The Natural History of Pliny, Volume 2 (of 6)

Camels are found feeding in herds in the East. Of these there are two different kinds, those of Bactria and those of Arabia;1700 the former kind having two humps on the back, and the latter only one; they have also another hump under the breast, by means of which they support themselves when reclining. Both of these species, like the ox, have no teeth in the upper jaw.1701 They are all of them employed as beasts of burthen, in carrying loads on the back, and they answer the purpose of cavalry in battle. Their speed is the same with that of the horse, but their power of holding out in this respect is proportioned in each to its natural strength: it will never go beyond its accustomed distance, nor will it receive more than its usual load. The camel has a natural antipathy to the horse.1702 It can endure thirst for four days even, and when it has the opportunity of obtaining water, it drinks, as it were, both for past and future thirst, having first taken care to trouble the water by trampling in it; without doing which, it would find no pleasure in drinking. They live fifty years, some indeed as much as one hundred. These animals, too, are liable to fits of frenzy.1703 A peculiar mode of castrating them, and the females, even, when required for the purposes of war, has been discovered; it renders them more courageous, by the destruction of all sexual feelings.