848 



DISH ASMS OF CATTLE. 



At the age of a year and a half, the two permanent middle in- 

 cisors have made their appearance. Fig. 1115 shows these, the 

 internal structure of the lower jaw at this age, and also the cells of 

 the teeth. vThe two middle teeth have come through the jaw, the 

 next two have not yet reached the surface, while the third pair are 

 just perceptible. 



At two years past, the jaw usually presents the appearance 

 shown in Fig. 1116, four of the permanent teeth being now seen. 

 After this the milk-teeth disappear slowly. At three years the third 

 pair of permanent teeth have but just appeared (Fig. 1117). At four 

 years the last pair of incisors will be through (Fig. 1118), but the 

 outside ones are not yet fully grown, as is the case in the horse at 

 the same age. The two inner pairs of permanent teeth are begin- 

 ning to wear at the 

 edges, as shown in the 

 cut. The ox can 

 hardly be said to be 

 full-mouthed until it 

 has reached the age 

 of five years. The 

 whole set has now be- 

 come somewhat worn 

 down at the top, and 

 on the two middle 

 teeth a dark line ap- 

 pears in the center, 

 along a line of harder bone. This can be seen in Fig. 1119. 



There now comes a period of a year or two, and sometimes 

 three, in which the teeth do not indicate so clearly the exact age. 

 During this period the judgment must be guided by the extent to 

 which the dark central lines are worn, which, however, will depend 

 in some degree upon the feeding and exposure of the animal. At 

 the age of seven these lines extend over all the teeth. At eight 

 years of age another marked change begins. A slow but percepti- 

 ble process of absorption begins with the two middle incisors, which 

 become smaller than the others. The dark lines have now become 

 worn into one in all but the corner teeth. At ten years of age four 

 of the central incisors (Fig. 1120) have become smaller, while the 

 central marks have grown fainter. At the age of eleven the six 

 inner teeth are smaller than the two outside ones. At twelve years 

 all the teeth have become smaller, the dark, lines have nearly disap- 

 peared, except in the corner teeth, and the inner edge is now worn 

 down to the gum. 



Pig. 1119.— The Te«Hi 

 at Five Years. 



Fig. 1120.^The Teeth 

 at Ten Years. 



