66 NORMAL HISTOLOGY. 



I. THE CARTILAGES. 



General Characters. — (1) The typical cell of cartilage is round or 

 oval in shape, rich in cytoplasm, and possesses one (rarely two) 

 nucleus of oval form and vesicular and reticulated structure. 

 Within the cytoplasm there are frequently one or more clear spots, 

 which are drops of homogeneous fluid, "vacuoles." The cells fre- 

 quently depart somewhat from this type. Where the tissue is 

 growing they are usually flattened on the sides turned toward their 

 nearest neighbors. This is because they are the offspring of a cell 

 that has recently divided, and are as yet separated by only a small 

 amount of intercellular substance. Under these circumstances each 

 cell is frequently surrounded by a thin layer of intercellular sub- 

 stance, probably of relatively recent formation, which differs a little 

 from that further from the cell and gives an appearance as though 

 the cell were enclosed in a capsule. With some dyes this recently 

 formed intercellular substance receives a somewhat different color 

 from that of the older intercellular substance. In older cartilage this 

 difference is no longer evident. Where cartilage is being replaced by 



Fig. 49. 



6 



Hyaline cartilage. Section of human costal cartilage: a, nearly spherical cell containing 

 two vacuoles ; b, recently formed intercellular substance (" matrix "), separating two cells 

 that have been produced by the division of a single cell. There are several other 

 examples of a similar grouping of cells, due to the same cause, in the figure. Between 

 the cells is the hyaline, nearly structureless " matrix." 



bone, " ossification," the cells are arranged in columns, with only a 

 -mall amount of intervening intercellular substance, and have a 

 general cubical form. 



