68 SERPENTS 



and hold fast the serpent's prej' while it is being swallowed. 

 Poisonous serpents have special teeth, called fangs, for mak- 

 ing deep wounds and filling them with i)oison. These are 

 set in the roof of the mouth, well forward, and while not 

 in use they lie up against the roof of the mouth. The tongue 

 of a serpent is very extensible, and capable of being thrust 

 out fully half the length of the head. Its greatest use is in 

 examining food, or possible food. From the fact that when 

 travelling the tongue is so frequently thrust out, even when 

 there is no excitement, it seems highly probable that it is 

 used to detect vibrations in the air. (R. L. Ditmars.) The 

 tongue is forked, and being entirelj" harmless, its sole use in 

 defence is to threaten and intimidate its enemies. 



The lower jaws are loosely attached to the skull, and 

 to each other at their front end, by ligaments so elastic that 

 when prey is being swallowed, the gape expands to enormous 

 proportions. Mammals, birds and fishes to be swallowed 

 are always seized head first, in order that the limbs, and also 

 the feathers or scales, if there be any, will lie snugly against 

 the body. Frogs and toads are usually taken hind feet first. 

 The lower jaw is forced forward and over the animal, always 

 one side at a time, as far as it will go; and when the teeth 

 are inserted, that side is drawn back. The upper part of 

 the head slides forward as far as possible, one side at a time, 

 to match the lower jaw. Sometimes it seems as if the lower 

 jaw will be torn loose from the head. Often after an animal 

 has vanished, the jaws are a bad misfit, and do not come 

 back into shape for half an hour. 



The skin stretches like India-rubber, and over a heavy 



