124 



THE ARTICULATIONS. 



cavities axe elongated and directed almost perpendicularly towards the 

 articular surface in the deep layer , ia the middle layer they are oblique, 

 and are parallel to the surface of friction in the superficial layer. 



(Under a high magnifying power 

 the fundamental substance, or matrix, 

 loses its homogeneous and amorphous 

 character, and appears to be granular 

 or faintly striated. In the midst of 

 this granular matrix, the lacunae or 

 cavities are observed to contain from 

 one to six different-sized cells. It 

 has been stated that a membrane lines 

 these spaces. In addition to the 

 granular matter observed in the cells, 

 it is not rare to find fat globules. 

 The nuclei of the cells vary from 



¥Tnnr *" WxTfr "^ ^^ i'^"^ ^'i diameter. 

 The cells multiply endogenously.) 



The cartilage cells are insoluble 

 in boiling water ; consequently, so far 

 as their chemical composition is con- 

 cerned, they are distinct from the 

 fundamental substance. 



The diarthrodial cartilages receive 

 neither vessels nor nerves. The 

 presence of cartilages of incrustation in the articulations is of the greatest 

 importance. When they are worn, absorbed, or transformed into bone in 

 consequence of certain articular maladies, the movements become painful and 

 very difiicult. With regard to the part they play in the economy, it may 

 be said that ; 1, They favour, by their smoothness, the gUding and displace- 

 ment of the bones , 2, They attenuate, by their suppleness and elasticity, 

 the violent shocks to which the articulations are exposed ; 3, They resist the ■ 

 wear and deformation of the articular surfaces. 



Complementary Fibro-cartilagbs. — There are several kinds of com- 

 plementary fibro -cartilages : — Some {interosseous) represent circular cushions 

 which bolster the margins of certain cavities, filling up the notches which 

 might render them imperfect. They increase the depth of these cavities 



Fig. 77. 



SECTION OF BKANCIIIAL CARTILAGE OF 

 TADPOLE. 



u, Group of four cells separating from each 

 other ; 6, Pair of cells in apposition ; c, c, 

 Nuclei of cartilage-cells ; d. Cavity con- 

 taining three cells. These cells are im- 

 bedded in the finely-granular matrix, or 

 fundamental substance. 



FiBRO-CAKTiLAGE ; MAGNIFIED 155 TIMES. Showing interlacement of fibrous 

 fasciculi, with scattered groups of cartilage-cells. 



and protect their borders from injury. Others (interarticular) are inter- 

 posed between articular surfaces when these do not exactly fit each other, as 



