36 AMPHIBIA. 



even to their termination on the Schneiderian membrane of the nose, and there is not 

 a ganglion. The optic tract proceeds from the optic nerve and thalamus ; it joins its 

 fellow in a commissure from which each optic nerve proceeds to terminate in the 

 retina. The third arises in the track of the pyramidal body ; it gives a branch to 

 join one from the first trunk of the fifth, to form ciliary nerves, and then gives a 

 branch to the levator, depressor, adductor, and inferior oblique muscles of the eye. 

 The fourth nerve arises from the roof of the ventricle just behind the optic lobes, and 

 terminates in the superior oblique muscle. The fifth arises in the track of the 

 restiform body ; it has not a very distinct smaller portion for joining the third trunk, 

 but there is a greater resemblance to the form of the Gasserian ganglion than in 

 fishes : it is divided into three trunks ; the first passes forwards, gives a branch to join 

 one from the third nerve for forming ciliary nerves, it then passes underneath the 

 attollent and superior oblique muscles of the eye, gives filaments to the upper eyelid, 

 and enters the nose, where it becomes intimately united with a portion of the olfactory 

 nerve, and divides into several branches, some of which are seen passing upon the 

 Schneiderian membrane, covering the septum, and then, through perforations in the 

 palate, to the surface between the bone and horny covering at the anterior part of the 

 palate and beak. In the snake, it passes forwards first within the cranium, then into 

 the orbit, and gives off a ciliary branch and one to the upper eyelid, and from this 

 part it passes to the Schneiderian membrane, in which it becomes connected with the 

 olfactory nerve, and then terminates on the skin at the end of the nose. In the turtle, 

 the second trunk gives filaments to a muscle of the lower jaw, then passes on the floor 

 of the orbit, gives filaments to the large lachrymal gland and the lower eyelid, and 

 divides into branches, to terminate on the surface of the lower jaw beneath the horny 

 covering. In the snake, after communicating with the sympathetic, it gives filaments 

 to the membrane of the mouth, palate, and nose ; it passes out of its canal in the 

 upper jaw, and terminates in branches on the upper lip. In the turtle, the third trunk 

 gives branches to the temporal and other muscles of the lower jaw, and then divides 

 into branches, which terminate on the surface of the lower jaw, beneath the horny 

 covering ; it sends two large branches to a portion of muscle analogous to the 



