212 



Scientific Proceedings (68). 



127 (1059) 



The inhibitory effect of adrenalin upon the sphincter of the pupil. 

 By Don R. Joseph. 



[From the Department of Physiology, Saint Louis University.} 



The sphincter muscle from the eyes of cattle, sheep and hogs 

 was tested as quickly as possible after death. Two methods were 

 used: (a) A strip, containing the sphincter, was cut from the 

 pupillary border of the iris, connected with a lever and kept in a 

 bath of either saline, Ringer's solution or aqueous humor, at 38 

 to 40 degrees Centigrade — in some cases with oxygen streaming 

 through, (b) In other cases the sphincter was only partly excised, 

 but connected with the registering apparatus in such a way that 

 contraction or relaxation of the sphincter alone could affect the 

 lever. In these experiments the iris was kept in an enclosed, 

 warmed, air chamber and adrenalin dropped upon it from a pipette 

 at the time of the test. The 1 : 1,000 Parke Davis solution was 

 used. 



Over 50 experiments are included in this report. Adrenalin 

 produced, practically without exception, a relaxation of the 

 sphincter. This was true for each of the three species of animals 

 tested. The relaxation began promptly and at first was rapid so 

 that the lever traced very nearly a vertical line on the drum. 

 Later the rate of relaxation slowly decreased but in most cases 

 continued until it seemed to be maximal. No recovery was seen 

 even when the adrenalin bath was replaced with a fresh non- 

 adrenalin-containing bath. That the sphincter was still irritable, 

 however, was demonstrated by the addition of physostigmin, when 

 a good contraction usually resulted. 



This inhibitory effect of adrenalin indicates that the cervical 

 sympathetic supplies inhibitory nerve fibers to the sphincter 

 muscle of the iris. 



