CH. V.] 



DEVELOPMENT OF CARTILAGE. 



57 



cartilage originates from mesoblast ; the cells are utibranched, 

 and the disposition of the cells in fully formed cartilage in 

 groups of two, four, &c., is due to the fact that each group has 

 originated from the division of a single cell, first into two, each 

 of these again into two, and so on. This process of cell division 

 is accompanied with the usual karyokinetic changes. 



Each cell deposits on its exterior a sheath or capsule ; on 



Fig. 81. Plan of multiplication of eelln in eaitilage. n, cell in its capsule, b, divided into 

 two, i-iu-h with a capsule, e, primary capsule disappeared, secondary capsules coherent 

 with matrix. </, tertiary division, t, secondary capsules disappeared, tertiary coherent 

 with matrix. (After Sharpey.) 



division each of the daughter-cells deposits a new capsule within 

 this, and the process may be repeated (see fig. 81). 



Thus the cells get more and more separated. The fused 

 capsules form a very large part of the matrix, and indications of 

 their previous existence may sometimes be seen in fully formed 

 cartilage by the presence of faint concentric lines around the cells 

 (see fig. 77). 



In a variety of cartilage found in the ears of rats and 

 mice called cellular cartilage, the cells never multiply to any 

 great extent, and they are only separated by their thickened 

 capsules. 



But in most cartilages the cell-capsules will not explain the 



