Cartilage

Cartilage, or GRISTLE, is a firm elastic substance, of a pearly whiteness, presenting to the naked eye a uniform and homogeneous appearance. Cartilages may be divided into the temporary and the permanent. The temporary cartilages are substitutes for bone in the earlier periods of life, and after a certain time become ossified. At birth the extremities and larger eminences of the long bones and the margins of the flat bones are still cartilaginous, and this cartilage does not altogether disappear till the period of puberty. The permanent cartilages are either articular or non-articular. Articular cartilages are attached to the extremities of bones, and enter into the formation of joints. Non-articular cartilages are usually more flexible than the articular. They are sometimes attached to bones to lengthen them out, as, for instance, the costal or rib cartilages which form a considerable part of the framework of the thorax, and impart elasticity to its walls. They are present in the nose, the auditory canal, and the Eustachian tube. In other cases they form the basis of distinct organs, as the larynx, the trachea, and the eyelids. The physical properties of cartilages, especially their elasticity, resisting power, and incapability of extension, are such as to fit them admirably for the functions which they have to perform in the animal economy. See CELL, BONE, LARYNX; and for the chemical constituents, see ANIMAL CHEMISTRY, GELATIN, and GLUTEN. Cartilage is liable to inflammation, to ulceration, and to ossification; for the diseases of the larynx, see that article.