98 MECHANISM AND. PUKPOSE OF THE BATTLE. 



larger-sized species. They show no accurate index of age,* as was for- 

 merly supposed, but may be lost and replaced irregularly, the repair of 

 such an accident proceeding rapidly. 



The crepitating sound of the rattles is a mechanical result of their jar- 

 ring, and may be produced by shaking them in your hand, or accidentally 

 by the animal in moving along uneven ground. This, however, is hardly 

 audible, and the sound becomes so only by increased agitation of the tail, 

 which can be made to vibrate with singular swiftness. As a continuous 

 and sustained action, this has no parallel anywhere that I know of in the 

 higher animals, and is only approached by the whirring speed of a hum- 

 mingbird's wings, making mist of their invisible motion while poising 

 before a flower. Similarly the motion of the rattle in an excited snake 

 cannot be followed b}' the eye, its shape disappearing in a fan of light. 

 The enormous muscular and nervous force involved is shown, also, in the 

 fact that this inconceivably rapid movement of the tail can be sustained 

 for several hours without an instant's rest, as I have repeatedly witnessed 

 in various species. 



What is the purpose of this vibration of the tail and the loud rattling? 

 Does it serve any use to the creature 2 If so, what ? 



Naturalists are not agreed upon the proper answer to these questions, 

 but certain facts seem made out, one of which, not to be forgotten, is 

 that many other serpents outside the Crotalidm set their tails into swift 

 vibration when teased or excited. Another point is the close resemblance 

 between the sound of the snake's rattling and the crepitation of the wings 

 of certain cicadse and locusts. The view has been advanced that the rat- 

 tling of the serpent was an imitative sound, operating to attract within 

 reach of his fangs such animals — especially birds — as feed upon these 



* An odd note in Thomas Morton's " New English Canaan," 1632, is worth quoting : 

 " There is one creeping beast or creeple (as the name is in Devonshire) that hath a rattle 

 at his tayle, that doth discover his age." That progress towards a knowledge of truth was 

 slow, is shown by the following quotation from the generally very intelligent book writ- 

 ten by Thomas Campanius (of Stockholm), printed in 1702, concerning "New Sweden," 

 or what is now southern New Jersey. He says : " There is here also a large and horri- 

 ble serpent which is called a rattlesnake. It has a head like that of a dog, and can bite 

 off a man's leg as clear as if it had been hewn down with an axe. There are horny joints 

 in their tails, which make a noise like children's rattles, and when they see a man, they 

 wind themselves in a circle and shake their heads, which can be heard at the distance of 

 a hundred yards, so that one may put himself on his guard. These snakes are three 

 yards long, and thick as the thickest part of a man's leg ; they are as many years old as 

 they have rattles in their tails ; their color is brown, black, and yellow. Their skins are 

 much sought after by pregnant women ; they tie them round their bodies, and are quick- 

 ly and easily delivered." It would be hard to find a better example of exaggeration. 



