In brute animals these effects are quicker and greater; for, partaking more of the nature of the soil than man, and their food being more uniform and unprepared, the quality is more decisive, and, consequently, its influence stronger; and because as the animals cannot clothe nor shelter themselves, nor make use of the element of fire, they remain constantly exposed to the impressions of the air, and inclemencies of the climate. For this reason every animal has chosen its zone and country according to its nature; for the same reason they remain there, and instead of extending or dispersing themselves, like the human race, they generally continue in those places which are most agreeable to their constitutions. When driven by man, or carried away, or forced by any revolution of the globe to forsake their native country, their nature undergoes such great and strong alterations, that they are no longer to be known, except by attentive inspection, experiment, and analogy. If to these natural causes of alteration in free animals we add that of the empire of man over those which he has reduced to slavery, we shall be surprised to see how far tyranny is able to degrade and disfigure Nature; we shall perceive on all the animals which are reduced to slavery, the stigmas of their captivity, and the impressions of their fetters; we shall find that those wounds are deeper, and more incurable, in proportion to their antiquity; and that in the state wherein we have reduced domestic animals it would perhaps be impossible to reinstate them in their primitive form, and to restore to them those other natural attributes of which we have deprived them. Thus, the temperature of the climate, the quality of the food, and the evils arising from slavery, are the three causes of the changes and degeneration of animals. The effects of each deserve to be particularly considered, and their relations, when viewed in detail, will present a picture, in the foreground of which we shall see Nature such as she is at present, and in the distant perspective what she was before her degradation.