MORPHOLOGY OF EYE MUSCLE NERVES /5 



appears to favor the conclusion that the cell clusters at the roots 

 of the nerve anlage are of mesenchjaiiatous and medullary der- 

 ivation. The inference that cells derived from the mesoceph- 

 alic ganglion migrate centrad as far as the roots of the nerve 

 anlage does not appear to the writer to be well established. 

 In agreement with Gast, however, I find that penetration 

 of the fibrillar bundle begins at proximal and distal extrem- 

 ities of the nerve anlage, where it divides into roots and pe- 

 ripheral branches, and the penetration proceeds in opposite 

 directions towards the middle stretch of the nerve. In the 

 phenomena presented in the histogenesis of the neurilemma 

 there appears to be no essential difference between that of the 

 oculomotor and a spinal somatic motor nerve. In both cases 

 the derivation of the neurilemma cells appears to be the same. 



i. To what an extent do the emigrated medullary elements go to 

 form the sympathetic? That a ciliary ganglion is associated with 

 the oculomotor nerve in selachians seems proved by the consensus 

 of opinion of investigators on the basis of anatomical, histo- 

 logical, and embryological evidence. Anatomical evidence of 

 its presence has been presented by Schwalbe ('79), Jegorow 

 ('86-87), and Allis ('02); on the basis of histological structure 

 by Haller ('98); and on embryological grounds by VanWijhe 

 ('82), Beard ('85), Ewart ('90^, Dohrn ('91), Miss Piatt ('91), 

 Hoffman ('99), Gast ('09). Physiological evidence of a func- 

 tional ciliary ganglion in selachians is wanting. 



Furthermore, that the ciliary ganglion belongs morphologic- 

 ally and physiologically with the sympathetic system has been 

 held by many investigators since its discovery in man by Schacher 

 (1701) and the suggestion of its sympathetic character by Arnold 

 ('31). Later, doubt as to its sympathetic nature was raised 

 by Schwalbe ('79), who became an exponent of the view that 

 it is a cerebro-spinal ganglion and who initiated the long con- 

 troversy regarding its nature which has not yet been ended. 

 Carpenter ( '06) has so admirably reviewed the literature dealing 

 with this problem that it appears unnecessary to enter into 

 an extended discussion of the various arguments for and against 

 its cerebro-spinal character. That the ciliary ganglion is, in part 



