EFFECT OF THE VENOM OF HELODERMA SUSPECTUM ON 



THE ISOLATED HEART. 



By Thomas Stotesbury Githens. 



In order to determine whether or not the influence of the venom of the 

 Gila monster on blood-pressure was dependent upon a paralyzing action on the 

 cardiac muscle, and also to determine the effects of this venom on muscle-tissue 

 in vitro, two series of experiments were carried out, one on strips of the cardiac 

 muscle of the turtle, the other on the isolated heart of the frog. The results 

 seem to show that the direct action of the venom on the heart-muscle plays 

 only a small part in the toxic action exhibited when it is injected into the 

 living animal. The venom seems to exert a slight toxic action on the isolated 

 heart, but does not exert a noticeable cytolytic influence upon heart-muscle 

 tissue in vitro. These results agree with physiological tests which show that 

 the venom of the Gila monster, like some snake venoms, acts mainly on the 

 respiratory center, and that the heart continues to beat after respiration has 

 ceased. The strips of muscle which were exposed to the action of the venom 

 usually ceased to beat someAvhat sooner than the controls, but not enough to 

 indicate a very marked toxic action on the heart. The isolated heart, trans- 

 fused with solutions of venom, was markedly affected only by very high 

 concentrations. 



ACTION ON STRIPS OF TURTLE HEART. 



The technique of this series was as follows : The heart was removed and 

 the ventricle cut into four longitudinal strips, extending from the base to the 

 apex, the auricle being used as a fifth strip. No difference was found in the 

 behavior of the auricle, except that the latent period was somewhat shorter. If 

 such strips are placed in 0.7 per cent NaCl solution, they will begin to contract 

 rhythmically in from 30 minutes to 2 hours, these rhythmic contractions con- 

 tinuing about the same length of time and then gradually ceasing. If small 

 amounts of calcium and potassium are now added to the NaCl solution, or if 

 the strips are transferred to Ringer's solution, rhythmic contractions will again 

 begin. If the contractions cease they may often be induced to recommence by 

 transferring back to 0.7 per cent NaCl solution for a time and returning once 

 more to the Ringer's solution. The length of time during which contractions 

 continue is more or less irregular, even under the best conditions. In our 

 experiments the controls lived from 9 to 36 hours. 



In some experiments the venom was dissolved in 0.7 per cent NaCl solu- 

 tion and the strips placed in this on their removal from the body, and when the 



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