THE CRANIAL NERVES OF ONE OF THE SALAMANDERS 89 



makes its exit through the lateral edge of the parieto-frontal bone. 

 Outside the cranium its course was traced only a short distance. 



V. The trigeminus is, next to the olfactory, the largest of the cranial 

 nerves. It arises from the antero-lateral angle of the medulla, and 

 passes forward and outward to the Gasserian ganglion. This large 

 ganglion lies inside the cranium just back of the posterior extension 

 of the cerebral hemispheres. In some Urodela, it is described as lying 

 inside the cranium, in some as lying in the foramen, and in others as 

 lying outside the cranium. Arising from the ganglion are the three 

 usual branches. They make their exit by two foramens. In the 

 manner of exit of these branches there is considerable variation in 

 Urodela. They may pass out through one, two, or three foramens. 

 In Plethedon the maxillary and mandibular branches leave the cranium 

 through a common passage in a lateral direction and the ophthalmic 

 by a separate passage in a forward direction. 



The ophthalmic takes a course directly forward just outside the 

 cranium. It soon divides into two branches. One of these extends 

 dorso-lateral and breaks up in the muscles in front of the eye. In 

 the accounts of this nerve in other Urodela, I find no description of 

 this nerve. It is probable, however, that it is represented in Ambly stoma 

 by three small twigs described by Coghill.' The other branch of the 

 ophthalmic continues forward, and at about the level of the anterior 

 part of the brain it breaks up into three terminal branches, mesial, 

 lateral, and ventral. The mesial terminal branch turns inward and 

 then extends forward in the floor of the nasal capsule to innervate the 

 gland of the snout. The lateral terminal branch passes forward near 

 the surface of the antero-lateral part of the snout. The ventral terminal 

 branch soon unites with the palatine branch of VII. From here it 

 continues forward to innervate the anterior part of the roof of the 

 mouth. 



As before noted, the maxillary and mandibular make their exit by 

 a common foramen. The maxillary is dorsal, and is by far the smaller 

 of the two. It passes off laterally and curves forward in two parts. 



1 G. E. Coghill. "The Cranial Nerves of Amblystoma tigrinum." Jr. Comp. Neur., 12: 220, 

 221. 1902. 



