The word cartilage is employed too vaguely. It designates, in the common acceptation, bodies whose organization differ essentially. The cartilages of the nose and those of the articular surfaces have certainly but a very remote analogy between them; it is necessary then to establish a line of demarcation. I have endeavoured to do it by making two systems of them; one comprehends the cartilages properly so called, the other, the fibro-cartilaginous substances, such as those that are between the vertebræ, those in the middle of some articulations, &c. As this last is a compound of the fibrous and cartilaginous system, I shall not treat of it until I have spoken of the fibrous system. By thus limiting the sense of the word cartilage, it gives us the idea of a hard, elastic, white substance, having an inorganic appearance, though it has a real organization. We find this animal substance in different parts of the body; it is met with especially, 1st, at the articular extremities of the moveable bones; 2d, on the articular surfaces of the immoveable bones; 3d, on the parietes of certain cavities, which it contributes in great measure to form; such are the cartilages of the nasal partition, of the ribs, the larynx, &c. Hence three different classes, which exhibit varieties in their forms, in their organization, &c. ARTICLE FIRST. OF THE FORMS OF THE CARTILAGINOUS SYSTEM. The forms of the cartilages vary according to the class to which the cartilage belongs. I. _Forms of the Cartilages of the Moveable Articulations._ In every moveable articulation, there is at each osseous extremity, a cartilage which covers this extremity, which facilitates by its suppleness the motion of the two bones, the very hard substance of which would occasion by friction too great a shock; which reflects by its elasticity a considerable part of the motion, thus made more extensive; which breaks, by yielding a little, the violence of the shocks the limbs experience, and which thus render these shocks less dangerous. The general character of the internal conformation peculiar to these cartilages is that of being always less thick than broad, of having a thickness which is in the ratio of their breadth: so that the cartilages of the great articulations exceed in this respect two, three, or four times even, those of the smaller articulations; and these cartilages are moulded upon the articular forms and exhibit two faces and a circumference.