St. George Jackson Mivart and Hans Friedrich Gadow

“ 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 moultings — the 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. ”

“ First they try to slink away; when overtaken or cornered they use every means of frightening the foe by swelling up, puffing, rattling and threatening attitudes; it is as a rule not until they are touched, or provoked by a rapid movement, that they retaliate, but then they strike with fury. ”

“ 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 10 to 20 yds. ”