262 GENERAL ZOOLOGY 



bright red and black around the body. They have a 

 poisonous spittle^nd bite viciously when molested. When 

 their bodies are well nourished the tails become swollen 

 with stored fat, and they can then live for some time with- 

 out food. 



Snakes are not only without limbs but show various 

 other adaptations correlated with their slender forms. 

 One lung is usually rudimentary, the visceral organs are 

 peculiarly arranged, and there is no urinary bladder. The 

 two halves of the lower jaw are connected by an elastic 

 ligament, and are loosely fastened to the skull. This 

 arrangement makes it possible for a snake to swallow 

 animals which greatly exceed its own body in diameter. 

 Snakes move by waving the ventral scales backward and 

 wiggling the body. Muscles lead from the scales to the 

 ribs, which help materially in locomotion. There is great 

 variation in the size of snakes a python may have a 

 length exceeding thirty feet and weigh over three hundred 

 pounds; some of the burrowing snakes are less than six 

 inches in length and no thicker than a goose quill. 



Snakes may be viviparous or oviparous; that is, the 

 young of some species are born and those of others hatch 

 from eggs. The garter snakes bear their young in such 

 condition that they are soon able to shift for themselves. 

 The milk snake "lays eggs in holes in the ground. 



Though there are many venomous snakes, the harmless 

 species greatly outnumber them. Of the one hundred 

 and eleven species in the United States less than twenty 

 are poisonous. The venomous snakes have a poison gland 

 on either side of the head which is connected with a grooved 

 or hollow fang in the mouth; the non-poisonous species 

 have the jaws armed with sharp backwardly directed teeth 

 which hold the food and help in swallowing. There are 

 two types of poison fangs grooved and tubular. The 

 former is more primitive, and the hollow type has ap- 

 parently been derived from it by a closing over of the 

 groove. The grooved fang is usually fastened immovably 



