Oil. V.] 



CARTILAGE 



39 



densely fibrous that no cells can be seen ; but in other parts con- 

 tinuous with these, cartilage-cells are freely distributed. 



Yellow or Elastic Pibro-Cartilage is found in the pinna of the 

 external ear, in the epiglottis and cornicula laryngis, and in the 

 Eustachian tube. 



The cells in this variety of cartilage are rounded or oval, with 

 well-marked nuclei and nucleoli (fig. 52). The matrix in which they 

 are seated is pervaded in all directions by fine elastic fibres, which 

 form an intricate interlacement about the cells : a small and variable 

 quantity of non-fibrillated hyaline intercellular substance is present 

 around the cells. 



Development of Cartilage. Like other connective tissues, car- 

 tilage originates from mesoblast ; the cells are unbranched, and the 



Illlllllillllllillllllllllll 



-c 



d 



Illlllllllllllllllilllllllllllllllllllllpp 



Fio. 53. Plan of multiplication of cells in cartilage. a, Cell in its capsule ; b, divided into two, 

 each with a capsule ; c, primary capsule disappeared, secondary capsules coherent with matrix ; 

 d, tertiary division ; e, secondary capsules disappeared, tertiary coherent with matrix. 

 (After Sharpey.) 



disposition of the cells in fully formed cartilage in groups of two, 

 four, etc., 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 division 

 each of the daughter-cells deposits a new capsule within this, and 

 the process may be repeated (see fig. 53). 



