SNAKE (AS. snacu, (Neel. snahr, snokr, snake, from AS. snieun, to creep, Eng. sneak; ultimately connected with Skt. nflga, snake), or SERPENT. A reptile representing the highly specialized saurian order Ophidia. Snakes differ from their nearest relatives the lizard, primarily in having the two halves of the lower jaw con nected by an elastic band. They agree with them in many particulars, and the external resem blance is so close in some cases that the true relationships were long confused. Although snakes as a whole form an ascending series, de generaey has played an important part in their phylogenetic history. This degeneracy consists mainly in the reduction of the mechanism for rapid movement, the shortening of the tail. and the decrease in the size of the eye and mouth. The most highly developed are those with a poison apparatus, and among these the rattle snakes seem most advanced. The form is greatly elongated and ordinarily cylindrical, but in the sea-snakes (q.v.) is likely to be laterally com pressed in adaptation to an aquatic life. The body is clo,thed in scales (q.v.), which are folds in the skin. lacking osteoderms and covered with a horny epidermis. Ordinarily they overlap, like tiles on a roof, but sometimes are flat and edge to edge, like tiles in a floor. They are small on the back and sides, lie in a definite number of equilateral longitudinal rows, and frequently are ridged or 'keeled hut on the ventral surface (except in the burrowers and sea-snakes) are so large as to reach from side to side, forming 'ab dominal sautes' (gastroleges in front of eloaca and wrosteges behind), each attached at both ends to a pair of ribs. The scales are often enlarged on the head into plates or shields. (See illustration.) The arrangement and shape of both the head plates and the gastrosteges are of great service in classification. In some the nasal plates are broad cued. turned up, or bear curious appendages, as in llerpeton and the langaha (qq.v.). Periodically, usually several times a year, the snake sloughs off its corneous epidermis, which splits across the face, and then is peeled off by the animal scraping through a crevice or a fold of its own body; even the coating of the eye is included.
that they are capable of separation to a great extent. The teeth are simple. sharp, curved backward and solidly fixed in sockets. When broken or lost they are renewed. There are typi cally two rows on the upper jaw and two on the palate (maxillaries, palatines, and pterygoids), and each mandible of the lower jaw bears a single row; but vipers and rattlesnakes have none in the upper jaw except the poison fangs, which are depressible at will and fold back out of the way of food entering the mouth. The process of swal lowing is laborious. With a large victim this process may last for hours, the head and throat be stretched to almost bursting, and the snake become nearly exhausted by its efforts. A great amount of saliva is poured out in this process, but the story that snakes cover their prey with slime before swallowing it a fable.
Most snakes are earnivorous. Small mam mals, frogs, reptiles, and insects form the bulk of the diet of ordinary land species. Some of them eat eggs, and a few are fond of milk. .lany of them are of great assistance to the agriculturist by devouring the grasshoppers, mice. gophers, and other pests of the farm in great numbers. The stomach is long and nar row, as also are the lobes of the liver. Snakes drink much water when in active life; yet they possess no urinary bladder. The intestines are highly absorbent. The heart is placed well forward. The lungs are elongated, and when bibbed, as in boas and rattlesnakes, one lobe is far larger than the other. The trachea is long, is provided with air sacs, and opens far forward in the mouth, all of which arrangements guard against suffocation during the tedious process of swal lowing. The forcible expulsion of air from the trachea makes the hissing sound which is the serpent's only vocal utterance: but the bull snake has special tracheal arrangements (see illustration) by which its hiss may be increased to a sort of bellow.