We can understand two things by this expression; 1st, the absorption of fluids different from those naturally taken by the absorbents, as that of effused blood, &c. I have already spoken of this absorption; 2d, that which takes place in the cysts which are developed contrary to the natural order in the economy. Now this last exhibits a very singular phenomenon, when compared with preternatural exhalation. It, in fact, takes place with difficulty; it is rare that you see the fluids of encysted tumours enter suddenly the circulation by absorption, either in whole or in part, as this very often happens in the serous collections of the peritoneum, which, without being cured, have many alterations of increase and diminution. What physician has not observed that the urine flows more as the abdomen becomes flat, and that it is suppressed when it is filled? Observe on the contrary, that exhalation is renewed with great facility in encysted tumours; that if we empty them and do not remove their cysts, they are soon reproduced, as I have said. Is it that the absorbents are not developed in proportion to the exhalants in these tumours? I know not; but the fact is not less certain; observation of diseases proves it every day. SYSTEMS PECULIAR TO CERTAIN APPARATUS. GENERAL OBSERVATIONS. The former part of this work has been devoted to researches upon the systems common to the structure of all the apparatus, upon the primitive systems, which form if we may so say the nutritive parenchyma, the basis of all the organs, since there is hardly any one of these organs in which the arteries, the veins, the exhalants, the absorbents, the nerves and the cellular texture do not enter as a more or less essential part. Each is at first a texture of these common parts, then of other peculiar parts which particularly characterize them. The systems that will now be examined are not so generally extensive in the animal economy. They belong only to some particular apparatus; thus the osseous, the animal muscular, cartilaginous, and fibrous systems are especially destined to the apparatus of locomotion; thus the serous, mucous, and organic muscular systems enter especially into the digestive, respiratory and circulatory apparatus; thus the glandular system forms the apparatus of secretions, thus the cutaneous system enters principally into the external, sensitive apparatus, &c.