The domestic state has greatly contributed to vary the colour of animals, which was originally, in all, either brown or black. The dog, the ox, the goat, the sheep, and the horse, have imbibed all kinds of colours. The hog has changed from black to white; and pure white, without any spot, seems to mark the last degree of degeneration, and which is commonly accompanied with imperfections or essential defects. In the race of white men, those who are remarkably so, and whose hair beard, and eyebrows, are white, are often deaf, and also have red and weak eyes. In the black race, the fairest negroes are of a nature still more weak and defective. All those animals which are absolutely white have the defects of being hard of hearing and having red eyes. This kind of degeneration, though more common in domestic animals, is sometimes seen in the wild species; as in the elephant, stag, fallow-deer, monkies, moles, and mice, in all of which this colour is always accompanied with either a greater or a less weakness of body and dulness of sensation. But of all animals the camel seems to have the greatest and deepest impressions of slavery made upon him. He comes into the world with prominences on his back, and callosities on the breast and knees; these callosities are formed by the continual friction on those parts, as is plain from their being filled with pus and corrupted blood. As he never travels without being heavily loaded, the pressure of the burden has prevented the free extension and uniform growth of the muscular parts of the back, and produced a swelling in the surrounding flesh; the camel likewise being constrained at first to rest or sleep in a kneeling posture, in time it becomes habitual; and from supporting the whole weight of his body, for several hours in the day, on his breast and knees, the skin of those parts is rubbed off by pressing against the earth, and by degrees they become hard and callous. The lama, which passes his life, like the camel, under the pressure of heavy burdens, and likewise rests on his breast and knees, has similar callosities, which are perpetuated by generation. The baboons and monkies, which, whether sleeping or waking, are generally in a sitting posture, have also callosities on their posteriors. This callous skin is even adherent to the bones, against which it is continually pressed by the weight of the body. But the callosities of the baboons and monkies are of a dry and healing nature, as they do not proceed from the oppression of any superabundant weight, but, on the contrary, are only the effects of natural habits, for these animals remain longer in a sitting than in any other posture. The callosities of the monkey are like the double skin on the sole of a man's foot. This is a natural callosity, which our habit of walking or standing renders thicker and harder, according to the greater or lesser degree of friction we effect by exercise.