EFFERENT FIBERS OF THE OPTIC NERVE 227 



following the same general courses as do the branches of the 

 oculomotor nerve. In man, where the ciliary nerves have been 

 traced rather carefully, autonomic fibers supply the sclerotic and 

 choroid coats, ciliary muscle, iris, and cornea of the eyeball 

 (Carpenter, '06). The ciliary ganglion of fishes according to 

 Onodi ('01) also receives fibers from the trigeminal nerve, the 

 relation being more intimate than Schwalbe (79) believed. 



The action of atropine upon sympathetic nerves is to paralyze 

 the endings of the postgangUonic fibers. If the mechanism that 

 inhibits pigment migration involves sympathetic nerves, it was 

 thought that it might be possible to eliminate its action by the 

 use of this drug. 



By supplying fishes with water through a tube, they could be 

 retained indefinitely in the air. Dark-ada])ted fish with severed 

 optic nerves were brought into the light, and occasionaly during 

 the course of an hour small amounts of a 0.5 per cent solution of 

 atropine sulphate were introduced into the orbit. Subsequent 

 examination of the retina showed that a migration of pigment to 

 the light phase had occurred. 



The i)ossibility of a direct stimulation of the pigment cells 

 presented a difficulty, however, that had to be tested, for Spaeth 

 ('13) found that a 1.0 per cent solution of atropine caused a rapid 

 expansion of the melanophores of Fundulus. When dark-adapted 

 eyes were placed in a 0.5 or 1.0 per cent solution of the dnig and 

 were returned to darkness for an hour or more, the pigment did 

 expand to an extent which nearly equalled that caused l)y in- 

 complete light adaption. 



It is certain, therefore, that any evidence gained from experi- 

 mentation of the kind described is valueless, and it is doubtful 

 if much more dependence can be placed on the significance of a 

 pigment migration when atropine was painted on to the eye 

 muscles in such limited amounts that a direct stimulation of the 

 pigment cells seemed improbable, or when small quantities of 

 atro]:)ine were injected into the cranial cavit3\^ 



^ The use of nicotine, which paralyzes the synapse of the preganglionic fiber 

 with the sympathetic nerve cell, might furnish more interesting results, provided 

 it did not have a toxic effect on the pigment cells. Unfortunately, no experi- 

 ments of this kind were performed. 



