54 APPLIED IMMUNOLOGY 



nature and mode of action of snake venoms have been 

 studied extensively, especially by Calmette and Flex- 

 ner and Noguchi. Their researches have shown that 

 poisonous snakes can be classified into two broad 

 groups, according to the effects produced by the 

 toxins of their venom. To one group belong the 

 cobras, whose venom is principally in the nature of a 

 neurotoxin, acting especially on the respiratory centre 

 in the medulla, while in the other group, containing 

 the vipers and rattlesnakes, the venom contains a 

 hemorrhagin, and causes extravasation of blood in 

 various regions of the body. In addition, all snake 

 venoms possess hsemolytic properties, found most 

 markedly in cobra venom. Against the neurotoxin 

 of cobra venom, Calmette has successfully produced 

 an antitoxin (antivenin) by injecting horses with the 

 venom. This is only of therapeutic value, however, 

 against cobra bites, and is useless as an antidote 

 for rattlesnake bites. Attempts have been made, but 

 unsuccessfully so far, to produce a reliable antihemor- 

 rhagic serum for the treatment of rattlesnake bites. 



The antivenin of Calmette may be injected in 

 doses of 10 to 20 e.c. To be of any value it naturally 

 must be used as soon as possible after the bite is re- 

 ceived, and is probably useless after 3 or 4 hours. 

 The serum has, therefore, only limited application as 

 a therapeutic measure. 



