i6o 



Scientific Proceedings (107). 



85 (1545) 



The effect of therapeutic doses of digitalis on the contraction of 



heart muscle. 



By Alfred E. Cohn and Robert L. Levy. 



[From the Hospital of the Rockefeller Institute for Medical Research, 



New York, N. Y.] 



That digitalis causes alterations in the heart resulting in 

 changes in the form of the electrocardiogram is now well known. 

 Robinson and Wilson have estimated in experiments on cats that 

 the quantity of digitalis which can induce a change is about 30 

 per cent, of the calculated lethal dose. So far, however, no evi- 

 dence has been presented to show that this amount of digitalis is 

 beneficial — except in cases of fibrillation of the auricles in which 

 block of auricular impulses, mainly through stimulation of the 

 vagus nerves, takes place. 



A beneficial action must be based on the ability of the drug to 

 increase the volume output of the heart, and it must be able to 

 do this in therapeutic doses, that is to say, in doses which influence 

 the T wave of the electrocardiogram or reduce the rate in auricular 

 fibrillation. We have accordingly injected this amount into 

 the veins of dogs, 11 of which received the tincture of digitalis 

 and 19 of which received g-strophanthin; and into cats, 5 of which 

 received g-strophanthin, and 9, the tincture of digitalis. 



Alterations in volume output were studied in curves obtained 

 by the use of the Roy and Adami myocardiograph. The curves 

 represent longitudinal linear alterations in the form of ventricles 

 and may, under the conditions of cardiac contraction, represent 

 changes in volume of the cavities and consequently of volume 

 output. The results are reported as changes in the degree of 

 contraction. The animals were anesthetized with ether only. 

 The chest was opened in the median line. Other details of the 

 technical procedure, which are important, will be given in the full 

 report of these experiments. 



The significant results concern the effect of these two drugs 

 on the T wave and on the degree of contraction (Table I). In 



