490 H. W. NORRIS AND SALLY P. HUGHES 



INTRODUCTION 



The earliest account of the nervous system of the caeciHans 

 seems to be that of Fischer ('43), describing that of Caecilia 

 (Siphonops) annulata. His account of the fifth, seventh, ninth, 

 tenth, and twelfth nerves is more nearly correct than that of 

 some later writers. He considers the caecilian cranial nerves 

 arranged on the general amphibian plan despite the external 

 differences between caecilians and other amphibians. He rec- 

 ognizes a well-defined sjniipathetic trunk arising anteriorly from 

 both the fifth and the seventh nerves. He describes and figures 

 an intmiate association between the sympathetic trunk and the 

 glossopharyngeal, vagus, and anterior spinal nerves. The lateral 

 line nerve of the trunk he considers derived from the third spinal 

 nerve. 



Wiedersheim ('79) describes the cranial nerves of Epicrium 

 (Ichthyophis) glutinosum and Siphonops annulatus in general 

 agreement with the account of Fischer. The double nature of 

 the olfactory nerve he homologizes with, that of a spinal nerve. 

 The optic nerve he finds in a vestigial condition, but fails to 

 trace it to the eyeball. Of the eye-inuscle nerves he makes no 

 mention. The double nature of the fifth nerve and the origin 

 of the ramus ophthahnicus (r. oph. profundus) independent of 

 the Gasserian ganglion are recognized. He describes a supposed 

 anastomosis between the ramus ophthalmicus and the ramus 

 maxillaris. The masseter muscle and the compressor muscle of 

 the orbital gland he believes innervated by the ramus maxil- 

 laris. In the facial nerve he finds no ramus palatinus, but be- 

 lieves the latter to be incorporated in the trigeminus. From 

 the facial nerve he finds an anastomosis entering the Gasserian 

 ganglion. The acusticus is a well-defined nerve. In the glosso- 

 pharyngeal- vagus group he describes and figures three nerves: 

 an anterior glossopharyngeal with the usual distribution, a middle 

 vagus, and a posterior nerve entering the sympathetic trunk. 

 Anastomoses of the ninth and tenth nerves with the sympathetic 

 are also described. A ramus lateralis of the vagus he does not 

 find. The hypoglossus is formed from the first and second 



