In the first periods of inflammations, in which the exhalants of the serous membranes are full of blood which is preternaturally introduced into them, the serum does not ooze in greater quantity from their free surface. Then as they are on the one hand very sensible, and very dry on the other, the motions of the organs that they cover are wonderfully painful. It is in these first periods that adhesions take place. If they are not formed either on account of the motion, or for other reasons, and if resolution of the inflammation does not take place, then happens to the serous surfaces what happens to a wound not united; they suppurate, but this suppuration is never attended with ulceration or erosion of their substance. However abundant the purulent collections may be, these membranes always remain sound; their texture is only more or less thickened; pus is thrown out by them, like the natural serous fluids, that is by exhalation. We know how much this fluid varies in consistence from milky serum, to the thickest false membrane that adheres strongly to the surface that has exhaled the materials of it. The nature of the fluids of the serous system is very evidently albuminous. The instant one of the membranes of this system is plunged into boiling water, I have observed that it is covered with a white layer which is concrete albumen, and which being removed some time after, leaves the surface nearly of its original colour. All the substances which coagulate albumen produce a similar layer upon the serous surfaces. The experiments of Hewson, who has collected some spoonsful of these fluids in the great animals, confirm their albuminous nature. Rouelle and Fourcroy who have analyzed the water of dropsies have also found albumen predominant in it. Observe upon this subject that all the white flakes swimming in this water, that the false membranes that form in it and the white fluids which give it the appearance of milk, appear to be only albumen which is found in different degrees of consistence. It might be said that the heat of inflammation has produced the same phenomenon during life, that common caloric does upon the white of an egg, the water of dropsies, &c. I shall not treat of the other accessory principles that enter into the composition of the serous fluids. ARTICLE SECOND. ORGANIZATION OF THE SEROUS SYSTEM. The first characters of the structure of these membranes are a white, shining colour, less brilliant than that of the aponeuroses; a variable thickness, very evident upon the liver, the heart, the intestines, &c. hardly discoverable upon the arachnoides, the omentum, &c.; a remarkable transparency whenever these membranes are raised for a considerable extent, or are examined where they are detached on both sides, as on the omentum.