OUR NATURAL ENEMIES.
No animal, perhaps, is so little known and understood as the snake. This is not because its study has been neglected or overlooked, as our scientific institutions are replete with fine collections of most of the reptiles, and exhaustive works upon their habits and customs. Yet, notwithstanding this, the snake continues to be the subject of ever-recurring stories, fabulous in the extreme, that seem handed down from generation to generation. Strange to say, many of these stories are current among those who, from the nature of their lives, would be expected to be well and accurately informed on the habits of the animals. Farmers and horticulturists are plentiful who religiously believe that the Milk Snake, the beautiful Ophibolus clericus, deprives milk-giving animals of their supply of milk. A statement often seen, and that has many believers, is that the Whip-snake of the South seizes its tail—which is supposed to have a sting—in its mouth, and rolls away in the form of a wheel, stopping suddenly and striking the enemy with the sting. Such fables are current by the score, and denial only strengthens belief.
More than a hundred species of snakes, nearly all having a wide geographical range, are found in America, north of Mexico. They constitute the first order, Ophidia, of reptiles, and have long, cylindrical bodies, are footless, without a shoulder-girdle, and invested with a coat of scales, which is shed in the summer months. Snakes have no eyelids in the strict sense of the term. Their eyes are permanently covered by a delicate membrane that takes the place of the lid, and this explains the stony stare, so disagreeable to many, that all snakes have.
The skeleton of snakes is so arranged as to allow the greatest freedom and flexibility. Numerous pieces of bone, hollow in front and convex behind, make up the long tapering backbone, which literally works on a ball-and-socket plan. Articular facets, that lock into each other, are found upon the processes of the vertebræ, and these strengthen and give to the backbone a greater degree of flexibility. A more remarkable arrangement, however, is found in the head, which enables the snake to prey upon animals that are larger than itself. The jaws seem a combination of elastic springs, having no gauge to their tension, the quadrate bones connecting the lower jaw with the skull being movable, thus allowing that enormous gape with which all are familiar who have seen a snake swallow its prey. Besides this, the bones of the jaw itself and palate are more or less movable, also tending to the larger distention of the throat.
As snakes do not tear or mutilate their prey, their teeth are not set in sockets, but serve merely to poison and stupefy the prey, or to prevent its escape, acting as hooks by which the body is hauled over the victim. The bones of the lower jaw, as we have seen, are not fastened closely to each other; so in swallowing prey the teeth on one side are advanced, and then those on the other side, and so on until the victim is hauled, hand over hand, as it were, into the snake’s throat.
Poisonous snakes, such as the rattlers, have two long, sharp fangs, each compressed and bent up, and forming a hollow tube, open at both ends. The upper portion of the hollow fang is fastened to a bone in the cheek, which moves with ease, so that, when not in use, the fangs can be packed away until needed.
All animals, man included, have doubtless in their saliva a deadly poison, though in the latter it is extremely diluted, and essential only to the digestion of food. In poisonous snakes, however, it is stored up in sacs, modifications of the salivary glands, and placed in each side of the upper jaw. From the poison-gland under the eye forward to the edge of the jaw, a delicate canal, which opens into the fang above the tube of the tooth, extends. Alongside of the latter may be seen rudimentary fangs, all ready to grow out should the large one be lost. To use the poison, the snake has merely to strike its prey, when the muscles of the jaw, which are admirably fitted for the part they have to play in the tragedy, press upon the glands, squeeze the poison through the little canal down through the hollow fang, and the work is accomplished.
In their actions, snakes are most graceful. The gliding motion, so characteristic, is effected by the movements of the large central scales, that are successively pushed forward, the hinder edges resting on the ground and constituting a support. These scales, or pushers, are fastened to the ribs by muscles, and by holding a snake by the hand the swelling movement can readily be felt.
Snakes vary much in color. They are generally adapted to their surroundings. Green Snakes are found in green grass and vegetation, while grey snakes affect rocky districts, where they are alike protected. Their skin is shed in one piece at various seasons of the year, being forced off by the snake forming a ring with its tail and squeezing the rest of the body through it, or by wriggling through entangled bushes. Poisonous snakes may be always recognized by their broad, flattened heads, generally short and thick bodies, and the almost invariable possession of a vertical keel along the centre of each scale. Long bodies, small heads devoid of distinct necks, and scales not keeled, characterize non-poisonous species.
Probably the best-known of our common kinds of poisonous snakes are the rattlesnakes. They belong to the dangerous family Crotalidæ, to which the copperheads and moccasins also belong, and are distinguished by the large, ugly head, absence of teeth in the upper jaw excepting the fangs, and the pit in the head.