RELATION SUPRARENAL GLANDS TO CIRCULATION 197 



three to five minutes' interval, the second also. Post-mortem examina- 

 tions showed that the ligatures in each case had successfully occluded the 

 lumbo-adrenal vessels. In two instances the suprarenals were dissected 

 free and tied off by mass ligatures directly while blood-pressure was being 

 recorded. 



In view of the evanescent nature of circulating epinephrin, the experi- 

 ments were continued only from ten to thirty minutes. It was assumed 

 that any direct results of suprarenal deficiency would occur within that 

 time. The results agreed consistently with those of Young and Lehman. 

 In only one case, after ligating off a gland, was any significant fall of 

 pressure observed. Usually, at the moment of tying the ligature -there 

 was a brief fluctuation of pressure, sometimes upward and sometimes 

 downward, but the original level was quickly regained. 



More recently Austmann, Halliday, and Vincent have also sub- 

 jected the problem to renewed study. They offered the criticism that the 

 time allowed in previous experiments was not sufficiently long to be com- 

 pletely convincing. In their series dogs were employed. The suprarenals 

 were extirpated or their blood-vessels ligated, and continuous records were 

 kept of the blood-pressure under simple ether anesthesia during periods 

 of from 12 to 40 hours. From control animals curves were similarly ob- 

 tained under ether anesthesia but with the suprarenals intact. With 

 a few individual exceptions, the curves were very similar in the two series. 

 The animals deprived of their suprarenal secretion lived as long as the 

 controls and the blood-pressure showed no greater tendency toward a fall. 



Bazett (1920) has again repeated the extirpation experiments on 

 cats and rabbits and has confirmed the results of earlier investigators to 

 the effect that the operation fails to produce any such prompt fall of blood- 

 pressure as the "tonus theory' 7 demands. 



It is obvious, therefore, that under the conditions of these experiments, 

 at any rate, the suprarenal glands do not discharge epinephrin in suffi- 

 cient quantity to have any significant direct effect upon blood-pressure. 



Vasodilator Effects of Epinephrin 



The first definite evidence that suprarenal extract may produce a fall 

 in blood-pressure was reported Try Moore and Purintoii in 1900. These ob- 

 servers set out to determine the threshhold doses of such extracts. Supra- 

 renal glands of cattle and sheep were split and the medullary portion me- 

 chanically separated from the cortex. Aqueous extracts were then made 

 of the material, the protein components being largely removed by boiling 

 in a slightly acid medium. Dilutions of 1 :100 to 1 :1000 were employed. 

 It was assumed that in such high dilutions the effect of any "foreign sub- 

 stances" that might be present in the concentrated extract would be re- 



