186 MICROBES AND TOXINS 



known. It is one of the dreams of biological chemistry to 

 discover an equivalent to cholesterin for the other toxins. 



Still more interesting is the fact that the peculiar anaemia 

 produced by injecting cobra-lecithid into an animal can be 

 prevented by giving cholesterin. It would seem that cholesterin 

 acts towards lecithin and lecithid, not only as an antagonist, 

 but as a remedy. 



There are, of course, facts which prevent us from regarding 

 as entirely similar the cobra-hsemolysin, on the one hand, and 

 the solvent properties or haemolysins of normal and immune 

 sera (sera derived from animals prepared by the injection of 

 blood corpuscles) on the other. These, however, do not 

 invalidate Kyes's conclusions in his experiments on the 

 lecithids. The study of snake-venoms has shown a participa- 

 tion of chemically-defined substances in phenomena hitherto 

 only known from the biological point of view. It would be 

 of immense interest, both theoretical and practical, to discover 

 an analogous mechanism in the effects of toxins. 



Certain animals enjoy a natural immunity towards snake- 

 venom, which, however, is never absolute. It is possible that 

 these animals have received from generation to generation 

 small doses of the venom as the result of being bitten, and 

 that they have in consequence elaborated an antivenom. 

 This forms the starting-point of artificial immunisation and 

 antivenom serum-therapy. It is known that the blood of 

 certain animals possesses normally a weak antitoxic action 

 against diphtheria and tetanus toxins ; these animals similarly 

 must have harboured tetanus and diphtheria bacilli. 



The animals possessing the most remarkable resistance 

 towards snake-venoms are the hedgehog and the mongoose. 

 To see the dramatic combats which take place when the 

 mongoose tackles the cobra, one has only to read Kipling's 

 marvellous tale of the war between " Rikki-Tikki " and " Nag " 

 in \hejungle Book, 



