XXXIII. (162) Or the creatures which are fit to be offered as sacrifices, some are land animals, and some are such as fly through the air. Passing over, therefore, the infinite varieties of birds, God chose only two classes out of them all, the turtledove and the pigeon; because the pigeon is by nature the most gentle of all those birds which are domesticated and gregarious, and the turtle-dove the most gentle of those which love solitude. (163) Also, passing over the innumerable troops of land animals, whose very numbers it is not easy to ascertain, he selected these especially as the best--the oxen, and sheep, and goats; for these are the most gentle and the most manageable of all animals. At all events, great herds of oxen, and numerous flocks of goats and sheep, are easily driven by any one, not merely by any man, but by any little child, when they go forth to pasture, and in the same way they are brought back to their folds in good order when the time comes. (164) And of this gentleness, there are many other proofs, and the most evident are these: that they all feed on herbage, and that no one of them is carnivorous, and that they have neither crooked talons, nor any projecting tusks or teeth whatever; for the back parts of the upper jaw do not hold teeth, but all the incisor teeth are deficient in them: (165) and, besides these facts, they are of all animals the most useful to man. Rams are the most useful for the necessary covering of the body; oxen, for ploughing the ground and preparing the arable land for seed, and for the growth of the crops that shall hereafter come to be threshed out, in order that men may partake of and enjoy food; and the hair and fleeces of goats, where one is woven, or the other sewn together, make movable tents for travellers, and especially for men engaged in military expeditions, whom their necessities constantly compel to abide outside of the city in the open air.