136 APPLIED BACTERIOLOGY 



China, Dr. Calmette, during the rainy season of the autumn 

 of 1891, was able to obtain a large number of the reptiles 

 known as the cobra di capello, which provided a sufficient 

 amount of venom for the subsequent investigations. 



It was found that the venom exercised remarkably rapid 

 toxic effects upon all classes of animals, the serpents them- 

 selves only proving refractory ; but even these succumbed 

 to very large doses of the venom. Unlike the toxins of 

 bacterial origin, serpent venom can stand a considerable 

 amount of heating without injury to its virulence. The 

 toxic character of cobra venom is in no way diminished by 

 half an hour's heating at 97° C, but its toxic character is 

 destroyed if the temperature is raised to 98° C. The venom 

 of some species of reptile will endure even a greater amount 

 of heat than this without injury, but others lose their viru- 

 lence at a somewhat lower temperature. The method em- 

 ployed by Dr. Calmette for the preparation of anti venomous 

 serum, as described by him in his paper before the British 

 Medical Association Meeting of 1896, is as follows : The 

 method of procedure for the purpose of vaccinating large 

 animals, such as horses, consists of injecting them with gradu- 

 ally increasing doses of the venom of the cobra, mixed with 

 diminishing quantities of a 1 in 60 solution of hypochlorite 

 of lime. The condition and weight of the animals are 

 watched, so that the injections may be lessened if the 

 animals do not thrive well. Injections of stronger and 

 stronger venom are made, first considerably diluted, and 

 then more concentrated. In order that the horses may 

 yield a thoroughly efficient serum, when they have acquired 

 a sufficiently perfect immunity, it is necessary to inject 

 the venom of as many species of reptile as possible. The 

 process of immunisation lasts at least fifteen months before 

 the animals yield a sufficiently active serum for practical 

 purposes. 



