ARTICULAR CARTILAGE. 



53 



lacing filaments and granules have been observed in it (fig. 59). During 

 life the protoplasm entirely fills the cavity or cell-space which it 

 occupies in the matrix; but after death, and in consequence of the 

 action of water and other agents, it tends to shrink away from the 

 capsule. The nucleus is round, and shows the usual intranuclear 

 network. 



In vertical section (fig. 60) the deeper cell-groups (c) are seen to be 

 arranged vertically to the surface, the more superficial ones (a) parallel 

 to the surface ; whilst in an intermediate zone the groups are irregu- 

 larly disposed (b). In the deepest part of the cartilage, next the bone, 

 there is often a deposition of calcareous salts in the matrix (calcified 

 cartilage, d). 



The disposition of the cells of cartilage in groups of two, four, and 

 so on, is apparently due to the fact that these groups have originated 

 from the division of a single cell first into two, and these again into 

 two, and so on (fig. 61). It would seem that the matrix is formed of 



B c 



ill 



FIG. 01. PLAN OF THE MULTIPLICATION OF CELLS OF CARTILAGE. (Sharpey.) 



A, cell in its capsule ; B, divided into two, each with a capsule; c, primary capsule, dis- 

 appeared, secondary capsules coherent with matrix : D, tertiary division ; E, secondary 

 capsules disappeared, tertiary coherent with matrix. 



successive portions, which are deposited around each cartilage-cell as 

 the so-called ' capsules,' each newly formed portion soon blending in its 

 turn with the previously formed matrix, whilst a new capsule is formed 

 within it. The division of the cartilage-cell, like that of other cells, 

 is accompanied by a process of karyokinesis. 



Embryonic cartilage is characterised by the cells being usually more 

 sharply angular and irregular, being even in some cases, markedly 

 branched, like those which occur at the junction of cartilage and synovial 

 membrane in the adult. The cells are also more closely packed, the 

 matrix being in relatively less amount. 



