138 IMMUNE SERA 



a great deal in their toxic properties, and this is 

 due to their relative contents of different consti- 

 tuents, as follows:' haemagglutinins, haemolysin, 

 hsemorrhagin, and neurotoxin. The first two act 

 exclusively on the blood cells, the haemorrhagin on 

 the endothelium of the blood vessels, and the 

 neurotoxin on the cells of the central nervous 

 system. The last named causes death by paralysis 

 of the cardiac and respiratory centers. The ven- 

 oms of the cobra, water-moccasin, daboia and 

 some poisonous sea snakes are essentially neuro- 

 toxic, although they have strong dissolving powers 

 for the erythrocytes of some animals. In study- 

 ing the haemolytic powers of the venoms of cobra, 

 copperhead, and rattlesnake, Flexner and Noguchi 

 found cobra venom to be the most haemolytic and 

 that of rattlesnake the least. They attribute the 

 toxicity of rattlesnake poison chiefly to the action 

 of haemorrhagin. The venoms of the water mocca- 

 sin and the copperhead also contain haemorrhagin. 



Unlike the bacterial toxins the action of the snake 

 venoms is preceded by no appreciable incubation 

 period. In addition to this the poisons are very 

 rapidly absorbed. Thus Calmette found that a rat 

 inoculated into the tip of the tail could not be saved 

 by amputating the tail orie minute later. Such 

 animals died within about five minutes of the time 

 required for control animals. 



The haemolysin and neurotoxin and perhaps also 



