176 W. B. CANNON 



suprarenal, veins repeatedly caused inhibition of the beating intestinal 

 strip, whereas that removed before excitement had no such effect. Since 

 excitement after removal of the suprarenal glands did not yield this re- 

 sult, and since the effective blood lost its inhibitory power when exposed 

 to oxygen (a procedure known to destroy epinephrin), the inference was 

 drawn that suprarenal secretion is stimulated by great emotion. 



In addition to these direct observations on the stimulating effect df 

 strong emotion on suprarenal secretion, there were other observations hav- 

 ing inferential value. In 1914, Cannon and Mendenhall, after showing 

 that clotting of the blood is hastened by stimulation of the splanchnic 

 nerves, found that great excitement will cause the same effect. The evi- 

 dence which they brought that injected epinephrin shortens the clotting 

 time, that when the splanchnic nerves are stimulated the suprarenal 

 glands are necessary for the effect, and that excitement induces faster clot- 

 ting only so long as the splanchnic nerves are intact, was confirmatory of 

 the view that excitement causes suprarenal discharge. 



In 1915, Lamson noted that injection of epinephrin would cause a 

 polycythemia, and that emotional excitement, such as fear and rage, 

 would likewise cause it. If an animal was frightened after removal of the 

 suprarenal glands, however, there was no increase in the red count. Lam- 

 son observed that asphyxia had the same effect as fright and that removal 

 of the suprarenals prevented the customary increase seen after asphyxia- 

 tion. 



The completely denervated heart can be used as an indicator of supra- 

 renal secretion in testing the influence of emotional excitement just as it 

 is used in relation to sensory stimulation and asphyxia. It is only neces- 

 sary to take somewhat greater pains in order to keep animals in normal 

 condition after operation. To denervate the heart, the stellate ganglia 

 are first removed under ether with aseptic t precautions ; later the right 

 vagus nerve is severed below the recurrent laryngeal branch ; and still 

 later, the left vagus nerve is cut in the neck. The heart is thus wholly dis- 

 connected from the central nervous system and any agency causing an in- 

 crease in the heart rate must exert its influence through the blood stream, 

 either mechanically or chemically. Electrocardiographic records of the 

 heart rate under these conditions show an increased rate during excitement 

 when the glands are present, and a failure of noteworthy increase when 

 they are absent ( Cannon (e), 1919). By both direct and indirect testi- 

 mony, offered by different observers using different methods, the evidence 

 is concordant that emotional excitement is accompanied by increased secre- 

 tion of the suprarenal medulla. 



