46 Journal of Comparative Neurology. 



Nervus opticus. — The optic is very similar to that of uro- 

 deles in general. There is a slight vestige of a lumen at the 

 base of the nerve. 



The nerves of the eye-muscles are all present but very 

 small. The oculomotor is the largest of the three and maintains 

 an independent course throughout its whole extent, leaving the 

 cranium by a special foramen slightly caudad of the optic fora- 

 men. In part of its course this nerve lies very close to ramus 

 ophthalmicus profundus of the fifth. The courses of the troch- 

 learis and abducens have not been determined. They are both 

 extremely minute, as would be supposed from the very degen- 

 erate condition of the eye-muscles. The point of origin of the 

 abducens appears to be somewhat variable. It has been figured 

 by Osborn as leaving the medulla on a level with the fifth 

 nerve, but transverse sections prepared by the writer show the 

 abducens taking its exit on a level with the cephalic roots of the 

 glossopharyngeo-vagus complex as it does in Rana, Diemctylus, 

 Salamandra, Amblystoma and other forms. 



Nervus trigeminus. — The distribution of the fifth nerve in 

 Cryptobranchus has been described by Fischer and more re- 

 cently by H. H. Wilder, though neither of these writers has 

 given a complete description. The first ramus, the r. ophthal- 

 micus profundus, after leaving the ganglion, traverses a canal in 

 the pterygoid bone, coming to the surface some distance cepha- 

 lad of the other two rami. It trends cephalad, passing mesad 

 of the eye-ball and dorsad of the optic nerve and all the eye 

 muscles except the superior oblique and superior rectus. The 

 greater part of the ramus passes cephalad to a point cephalad 

 of the eye, where it breaks up into numerous branches anasto- 

 mosing with branches of the superior maxillary ramus. The 

 nerve thus formed enters a groove in the superior maxillary 

 bone and sends branches to the skin of the upper lip through 

 three or four foramina and a small notch in the lateral border of 

 the anterior nares. This branch has been called by Wilder 

 ramus nasalis extemus. 



The two branches to the nasal capsule have been well de- 

 scribed by Wilder who designates the ventral and dorsal 



