286 THE SOLIDS. 



replaced in them by fibres endowed with elasticity ; a trans- 

 formation of structure of which we have seen that certain of 

 the true cartilages are susceptible. (See Plate XXXI.) 



The fibro-cartilages include those of the articulations which 

 are united by synchondrosis, as the invertebral cartilages, and 

 that of the symphysis pubis ; the epiglottis and the cuneiform 

 cartilages ; the articulating cartilages of the glenoid cavity, 

 and of the head of the superior maxillary bone ; the inter- 

 articular cartilage of the sterno-clavicular articulation; the 

 cartilages of the ear, of the Eustachian tube, of Santorini, 

 and those of Wrisberg. 



There are, however, other differences besides the structural 

 one alluded to : thus, fibro-cartilages are more opaque than 

 the true, are of yellow colour more or less deep, and are en- 

 dowed with a higher degree of elasticity and flexibility. 



The fibres do not follow the same distribution in every 

 fibre-cartilage : thus, in the tube of Eustachius, in the 

 symphysis pubis, 'in the interarticular cartilage of the sterno- 

 clavicular articulation, in those of the tempero-maxillary 

 articulation they are placed nearly parallel to each other ; 

 in the intervertebral cartilages they ascend vertically from 

 one osseous surface to the other ; in the cartilages of the 

 epiglottis and ear they are curved and interlacing. 



In the outer part of each intervertebral cartilage the fibres 

 form a distinct and compact stratum of a yellow colour, no 

 cartilage cells in that situation intervening between them ; 

 the number of fibres, however, gradually diminishes towards 

 the centre of the cartilage, which at the same time becomes 

 less and less dense and firm, until at length in the very axis 

 it is semifluid. 



The cells of fibro-cartilages do not differ very materially 

 in form and structure from those of true cartilages ; they 

 usually, however, contain more fat, are more readily separable 

 from the fibrous base in which they are lodged, and more 

 frequently encountered in the condition of parent cells. 



The cells of the intervertebral cartilages and of the epi- 

 glottis present some interesting forms and modifications : 

 thus, the cells which are situated in the harder parts of 



