PHAEMACOLOGY OF EPINEPHRINE 123 



an injection of epinephrine is not due to bulbar anemia. 687 

 That the apnoea is reflex in origin was demonstrated by Hey- 

 mans and Heymans 298 who obtained a cessation of respiration 

 in the head of a dog united to the body only by the vagi, after 

 injection of epinephrine into the trunk of the animal. The 

 apnoea is thus dependent upon afferent impulses transmitted 

 by the vagus or the nerve of Hering. The apnoea may be 

 abolished by cutting both vagi and denervating the carotid 

 sinus. 297 The reflex which leads to apnea is set up by the ele- 

 vation of blood pressure in the carotid sinus. 



When the bronchioles are in a state of tonic contraction, 

 epinephrine causes their relaxation. 608 This action accounts 

 for its therapeutic use in bronchial asthma. When the bronchi- 

 oles were not fully relaxed Dixon and Ransom 160 obtained fur- 

 ther dilatation after epinephrine injection, but Golla and 

 Symes 639 obtained constriction except in cases where it had al- 

 ready been established by the previous injection of some other 

 drug. The results of various experimenters differ widely, due 

 probably to differences in the state of tone of the bronchioles. 

 After paralysis of the constrictors by ergotoxine, epinephrine 

 produces dilatation of the bronchioles with greater ease than 

 normally. 



STOMACH AND INTESTINES 



Not only the plain muscle of the vascular system but other 

 involuntary muscle is also acted upon by epinephrine. Con- 

 traction or relaxation occurs depending upon the effect of 

 sympathetic stimulation under the same conditions. 



Epinephrine causes inhibition of the rhythmic movements 

 and the tonus of the alimentary tract, an observation first 

 made by Boruttau. 73 This is used as one of the most delicate 

 physiological tests for detecting and assaying epinephrine (cf. 

 Chapter VI). The relaxation of the stomach and intestines 

 by epinephrine is in accord with their innervation, for stimula- 

 tion of the splanchnic fibres arrests peristalsis and causes re- 



