VACCINATION AGAINST SNAKE-VENOM 243 



repeated every three or four days, while attentively following the 

 variations in the weight of the animals. The inoculations are 

 suspended as soon as emaciation supervenes, and resumed when the 

 weight becomes normal again. After four injections of chloridated 

 venom the chloride is omitted, and a direct inoculation made with 

 ome-half the minimal lethal dose of pure venom ; then, three -or 

 four days afterwards, the injection is increased to three-fourths of 

 the minimal lethal dose ; and finally, after the lapse of another 

 three or four days, a lethal dose is injected. 



If the animals prove resistant, the vaccination can thenceforth 

 be pushed on rapidly, and the quantity of venom injected each time 

 can be increased, testing the susceptibility of the organism by the 

 variations in weight. 



As a rule, three months are necessary for the vaccination of 

 a rabbit against twenty lethal doses. In six months we can 

 succeed in making it very easily withstand 100 lethal doses. 



The serum of rabbits thus treated soon, i.e., after they have 

 received from five to six lethal doses, exhibits antitoxic properties 

 in vitro ; these, however, are not very pronounced until after 

 prolonged treatment. They gradually become just as intense as 

 those observed in the case of animals vaccinated against diphtheria 

 or tetanus. 



In 1895 Fraser confirmed these results,^ and on May 15 in that 

 year exhibited before the Medico-Chirurgical Society of Edinburgh 

 a rabbit vaccinated against a dose of cobra-venom fifty times lethal. 



At once considering the possibility of obtaining serums highly 

 antitoxic against snake-venoms, and of practical utility in the thera- 

 peutics of snake-bites, I prepared to vaccinate a certain number of 

 large animals, horses and donkeys, in order to procure great quan- 

 tities of active serum. I at first experienced some difficulties in 

 providing myself with a sufficient store of venom. But thanks on 

 the one hand to the obliging collaboration of some of my old pupils 



' British Medical Journal, June 15, 1895. 



