1 88 Life and Immortality. 



snakes, however, it is stored up in sacs, modifications of the 

 salivary glands, and placed in each side of the upper jaw. 

 From the poison-gland under the eye forward to the edge of 

 the jaw, a delicate canal, which opens into the fang above the 

 tube of the tooth, extends. Alongside of the latter may be 

 seen rudimentary fangs, all ready to grow out should the 

 large one be lost. To use the poison, the snake has merely 

 to strike its prey, when the muscles of the jaw, which are 

 admirably fitted for the part they have to play in the tragedy, 

 press upon the glands, squeeze the poison through the little 

 canal down through the hollow fang, and the work is ac- 

 complished. 



In their actions, snakes are most graceful. The gliding 

 motion, so characteristic, is effected by the movements of 

 the large central scales, that are successively pushed for- 

 ward, the hinder edges resting on the ground and consti- 

 tuting a support. These scales, or pushers, are fastened to 

 the ribs by muscles, and by holding a snake by the hand the 

 swelling movement can readily be felt. 



Snakes vary much in color. They are generally adapted 

 to their surroundings. Green Snakes are found in green 

 grass and vegetation, while grey snakes affect rocky dis- 

 tricts, where they are alike protected. Their skin is shed in 

 one piece at various seasons of the year, being forced off by 

 the snake forming a ring with its tail and squeezing the rest 

 of the body through it, or by wriggling through entangled 

 bushes. Poisonous snakes may be always recognized by 

 their broad, flattened heads, generally short and thick bodies, 

 and the almost invariable possession of a vertical keel along 

 the centre of each scale. Long bodies, small heads devoid 

 of distinct necks, and scales not keeled, characterize non- 

 poisonous species. 



Probably the best-known of our common kinds of poison- 

 ous snakes are the rattlesnakes. They belong to the dan- 

 gerous family Crotalidae, to which the copperheads and 

 moccasins also belong, and are distinguished by the large, 



