Every fluid differing from the blood, can be separated from it to be afterwards transmitted to an organ, but in one of the three following ways; 1st, by secretion, a function characterized by the existence of a gland intermediate to the blood vessels that bring the materials to it, and the excretories which carry off the result; 2d, by exhalation, a function distinguished from the first, by the absence of this intermediate gland, and by the immediate continuity of the blood vessel and the exhaling duct; 3d, by transudation, a phenomenon purely physical, almost always happening after death, rarely observed during life, a simple transmission of a fluid by the pores of an organ, towards which it is mechanically determined. Let us examine which of these three modes is that chosen by nature to deposit the synovia upon the articular surfaces. _Is the synovia transmitted by secretion to the articular surfaces?_ We are indebted to Clopton Havers for the system which places in the glands the sources of the synovia. Many authors had designated obscurely before him these organs in the articulations; but he made them the particular object of his researches, described them in the different articulations, divided them into two classes, the one principal, the other accessory, and assigned them characters so evident, that according to him, they could not be forgotten. Reddish bunches, spongy, formed by membranes folded upon themselves, situated sometimes without, and sometimes within the articulations, always arranged so as to be protected from too strong a compression, and pouring out through ducts in the form of fringe the fluid they secrete; such are the characters drawn by Havers, which all anatomists since him admire, and the correctness of which the most modern and distinguished authors have acknowledged in their works.