The _ox_ should only be worked from three years old to ten; and he should then be taken from the plough to fatten, as the flesh will be better than if he be kept longer. The age of this animal is known by his teeth and horns. The first front teeth fall out when he is ten months old, and are replaced by others which are larger and not so white; at 16 months those on each side of the middle teeth drop out, and are replaced by others; and at three years old, all the incisive teeth are renewed; they are then all long, white, and even; and, in proportion as the _ox_ advances in years, they decay, and become unequal and black. It is the same with the bull and cow; so that neither sex nor castration makes any alteration in the growth or fall of the teeth, nor does either make any difference in the casting of the horns, for they fall off at three years equally from the ox, bull, and cow; these are replaced by other horns, which, like the second teeth, fall off no more, only those of the _ox_ and cow grow longer than those of the bull. The growth of these second horns is not uniform. The first year, that is to say, the fourth of the animal's age, two little pointed horns sprout, which are even, and terminate at the head by a kind of knob; the following year this knob grows from the head, pushed out by a cylinder of horn, which forms and terminates also by another knob, and so on; for as long as the animal lives, the horns continue to grow; these knobs are easily distinguished, and by which his age may be easily known, by adding three years to the number of intervals between the other knobs.