(A) The rattlesnake tail is made up of a series of loosely linked, interlocking chambers that when shaken, vibrate against one another to create the warning signal of a rattlesnake. Only the bottom button is firmly attached to the tip of the tail. (B) Scales on the underside of the snake (venter scales) provide the contact edges essential for the snake to move. At the end of the venter scales is an anal plate which protects the opening to the cloaca. The cloaca is a shared opening for waste and reproductive material to pass. (C) Snakes have dry keratinous scales. The size, arrangement, and number varies by species and location on the body. Generally, scales on the head are larger on top, smaller and more numerous on the sides and around the mouth and chin. (D) Body scales usually lie in linear rows with each having a fixed number of scales, typically an odd number ranging from 13 to 27. This number is species specific. (E) The body of the snake contains a string of vertebrae (bones that make up the spine). Typically, there are more than 120 in the body and tail and in some species as many as 585. In vipers, (1) the hinged fangs are located on a shortened bone (maxilla) that can rotate forward and backward. When not in use, the fangs fold backward against the roof of the mouth, where they are in a protective sheath. (2) In most venomous snakes, the delivery of venom is much like a hyperdermic needle. When the victim is first bitten with the fangs, muscles on the venom gland are compressed forcing the venom through the venom duct into the venom inlet on the fang, through the venom canal, and exiting the outlet channel into the wound. (3) Pit organs, present in boas, pythons, and pit vipers (which includes rattlesnakes) can sense infrared heat radiated from an object. Basically, this vision detects a temperature difference in an object and its surroundings. This is ideal for hunting warm-blooded mammals and birds at night.