CEREBRAL NERVES 241 



double intra-crariial or extra-cranial Gasscrian ganglion at the origin 

 of the former, and in Fishes (Fig. 179), divides into two main 

 branches, an ophthalmic (including a superficial and a deep or 

 profundus portion), and a maxillo-mandilular : in most terrestrial 

 forms (Figs. 180 and 181) the maxillary and mandibular nerves 

 arise separately. From the presence of these three characteristic 

 branches, often known as the first, second, and third divisions of the 

 trigeminal, its name is derived. It passes oat from the skull some- 

 times through a single aperture, and sometimes by two or three dis- 

 tinct ones. On the supposition that the mouth corresponds to a fused 

 pair of branchial clefts, the ophthalmic would correspond to the dorsal 

 branch of a branchial nerve, and the maxillary and mandibular to 

 the prebranchial and postbranchial branches ; the palatine branch 

 may be represented by a branch going to the roof of the mouth. 



The superficial branch of the first division is usually distinct in 

 Fishes, in many of which, however, and in higher forms, it may be 

 united with the deep branch. In Amphibians its homology has not 

 been clearly made out. 1 It passes dorsally over the eye-ball, crosses 

 the superficial ophthalmic branch of the facial, with which it may 

 become secondarily connected, and is distributed to the skin 

 anterior to and above the orbits. The deep branch passes below 

 the superior and anterior recti and superior oblique muscles, and 

 supplies the integument of the snout, the eyelids and conjunctiva, 

 the mucous membrane of the nose, and the lacrymal glands (e.g. 

 in Mammals). A connection of the profundus with the ciliary 

 ganglion arises secondarily. 



The second division of the trigeminal, like the superficial 

 and deep ophthalmic, is purely sensory. On it is a sphenopalatinc 

 ganglion derived from the sympathetic, and it is connected with 

 the facial. It extends first along the floor of the orbit, supplying 

 the lacrymal and Harderian glands when present, the conjunctiva, 

 the mucous membrane of the nose, and the roof of the mouth ; it 

 then passes to the upper jaw. supplying the teeth ; and finally, 

 as the infraorbital branch, perforates the skull to reach the integu- 

 ment in the region of the upper jaw, snout, and upper lip. 



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

 motor portion, which has the character of a visceral nerve, supplies 

 certain masticatory muscles and some of the muscles of the palate 

 and floor of the mouth. The sensory portion extends along the 

 rami of the lower jaw and divides into two main parts, a lingual 

 and a mandibular proper, the former of which is not well differenti- 

 ated in the Anamnia and Sauropsida. The lingual or gustatory 

 nerve innervates the mucous membrane of the mouth and tongue, 

 containing gustatory fibres from the chorda tympana (cf. under 

 facial nerve). 



The special mandibular branch, which may pass through the 

 inferior dental canal of the mandible, supplies the teeth and 



1 It possibly corresponds to the ramus frontalis of Mammals. 



