CARTILAGE 79 



grouped as a pair, forming a bisected elliptical figure, or they may divide 

 again, producing either a row of cells or a cluster of three or four (Fig. 

 66). Since the cells change their positions with difficulty in the dense 

 matrix, they are regularly found in very characteristic groups. It has 

 been asserted that certain cartilage cells undergo mucoid degeneration 

 and become lost in the matrix. In old cartilage dark spots, staining in- 

 tensely with haematoxylin, are suggestive of such a process. Such cells 

 must be carefully distinguished from tangential sections of the deeply 

 staining pericapsular matrix. 



Cartilage grows not only by the interstitial increase of the cells and 

 matrix in its interior, but more especially by appositional growth, through 



A B C 



FIG. 67. THE THREE TYPES OF CARTILAGE: A, HYALINE; B, ELASTIC; C, FIBROUS. (Radasch). 



a, b, Outer and inner layers of perichondrium; c, young cartilage cells; d, older cartilage cells; e, f, capsule 



surrounded by deeply staining matrix; g, lacuna. 



the formation of new cartilage over its external surface. Around every 

 cartilage in the adult, there is a connective tissue envelope, the perichon- 

 drium, containing undiflerentiated cells which multiply and become 

 transformed into cartilage cells (Fig. 67, A). These are added at the 

 surface, undergoing in a thin layer such changes as are shown in Fig. 66. 

 The young generations of cells are therefore at the periphery of the 

 cartilage, and the oldest cells, or the groups which they have produced, 

 are in the center. Between them an interesting series of cytomorphic 

 changes may be observed. Since the perichondrium is the formative 

 layer, a more or less perfect regeneration of cartilage may occur after 

 surgical operations if the perichondrium is left in place, but not otherwise. 

 The perichondrium contains vessels and nerves, none of which pene- 



