Of all the animals covered with hair, the ass is least subject to vermin, which apparently proceeds from the peculiar hardness and dryness of the skin, and for the same reason he is less sensible than the horse to the whip, and stinging of flies.
At two years and a half old the first middle incisive teeth fall out, and the others on each side soon follow; they are renewed at the same time, and in the same order as those of the horse. The age of the ass is also known by his teeth in the same manner. From the age of two years and a half, the ass is in a state to engender; the female is still more early and quite as lascivious, so that unless she is beaten to allay her ardour, she seldom conceives. The usual time of her being in heat is May or June; when pregnant it soon goes off, and at the tenth month milk is found in her dugs; she brings forth at the twelfth, and frequently there are found solid pieces of flesh in the liquor of the amnios, resembling the hippomanes of a foal. Seven days after delivery she is capable of receiving the male, so that we may say she is constantly rearing and engendering. She only produces one foal, and we have scarcely ever heard of her having two. At the end of five or six months the foal may be weaned, and it is even necessary if the mother is pregnant. The stallion ass should be chosen from the largest and strongest of his species; he must at least be three years old, but should not exceed ten; his legs should be long, body plump, head long and light, eyes brisk, nostrils and chest large, neck long, loins fleshy, ribs broad, rump flat, tail short, hair shining, soft to the touch, and of a deep grey.
The ass, like the horse, is three or four years in growing, and lives also like him 25 or 30 years; it is said the female usually lives longer than the male; but, perhaps, this happens from their being often pregnant, and at those times having some care taken of them, instead of which the males are constantly worn out with fatigue and blows. They sleep less than the horse, and do not lie down to sleep, except when they are exceedingly tired. The male ass lasts also much longer than the stallion; the older he is the more ardent he appears, and in general the health of this animal is much better than that of the horse; he is less delicate and not near so subject to maladies. The ancients knew of no disease they had but the glanders, and which, as we have already said, they are much less subject to than the horse.