Page:The New International Encyclopædia 1st ed. v. 18.djvu/322

SNAKE. 274 SNAKE. pned, hirned up, or bear curious appendages, as in Herpeton and the langaha (qq.v.). Periodically, usually several times a year, the snake sloughs off its corneous epidermis, which splits across ^^i-X^S^ PLATES AXD SCALES OF A TYPICAL SNAKE. 1, Side view of head of a cohlbrine snake; 2. front viev| 3. Top of head; 4, under Bide of liead and throat; 5, vent and anal plates; 6, side of a part of tlie bod.v. Nuniliers and letters: e, eye; n, nostril; 1, rostral plate; 2, nasal; 3. loreal; 4, preocular or anteorbltal; 5. postocular or post- orbital; 6. temporal; 7, internasal; 8, prefrontal; 9, frontal; 10, superciliary or supraocular; 11. parietal; 12. notch in rostral for protmsion of tongue; 13, labial; 14, infralabials; 15, gular; 16. mental; 17. submental; 18, abdominal scutes or gastrosteges; 19, dorsal scales; 20, keeled bod.T scales; 21, unkeeled lateral scales; 22, divided anal scute covering anus; 23, wrosteges. the face, and then is peeled off hy the animal scraping through a crevice or a fold of its own body; even the coating of the eye is included. NASAL APPE^^DAGE8 OF HERPETON. All snakes except the purely aquatic ones move by means of the abdominal scutes. No snake can leap from the ground, though the more active sometimes hurl themselves from bough to bough, or down to the ground. The vertebrse are extremely numerous, sometimes nearly 300, and are concave in front and convex behind, connected by free ball-and-socket joints, and provided with complicated processes, one effect of which is to prevent any considerable vertical motion. Every vertebra except the atlas bears a pair of ribs, articulating by the capit- ular head only, and united at their ventral ex- tremities (in the absence of any sternum) by cartilages attached to the gastrosteges. The ribs admit of much movement and liave an extensive and powerful musculature. The bones of the skull are not soldered together (except those of the brain-case), but are loosely joined by elastic cartilages. The two halves of the lower jaw are connected by a ligament so loose and elastic that they are capable gf separation to a great extent. The teeth are simple, sharp, curved backward and solidly fixed in sockets. When broken or lost they arc 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 de)iressil)Ie 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 liy 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 -is a fable. Most snakes are carnivorous. 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 species are fond of milk. Many 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 wlieii 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 wlien bilobed, 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 month, all of which arrangements guard against suffocation during the tedious process of swal- lowing. The forcilile 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. MOUTH OF A SNAKE. Open mouth of the bull or pine snake (q.v.) showingthe (black) tongue and opening of the windpipe : a, sheath of the tongue ; b, epiglottis ; c, glottis. Snakes have a Avell -developed nervous system, and are intelligent. Many may be tamed and show docility and regard for their friends. Most of them are very timid and harmless, endeavor ing to frighten their enemies by menacing atti- tudes (see HoGNOSE) or otherwise. Even the well-armed poisonous ones, though surten and resistant, are rarely aggressive. All have good eyes, and some of the many nocturnal forms very large ones ; but the eyes have no lids and are not movable. No external ear is present, but a com- plicated internal apparatus exists, so that snakes hear very well and are affected by musical sounds. The sense of taste is probably deficient, but that of smell is acute, and many serpents, as the