If we plunge a scalpel into a cartilage, the edges of the divided place re-act upon it and expel it. Pressed against a resisting body, the cartilaginous extremity of a long bone becomes flat and resumes its form when the compression ceases. The edges of the thyroid cartilage, when it is cut longitudinally in the operation of bronchotomy, immediately approximate each other. The division of the cricoid ring exhibits the same phenomenon. The cartilages of the last ribs, when forced in towards the abdomen, come out of themselves, &c. &c. All these phenomena are the evident result of an elastic power. Thus nature has placed the cartilages wherever, to produce her phenomena, there is a necessity of uniting a physical to the vital forces, as in the larynx, in the nasal septum, in order to produce a sort of vibration in the passage of the air, at the extremity of the ribs, in order to be the seat of a species of twisting necessary to the mechanical part of respiration, at the articular extremities, in order to diminish the force of blows, &c. It appears that the vital activity renders this property greater, which however remains very apparent after death. I presume that this is owing to the great quantity of gelatine they contain. 1st. We know that this substance possesses it in a very high degree, as is proved by the tremulous motion of jelly after it has become cold, by the examination of various animal glues, &c. 2d. If by ebullition we remove this substance from the cartilages, the nutritive parenchyma remains flaccid and soft. 3d. As the gelatine diminishes in our organs, the elasticity in them is less, as we see by examining the decrease of this property from the cartilages in which it predominates, to the fibro-cartilaginous organs in which it is in a smaller proportion, and to the fibrous bodies in which it is still less. It must be confessed however that many very gelatinous bodies, exhibit but very slight traces of elasticity; the skin is an example of this, and so are the tendons. Can the same substance, as it is differently operated upon by the organic laws, become the seat of properties wholly dissimilar? II. _Properties of Texture._ The cartilages are perhaps of all the organs, those in which the extensibility and contractility of texture are the least developed. We see them rarely distended and elongated; they break first. Diseases do not exhibit in the larynx those dilations so common in the other cavities, even the osseous ones. When divided, the edges, far from separating as in the skin, in a muscle, &c. approximate each other, as we have seen, by the effect of elasticity; we might say that this last property was accumulated in the cartilages at the expense of those of texture. III. _Vital Properties._