1st. The vital forces, the effect of which is to impart to all the organs which they animate a degree of tone sufficient to resist the entrance of the fluids, leave, when they are extinct, the fibres of these same organs in a state of laxity that renders them everywhere permeable. Thus transudation is now considered as hardly any thing else than a phenomenon that takes place only after death, which, if transformed into a vital one, would offer an evident exception to the laws of nature that are especially characterized by simplicity and uniformity. 2d. The fatty oozing takes place in the experiment noticed above, not only through the pores of the cartilages, but also through those of the whole surface of the bone; so that by reasoning from what has been here observed upon the dead body, it is evident that during life the whole bone would be, if you may so say, immersed in an atmosphere of synovia, a consequence, which being proved false by the most simple inspection, demonstrates the falsity of the principle deduced from it. 3d. The articulations of the cartilages of the larynx are lubricated like those of the bones, by the synovial fluid; and yet here all transudation of marrow is impossible, as it does not exist in the substances of the cartilages. 4th. The marrow is almost always sound in diseases which, affecting the articulations alter the fluid that lubricates them. And reciprocally the synovia does not take a different character in the affections of the interior of the bones, which have an influence especially upon the medullary organ. 5th. Finally, the experiment that I have made, and which has been stated in the article upon the marrow, evidently proves the non-transudation of this fluid. Desault, in order to explain the manner in which the synovia is separated from the blood, added to this pretended transudation of the marrow, an oozing furnished by all the parts contained in the articulation, such as the capsular and inter-articular ligaments, the internal fat, the cartilages, &c. A comparison will suffice to show the value of this hypothesis. What should we say of a system in which to explain the production of the serous fluid of the abdomen, the source of it should be placed in the liver, the spleen, the intestines, and in general in all the organs of this cavity? No doubt we should answer, that a fluid of the same nature, could not be furnished by parts of such different structure, that it is much more simple to search for a single source in the single membrane that covers all the gastric viscera. The application is exact and the analogy perfect between it and the articular cavity. We can, I believe, without fear of error, conclude from all that has been said above, that the synovia is not transmitted by transudation to the articular surfaces. I will now examine the last mode pointed out for the separation of the synovia. _Is the synovia transmitted by exhalation to the articular surfaces?_