In all the ginglymoid articulations, as in those of the elbow, the knee, the phalanges, the hand, the foot, &c. &c. the fibrous capsule is wholly wanting. The fibres, instead of extending and interlacing in the form of a membrane, are collected into fasciculi more or less thick, which form the lateral ligaments. There is only found in them the internal layer of the enarthrodial articulations, that is to say the synovial membrane, which does not contract here any adhesion with the periosteum, but is reflected upon the cartilages. By taking it at the place of this reflection, it can be detached far enough to prove that it has an external organization wholly different from that which the idea of a capsular ligament at first presents to the mind. This arrangement is very easily perceived by the least dissection, at the knee behind the tendon of the cruræus and the inferior ligament of the patella, at the elbow under the tendon of the triceps, at the phalanges under that of the extensor, &c. All the arthrodial articulations have also an analogous organization, as will be seen in the Descriptive Anatomy; so that it is ascertained that the fibrous capsules exist but in a very small number of articulations, that almost all have only synovial sacs which are spread out and reflected upon the osseous surfaces, without being attached around them, as all authors have said. I have proved this remarkable difference of the articulations by many dissections. Some anatomists were in the way to discover it, when they observed that the different capsules appeared to be wholly formed of cellular texture. It is in fact the texture of the synovial membrane, which differs essentially in this from the fibrous capsules. The mode of capsule for all articulations may be preserved, if it is wished, but different ideas must then necessarily be attributed to it. Compare, for example, the fibrous capsule of the femur with the synovial capsule of the knee; you will find on the one hand, 1st, a cylindrical sac with two great openings for the osseous extremities, and with many small ones for the vessels; 2d, a fibrous interlacing, similar to that of the tendons, the aponeuroses, &c.; 3d, a mode of sensibility analogous to that of these organs; 4th, the use of retaining strongly in place the articulated bones, which have only this bond to strengthen their union. On the other hand you will observe, 1st, a sac without an opening; 2d, a cellular structure, the same as that of the serous membranes; 3d, a sensibility of the same nature as theirs; 4th, the simple function of containing the synovia and separating it, the bones being tied by strong ligaments. Besides, the different reagents have upon the fibrous capsules an influence wholly different from that which they exert upon the synovial. Ebullition yellows them, renders them semi-transparent, softens them like tendons and gradually melts them like gelatine. The synovial ones boiled remain whitish, and furnish but