124 THE VENOM OF HELODERMA. 



ACTION ON THE ISOLATED HEART OF THE FROG. 



In this series hearts of leopard frogs (Rana pipiens) weighing from 60 to 70 

 grams were used. They were immersed in Ringer's solution of the composition 

 NaCl 0.6 per cent, NaHC0 3 0.03 per cent, CaCl 2 0.035 per cent, KC1 0.03 per 

 cent, and were transfused by a similar solution in which the venom was 

 dissolved. 



The venom solutions varied in strength from 0.01 to 2 per cent. Solu- 

 tions of less than 0.1 per cent had little if any effect. Solutions of 0.5 and 2 per 

 cent had respectively a moderate and a marked action in reducing the strength 

 of the contractions. Even after the heart had been exposed to the action of 

 such solutions for 15 to 30 minutes, washing out with fresh Ringer's solution 

 restored the strip at once to its former strength, showing that no marked toxic 

 action had been exerted and that no permanent structural change due to 

 cytolysis had been produced. 



PROTOCOLS. 



Heart No. 1. Ringer's solution for 6 minutes until normal rhythm was 

 established. Venom 0.01 per cent, renewed every 5 minutes for 24 minutes. 

 Heart stops beating, but on single touch gives a long series of beats of same 

 rate and strength as before the action of the venom. 32 minutes, Ringer; 47 

 minutes, venom 0.02 per cent; 60 minutes, beats as strong as ever, becoming 

 slower; on touch, series of rapid beats; 70 minutes, Ringer, beats continue slow; 

 78 minutes, venom 0.1 per cent, beats continue to become slower but show no 

 change in force; 102 minutes, venom 0.5 per cent, beats continue 5 minutes, 

 with no loss in strength. 



Heart No. 2. Ringer's solution to establish rhythm; 13 minutes, venom 

 0.2 per cent, beats grow weaker, but on renewing venom return to original 

 strength, 22 minutes, no loss of strength: 33 minutes, beats much reduced; 

 Ringer, beats immediately restored to full strength. 



Heart No 3. Ringer's solution for 9 minutes; venom 0.5 per cent; 24 

 minutes, heart beating in groups but strongly ; 26 minutes, heart stops, stimula- 

 tion causes single beats or short groups; 39 minutes, Ringer, heart begins again 

 in widely separated groups, beats of full strength but apparently some loss of 

 spontaneous impulse. 



Heart No. 4- Ringer, heart beating strongly in groups; 20 minutes, venom 

 2 per cent, beats immediately, much weaker but no change in rhythm; 32 min- 

 utes, Ringer, beats immediately restored to full strength; 42 minutes, venom 2 

 per cent, beats weaker and grow weaker until 52 minutes when put into Ringer 

 solution, beats immediately restored to full strength, that is, about 1.25 to 1.5 

 times as high as those under the influence of venom 2 per cent. 



