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RATTLESNAKE, a distinctively American group of poisonous serpents characterized by a peculiar horny rattle appended to the tail. They belong to the suborder Solenoglypha, all the members of which are poisonous and have the fang-bearing maxillary bones erectile. To this suborder belong the Old World families of Viperidæ (vipers) and the Crotalidæ, or pit-vipers, which inhabit both hemispheres. The latter have the maxillary bone deeply excavated to lodge a sensory pit of unknown function opening on the face between the eye and nostril. There are two subfamilies, the Lachesinæ, which have no caudal rattle, and the Crotalinæ, or rattlesnakes. The former includes the copperhead, water moccasin and fer-de-lance (qq.v.), the banana snake, whose presence in bunches of this fruit so often causes consternation on fruit ships and in storage houses, and numerous others of tropical America, India and the Malay Islands.

The Crotalinæ, or rattlesnakes, represent the highest type of serpent development and specialization. The caudal rattle, from which they take their name, consists of a series of dry horny epidermal rings so loosely fitted that any movement causes them to knock together with a sharp rustling rattle. They are formed in the following manner: Several of the terminal vertebræ of the tail are coalesced to form a dilated vertically enlarged plate. This is covered with a thick vascular skin so cut by an annular constriction as to form a larger anterior, and a smaller posterior knob, which together may be considered to be a mold on which the joints of the rattle are formed. The epidermis covering this region is especially thick, and in the young snake forms a button and ring, which are the only indications of the rattle. When the snake sloughs the horny covering is loosened here as elsewhere and a new layer is formed beneath it; but instead of being cast off with the rest of the epidermis, the open end of the old horny ring fits over and by its elasticity clasps the new knob at the end of the tail, and by this means remains attached. With each subsequent molt a new ring and button are added, the latter serving to hold its predecessor in the series, and which continues to increase in size with the growth of the snake and its caudal knob. As well-fed snakes may slough three or four times a year, and as the rings sooner or later become worn out and detached, it is evident that the popular belief that the number of joints in the rattle indicate the years of the snake's age is unfounded. Rattles of more than 12 joints are rare, but one having 21 is known. When the snakes are irritated or angry, the end of the tail is more or less elevated and vibrated rapidly, producing a sound audible at a distance of 30 or 40 paces. Many snakes, both venomous and innocuous, have this habit of vibrating the tip of the tail when angry and many have a hard horny spur or cap at its end, but no others retain this through a succession of molts. Many fantastic theories have been proposed in explanation of the utility of the rattle, but it is probably little more than a recognition character, which helps to bring the sexes together and to segregate the species. However, it is probable that its sounding formerly saved the lives of many rattlesnakes by warning large animals acquainted with their deadly powers from the vicinity, but since the advent of the white man it has had a precisely opposite result.

Poison. — The venom apparatus of the rattlesnakes is the most complete and effective contrivance imaginable for injecting the poisonous fluid into the circulation of a victim. The maxillary bones are very short and are freely movable on an articulation with the prefontals. Upon them are attached the venom fangs at such an angle that with the movements of the maxillary they may be depressed in a fold of mucous membrane or erected vertically in the very front of the mouth in a most effective position for striking. The tooth substance of the fang is folded into a tubular form, with an opening at the base to receive the end of the venom duct and another near the front face of the needle-pointed tip. Behind the functional fang, which may be nearly an inch long in large snakes, is a succession of smaller reserve fangs, which become functional in order as their predecessors are lost. The venom gland, which corresponds to the parotid salivary gland of other animals, is situated on the cheek and has a duct running to a sinus at the base of the fang. All of the muscles and other parts are so arranged that the same movements that open the mouth and press the horizontal pterygoid bones forward to erect the maxillaries with their fangs also compress the poison gland and squeeze out its secretion. Cope describes the biting movement as three-fold: “First, there is the spring of the body, which never exceeds two-thirds of its length; second, the bite proper, caused by the seizing of the jaws; and, third, the clutch with the fangs themselves, which are moved freely backward and forward.” This movement of the fangs may be easily seen by holding a rattlesnake so that it cannot strike, when drops of the pale yellow venom may be seen to fall from their tips and are sometimes blown from the mouth by forcible expirations. The active principles of the venom are several soluble proteids, one of which has a disorganizing effect on tissues with which it comes in contact and another is a powerful heart and respiratory depressor. The immediate effect of a bite is severe burning pain followed in 10 or 15 minutes by prostration, with dizziness, vomiting and cold sweats; the heart action is very feeble and the pupil dilated. This condition gives way in from 12 to 15 hours to one of fever and difficult respiration, while the part affected becomes greatly swollen and the neighborhood of the wound suppurates. Death may occur in either of these stages or as a result of secondary gangrene. Treatment to be effective must be prompt and thorough. A ligature should be applied above the wound and the latter enlarged with a clean knife until the blood flows freely. Permanganate of potash, bleaching powder, chromic acid, silver nitrate or other substances which render the active albumens insoluble should be applied to the wound. Small and frequent doses of whisky, strychnine or ammonia should be administered as a stimulant, but an excess of alcohol may increase the depression. Every effort should be made to press or draw the poison from the wound before the ligature is removed, but sucking with the mouth is always dangerous.

Species of Rattlesnake. — Of rattlesnakes three species of Sistrurus and 16 of Crotalus have been described, three of which are South and Central and the rest North American. None occurs in the West Indies. The species of Sistrurus are small snakes with the snout and frontal region of the head covered with large plates. The ground rattlesnake or massasauga (S. catenatus) is found on low prairie lands from Ohio and Minnesota southward, but is now rare or exterminated in all settled parts. It reaches a length of three feet and is not considered especially dangerous. About six young are born alive in September; and this is one of the snakes for which it is pretty clearly established that the newly-hatched young seek refuge from danger in the mouth and gullet of the mother. A related species (S. miliarius) is found in the Southern States.

In the genus Crotalus the entire top of the head is covered with small scales. The common or banded rattlesnake (C. horridus) was formerly abundant throughout the entire eastern United States and it is the only species found in southern New England and the Middle States, but has been largely exterminated by the white man and his companion, the hog. The latter in roaming the woods in search of mast, etc., never fails to kill and devour the rattlesnake whenever possible. It is commonly believed that the hog is immune to snake-bites, but the truth is that the poison is dissipated in the thick skin and layer of subcutaneous fat and never reaches the vascular tissues beneath. This rattlesnake prefers sparsely wooded rocky ridges with sunny exposures and in such localities is still common in the mountains from Pennsylvania to Tennessee. It is a sluggish and generally peaceful creature, and seldom bites except to secure food, unless it be trod upon or startled. When about to strike it coils with the head in the middle and elevated and the rattle sounding, delivers a lightning-like blow and immediately recoils or slowly retreats. It seldom attacks without provocation or follows a foe. All kinds of small mammals, especially mice, and occasionally birds, are its food, and it drinks water freely. The cold months of the year are passed in hibernation and frequently large numbers of these snakes congregate in caves or beneath rocks for this purpose. Mating takes place in the early summer and about September from six to nine young about nine inches long are born alive. A length of five feet is sometimes attained, but ordinary examples seldom exceed four. Among the natural enemies of the rattlesnake are the kingsnake and blacksnake, birds of prey and herons. The diamond or water rattlesnake (C. adamanteus) reaches a length of more than eight feet and a circumference of 15 inches and is not only the largest of the rattlesnakes, but the bulkiest of all poisonous snakes, being exceeded in length only by the slender snake-eating cobra. It inhabits the Southern States and is particularly abundant on the Florida Keys. Except that it prefers the vicinity of water, in which it swims freely, its habits are much like those of the common species. Because of its great size, and the large amount of venom that it secretes, this is an extremely dangerous reptile; it is also sometimes inclined to be aggressive. The prairie rattlesnake (C. confluentus) inhabits most parts of the Western plains and deserts and is exceedingly abundant in unsettled regions. This is the species which plays a part in the famous triple alliance of prairie-dog, owl and rattlesnake, which, although popularly supposed to be a most amicable arrangement, is at best a state of armed neutrality and frequently of open warfare. The owls and snakes seek the burrows of the marmot as safe retreats and nesting sites, as well as for the purpose of feeding on the young marmots, while the latter frequently show their resentment of the intrusion in a variety of ways. A very distinct species is the horned rattlesnake (C. cerastes), in which the superciliary scales are produced into a pair of prominent horns surmounting the eyes. It is abundant in the desert region of the Southwest, especially about Death Valley, and is known in Arizona as “sidewinder” from its peculiar habit of retreating sidewise from an intruder. Several other species inhabit these hot dry regions.

Service to Man. — Rattlesnakes possess a certain economic importance. As checks on the increase of the native mice and rats, they, in common with many other snakes, perform an important service. Their venomous qualities are such a menace to man and beast as to render their destruction both expedient and certain in all thickly settled districts. By the Indians and by the whites in certain parts of the South their flesh is relished; an oil or salve, supposed by the credulous to possess peculiar medicinal virtues, is claimed to be manufactured from their livers and other fatty parts; and the use of the skin for making purses, belts and other small articles is well known. Certain tribes of Indians employ these snakes in their ceremonials and others formerly poisoned the tips of their war-arrows with rattlesnake venom, while the rattles always figured among the charms of the medicine-man.

Bibliography. — Cope, 'Report U. S. National Museum for 1898'; Stejneger, 'The Poisonous Snakes of North America' (1893); Mitchell and Reichert, 'Researches Upon the Venom of Poisonous Serpents' (Washington 1886); Ingersoll, 'Country Cousins' (New York 1885).

University of Pennsylvania.