182 THE VIVARIUM. 
A slough when perfect is an exact copy of the exterior of the 
Suake from which it came. The portions which covered the 
eyes are very curious and interesting. They may be likened, 
and have been so likened, to tiny watch glasses. In the inverted 
slough their edges stand up from the rest of the cuticle. They 
are also far more transparent than any other part of the slough. 
A good plan to find out the exact length of a snake is to take 
the measurement of its unstretched slough. A snake, when 
alive, is a very difficult subject to gauge accurately. It is gener- 
ally longer than it seems to be. It is never straight. 
If a series of sloughs of any particular Snake be kept, a good 
idea of the rate of the animal’s growth may be obtained. 
Snakes are divided by Dr. Giinther into the five following 
groups: (1) The Burrowing Snakes; (2) The Ground Snakes ; 
(3) The Tree Snakes; (4) The Freshwater Snakes ; (5) The Sea 
Snakes. 
(1) The Burrowing Snakes live chiefly under the ground, and 
do not often come above its surface. They have a stiff, cylin- 
drical body covered with smooth and polished scales well adapted 
for their habit of life. The scales are of the same character all 
over the body, with the exception, sometimes, of very narrow 
ventral scutes. The head is small and provided with a narrow 
mouth which contains comparatively only a few teeth. The eyes 
are either very small or rudimentary; the tail is short and 
strong. These Reptiles possess signs or traces of a pelvis; and 
they feed on worms and other invertebrate animals, None have 
any power of giving poisonous wounds. 
(2) The Ground Snakes, as their name implies, live chiefly on 
the ground, seldom either climbing trees or entering water. 
However, when needful they can both climb and swim. Their 
cylindrical and very flexible body is covered, above, with smooth 
or keeled scales, and below, with broad scutes (Fig. 54). Of all 
Snakes, these are perhaps the most beautiful and typical in shape, 
being exceedingly well-proportioned in every part. The non- 
poisonous representatives of this group are more numerous than 
the poisonous. They all feed upon such animals as small mammals, 
birds, frogs, and the like. The greater preportion of all Snakes 
belong to this group. 
