178 W. B. CANNON 



that suprarenal secretion is constant and unvarying. In consideration of 

 the faster flow the positive evidence which was obtained that epinephrin is 

 actually concentrated in the circulating hlood at that point in times of 

 stress shows, definitely, that there is an increased secretion from the 

 glands. 



The D enervated Heart. Stewart and Rogoff(&) have offered several 

 arguments opposed to the conclusion that effects seen in the denervated 

 heart are satisfactory proof of increased adrenal secretion (1918). These 

 arguments are as follows: 



1. They point out that after removal of the suprarenal glands sciatic 

 stimulation still increases the heart rate. That is true. But the amount 

 of increase is much less than when these glands are present. Cannon 

 and Rapport found that with suprarenal connections intact the average 

 acceleration of the denervated heart in 104 observations was 29 beats per 

 minute; and after removal of the glands it was, in 163 observations, only 

 6 beats per minute. Furthermore, if the hepatic nerves were severed 

 when the suprarenals were excised, sciatic stimulation had no effect or 

 caused an insignificant increase of only 2 beats per minute. And yet 

 with the hepatic nerves cut and the suprarenal connections preserved, 

 reflex stimulation evoked the usual great acceleration of the heart. 



2. They state that there is nothing strange about an increase in 

 the rate of the denervated heart when the central end of the sciatic is simu- 

 lated: u lt is obviously dependent upon the better blood flow through 

 the coronary arteries. " This statement they do not support with any 

 good evidence. With reference to it, testimony regarding the effects of 

 blood pressure (and, therefore, blood flow) in the isolated heart must be 

 relied upon. Martin, Magrath and Kennedy, MacWilliam, Lehndorff, 

 Knowlton and Starling, and Cannon (e) (1919) have reported that the rate 

 of such a preparation is not dependent on the blood pressure, i. e., the 

 rate remains uniform (after suprarenal removal, in Cannon's experi- 

 ments), although blood pressure is varied through wide ranges. Guthrie 

 and Pike likewise testify that the denervated heart in situ does not beat 

 more rapidly with a rise of pressure, unless the circulation has been stopped 

 for Comparatively long periods." After the heart has been thus asphyxi- 

 ated, the rate varies directly with the pressure in the aorta. This condi- 

 tion was not present, however, in our experiments. The explanation of 

 the faster cardiac beat in terms of a better blood flow is therefore not 

 only without support but is abundantly contradicted by competent ob- 

 servers. 



3. The third argument offered by Stewart and Rogoff is that the 

 rise of blood pressure, by increasing the rate of blood flow through the 

 denervated heart, increases the amount of epinephrin passing in unit time, 

 and the organ responds to the increased amount even without change in 

 the rate of suprarenal secretion. In answering this argument, Cannon (e) 



