RATTLE-SNAICE. 73 



The rattle is placed with the broad part perpendicular to the 

 body, and not horizontal ; and the first joint is fastened to the last 

 vertebra of the tail by means of a thick muscle under it, as well as 

 by the membranes which unite it to the skin ; ail the remaining 

 joints are so many extraneous bodies, as it were, or perfectly un- 

 connected to the tail by any other means than their curious inser- 

 tions iuto each other. 



The number of joints in the rattle of different individuals is very 

 various, from five to twelve, fifteen, twenty, or even, according to 

 some accounts, as many as forty. The pieces of which it consists 

 are successively formed, each having been once attached to the 

 muscle of the last vertebra of the tail, and driven on by the gradual 

 formation of a young or immature one beneath it; but as it is not 

 known whether these successive formations of new joints in the 

 rattle correspond with the general changes of the skin, and as the 

 part is also liable from its nature to occasional mutilations, it cannot 

 be considered as a proper test of the animal's age. 



The length of the individual dissected by Dr. Tyson, was four 

 feet five inches; the girth of the body in the largest part six inches 

 and a half; that of the neck three inches, and of the extremity of 

 the tail, near the rattle, two inches. 



[Catesby. Tyson. Grew. Phil. Trans. Shaw. 



SECTION IX. 



Great Boa. 

 Boa constrictor. Linn. 

 The genus boa is remarkable for the vast and almost unlimited 

 size of some of the principal species, which in India, Africa, and 

 South America, are occasionally found of not less than twenty, 

 thirty, and even thirty-five feet in length, and of a strength so pro- 

 digious as to be able to destroy cattle, deer, &c. by twisting around 

 them in such a manner as to crush them to death by continued pres- 

 sure *, after which they will swallow them in a very gradual manner; 



* This practice of larger serpents seems to have been well known to the 

 ancients ; thus Lucan, speaking of the monstrous African snakes, (which he 

 also represents as furnished with wings,) tells us they destroy oxen, and evea 

 elephants, by writhing around and crushing them to death. 



** Vos quoque, qui cunctis innoxia numina terris 

 Serpitis, aurato nitidi fulgore Dracones, 



