264 



The Study of Animal Life part hi 



growing slowly and without that definite limit which punctuates 

 the life -history of most animals, attaining, moreover, a great 

 age, freed after youth is past from the attacks of almost every 

 foe but man. The teeth are firmly implanted in sockets ; the 

 limbs and tail are suited for swimming, and also for crawling ; the 

 heart is more highly developed than in other reptiles, having four 

 instead of three chambers. The animals lie in wait for victims, 

 and usually drown them, being themselves able to breathe while 

 the mouth is full of water, if only the nostrils be kept above the 

 surface. 



In many ways Reptiles touch human life, the poisonous snakes 

 are very fatal, especially in India ; crocodilians are sometimes 

 destructive ; turtles afford food and " tortoise shell ;" lizards are 

 delightfully beautiful. 



8. Birds. — What mammals are to the earth, and fishes to the 

 sea, birds are to the air. Has anything truer ever been said of 



Fig. 55. — The Collocalia, which from the secreted juice of its salivary glands 

 builds the edible-bird's-nest. (Adapted from Brehm.) 



them than this sentence from Ruskin's Queen of the Air} "The 

 bird is little more than a drift of the air brought into form by 

 plumes ; the air is in all its quills, it breathes through its whole 

 frame and flesh, and glows with air in its flying, like a blown 



