HISTOLOGY 



103 



The external surface of cartilage is invested by a connective-tissue 

 membrane, the perichondrium (Fig. 99) which contains blood-vessels 

 but they do not penetrate into the cartilage. Hence cartilage cannot 

 occur in thick masses. 



In growing cartilage, cells from the perichondrium become cartilage 

 cells and add cartilage to the exterior of the mass already formed. At 



»• -"S^ 



Capsule. 



o? 





:*■-. 



<^;^. 



. Matrix. 



'^erichond. 



-Bl.v. 



^ 



Fig. 99. — Hyaline cartilage, with perichondrium; from human trachea. Bl.v., 

 blood-vessel; x, cartilage cell whose nucleus is not in section; y, new matrix forming 

 between two cells resulting from a recent division of a cartilage cell. (From Bremer, 

 "Te.xt-book of Histology.") 



the same time deep cartilage cells divide. The resulting cells secrete 

 matrix substance whereby they become separated, each to lie in a lacuna 

 of its own. 



Hyaline cartilage (Fig. 99), usually bluish and clear, is nearly devoid 

 of fibrous material. In fibrocartilage the matrix contains fibers similar 

 to those of ordinary connective tissue. Elastic cartilage contains numer- 

 ous elastic fibers. Calcified cartilage is rendered white and relatively 

 hard by deposit of calcium salts in the matrix. 



