THE RATTLESNAKE 125 



themselves are mere modifications of the general skin 

 of the body, but the •' rattle " has a more solid foundation. 

 The real tail of birds (as we saw when considering the 

 turkey) is made up of a short fleshy structure supported 

 by a special modification of the terminal segments of the 

 backbone. The same is the case with i-espect to the 

 rattle of this serpent. Its three terminal segments (or 

 vertebrae) become united together into one solid whole, 

 and also become enlarged in size and specially modified 

 in form, being swollen at the hinder end. This bony 

 structure is covered with a special development of the 

 soft deeper skin from which all the outer skin and 

 scales of the body are formed, the soft structure beiiig so 

 subdivided by grooves as to form three segments, whic]i 

 themselves become coated with three corresponding dense 

 layers of outer skin, or, as it is technically called 

 " epidermis," thus forming three horny rings. These con- 

 stitute all the rattle there is in young snakes which have 

 not yet shed their skin. Snakes and men shed their skin 

 differently. In us the outer skin is thrown off in very 

 minute separate portions, so that the process is not ordi- 

 narily, noticed. In snakes all the skin is shed at once as 

 one continuous whole — even the skin of the eyeballs 

 being shed with the rest, and thus snakes get a little 

 blind during the process of its detachment. When the 

 first moult in rattlesnakes draws near, fresh skin is formed 

 beneath the old covering of the hinder end of the tail. 

 When the moult actually takes place, the old covering 

 of the tail end is not cast oft' (being held by the swollen 

 end of the bone before noted), but remains as a loose 

 appendage, thus becoming the first formed joint of the 

 future perfect rattle. The rattle, in fact, grows perfect 

 by the accumulation of rings in this manner, one being 

 thus made loose and yet retained, at each succeeding 



