When on the ground they are exposed to all their enemies, and as their flesh is not absolutely bad they are sought after both by men and beasts of prey. They seem to multiply but little, or if they produce often it is only a small number at a time, as they are furnished with but two teats: every thing, therefore, concurs to their destruction, and the species supports itself with great difficulty. Although they are slow, heavy, and almost incapable of motion, yet they are hardy, strong, and tenacious of life; they can exist a long time deprived of all food; they are covered with a thick, coarse fur, and being unable to take much exercise they waste little by perspiration, and therefore they fatten by rest, however poor their food. Though they have neither horns nor hoofs, nor incisive teeth in the lower jaw, they belong, notwithstanding, to the number of ruminating animals, and have four stomachs, so that they may compensate for the quality of their food by the quantity they take at a time; and what is still more singular, instead of having, like other ruminating animals, very long intestines, they are very short, like those of the carnivorous kind. The ambiguity of Nature seems somewhat discovered by this contrast. The sloths are certainly ruminating animals, as they have four stomachs; but they are deficient in all the other external and internal characters which belong to all animals in that class. There is also another singularity in these animals, instead of distinct apertures for the discharge of the urine, excrements, and the purposes of generation, these animals have but one, which terminates in a common canal, as in birds. Finally, if the misery which results from a defect of sensation be not the greatest of all, the miserable state of these animals, although very apparent, seems not to be real, for they appear to have little or no sensation, and their dull and heavy look, their indifference to blows, which they receive without being in the least affected, prove their insensibility. But what still further demonstrates this fact is, their not instantly dying upon their hearts and bowels being taken out. Piso, who made this cruel experiment, says, that the heart, after being separated from the body, beat forcibly for more than half an hour, and that the animal continued to contract its limbs in the same manner as when asleep.[AM] From these circumstances this quadruped approaches not only the tortoise but also other reptiles who have no distinct centre of sensation: thus all these animals are miserable without being unhappy; and Nature, even in her most unfinished productions, appears always to act more as a real parent, than a step-mother.