Though organic sensibility is everywhere given to the exhalants, it varies however remarkably in each system; that of the mucous exhalants is not the same as that of the serous. In general the exhalants entering as it were like elements into the texture of each system, partake completely of the organic properties of that system; or rather their properties are the same. Hence, 1st, why each separates the fluid that is peculiar to it; why consequently, when much water is introduced into the circulation by drinking, the cutaneous exhalants, and never the serous, appropriate it to themselves, and transmit it out of the blood; when we run much and a general agitation is consequently given by the heart to the mass of blood in circulation, the cutaneous exhalants, being more powerfully excited by this impression than the serous, the synovial, &c. separate more sweat; 2d, why the serous do not pour out fat, the medullary serum, &c. though the mass of blood that enters the capillaries that are continuous with these exhalants, is everywhere the same; 3d, why when the exhalants pour out fluids that they are not accustomed to, or when their natural fluids are altered, these fluids differ essentially from each other; why, for example, after inflammation, it is only upon the serous surfaces that we see a milky serum; why nothing resembling pus flows from the inflamed medullary membrane; why the fluids, the result of the inflammation of the synovial membranes, are very different from those that the serous surfaces produce, &c.; 4th, why certain exhalants have a much greater tendency than others to admit blood and pour it out upon their respective surfaces, of which we see an example in the mucous exhalants, which are so disposed to suffer this fluid to pass, that a thousand circumstances occasion hemorrhages from them; 5th, why among the mucous exhalants themselves, some have a much greater tendency than other to permit the blood to pass, &c. &c. All these phenomena are evidently derived from the particular modifications that distinguish the organic sensibility and contractility in each kind of exhalants. II. _Of Natural Exhalations._