624 



THE PEOPLE'S FARM AND STOCK CYCLOPEDIA. 



rough surface of the mill-stone, by which their grinding power 

 is improved. 



The temporary or milk teeth differ in shape from the perma- 

 nent. They are smaller, and the neck, or fang, is constricted, 

 while in the permanent teeth, which go on growing as they 

 wear off on top, the diameter is greater and gradually dimin- 

 ishes, holding the thickness well. 



Fro. 1. MT:LK INCISORS. 



The natural size and form and markings of the milk incis- 

 ors of lower jaw are shown in Fig. 1. The two central teeth 

 are called nippers, and are seen in the mouth at birth. The 

 pair, one on each side of nippers, are called also middle teeth, and 



FIG. 2. Six MONTHS' MOUTH. 



appear about the middle of the second month. By the sixth 

 or ninth months the next outside pair, called corner teeth, ap- 



