376 



INTEODUCTION TO ZOOLOGY. 



Another appendage to the head, and of great value in a 

 commercial ])oint of view, is that which is popularly, though 

 not very correctly, termed " whale-bone," It is not bone, but 

 a series of horny plates, the substitutes of the true teeth, which 

 in the whale are altogether wanting. The position of these 

 plates is shown in the annexed figure {Fig. 296) ; they form 



a complete fringe suspended 

 from the margin of the ujjper 

 jaw, and when the whale 

 closes its enormous mouth, they 

 act as a seive, permitting the 

 water to pass through, and 

 enabbng the animal to retain 

 the small gelatinous and mol- 

 luscous creatures on which it lives. The " Baleen" or Whale- 

 bone, is so important an article of trade, that hundreds of tons 

 are annually brought into Britain, won by her intrepid mariners 

 among the perils of the Ai'ctic seas. 



Teeth. — We now pass on to the teeth, viewed as instruments 

 for the mastication of food. In man they are thirty-two in 

 number, when the series is complete ; and the number is the 

 same both in the Orang and Chimpanzee.* They are of three 



Fig. 296.— Skull ot Whale. 



Fig. 297.— Teeth of Has. 



J v_ 



Molars. 



Premolars. Canine. Incisors. 



kinds, the incisor or cutting teeth, the canine, which attain a 

 large development in the l)og and carnivorous animals, and 

 hence derive their name ;t and the molar or grinding teeth. 



" Owen's Odontography. 

 t Latin, canis, a dog. 



