142 



AGE OF THE DOMESTIC ANIMALS. 



and the wearing surface is much softer ; the mastication is not 

 complete, and the animal shows the effect of a lessened nutrition. 

 Superior Jaw. — What has been said of the lower jaw ap- 

 plies to the upper, but the changes in them are less frequent. 



FIG. 149. Fig. 150. 



Lower molar aich of a very old horse. Molar arches (right) of a very old horse. 



Lower jaw to the left of figure. 



The separation of the roots in the upper jaw is less common, as 

 these teeth are longer and contain a greater amount of enamel. 



EXCESS OF LENGTH OF THE CROWNS. 



Excess of length of the crowns or portions of them is of 

 rather common occurrence. As the upper molars are broader as 



