524 JOURNAL, BOMB A Y NA TURAL HISTORY SOCIETY, Vol. XI. 



hours. The maximum preventive effect is obtained by injecting the 

 venom twelve hours after the serum. 



The immunity acquired by the injection of serum is thorough, but 

 it disappears after an interval which, according to my experiments, 

 does not exceed eight days. It is then not lasting, differing in this 

 respect from the immunity produced by the poisons themselves. The 

 latter holds good in the case of hypervaccinated rabbits for at least 

 ten months. 



The antivenom serum is more active and efficacious for a longer 

 time according as the animals which furnish it are more highly im- 

 munised. 



The fol lowing is the method by which we ascertained the length of 

 time during which the injection can prevent death after the inocula- 

 tion of a twice fatal dose of venom in our animals. 



We inoculated a certain number of rabbits, let us say under the 

 skin of the thigh, with the same dose of venom — 1 milligr. of cobra 

 poison — and we treated all these animals, with the exception of some 

 for control purposes, with subcutaneous injections of the serum of a 

 horse active to the 20,000th. The control animals, not thus treated, 

 died in from three to four hours. 



The rabbits which had half a cubic centimetre of therapeutic serum 

 half an hour, three quarters of an hour or one hour after the venom, 

 all resisted the poison. 



Those which got the therapeutic serum between one hour and one 

 hour and a-half after the venom, resisted in the proportion of two in 

 three. 



The injection of 1 c. c. of serum one hour and a-half after the poison 

 is, as a rule, followed by recovery. 



This interval once passed, recovery is no longer possible, because the 

 rise of temperature and the bulbar phenomena characteristic of the 

 poisoning have already begun to show themselves. 



In man it is possible that intervention by means of the antivenom 

 serum may bo efficacious much later on, as it is rare for bulbar symp- 

 toms to be manifested under three hours. 



In the commonest cases death supervenes between ten and twelve 

 hours after the bite, and even later still when the bite is caused by the 

 Crotalus bothrops, and the snakes of Australia. 



