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Bible Encyclopedias
Rattlesnake
1911 Encyclopedia Britannica
or Rattlesnakes are a small group of the sub-family of pit-vipers (Crotalinae, see Snakes; Viperidae), characterised by a tail which terminates in a chain of horny, loosely connected rings, the so-called "rattle." The "pit" by which the family is distinguished from the ordinary vipers is a deep depression in the integument of the sides of the snout, between the nostrils and the eye; its physiological function is unknown. The rattle is a complicated and highly specialized organ, developed from the simple conical scale or epidermal spine, which in the majority of snakes forms the termination of the general integument of the tail. The bone by which the root of the rattle is supported consists of the last caudal vertebrae, from three to eight in number, which are enlarged, dilated, compressed and coalesced (fig. r, a). This bone is covered z FIG. I. - Rattle of Rattlesnake (after Czermak).
I. Caudal vertebrae, the last coalesced in a single bone a. 2. End of tail (rattle removed); a, cuticular matrix covering terminal bone. 3. Side view of a rattle; c and d the oldest, a and b the youngest joints. 4.4. A rattle with joints disconnected; x fits into b and is covered by it; z into d in like manner.
with thick and vascular cutis, transversely divided by two constrictions into three portions, of which the proximal is larger than the median, and the median much larger than the distal. This cuticular portion constitutes the matrix of a horny epidermoid covering which closely fits the shape of the underlying soft part and is the beginning of the rattle, as it appears in young rattlesnakes before they have shed their skin for the first time. When the period of a renewal of the skin approaches a new covering of the extremity of the tail is formed below the old one, but the latter, instead of being cast off with the remainder of the epidermis, is retained by the posterior swelling of the end of the tail, forming now the first loose joint of the rattle. This process is repeated on succeeding moultingsthe new joints being always larger than the old ones as long as the snake grows. Perfect rattles therefore taper towards the point, but generally the oldest (terminal) joints wear away in time and are lost. As rattlesnakes shed their skins more than once every year, the number of joints of the rattle does not indicate the age of the animal but the number of exuviations which it has undergone. The largest rattle in the British Museum has twenty-one joints. The rattle consists thus of a variable number of dry, hard, horny cup-shaped joints, each of which loosely grasps a portion of the preceding, and all of which are capable of being shaken against each other. If the interspaces between the joints are filled with water, as often happens in wet weather, no noise can be produced. The motor power lies in the lateral muscles of the tail, by which a vibratory motion is communicated to the rattle, the noise produced being similar to that of a child's rattle and perceptible at a distance of from Io to 20 yds.
