going to the tongue and the mandibularis to the skin of the lower 

 jaw, chin and lower lip, and to the lower teeth. In mammals there is 

 a weak auricularis superficialis nerve arising from the mandibularis 

 and going to the temporal region and to the conch of the ear. 



Two ganglia of the sympathetic system are associated with the trigeminal: the 

 otic ganglion near the exit from the skull and the submaxillary where the lingualis 

 bends to enter the tongue. From the otic a trunk (Jacobson's commissure, p. 165) 

 runs back to connect with the ninth nerve. 



The fifth nerve is usually compared to a post-otic nerve (vide infra) in that the 

 mouth is regarded as the homologue of a pair of gill clefts, the maxillary being 

 the pre- and the mandibularis the post-trematic nerves (see nerve IX, below). 

 The homologies of the ophthalmicus are less certain. Some facts seem to point 



