Chap. IV. IN ANIMALS. 107 



Gardens, when the rattle-snakes and puff-adders were 

 greatly excited at the same time, I was much struck at 

 the similarity of the sound produced by them; and al- 

 though that made by the rattle-snake is louder and 

 shriller than the hissing of the puff-adder, yet when 

 standing at some yards distance I could scarcely distin- 

 guish the two. For whatever purpose the sound is pro- 

 duced by the one species, I can hardly doubt that it serves 

 for the same purpose in the other species; and I conclude 

 from the threatening gestures made at the same time 

 by many snakes, that their hissing, — the rattling of the 

 rattle-snake and of the tail of the Trigonocephalus, — 

 the grating of the scales of the Echis, — and the dilata- 

 tion of the hood of the Cobra, — all subserve the same 

 end, namely, to make them appear terrible to their ene- 



9 ft 



mies. 



It seems at first a probable conclusion that venom- 

 ous snakes, such as the foregoing, from being already 

 so well defended by their poison-fangs, would never be 

 attacked by any enemy; and consequently would have 



I do not, however, wish to doubt that the sounds may 

 occasionally subserve this end. But the conclusion at 

 which I have arrived, viz. that the rattling- serves as a 

 warning 1 to would-be devourers, appears to me much more 

 probable, as it connects together various classes of facts. 

 If this snake had acquired its rattle and the habit of 

 rattling, for the sake of attracting prey, it does not seem 

 probable that it would have invariably used its instru- 

 ment when angered or disturbed. Prof. Shaler takes 

 nearly the same view as I do of the manner of develop- 

 ment of the rattle; and I have always held this opinion 

 since observing the Trigonocephalus in South America. 



28 From the accounts lately collected, and given in 

 the ' Journal of the Linnean Society,' by Mrs. Barber, 

 on the habits of the snakes of South Africa: and from 

 the accounts published by several writers, for instance 

 by Lawson, of the rattle-snake in Xorth America, — it 

 does not seem improbable that the terrific appearance 

 of snakes and the sounds produced by them, may like- 

 wise serve in procuring prey, by paralysing, or as it is 

 sometimes called fascinating, the smaller animals. 



