SNAKES AND THEIR POISON 
123 
out of the way of anything advancing on them, especially if they 
feel certain of being observed. They then puff themselves up 
to nearly twice their natural circumference and wickedly wait 
for a chance to bite, while their little eyes gleam with ferocity, 
as if perfectly aware of the power lying in the venom nature has 
endowed them with. They strike backward from choice, throw¬ 
ing their whole muscular force into the bite, deeply imbedding 
their long fangs, and squirting out the fluid poison through their 
perforated fangs into the obstacle they strike. 
The poison itself is the secretion of the parotid gland, 
situated in human beings fbelow and in front of the ear, but 
fortunately in our case of innocuous quality. This poison in 
serpent's, when the gland is excited, pours through a duct into a 
muscular bag encasing the fangs, and when the fangs, which at 
rest lie in a groove along the roof of the mouth, are erected and 
protruded for striking, the bag closes round each one of them 
separately, leaving the lower orifice of the canal, where it per¬ 
forates the fang, free. As soon as the fang is inserted into the 
flesh the bags contract, squirting the poison out in little jets at 
each contraction, into the flesh or the bitten part. Without 
this forcing action of the bag, the mere insertion of a fang would 
not be sufficient to introduce much venom into a wound. It 
is no unusual occurrence for a fang to break off* at its base 
during the bite, and remain in the wound; then its loss is 
supplemented in time by another fang, already formed in the 
mouth and lying simply attached by fibrous tissue to the roof 
of the mouth, from whence it descends to replace its missing 
forerunner. In fact, a minute examination will reveal more 
than one loose fang, each one smaller in size than the other, 
awaiting their turn to grow on to the bone fixed in the upper jaw 
—os hamatnm —which supports the full-grown fang. This fact 
leads one to the natural inference that it is a frequent occurrence 
for an adder to require a new set of fangs. 
The action of this viper’s poison varies in intensity according 
to the circumstances under which the bite takes place. Given 
a healthy strong snake ready for the fray, and a hot day, on 
