SERPENT, in zoology, the ophidia, an order of reptiles popularly distinguished from the rest of the class by having a very elongated body and no external limbs. They are very widely distributed, abounding in the tropics, where they at tain their greatest size, absent only from the Arctic and Antarctic regions, and they are mentioned in the earliest records of the human race. The length of the body is a marked feature. The number of vertebra varies greatly, more than 400 occurring in some of the great pythons. No sacrum exists, and there is no dis tinction between or divisions of the spine into cervical, dorsal, and lumbar verte bra. A notable feature is the large num ber of ribs; almost all the vertebra, with the exception of the atlas or first, bear ing these. The ribs articulate with the transverse processes of the vertebra, and are not attached inferiorly to any breast bone, but are imbedded in cartilages which are in turn connected with the great scales or scuta that cover the ventral surface of the body. The premaxilla are represented usually by a single small bone, which rarely has teeth, and is joined to the maxilla by fibrous tissue only. The floor of the skull is flat, while in front it diminishes greatly in height. The hyoid is very rudimentary, and is represented by two cartilaginous filaments, uncon nected in any way with the skull. In the pythons a pair of rudimentary hind limbs exists, and traces of a pelvis are also found.
Locomotion is effected by the muscular contractions of the body, the animals moving literally on the ends of their ribs. Teeth are borne by the premaxillary bones, by the maxillaries, palatine, and pterygoid bones, and by the dentary part of the mandible. One of the most singu lar developments of teeth in serpents and indeed in the entire animal kingdom, oc curs in a little African snake—Rachiodon. In this snake, the ordinary teeth are very small, but the lower or inferior spines of some eight or nine vertebra of the neck are long, and their enameled tips project into the interior of the gullet, so that when the snake swallows an egg, the brittle morsel passes entire into the gul let, and is broken only when fairly on its way into the stomach. The teeth of ser
pents are not implanted in sockets, but become ossified to the surfaces of the bones which bear them. They are re placed when worn away or injured by new teeth developed at the bases of the former ones. In the typically poisonous serpent (e. y., the rattlesnake) the upper jaw bears two largely developed teeth termed fangs. Each fang has a very deep groove running down its anterior aspect, and the margins of this groove are opposed so as to convert it into a canal—hence the fangs are said to be canaliculated. This canal opens by a wide aperture above into the poison gland, so that by the compression, muscular and friable, of the gland, the poison flows down the canal and is ejected, through the lower minute aperture, into the wound made by the fang.
The poison of different serpents varies in intensity and virulence, but appears to take effect on the blood. The most effective treatment for snake-bite is to tie a ligature tightly round the limb, above the wound, and to excise the part freely, and then to suck the blood re peatedly, and cauterize the parts deeply before removing the ligature. In suck ing a poisoned wound, the danger con sists in there being a crack or wound in the mouth by which the poison may be absorbed.
The digestive system of serpents pre sents nothing worthy of special remark, save that the intestine ends in a cloaca opening transversely. There is no urinary bladder, and the heart (as in all reptiles save the Crocodilia) is three-chambered.
Serpents are divided into three groups: innocuous, venomous colubrine, and viper ine, the last two groups possessing poi son fangs, the boas, which kill their prey by constriction, belonging to the first. Broadly speaking, the innocuous serpents are oviparous, the venomous are ovovivi parous. Most of the former deposit the eggs in a long string in some heap of decaying vegetable matter, and leave them; while some of the larger serpents coil round their eggs, and hatch them by the heat 0.: their bodies. Some of the innocuous kinds are capable of being tamed; the rat snake (Ptyas macosus) is often kept in houses in India for the purpose of destroying rats and mice.