52 



THE CONNECTIVE TISSUES 



[CH. V. 



the latter situation the nodule of fibro-cartilage is called a sesamoid 

 fibre-cartilage, of which a specimen may be found in the tendon of 

 the tibialis posticus in the sole of the foot, and usually in the neigh- 

 bouring tendon of the peroneus longus. 



White fibre-cartilage (fig. 79) is composed of cells and a matrix. 

 The latter is permeated by fibres of the white variety. 



In this kind of fibro-cartilage it is not unusual to find portions so 

 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 



FIG. 79. White fibro-cartilage. (Cadiat.) 



FIG. 80. Yellow or elastic fibro-cartilage. 

 (Cadiat.) 



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. 80). 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 

 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. 



