Snakes

Snakes (Ophidia), an order of Reptiles (q.v.), the members of which are well known from their generally long, lithe bodies, their gliding motion, the absence of external limbs, and the ternble power possessed by many of them of inflicting deadly wounds by means of their poisonous fangs. In some of these points they resemble other animals; in shape some are not to be distinguished from limbless lizards - often confounded with snakes - and limbless fish; while poison-fangs are possessed by at least one lizard, the Heloderm (q.v.) The skin is covered with scales, and is shed periodically; sometimes, as in the case of the Common British Snake (Tropidonotus natrix), several times in the year. There are no external ear-openings, and the nostrils are near the extremity of the head. Eyelids are absent, but the transparent skin covers and protects the eyes. Most of them possess scent-glands near the vent, and when irritated they pour forth the ill-smelling secretion very freely. The vertebrae, hollow in front (procoelous), are very numerous, and the ribs function as limbs, by means of which these creatures row their way along on any surface not absolutely smooth. The skeleton of the head is remarkable for the mobility of the bones of the lower jaw, which can be entirely separated from the base of the skull proper, thus enlarging the capacity of the mouth and throat. It is owing to this arrangement, and to the elasticity of the skin, that snakes can swallow prey so much bigger round than themselves. In some snakes, the Boas, for example, there are traces of a rudimentary pelvis and of equally rudimentary hind legs. The tongue, which is cleft at the tip, can be drawn back, and moved freely in any direction, and serves as an organ of touch but no snake uses it, as the Boas were said to do, to lubricate the prey with saliva before swallowing it. The poison-gland is a specialised salivary gland; and the poison-fangs, borne on the upper jaw, are furnished with a canal or a groove down which the poison flows into the wound when a venomous serpent strikes. Most snakes are oviparous; some few are viviparous, and the pythons incubate. One case has occurred in the Zoological Gardens, Regent's Park, and another was reported from Leipsic in 1893. Snakes are widely distributed, but attain their greatest development of size and numbers in tropical countries, where, as might be expected, the most venomous forms are found; and in India the deaths from snake-bite are extremely numerous. Many so-called specifics have been recommended; but the treatment which Sir Joseph Fayrer (Thanatophidia of India) recommends is the application of a ligature above the bite, scarification or cautery of the wound. and keeping up the patient's strength. In Britain there are three representatives of the order, the Ring Snake and the Viper (both of which see), and the Smooth Snake (Coronella laevis), confined to the south of England. In habit snakes are mostly, terrestrial, some are arboreal, and a few are marine. [SEA-SNAKES.] Most of them prey on mammals, birds, and reptiles, and amphibians, and some on molluscs and insects, while most are fond of milk, and one South African snake (Rachiodon) subsists on eggs, which are broken by the so-called gular teeth - really the inferior spines of the anterior vertebrae. The contents flow down the throat, and the shell is rejected. The following classification of the order is that generally in use:-

BLIND SNAKES (Typhlopidae), the lowest of the order, small burrowing forms that feed on worms and insects. They are found in tropical countries and Australia. There is one European species.

HARMLESS COLUBRIFORM SNAKES (Colubriformes). These are harmless to man, but some of them have the teeth grooved, showing intimate connection with the next group. Here belong the Boas, Pythons, Tree-Snakes, and our British snakes.

COLUBRIFORM VENOMOUS SNAKES (Colubriformes venenosi), as the Cobras, Hamadryas (snake-eating snake), Coral-Snakes, and Sea-Snakes, with erect grooved teeth and poison glands.

VIPERIFORM SNAKES (Viperiformes), with erectile, perforated teeth, and poison-glands, as the Vipers, Rattlesnakes, etc.

But, as the poison of snakes is a question of degree rather than of kind, the old division into Harmless and Venomous Snakes will probably lapse in favour of the classification introduced by Mr. Boulanger in his Catalogne of Snakes in the British Museum (Natural History), vol. i., where characters of the skull are taken as the basis of grouping. He recognises the following families:- Typhlopidae, Glauconiidae, Boidae, Ilysiidae, Uropeltidae, Xenopeltidae, Colubridae, Amblycephalidae, and Viperidae.