SYMPATHETIC GANGLIA 245 



Ciliary ganglion 



The existence of a ciliary ganglion in the Urodela is somewhat 

 doubtful. Herrick ('94) found no trace of a ciliary ganglion in 

 Amblystoma punctatum. According to Coghill ('02), the ciliary 

 ganglion in Amblystoma tigrinum is ''transitory and probably 

 at no time functional." Norris ('06) found no ciliary ganglion 

 in Amphiuma. McKibben ('13) reports that he found no "group 

 of cells corresponding to the ciliary ganglion " in Nectiirus. 



The oculomotor nerve arises, in larvae of Amblystoma, from 

 the ventrp-lateral aspect of the mesencephalon as a slender 

 strand of fibers accompanied by relatively few large cells. In 

 larvae 13 mm. in length, this nerve may be traced from its origin 

 into the orbit where it terminates among aggregates of mesen- 

 chymal cells which represent an early stage in the differentiation 

 of the eye-muscles. Near the tip of the growing nerve may be 

 observed a few large nuclei apparently identical with the nuclei 

 of the cells accompanying the fibers of the nerve-trunk. The 

 number of cells aggregated at this point does not increase mate- 

 rially as development advances and no fibrous connection could be 

 observed between them and the Gasserian ganglion. A permanent 

 ciliary ganglion is probably not developed in this species. 



In larvae of the frog the oculomotor nerve is somewhat larger 

 than in larvae of Amblystoma and a larger number of cells be- 

 comes aggregated at its growing tip. In transverse sections 

 taken at the level of the origin of the oculomotor nerve in early 

 larvae, medullary cells may be frequently observed pushing 

 from the mantle layer in the wall of the mesencephalon into the 

 root of the oculomotor nerve as it traverses the marginal veil. 

 Similar cells are present in the oculomotor nerve just outside 

 the external limiting membrane as well as along the entire course 

 of the nerve. It is probable, therefore, that medullary cells ad- 

 vance peripherally along the oculomotor nerve and that such is 

 the origin of the cells which become aggregated in the path of 

 the nerve and give rise to this ganglionic enlargement which, in 

 larvae of the frog, probably represents the anlage of a permanent 

 ciliary ganghon. 



