124 MEDULLA 



laxation of the gut. Certain parts of the intestinal tract, 

 however, receive motor fibres from the sympathetic and these 

 (the pyloric, ileo-colic, and internal anal sphincters and the 

 muscularis mucosae) are contracted by epinephrine. Pressor 

 doses in man do not affect the intestinal movements. 165 



Although inhibition is the typical reaction of the gut to 

 epinephrine, excitatory effects are occasionally obtained. This 

 is explained by assuming an occasional preponderance of motor 

 over inhibitory sympathetic fibers. Hoskins 308 showed that 

 doses below the threshold for inhibition will frequently cause 

 an increased tone and rhythmical activity. In the rabbit 

 epinephrine causes relaxation of the internal anal sphincter 

 and the oesophagus as does also stimulation of the sympa- 

 thetic nerves to these tissues. 



In birds and amphibia where the sympathetic nerves are 

 mainly motor in function, epinephrine causes contraction. 



THE EYE 



The intravenous injection of epinephrine causes elevation 

 of the lid, retraction of the nictitating membrane, and dilata- 

 tion of the pupil. These effects are, however, much more pro- 

 nounced after extirpation of the superior cervical ganglion 

 with subsequent degeneration of the post-ganglionic fibers. 

 Likewise the application of epinephrine to the conjunctiva 322 

 does not affect the pupil unless the superior cervical ganglion 

 has been extirpated. 



The reaction of the enucleated frog's eye immersed in iso- 

 tonic saline has been used as a test for epinephrine. 174 Al- 

 though sensitive to epinephrine in a dilution of 1 to 20 million, 

 the method is not specific. 



In rabbits after superior cervical ganglionectomy, dilata- 

 tion of the pupil results from the subcutaneous injection of 0.6 

 cc. of a 1 : 1000 solution of epinephrine. Occurring within 15 

 minutes after the injection, the reaction lasts for over 2 hours. 

 During its maximum dilatation, the pupil does not react to 



