RENDERING ANIMALS IMMUNE. 391 
(nicotine) from a pipe stem will, if a small quantity be placed 
in a snake’s mouth, instantly paralyze it. It grows utterly limp 
and ceases to breathe, but sometimes revives in about an hour's 
time. This fact should be remembered by collectors. 
RENDERING ANIMALS IMMUNE. 
The following extract, written by Dr. J. G. McPherson on 
Dr. Fraser’s experiments with the immunization of animals, 
will give an idea of the process of rendering animals immune to 
the bites of snakes :—‘‘ Having ascertained the minimum dose 
required to cause the death of an animal, he started below that 
amount and gradually increased the dose after intervals of ten 
days. By this process of gradual increases in the dose of snake 
poison, he found the animal receiving as much at one time as 
fifty times the amount of the miniraum lethal (fatal) dose, 
without it causing any perceptible bad effects. In the mean- 
time, Professor Fraser has not carried his experiments of quantity 
further than fifty times a fatal dose at one time; but still when 
he had got to that point the animal was receiving in a single 
dose without being affected, enough venom to kill fifty animals 
of the same size and weight. One of the animals which he had 
treated by this gradual increasing quantity had in two months 
received enough poison to kill 370 animals of equal size and weight, 
supposing that each just got the minimum fatal dose He 
then described a second series of experiments in which he used 
the blood serum of these animals which had been immunized, as 
an antidote for the venom. He mixed an equal part of this 
blood serum and venom together, and injected the mixture 
into a fresh animal. This produced no poisonous effect, the 
serum counteracting the toxic properties of the venom. Next 
he injected some of the immunized blood serum, which he has 
named ‘anti-venene, into a fresh animal, and then some 
venom afterwards, but the serum hindered any action of the. 
venom. 
“Then he took another fresh animal and injected venom, 
waiting till symptoms of poisoning were manifest ; at once he 
injected his anti-venene, and put a stop to any further action of 
the poison. All this points to the conclusion that the blood 
serum of an animal that has been able to stand fifty fatal doses 
