LEVELING, PROGRESSIVE USE, ETC. 65 



Girard thought that the pinchers were leveled at ten 

 months, the intermediate at one year, and the corner teeth at 

 fifteen to twenty-four months, but this is too definite; the 

 leveling of the temporary incisors is somewhat irregular, and is 

 considerably modified by the depth of the cups, the amount of 

 cement which they contain, and the character of the food upon 

 which the animal is fed. Experience will teach the observer 

 to place much value on the condition of the corner teeth, the 

 amount of wear of the superior incisors, and upon the color, 

 which gradually becomes darker. At the end of this period 

 the pinchers become broken, loose, and ready to fall from their 

 sockets ; they are less solidly fixed in the jaw and may be 

 broken ofi", or are pushed out naturally by the permanent teeth, 

 which replace them. 



During this period, especially during the second year, the 

 variations in the amount of wear of the teeth in different animals 

 may be very marked ; but, by a careful comparison of the use 

 which each pair of teeth — pinchers, intermediate, and corners — 

 have undergone, and, with close observation of the development 

 and size of the bones, taking into consideration the intermaxil- 

 lary bones, and the width and thickness of the body and 

 branches of the maxilla, a very close differentiation of a month 

 or two may be made. Especial note must be made of the 

 amount of gum which still covers the crown of the teeth, or 

 their freedom from the gums, the discoloration on their surface, 

 the polishing off* of the small striations, and the evidence of the 

 protrusion of the permanent teeth under the gums behind the 

 deciduous teeth. 



