SUBSTANCES WHICH ACTIVATE COBRA VENOM. 



451 



The activating substance itself is therefore thermostable. If, 

 however, the decanted haemoglobin solution is again added to the stro- 

 mata and this mixture heated to 62 C. inactivation will again ensue. 

 (See Table VIII.) 



TABLE VIII. 



From this it appears that the inactivation of the native blood 

 solution depends on this: that on heating to 62 C. the active substance 

 combines with the haemoglobin in such fashion that it is no longer 

 able to combine with the cobra amboceptor. Hence in view of the 

 readiness with which lecithin combines with albuminous substances, 

 etc., we believe that the activating property of dissolved blood-cells 

 which we previously described as an "endocomplement action" is 

 really due to the presence of lecithin or lecithin-like substances in the 

 stroma. 1 



We have convinced ourselves of the correctness of this assump- 

 tion also by the fact that lecithin is bound by crystallized horse 

 haemoglobin by heating for half an hour to 62 C. 2 An experiment 

 of this kind is reproduced in Table IX. 



A solution of haemoglobin heated for half an hour to 62 C. is also 

 able to inhibit the activating property of lecithin when digested with 

 this for half an hour at 37 C. 



The lecithin character of the activating substance present in the 

 red blood-cells is confirmed by a number of other observations which 

 deal with the analogous character of cobra-venom haemolysis on the 



1 We were able to completely extract the activating substance from the 

 stromata suspensions by means of alcohol. Besides this, in activating with 

 stromata in the presence of excess of cobra venom, one observes an inhibition 

 of haemolysis due to the deflection of the lecithin. 



2 We are much indebted to Prof. Hiifner of Tubingen for this haemoglobin. 



