522 JOURNA L t BOMB A Y NA TURAL HISTORY SOCIETY, Vdl . XI. 



The first method is capable of giving a very solid immunity against 

 considerable doses of poison, but it is slow, and its application requires 

 very careful surveillance. If animals are injected with increasing 

 doses at shoi't intervals, they speedily become thin and succumb. It is 

 necessary to begin with very weak doses, continued for a long time, 

 and to increase the quantity of Venom injected little by little, until, 

 after four or five months of treatment^ the animals are able to stand 

 without being ill a dose which would kill 100 fresh animals. 



The surest method to adopt in vaccinating any animals, whether 

 rabbits, guinea-pigs, dogs or horses, consists in injecting at first, for 

 four weeks, increasing quantities of venom mixed with decreasing 

 quantities of a solution of 1 in 60 of hypochlorite of lime. The ini- 

 tial dose of venom, of course, varies according to the relative toxicity 

 of the latter; it should not exceed half the minimum fatal dose. 



The variation in weight of the animals must be carefully observed, 

 and the intervals between the injections regulated according to the 

 state of health. In this way one succeeds little by little in setting up 

 a toleration, first of four to five times the fatal dose, then of doses 

 double, triple, and at last centuple and even more. 



The serum of animals immunised against venoms by either of the 

 preceding methods possesses properties similar to those which Behring 

 and Kitasato, Roux and Vaillard ascertained to exist in the serum of 

 animals immunised against tetanus and diphtheria. 



This fact mentioned by me in the Societe de Biologie (February 

 10th, 1894) had been observed at the same time by M.M. Phisalix 

 and Bertrand in the case of guinea-pigs vaccinated against the venom 

 of the viper by the method described by these experimenters. It was 

 confirmed a year later by Professor Fraser of Edinburgh (British 

 Medical Journal, June, 1895), who successfully repeated almost all the 

 experiments of which I had published the results in the Annales de 

 VInstitut Pasteur (May, 1894, p. 275.) 



If 1 milligramme of cobra poison or 4 milligrammes of viper's 

 venom is mixed in vitro with a small quantity of serum from an immu- 

 nised rabbit, and if with this mixture a fresh rabbit is inoculated, the 

 latter experiences no discomfort. 



It is not necessary that the serum should be taken from an animal 

 vaccinated against a venom of the same origin as that introduced 



