260 



DR JAMES A. GUNN ON 



and diminish the completeness of systolic contraction, actual arrest in almost complete 

 diastole being produced by a solution of 1 in 10,000. 



The slowing of the heart is uninfluenced by simultaneous perfusion with atropine, 

 and is therefore probably due to an action on the cardiac muscle, and not to stimula- 

 tion of the vagal terminations. 



In its action on the frog's heart, harmaline resembles quinine, which produces, in 

 much the same concentrations, slowing of the heart (which is not prevented by 

 atropine) and arrest in diastole. 



(b) Blood-vessels. 



To ascertain any changes produced by harmaline in the blood-vessels of the frog, 

 the following method was used. After exposure of the heart of a pithed frog, the venae 



1 











































































































H 



u 









































































































C- 



C. 





















































































































































































































i 



>— i 



►— « 



i— i 















s 



s 





















» , 









































































































f 





































ft 









f 





>* 





r 













5 



















































































l 9 























































































( 



y-i 



X 



i>-l 



m: 



> -■ 





N 



^ 



►-7 



?u 



i£ 



isr 



£ 



»>cC<<iiin, 



' 

























































































































































































































r\ 









































































































-i 



V 

















































































































































































































































































































































































































































































































































t 

























































































































































































































































































































































































































































































































































m 



lyi 



XX. 



Xi 



■o 



— 







/ 



•? 



















X 



o 



















3 



O 



















4 



o 



















6~ 



o 



Fig. 8. 



cavae were cut across and a fine cannula was tied into the left aorta, the right aorta 

 being ligatured. This cannula was connected with a series of Mariotte's flasks which 

 contained the fluids to be perfused. The amount of fluid exuding per minute from 

 the cut venae cavae was accurately measured. Ringer's solution was used as the 

 normal solution and as the solvent for harmaline. 



The results of these perfusion experiments may be shortly stated as follows : — 

 A solution of 1 in 1000 reduced the flow from 2 '6 c.c. per minute to 0*6 c.c. per 

 minute in thirty minutes ; a solution of 1 in 5000 (see fig. 8) reduced the flow from 

 3 "2 c.c. per minute to 0*9 c.c. per minute in thirty minutes ; a solution of 1 in 10,000 

 reduced the flow from 2'5 c.c. per minute to 17 c.c. per minute in forty minutes; 

 a solution of 1 in 20,000 reduced the flow from 2*1 c.c. per minute to 1*5 c.c. per 

 minute in sixty minutes ; while solutions of 1 in 25,000 and 1 in 40,000 had no effect 

 on the vessels in forty minutes. 



As there occurred in the frogs during these perfusions practically no oedema, it is 



