The absorption of the lacteals, which, in an ordinary state, introduces into the blood only nutritive substances, can then often be a way open for the admission of many morbific principles. Thus in the lungs, the vessels which take from the air the substances proper to colour the blood, often draw in principles injurious to their functions, according to the different alterations that their sensibility can experience. In the ordinary state, the kind of organic sensibility and of tone of the cutaneous and mucous absorbents, shuts out all external substances that are hurtful. But when this kind is changed, the way can in an instant be open to them. Does not pus remain without mischief on the cellular texture, in most wounds? Let an imprudent application raise there a little the forces of the absorbents, it is taken up by them; the ulcer dries up; the pus passes into the blood; and then follows the whole sad train of the symptoms of re-absorption which commences. We can say, that a thousand channels are incessantly open in our organs, to morbific principles. The organic sensibility, placed as a sentinel at their mouths, indicates according to the manner in which it is affected, to the insensible contractility when it is necessary to open or shut them. It is exhalation that contributes to the formation of most tumours; it is absorption that serves for their cure. If I were to run over the phenomena of absorption in the different ages, sexes, seasons and climates, I could show constantly the differences of organic sensibility always preceding the differences of this function. I shall speak of them in the different ages. The causes that vary the natural type of the sensibility of the absorbents, are, as in all the other functions, direct or sympathetic; 1st, direct, as when by previous friction on the skin, we excite the absorbents, and force them to act, which they would not have done without this; 2d, sympathetic, as when the absorbents, feeling the affection of a distant viscus, increase or diminish their action, according to the kind of influence they receive. We have spoken of this phenomenon in the sympathies of the different systems. III. _Motion of the Fluids in the Absorbents._ The fluids once absorbed on the different surfaces of which we have spoken, are carried by a successive motion to the common trunks, which transmit them to the black blood. We know not the laws of this motion. It is evident from many observations formerly made, that it has much analogy with the motion of the venous blood; but it is also distinguished from it by some differences. It appears to be in general more slow. The thoracic duct opened when it is full of chyle, does not throw out its fluid as far as a vein of the same size.