392 THE SNAKES OF SOUTH AFRICA. 
with impunity at a time by the increasing dose process, is really 
an antidote to the poison of snakes.”’ 
However, subsequent experiments have shown that this anti- 
venene is a perfect antidote only to the venom of the species of 
snake to which the animal was rendered immune. 
VENOMS DIFFER IN THEIR ACTION. 
The venom of every species of poisonous snake, as has already 
been pointed out, is different in its composition, although its 
various parts cannot be chemically separated as efficiently as 
we would wish. 
We have, however, abundant evidence of this fact by extensive 
observations of the effects of the different venoms on animals. 
In Australia a professional snake-catcher rendered himself 
immune to the bite of a common highly venomous snake, and 
in the presence of men of science allowed himself to be bitten 
repeatedly. No poisonous symptoms supervened, although the 
bite from this particular species of snake would, in most cases, 
cause rapid death in any one not immunized. 
This man acting under the impression that in consequence 
he was immune to the venom of other species of snakes, once 
carelessly handled a Denisonia superba, but was bitten, and died 
the following day. 
How TO BECOME IMMUNE. 
A man can, with patience, render himself immune to the 
bites of venomous snakes. For instance, if he desires to be 
immune from the venom of a Puff Adder and Cape Cobra, it 
would be necessary for him to inject under his skin an exceedingly 
small dose (the fraction of a drop) of the mixed venoms of these 
two snakes, and after the lapse of a fortnight or longer, inject a 
slightly larger quantity, and continue the process every two weeks 
with increasingly large doses, until he is able to tolerate enough 
venom at a dose as would kill half a dozen men. The operation 
would, however, be very tedious and prolonged, and would have 
to be repeated over again with the venom of other species of 
venomous South African Snakes if he desired to be quite immune 
to the venoms of them all. If, however, a man was immune 
to the venom of the two typical representatives of the great 
snake families, viz. the Cobra and Puff Adder (Colubrine and 
