CARPENTER: DEVELOPMENT OF THE OCULOMOTOR NERVE. 145 



Comparative studies of the anatomical connections of the ciliary gan- 

 glion have been made by Schwalbe ('79), Jegorow ('86-87), Holtz- 

 mann ('96) and Onodi (:Ol). 



Schwalbe, in his extensive and much-quoted work on " Das Ganglion 

 oculomotorii," shows that the ciliary ganglion is represented in the lower 

 vertebrates by groups of ganglion cells distributed along the course of 

 the oculomotor nerve. Passing upward towai-d the higher forms, the 

 cells become more closely associated into a compact body, this change 

 being accompanied by a gradual withdrawal of the ganglion from the 

 trunk of the oculomotor nerve through the formation of a radix bre- 

 vis. However, not all the higher vertebrates possess short roots, since 

 in many mammals (sheep, calf, dog, rabbit) none exists, the ganglion 

 being placed directly on the trunk of the oculomotor. Schwalbe denies 

 the existence of a connection between the ciliary ganglion and the tri- 

 geminal nerve in several species, and believes the sympathetic root to be 

 confined to mammals. He, therefore, asserts that the ciliary ganglion 

 belongs primarily to the oculomotor, which he considers entitled to the 

 rank of an independent segmental nerve. 



Jegorow's researches on "le ganglion ophthalmique " were, like those 

 of Schwalbe, very comprehensive. As far as the anatomical relations of 

 the ganglion are concerned, he differs from the latter writer chiefly in 

 regard to the importance of the connection with the trigeminus. This 

 he regards as constant, and necessary for the existence of the ganglion, 

 throughout the vertebrate series. 



Holtzmann found the ciliary ganglion in amphibians, birds and mam- 

 mals more intimately connected with the oculomotor than with the 

 trigeminus. Although he found neuraxons joining the ciliary ganglion 

 with the fifth nerve where Schwalbe believed no connection existed, he 

 does not regard these neuraxons, in certain cases, as constituting a phys- 

 iological radix longa. 



The examination of many selachians as well as several bony fishes 

 and mammals convinced Onodi that the connection between the ciliary 

 ganglion and the trigeminus is more intimate than Schwalbe's researches 

 show. In selachians he frequently found a macroscopic ciliary ganglion 

 external to the trunk of the oculomotor. The ganglionic groups con- 

 nected distally with the third and fifth nerves he considers sympathetic 

 in nature, and in support of this view calls attention to nerve fibres 

 extending from them to form a plexus about the wall of a neighboring 

 blood vessel. 



The observations which have already been made on the anatomical 

 vol. xlviii. — no. 2 10 



