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 
one-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, 4.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. 
