EMERGENCY FUNCTION OF SUPRARENAL MEDULLA 179 



checked the rise of blood pressure by thoracic compression while stimulat- 

 ing the sciatic, and permitted the pressure to rise immediately thereafter. 

 The heart rate increased just as much during stimulation as it had in 

 a previous test when no check was applied, and it did not increase any 

 jwilfier when the pressure was allowed to rise. The heart rate, when 

 fastest, was not near the maximum, and consequently it could have been 

 faster. In commenting on this experiment, Stewart and Rogoff() argue 

 (1920) that thoracic compression by checking venous return alters the 

 concentration of the secreted epinephrin, and consequently the heart 

 is accelerated; and that when the pressure rises, the concentration be- 

 comes proportionally diminished, and therefore no change in the rate is 

 seen. For this argument to be sound, it would be necessary to prove 

 quantitatively that checking the venous return did in fact have the effect 

 which is claimed. This was not done. On the other hand, the test has been 

 made by Cannon and Rapport of passing a constant flow of epinephrin into 

 the inferior cava after removal of the adrenal glands, and holding the pres- 

 sure down during stimulation of an afferent nerve. There was no increase 

 of heart rate. The explanation given by Stewart and Rogoff is, therefore, 

 not sustained by experiment. 



4. A fourth argument presented by Stewart and Rogoff, and one 

 which they reiterate frequently, is that afferent stimulation by constricting 

 splanchnic vessels lessens the blood flow through the liver ; in consequence 

 the secreted epinephrin contained in the cava blood is less diluted (i. e., 

 more concentrated) than normal and therefore has more stimulating 

 power. So far as the denervated heart is concerned, it is not the con- 

 centration in the inferior cava but the concentration in the coronary 

 vessels, which is effective. Recently Cannon and Rapport have tested this 

 fourth argument, after cutting the mesenteric nerves, tying the carotids, 

 subclavians, and renal vessels, and the aorta and inferior cava below the 

 renal branches, and placing a tight ligature about the inferior mesenteric 

 artery and nerves (referred to later as a "reduced" animal). Thus the 

 possibility of a shift of the circulation was reduced to a minimum. Never- 

 theless, under light ether anesthesia, brachial stimulation for 30 seconds in- 

 creased the rate of the denervated heart in 25 instances by an average of 

 26 beats per minute (in 13 cases more than 30 beats). During stimula- 

 tion, the changes of blood pressure were insignificant (in 17 of the 25 

 instances less than 10 mm. Hg) or were only moderate variations up 

 or down. There was no possibility under these circumstances of any 

 great concentration of secreted epinephrin because of failure of blood to 

 pass through constricted splanchnic vessels, for the nerves which would 

 cause constriction of these vessels had been previously cut. The increased 

 rate <5ould not have been due to a a redistribution of blood," for the possi- 

 bilities of any considerable redistribution of blood were lacking. The only 

 explanation that appears is that the output of epinephrin was increased. 



