CARTILAGE (Fr.. from Lat. cartilago, gristle). A firm elastic substance, of a pearly whiteness, presenting to the unaided eye a uni form and homogeneous appearance. Cartilages may be divided into the tem pore ry, the pernio went, and the arcidental. The temporary carti lages are substitutes for bone in the earlier periods of life, and after a certain time be come replayed by bone. (See BoxE.) At birth the extremities and larger eminences of the long bones and the margins of the flat Is flies are still cartilaginous, and this cartilage does not alto gether disappear till the period of puberty. The permanent cartilages arc either articular or non articular. Articular cartilages are attached to the extremities of bones, and enter into the formations of joints. :Von-articular cartilages arc usually more flexible than the articular.
They are sometimes attached to hones, to lengthen them out, as, for instance, in the nose, or the auditory canal. (See Exn.) In other eases they form the bases of distinct organs, as the larynx, the trachea. and the eyelids. Accidental cartilages are cartilaginous concretions. which are occasionally found in situations where they do not normally occur. and are of no general interest. The physical properties of cartilages, especially their elasticity, resisting power, and incapability of extension, are such as to lit them admirably for the functions which they have to perform in the anima] economy.
Cartilage belongs to the group of tissues termed connective tissues. The matrix or inter cellular portion of cartilage is dense and firm, and the different varieties of cartilage are recog nized by the nature of the matrix. In the variety
called liyalin cartilage, the matrix is apparently homogeneous. though Leidy has shown that it is really composed of bundles of tine fibrous con nective tissue. Lying in this matrix are the cartilage-cells. These are oval or irregular, granular, nucleated bodies. and are arranged sin gly, in pairs, or in fours. The cartilage-cell or group of cells is surrounded by a clear cell space. Hyalin cartilage is the form of cartilage which makes up the skeleton in the embryo, and in which the bones of the body with the exception of the head and face are developed. In the adult it is found as articular cartilage, the car tilages of the nose, Eustachian tube, larynx. trachea, bronchi, costal cartilages, etc. In the variety called fibro-eartilage, the matrix is com posed of fibrons connective tissue, in which are inhedded the cartilage-cells. These cells may occur singly or are more commonly arranged in rows of two or more, lengthwise of the bundles of fibres. Fibro-cartilage is found in the inter vertebral disks, and around the edges of sonic joints. In the variety called elastic cartilage, the matrix is rich in elastic fibres, giving the tissue a glistening yellow appearance. The cells are situated in cell-spaces and may occur singly or in pairs. resembling the arrangement noted in hyalin cartilage. Some of the smaller cartilages of the body are of this variety, the epiglottis, part of the Eustachian tube, the external ear cartilage, the arytennid eartilages, etc. Consult Stiihr, Test-Book of Histology (Philadelphia, 1901).