DIGESTION. THE TEHTH. 



61 



Fiy. 18. 



Fig. 19. 



43. The torm of the teeth also varies in different animals, and 

 we remark, that these differences are in accordance with the 

 nature or kind of aliment upon which these beings are destined 

 to be nourished. 



44. Thus, with the dog, the cat, and 

 other carnivorous animals, the molar 

 teeth are sharp, and fitted to cut flesh, 

 like scissors (Tig. 18.) ; with the mole 

 and hedge-hog, that live upon pretty 

 hard insects, these teeth are armed 

 with conical points, which dovetail or 

 fit reciprocally, and enable these ani- 

 mals to crush their prey with facility. 



With the frugivorous animals, monkeys, for example, the same 

 teeth are large, and their crown is armed 

 with rounded elevations, suitable for crush- 

 ing fruits; and with the ox and horse, which 

 browse or crop the grass, the crown of these 

 teeth is still larger, and its surface is flat and 

 striated like a mill stone. (/'% 19.) 



45. In man, the deciduous or milk teeth, 

 begin to appear about the sixth or seventh 

 month, and fall about the seventh year. Tney 

 are in number, twenty ; namely, in each jaw : 



Four Incisor, 



Two Canine, (one on each side,) 



And four molar, (two on each side.) 



46. The permanent, or teeth of second 

 dentition, are in number, thirty-two. 



47. The incisor and canine are the same in 

 number as in the first dentition ; but in place of two molars on 

 each side of each jaw, there are five. The total number of molar 

 teeth in adult man is consequently twenty; ten in each jaw. 



Explanation of Fig. 18. Teeth of an animal of the order oarnaria, t, 

 incisor, a. canine, m. molar teeth. 



Rrpta nation of Fi<r. 19 Teeth of an animal of the order rodentia, * 

 incisor teeth, /^ molar teeth 



43. Is the form of the teeth thi same in all animals ? 

 4 i. Does the form of the teeth of an animal bear any relation to its 

 peculiar food ? 



45. At what age in man do the first teeth begin to appear? When do they 

 fall ? What is the number of the deciduous teeth ? What is the number of 

 each kind ? 



46. What is the number of the permanent teeth ? 



47. How do tl.e permanent differ from the deciduous teeth ? How many 

 molar teeth is natural to an adult man? 



