54 



THE TISSUES. 



the larger cartilages of the larynx, the trachea and bronchi, 

 and in the embryo is the precursor of most of the bones. The 

 cells are prominent and rounded, with large nuclei and dis- 

 tinct capsules, and are imbedded in an apparently homogeneous, 

 hyaline, tough matrix, which yields chondrin. Instead of 

 being really homogeneous, the matrix is said to have a delicate 

 fibrillar structure. The means or channels by which nutrient 

 fluids can penetrate to the interior of hyaline cartilage for its 

 nutrition are not known. The cartilage-cells divide in two 

 within the capsule of the parent-cell, which is thus as it were 

 cast off, and each daughter-cell then acquires a new capsule. 

 By the repetition of this process t\vo or three generations of 

 cells may sometimes be found within the remains of the cast- 

 off capsule of the single original parent-cell. The capsules 

 thus cast off are gradually transformed into the matrix, which 

 is partly developed in this way. The ground-substance near 

 the cells stains differently from that more remote. Owing to 

 their mode of division the cells in costal cartilage tend to 

 occur in groups ; in articular cartilage they form rows perpen- 

 dicular to the surface. 



Some of the cartilages are surrounded by a fibrous mem- 

 brane, the perichondrium j containing fusiform or flattened con- 

 nective-tissue cells. The lowermost of these cells take on the 

 characters of cartilage-cells, become thicker and more rounded, 

 and the edge of the cartilage shows a gradual transition from 

 these cells to the typical cartilage-cells in the interior. In 

 this manner the cartilage is produced or grows from the lower 

 layer of the perichondrium. 



FTO. 23. 



Fibro-cartilage, from human inter vertebral disc (Schaferj. 



White fibre-cartilage (Fig. 23) forms the intervertebral discs 

 and other cartilages entering into the construction of certain 



