ARTIFICIAL IMMUNIZATION 231 
dose of venom capable of killing a rabbit in about 20 minutes was injected into 
each of them, and into 2 control rabbits at the same time. The controls died 
in 16 and r7 minutes after the injection, respectively, while the 6 animals which 
had received the antivenin beforehand showed no symptoms of toxication. 
In the second series 8 rabbits received simultaneously equal doses of venom, 
sufficient to kill them within 2 hours. These venomized rabbits were then 
divided into four sets. To the first two animals 3 c.c. of antivenin were given 
intravenously 30 minutes after the injection of venom. To the second set 
the same quantity of antivenin was administered after 1 hour. One of the 
third set expired at the moment when, after 90 minutes, an attempt was made 
to inject the antivenin; while the other, though seriously ill, was successfully 
treated with 5 c.c. of the serum. The fourth set was left untreated and they 
both died in 100 minutes and ros minutes, respectively. 
Calmette showed that the effect of the same dose of venom administered 
into the marginal vein of the ear of a rabbit can be neutralized by the 
injection of 3 c.c. of antivenin into the marginal vein of the opposite side, 
2 and 5 minutes after the injection of venom. The rabbits treated with anti- 
venin before and after the injection of venom, in both series of experiments, 
all survive. The venom employed was a mixture of the venom of Naja 
tripudians and that of Bungarus ceruleus. 
Calmette gives his standard of antitoxic units and emphasizes the variation 
of susceptibility of diverse animals to venom. Thus the quantity of the anti- 
venin necessary to save a more susceptible species from 1 minimal lethal dose 
is larger than for the less sensitive species. Calmette employed rabbit for 
the test-animal. 
The duration of acquired immunity against venom is longer with the 
animal which received a larger dose at the last injection. Rabbit inured to 
rt minimal lethal dose was still resistant in 2 months, while with guinea-pig 
it was only one month. A rabbit immunized to stand one single dose of 
0.006 gm. (120 minimal lethal doses) when tested 8 months after the last inocu- 
lation was not killed by injection of thrice the dose which kills the control in 
20 minutes. 
The duration of passive immunity secured by injecting antivenin is usually 
not over 2 to 4 days. A dose of 20 c.c. of antivenin administered to a 
normal rabbit protects it from a dose of venom, intravenously given, capa- 
ble of killing the control in 15 to 20 minutes, only for a period of 7 days. 
The daily injection of antivenin during two weeks may give the rabbit 
immunity which lasts for 20 to 25 days.!. Transmission of immunity 
against venom is seen to occur from a female guinea-pig to the offspring, 
but never from the male. 
In the following I shall briefly record, chronologically, the work of different 
investigators in regard to the production of antivenins for different kinds of 
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1 In his paper Calmette discusses the nature of the toxic principles of different venoms, showing that the 
neurotoxins resist heating to 75° to 80° C., while the local poisonous substances are made 
inactive. He expresses his view of the unitary nature of the neurotoxins of various venoms. 
