RELATION SUPRARENAL GLANDS TO CIRCULATION 199 



tions, Hoskins and McClure, in 1912, reinvestigated the matter. Dogs 

 were used as experimental animals. Systematic study showed that if 

 epinephrin is injected by vein at a slow but gradually increasing rate, 

 at first no effect at all is apparent. As the dosage is increased the first 

 effect to appear is depression. This may or may not be preceded by a 

 brief inconsequential rise of pressure. In one instance a record was ob- 

 tained, showing a pure hypotensive effect which persisted for several 

 minutes, the blood-pressure promptly returning to normal when the in- 

 jection was discontinued. With still larger doses it was found that a 

 pressor effect appeared, which might exactly cancel the depressor effect, 

 leaving the pressure, after a slight initial fluctuation, at a normal level. 



4-i i i i i ri t i ! ! ! i' ! i i r i i t 



120 mm. .1 c.c. .2 c.c. .5 c.c. 



Fig. 1. Graph showing transition from pure depressor to predominantly pressor 

 reaction in cat from intravenous injections of epinephrin. Doses, 0.1, 0.2, and 0.5 c.c. 

 1:10,000 solution. Time, half minutes. (After Cannon and Lyman, Am. J. Physiol.) 



Still larger doses brought about the well-known pressor reaction. In one 

 typical instance in which the point was specifically under investigation, 

 although the characteristic depressor reaction appeared with the injection 

 of 3 c.c, of 1 :1,000,000 solution of epinephrin per minute, it was not until 

 a dose of 17 c.c. per minute was used that a minimal sustained rise oc- 

 curred. Since pure isolated epinephrin was used in these experiments, 

 the only apparent explanation of the depressor effect was that some vaso- 

 dilator mechanism had been brought into play. 



In 1913 Cannon and Lyman subjected the problem to elaborate study. 

 Cats were used as experimental animals. Epinephrin was injected by 

 jugular vein and the dosage was accurately controlled, as was also the 

 speed of injection, both of which are important factors in the type of re- 

 action elicited. Blood-pressure was recorded from the femoral or carotid 

 artery. It was found that by varying the doses all degrees of reaction 

 from a fall of 22 per cent to a rise of almost any desired magnitude could 

 be obtained (Figs. 1 and 2). The depression was not accompanied by 



