POISONOUS SNAKES OF NORTH AMERICA. 389 



The suake experimented with was one which had been kept about nine months, and 

 was not as energetic as one recently caught, but the note of his rattle was as usual. 

 His head was secured by means of a wire around the neck, and at the end of his rattle 

 was attached a short piece of thin copper wire by means of sealing wax; then the 

 tail was taken in hand and the point of the copper pen directed against the smoked 

 revolving drum of a Marey-Secretan apparatus. A tuning fork was run over the 

 drum to determine the rate of movement of the drum. By an analysis of the curve 

 it was found that the rate of vibration of the tail was about 60 per second. 



Dr. Ott, it should be added, admits the possibility that the number of 

 vibrations recorded are less than the actually normal number. Remem- 

 bering the fact that the snake experimented upon was less than nor- 

 mally energetic, the result agrees tolerably well with that obtained by 

 Feoktistow seven years later. 



The question, "For what purpose does the suake rattle?" is still an 

 unsolved one. Possibly it will ever remain so if we continue to look 

 for one single purpose which may be considered so important in the 

 animal's economy as to have brought about development of such a 

 specialized instrument. Philosophers when attem])ting to explain 

 the utility to the snake of acquiring the rattle have often failed, 

 because it seemed evident that the rattle, so far from being useful 

 to the snake, in most cases appears to be a disadvantage, which 

 has led to the almost total extinction of the Rattlers in the cultivated 

 and more densely inhabitated districts of the country. It must not 

 be forgotten, however, that the rattle was evolved long before man 

 appeared upon the stage, and that the question of its disadvanta- 

 geousuess in the struggle against his supremacy could have no influence 

 upon its evolution. The history of evolution is full of similar examples 

 of animals having acquired an advantageous character which, when 

 new enemies appeared, was turned against the owner because it could 

 not be undone or raodilied to suit the new conditions, thus leading 

 directly to his extermination. 



The theories of the use of the rattle are numerous, even though we 

 exclude from the discussion the one that it is " a providential arrange- 

 ment to prevent injury to innocent animals and man." 



An interesting discussion of this question was started by Prof. N. S. 

 Shaler about twenty years ago, in a paper entitled " The Rattlesnake 

 and IS^atural Selection,"* in which he receded from the position previ- 

 ously held by him that "the tail appendage ot the Rattlesnake was not 

 to be explained on the doctrine of natural selection, inasmuch as it could 

 contribute in no way to the advantage of the animal." Having once him- 

 self in the field mistaken the rattling for the sound nmde by the " locust," 

 Cicada rhnosa, Say, he conceived the idea that the object of the noise 

 is to decoy insect eating birds " into the range of the serpent's spring" 

 by an imitation of the cicada's sound, and he consequently admitted 

 that the case of the Rattlesnake did no longer seem " the bar to the 

 acceptance of the theory it once did." 



* American Naturalist, vi, 1872, pp. 32-37. 



