394 SIR THOMAS R. FRASER AND MR ALISTER T. MACKENZIE ON 



clearly that with large doses there is an initial increase in the rate of the heart's 

 contractions. They show that small doses of extract of S. sarmentosus tend to 

 produce arrest of the heart in diastole, whereas large doses usually cause the heart to 

 stop in systole. The increase in the range of cardiac movement, systolic and diastolic, 

 is further emphasised, and it is seen that the auricles share it with the ventricle. The 

 lengthening of the diastolic pause is well seen in the graphic records. (Plate VI.) 



(b) Blood-vessels. 



To investigate the action of S. sarmentosus on the blood-vessels, experiments were 

 performed on frogs {Rana temporaria) whose brain and spinal cord had been destroyed. 

 A cannula was tied into the ductus arteriosus, and the sinus venosus was divided. 

 Ringer's solution was perfused from a constant level, maintained by Marriotte's 

 flasks. When the blood had been entirely washed out of the vessels, the outflow was 

 collected in graduated glass measures, and the amount passing through the vessels each 

 minute was thus obtained. When a normal flow was established, the contents of one 

 of the other Marriotte's flasks containing a solution of extract of S. sarmentosus in 

 Ringer's solution was perfused instead of simple Ringer's solution. In this way, the 

 effect of Strophanthus upon the blood-vessels was obtained. In some experiments a 

 solution of digitalin (pure, Merck) in Ringer's solution was perfused after the 

 Strorjhanthus solution in order to emphasise the difference in their effects on the blood- 

 vessels. 



In these experiments, the level of the solutions above the ductus arteriosus was 6|- 

 inches ; the temperature of the laboratory varied from 52° to 56° F. Ringer's solution 

 by itself had practically no effect on the calibre of the blood-vessels in two hours. 



The following experiments are representative of the series : — 



[Experiment LXV. 



