THE ANATOMY OP THE OX 215 



the permanent pair disappear, and a permanent pair 

 come in their places. About three years of age the third 

 pair comes in, one on each side of the four, and finally at 

 three and one-half to four years of age, the corner milk 

 teeth are supplanted by permanent incisors. Thus it can 

 be assumed that two of these new teeth indicate about a 

 yearling, four a two-year old, six a three-year old and eight 

 a three- to four-year old. Some consider six teeth as a 

 sign of a four-year old and eight as a five-year old. There 

 is some variation in the appearance of these permanent in- 

 cisors, due to feeding and condition. Cattle mature earlier 

 to-day than they did fifty years ago, and no doubt this 

 characteristic also influences an earlier appearance of the 

 teeth. At six years the teeth are in most perfect form, but 

 a little flattened on top, and with the central pair show- 

 ing dark lines in the center. From now on the age can only 

 be guessed at. The teeth gradually wear down, and change 

 to a more slanting position. Various conditions affect the 

 teeth and their importance as indicating age. Those used 

 the most for grazing will show the greatest wear. At 

 seven years the dark lines in all the teeth are yet more 

 visible, and at eight especially so in the central ones. At 

 nine the middle two begin to show reduced size, and at 

 ten the four central ones are smaller than the others. Thus 

 the teeth wear off from central to outer pair, so that often 

 one will see cows fifteen years old or older that have no teeth 

 excepting small stumps, or no incisors at all. 



