Ill THE SERVICE OF TAILS 95 



serpent; and are they aroused, this agitation be- 

 comes very marked indeed. I do not suppose that 

 the puma which lies in wait for the guanacos, and 

 attracts them by his Hfted tail as hunters some- 

 times toll up the pronghorn by lying on their faces 

 and kicking up their heels, thought that strategy 

 out and put it into deliberate execution ; but the 

 waving of the tail was practically involuntary, and 

 he has learned to adapt his hunting to a method 

 whose success we can explain, but which he prob- 

 ably never has fathomed or sought to fathom, for 

 that matter. 



Serpents give a conspicuous example of this 

 nervous condition of the tail. Every snake, when 

 excited, elevates the tip of it, which is highly sen- 

 sitive to touch, and vibrates it with more or less 

 rapidity. This is most marked in the viperine 

 species, and it is here that we find the horny tips, 

 and the rattles of the rattlesnake, which can be 

 agitated with such extreme rapidity as to make 

 merely a fan of light — the eye cannot follow the 

 motion — and can be sustained for hours. There is 

 good reason to believe that the presence of the 

 rattle is connected with, if not the result of, this 

 maximum nervousness. How great the importance 

 of this is in the economy of this kind of serpent, 

 and the way in which it is important, I have en- 

 deavored to show elsewhere.^ The rattling of the 



1 " Rattlesnakes in Fact and Fancy," — Chapter IX of my book 

 " Country Cousins," published by Harper & Brothers, New York, 1 884. 



