ACTIOiN OF CALMETTE'S COBRA ANTIVENIN UPON THE 

 VENOM OF HELODERMA. 



By Moyer S. Fleisher asd Leo Loeb. 



The question whether the antivenin prepared by Calmette through injec- 

 tion of cobra venom into horses exerts any influence upon the venom of Helo- 

 derma seemed to us of sufficient interest to warrant the carrying out of some 

 experiments in this direction. 



The raajoritj' of the investigators in the field of snake venoms have come 

 to the conclusion that antivenins have a definite specific relation to the venom 

 which served as antigen. This specific relation is of twofold character. In 

 the first place, the venoms of various snakes contain apparently several poison- 

 ous substances, which exert a totally different pharmacologic action, as, for 

 instance, the neurotoxin, the hemorrhagin, and the substance causing throm- 

 bosis. The chemical relationship of these substances is uncertain at present, 

 and very divergent opinions concerning it have been expressed. 



As far as the immunizing power of snake-venom antisera is concerned, 

 all investigators admit that an antivenin prepared from a venom that contains 

 only neurotoxin is powerless against the hemorrhagin or coagulin, which are 

 contained principally or side by side with neurotoxin in various venoms. Sera 

 prepared from hemorrhagins as antigen do not neutralize the neurotoxin of 

 snake venoms. 



There exi.sts, however, possibly a second kind of specificity. Are the 

 neurotoxins of the various snake venoms identical, or do they differ among each 

 other? The same question may be asked in regard to the hemorrhagins. Here 

 also the majorit}'' of investigators believe that there is a decided specificity of 

 the various neurotoxins or hemorrhagins, and consequently a specificity of the 

 antivenins prepared with certain neurotoxins or hemorrhagins. This view is 

 to a great extent based upon the results obtained by Lamb and is also upheld 

 by Noguchi. According to this view the antivenin prepared bj' the injection 

 of cobra neurotoxin protects only against cobra neurotoxin, or perhaps, though 

 very much less, against the neurotoxin of very nearly related snakes, while it is 

 powerless against all other neurotoxins. Calmette, on the other hand, main- 

 tains that the neurotoxins of the various snake venoms are identical and that 

 the antivenin prepared with cobra venom as antigen protects against the neu- 

 rotoxins of other snake venoms. 



Under these conditions it was of interest to determine whether the cobra 

 antivenin possesses any protecting influence against heloderma venom. Helo- 

 derma venom exerts its lethal influence exclusively through a neurotoxin; 

 from a pharmocologic point of view it resembles closely cobra venom, although 



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