HABITS. 
179 
Although a few members of the suborder subsist on eggs, snakes 
Habits. & ... .. 
as a rule capture and devour living animals, which are in all cases 
swallowed whole, as these reptiles have no apparatus for rending or masticating 
their food. And it is in order that they may be able to swallow larger animals 
than would otherwise be possible, that they have the power of dilating their jaws 
in the manner already indicated. Not only can the jaws be thus enlarged, but the 
throat and stomach are capable of dilatation, owing to the circumstance that 
the lower ends of the ribs, from the absence of a breast-bone, are quite free; and 
in swallowing, a snake seems gradually to draw itself over the object to be devoured. 
The majority of snakes devour their prey alive, and a frog may be seen struggling 
in the stomach of a common English water-snake long after it has been swallowed. 
Other snakes, however, kill their prey either by striking it with their poison-teeth, 
after the manner of the vipers, or by encircling and smothering it in the folds of the 
body, like the boas. Although the process of digestion is very rapid, snakes feed 
but seldom; and it has been asserted that two or three frogs are sufficient to supply 
the needs of the English water-snake for a whole year. All snakes drink much, 
water being absolutely essential to their existence. 
As might have been expected from their numbers, snakes exhibit great 
diversity in their modes of life; and while those of the tropical regions remain 
active throughout the year (unless they lie by during periods of drought) the 
species inhabiting colder regions hibernate during the winter. The most remark¬ 
able diversity from the ordinary mode of ophidian life is displayed by the blind- 
snakes, which lead a completely subterranean existence, very seldom making their 
appearance above the surface. The great majority of serpents are terrestrial in 
their habits, seldom entering the water or climbing trees; and these ground- 
snakes, as they may be called, are characterised by their cylindrical form and the 
width of the shields on the inferior surface of the body. Tree-snakes, on 
the other hand, which are mostly remarkable for their brilliant coloration, lead 
an almost completely arboreal life. Frequently they have the body very slender, 
or the shields on its under surface may be keeled in order to afford a firmer hold 
in climbing; while in other instances the tail is prehensile. It is among this 
group that the egg-eating species are found. Then, again, we have freshwater- 
snakes, which swim and dive with facility in the waters of rivers and lakes, where 
they spend a large portion of their time, feeding on such aquatic creatures as they 
can capture therein. As a rule, these snakes are distinguished by having the 
nostrils placed at the top of the muzzle, and likewise by the tapering form of the 
tail. Lastly we have the sea-snakes, which, while having the nostrils situated as 
in the last group, are distinguished by the lateral compression of their tails. In 
all cases extremely poisonous, these snakes are almost entirely pelagic in their 
mode of life, and seldom approach the land, although in one genus the shields 
on the under surface of the body are sufficiently developed to admit of terrestrial 
progression. 
By far the greater majority of the members of the suborder lay eggs, of an 
oblong form and enclosed in soft leathery shells, which are hatched by the natural 
heat of the places where they are deposited. The pythons, however, incubate 
their eggs, and at such periods develop a temperature a few degrees above that 
