SNAKE VENOM 27 



Uventioth days after injection. The only explanation 

 offered is that part of the serum used as an injection 

 remains unaltered in the subject, while the remainder 

 sensitises the serum of the subject. In fact, a sort of 

 auto-anaphylaxis occurs. 



Snake Venom. The venoms of different species of 

 poisonous snakes differ greatly in composition. Some 

 appear to contain proteolytic enzymas which are supposed 

 to produce the softening of the inuscles in the animals 

 attacked. Cobra venom contains a hsemolysin, innocuous 

 by itself, but activated by normal complement in the 

 blood-serum of the victim. This hsemolysin is also activated 

 by lecithin. 



Rattlesnake venom acts partly by lysis of the endothelial 

 lining of bloodvessels, the specific toxin from its effects 

 being called ' haernorrhagin.' Other venoms, such as that 

 of the krait, produce intravascular thrombosis through an 

 almost instantaneous coagulation of the blood. Many 

 venoms are neurotoxic, the neurotoxins of different species 

 selecting different sites for activity, one acting on the 

 respiratory centre, another on the nerve endings in muscle. 

 Serpent venom, unlike true bacterial toxins, is unaffected 

 in virulence by a considerable degres of heating. 



Antivenin or Antivenomous Serum. Calmstte injects 

 horses with gradually increasing doses of cobra venom 

 mixed with diminishing quantities of a 1 in 60 solution of 

 hypochlorite of lime. When they have acquired sufficient 

 immunity, the venoms of as many species of reptile as 

 possible are injected. The process of immunisation lasts 

 at least fifteen months. 



Calmette's serum is active to the extent of 1 to 200,000 

 that is to say, it is sufficient to inject as a prophylactic 

 dose a quantity of serum into a rabbit equal to o^oooo of 

 its body-weight; 0-5 c.c. of this serum is sufficiently active 

 to protect a rabbit against a dose of venom, which other- 

 wise would be lethal in three or four hours, if it is not 

 injected later than half an hour after the bite. The dose 

 of the antivenin for a human being is, according to Calmette, 

 10 to 20 c.c., but Lamb and Hanna consider that it should 

 be 30 to 40 c.c., injected as soon after the bite as is prac- 

 ticable. 



It has been asserted that cobra antivenin protects 

 animals against any snake poisons; but Martin and 



