124 



THE ARTICULATIONS. 



Fig. 76. 



cavities are elongated and directed almost perpendicularly towards the 

 articular surface in the deep layer ; in the middle layer they arj oblique, 

 and are parallel to the surf ace '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 



irW to Woo- f an * ncn * n diameter. 

 The cells multiply endogenously.) 



The cartilage cells are insoluble 

 a, Group of four cells separating from each in boiling water ; consequently, so far 



SECTION OF BRANCHIAL CARTILAGE OF 

 TADPOLE. 



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

 Nuclei of cartilage-cells ; o?, Cavity con- 

 taining three cells. These cells are im- 

 bedded in the finely-granular matrix, or 

 fundamental substance. 



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

 be said that : 1, They favour, by their smoothness, the gliding and displace- 

 ment of the bones , 2, They attenitate, 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-CARTILAGES. 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. 



FIBRO-CARTILAGE ; MAGNIFIED 155 TIMES. Showing interlacement of fibrous 

 fasciculi, with scattered groups of cartilage-cells. 



and protect their borders from injury. Others (inter articular} are inter- 

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



