SNAKES 22

closely together, thereby producing alternate bends of
the body on the corresponding side. The hinder
portion of the body being drawn after, some part of
it finds another support on the rough ground or
a projection, and the anterior bends being stretched
in a straight line, the front part of the body is
propelled in consequence.’ In short, the ‘soundless,
causeless march of sequent rings,’ as Ruskin calls it,
is an exceedingly rapid wriggle.

A snake’s heart has three chambers ; his teeth are
~ not fitted into sockets, but look as if they were mere
projections of the jawbone, and in some cases are
quite rudimentary. His tongue is forked and retracted
into a sheath; his fang, when he has one, is quite a
different thing, being a long tooth in the front of the
upper jaw having a hole down it through which he
can squirt the poison when he strikes.

The one thousand six hundred species of snakes
are divisible into four groups—the burrowing snakes,
the harmless snakes, the poisonous snakes, and the
vipers. The burrowing snakes (Zyphlopide) have
teeth in one jaw only, and are generally smaller than
earthworms. They are found in Europe, Asia, Africa,
America, and Australia, but no one but a naturalist
takes the slightest notice of them. The vipers attract
much more attention, owing to the perfection of their
poisoning apparatus. The group includes the rattle-
snakes (Crotalide), which are distinguishable from the
true vipers by the pit between the eyeand the nostril,
and by the rattle on the tail, which is apparently
formed of epidermic remnants of previous skins. The
vipers are chiefly African; the rattlesnakes—there

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