CHAPTER VII 

 THE TEETH OF MAMMALS 



The Mammalia are the highest of the Verte- 

 brates and the most elevated in structure of the 

 entire animal kingdom. They are more highly 

 organized and the organs are more specialized 

 than either Fishes or Reptiles, being the highest 

 result of the evolution of life that has been pro- 

 gressing on the earth since its creation. They 

 live upon the land and in the air and water, and 

 the variety of organization is very great to adapt 

 them to the varied life of these elements. 



They are so named from possessing mammary 

 glands, by which they suckle the young during the 

 first stages of existence. Mammals are vivip- 

 arous, — i.e., the young are born alive, — while all 

 the classes below them are generally oviparous, — 

 i.e., the young are born from eggs. They are first 

 nourished by the milk of the mammary glands. 

 In size mammals vary from that of the tiny har- 

 vest mouse of Europe (weighing scarcely an 

 ounce) to that of the great whales or the extinct 

 mammoth. The body is bare or is covered with 

 a variety of hairy growths, or horny plates, as the 



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