154 REPTILES 



able joints or bells may enter into the composition of the rattle. 

 According to an American writer, the general history of the 

 rattle is somewhat as follows : — 



"As a snake in its wild state sheds its skin about three times 

 during the warm months, the same number of rattles should be 

 added during the year. To determine the age of a rattlesnake 

 from the number of joints of its rattle is a very uncertain pro- 

 position. When the rattle has attained from ten to twelve 

 joints, it usually remains at about that number, as several joints 

 are lost annually through wear. It is only possible to estimate 

 the age of a snake from the number of joints of the rattle when 

 that appendage is of a tapering character and still possesses the 

 ' button ' of the snake's birth. The growth of the snake is in- 

 dicated by such a rattle in the increasing size of each ring from 

 the button to the tail. By allowing three rattles for a year, the 

 reptile's age may be determined with reasonable accuracy. 

 When a snake's rattle possesses all the joints or rings of a uni- 

 form size, the snake is old. The tapering portion of the rattle 

 grown in its youth has been lost, together with an uncertain 

 number of succeeding joints, and the snake has ceased to grow. 



" These snakes are unable to produce any sound with the 

 rattle until they are about three months old. By that time one 

 skin has been cast, a new joint uncovered on which is attached 

 the ' button ' of birth, and a second joint has developed to such 

 an extent that the one preceding it has become dry and brittle. 

 On the latter, the ' button ' whirs feebly when the tail is vib- 

 rated. In the Reptile House at the New York Zoological 

 Park a specimen of the diamond-backed rattlesnake, now fifteen 

 months old, and born in the building, possesses 'five rattles,' or 

 ' four rings,' and a ' button '. This snake measured fourteen 

 inches at birth. At the present time it measures three feet, six 

 inches. The length of a full-grown diamond-backed rattle- 

 snake is usually about six feet." 



Originally it was considered that the rattlesnake was 

 provided with its noisy rattle in order to warn other creatures 

 of its approach, and thus enable them to get out of harm's way. 

 Such a view may, however, be dismissed as childish ; and, as 

 Darwin pointed out, it is far more probable that the object of 

 the rattle, like the expanded hood of the cobra and the inflated 

 head of the puff-adder with its accompanying hiss, is to alarm 



