Extensibility is very often brought into action in the fibro-cartilaginous system. I have seen a polypus that had so dilated the anterior openings and consequently the fibro-cartilages of the nostrils, that their diameter was at least treble. The external and cartilaginous extremity of the meatus auditorius often exhibits from the same cause, an analogous distension. In the various twistings of the vertebral column, the portion of the fibro-cartilages corresponding to the convexity of the curvatures, is evidently elongated, whilst the opposite portion is contracted. This extensibility is moreover subjected in many cases to the same law as in the fibrous system, that is to say that it cannot be put into action but in a gradual and insensible manner. The contractility of texture is observed when, in the cases of which I have spoken, the cause of distension disappears. Thus after the extraction of the polypus mentioned, the nostril gradually resumes its natural diameter. I have removed in a dog a tendon from its groove, by cutting it at one extremity, and drawing it by the other, so as to leave untouched and empty the sheath that contained it; this sheath and the fibro-cartilage have gradually contracted and the cavity has disappeared. In the carcinoma of the eye, in which the eye-lids were not removed, the tarsi which become much elongated with these moveable veils, gradually contract and resume their dimensions, after the extirpation of the tumour which distended them. It is necessary however to distinguish these phenomena from those which are the product of elasticity; these last are prompt and sudden; the fibro-cartilage of the ear, powerfully stretched, yields a little, and immediately goes back again; the others, on the contrary, are characterized most often by a remarkable slowness. III. _Vital Properties._ All the vital properties appear to be but little developed in the fibro-cartilages; there is no animal sensibility or contractility in the natural state; the first appears however in inflammation. Organic sensibility and insensible contractility are only found in the degree necessary for nutrition. There is no sensible organic contractility. This obscurity in the vital properties, gives to all the phenomena of the life of the organs of which we are treating, a remarkable slowness. I have observed that in making in the ears of a dog a longitudinal section, and afterwards uniting the wound by a suture, the skin, at the end of a few days, is entirely closed; but it is only at the expiration of a much longer time, that the union of the cartilage takes place below, as we can see by examining the parts after the union of the integuments. I presume that the same thing happened in the operation of tracheotomy formerly employed, in which the soft parts forming at first the cicatrix, keep in contact the cartilaginous semi-rings, which finally unite together.