Occasional Notes. 341 
to the idea of immunity in the former case. In the 
present state of our knowledge, however, as to the 
constitution and aftion of snake-poison, and the nature 
and a6lion of the virus of small-pox and rabies, no such 
comparison is warrantable. For while in the latter cases, 
immunity from direful disease is caused by the intro- 
duction into the system of what practically amounts to 
a mild and harmless form of the same thing in order to 
make the system sterile or barren against the attack of 
the virulent form, nothing comparable takes place in 
inoculation against snake-bite. Inoculation with mild 
doses or small quantities of snake-poison which may be 
insufficient to kill, do not protect against the dread 
action of a larger quantity. Moreover, the effe£t of an 
inje6lion of an appreciable quantity of snake-poison into 
the system, is rapid and almost immediate, death resulting 
within a few minutes or at most a few hours, the 
slightly variable time being dependent upon the amount 
of the poison, the degree of virulence of the snake, and 
other appreciable conditions. There is here in the 
chara6teristic aCtion of snake-poison no prolonged time 
of incubation, as in the characteristic aCtion of the virus 
of the zymotic diseases. And though in one species of 
Indian Colubrine snake (Bungarus fasciatus), a pro- 
longed period of some days is sometimes known to 
occur before death, apparently dependent on the size and 
vigour of the snake, and thus upon the amount of poison 
injeCted, an incubatory period is negatived by the fa£t that 
the normal aCtion of the poison of this snake is as rapid 
and immediate as in other poisonous snakes generally, 
where the a6lion is comparable in its effects rather to such 
a definite poison as strychnine than to a %i ferment. " 
XX 
