pecies are known in Brazil, the
biggest one being identical with the Guiana bushmaster, and the most
common one, the jararaca, being identical, or practically identical
with the fer-de-lance. The snakes of this genus, like the rattlesnakes
and the Old World vipers and puff-adders, possess long poison-fangs
which strike through clothes or any other human garment except stout
leather. Moreover, they are very aggressive, more so than any other
snakes in the world, except possibly some of the cobras. As, in
addition, they are numerous, they are a source of really frightful
danger to scantily clad men who work in the fields and forests, or who
for any reason are abroad at night.

The poison of venomous serpents is not in the least uniform in its
quality. On the contrary, the natural forces--to use a term which is
vague, but which is as exact as our present-day knowledge permits--
that have developed in so many different families of snakes these
poisoned fangs have worked in two or three totally different fashions.
Unlike the vipers, the colubrine poisonous snakes have small fangs,
and their poison, though on the whole even more deadly, has entirely
different effects, and owes its deadliness to entirely different
qualities. Even within the same family there are wide differences. In
the jararaca an extraordinary quantity of yellow venom is spurted from
the long poison-fangs. This poison is secreted in large glands which,
among vipers, give the head its peculiar ace-of-spades shape. The
rattlesnake yields a much smaller quantity of white venom, but,
quantity for quantity, this white venom is more deadly. It is the
great quantity of venom injected by the long fangs of the jararaca,
the bushmaster, and their fellows that renders their bite so generally
fatal. Moreover, even between these two allied genera of pit-vipers,
the differences in the action of the poison are sufficiently marked to
be easily recognizable, and to render the most effective anti-venomous
serum for each slightly different from the other. However, they are
near enough alike to make this difference, in practice, of
comparatively small consequence. In practice the same serum can be
used to neutralize the effect of either, and, as will be seen later
on, the snake that is immune to one kind of venom is also immune to
the other.

But the effect of the venom of the poisonous colubrine snakes is
totally different from, although to the full as deadly as, the effect