GENERAL PROPERTIES AND ACTIONS OF THE VENOM. 



91 



rabbit serum. All the mice which received 0.2 mg. of dry venom died approxi- 

 mately at the same time after the injection, even when the injected venom 

 stood for an hour after having beenmixed with 0.5 c.c. of immune serum. Sim- 

 ilar results were obtained when 1.4 mg. of venom were injected, even though 

 1 c.c. and 2 c.c. of immune serum had been added. 



The injection of 0.4 or 0.6 mg. of venom plus 1 c.c. of immune serum was 

 not lethal when the venom and serum of the immunized rabbit were allowed to 

 stand until a precipitate had formed, whereas the injection of the same quan- 

 tities of venom without serum caused death. 



We conclude from these experiments that although repeated injections of 

 venom into rabbits enable them to resist the toxic effect of large doses of venom, 

 no distinct antitoxin had been produced. It may be noted that in some cases 

 the previous injection of immune-rabbit serum or the mixing of the venom 

 with immune-rabbit serum before the injection of venom into mice delayed 

 slightly the lethal effect of the venom, so that we may perhaps conclude that 

 a very small amount of antitoxin had been produced. Had it been possible to 

 carry the immunization of the rabbits further, an antitoxin might have been 

 produced. It is, however, quite apparent that relatively enormous quantities 

 of venom — more than we could devote to this problem — would have been 

 required in order to accomplish the production of an antitoxin, and it was 

 doubtful whether, even in the case of perfect success, the results would have 

 been of sufficient theoretical interest to justify such an expenditure of venom 

 and of effort. 



Antitoxic power of the serum of rabbits immunized against heloderma venom. 



•Rabbit bled May 23, 1909. tEabbit bled May 27, 1909. JStanding 4 hours showed precipitate. 



