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with each other, and in the rest of their circumference are rounded. They consist of clear translucent protoplasm in which fine interlacing filaments and minute granules are sometimes present; imbedded in this are one or two round nuclei, having the usual intranuclear network. The cells are contained in cavities in the matrix, called cartilage lacunæ; around these the matrix is arranged in concentric lines, as if it had been formed in sucessive portions around the cartilage cells. This constitutes the so-called capsule of the space. Each lacuna is generally occupied by a single cell, but during the division of the cells it may contain two, four, or eight cells.

FIG. 292– Human cartilage cells from the cricoid cartilage. (See enlarged image)

The matrix is transparent and apparently without structure, or else presents a dimly granular appearance, like ground glass. Some observers have shown that the matrix of hyaline cartilage, and especially of the articular variety, after prolonged maceration, can be broken up into fine fibrils. These fibrils are probably of the same nature, chemically, as the white fibers of connective tissue. It is believed by some histologists that the matrix is permeated by a number of fine channels, which connect the lacunæ with each other, and that these canals communicate with the lymphatics of the perichondrium, and thus the structure is permeated by a current of nutrient fluid.

Articular cartilage, costal cartilage, and temporary cartilage are all of the hyaline variety. They present differences in the size, shape, and arrangement of their cells.

FIG. 293– Vertical section of articular cartilage. (See enlarged image)

FIG. 294– Costal cartilage from a man, aged seventy-six years, showing the development of fibrous structure in the matrix. In several portions of the specimen two or three generations of cells are seen enclosed in a parent cell wall. Highly magnified. (See enlarged image)

In Articular Cartilage (Fig. 293), which shows no tendency to ossification, the matrix is finely granular; the cells and nuclei are small, and are disposed parallel to the surface in the superficial part, while nearer to the bone they are arranged in vertical rows. Articular cartilages have a tendency to split in a vertical direction; in disease this tendency becomes very manifest. The free surface of articular cartilage, where it is exposed to friction, is not covered by perichondrium, although a layer of connective tissue continuous with that of the synovial membrane can be

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