CAIU'ILAGE. 121 



the microscope. Fibro-cartilage is characterised by a matrix of 

 librous tissue ; while the cellular variety consists of an aggrega- 

 tion of cells without a matrix. 



Hyaline cartilage is distinguished by the following names, 

 according to the purpose it serves : — Articular, when it encrusts 

 the articular surfaces of bones, helping to form joints by supply- 

 ing a smooth elastic cushion, which diminishes both concussion 

 and friction ; Costal, when it supplies elastic prolongations 

 (hgemapophyses) to the ribs, connecting them distally with the 

 sternum; Memhraniform, when it appears as thin plates, form- 

 ing permanently open tubes — the trachea or wind-pipe is com- 

 posed of this kind of cartilage. 



In articular or encrusting cartilage the matrix is abundant, 

 and the cells vary in form, those near the surface being flatter 

 and more numerous. It is a ,-, 



always thickest in the young, .^• 



becoming thinner as the sub- ,.-'^" 



jacent ossification proceeds. It (/ T ' > cJ 



is thickest in the centre of 

 convexities, thinnest in the 

 centre of cavities. In tlie adult 

 it is non- vascular, being nour- ■'•' 



ished by a vascular zone in ' < ", ~~--'.:i3-- 



the synovial membrane, called : 



the circulus articulivasculosus, ^''''- '^^• 



n 1 • 1 xi j_ 'i' Sectiiiii of liviiliiie cartilage, o, Four separating 



from which the nutritive ma- ,,„, , ,,^ -^.^^ ,,i,s iu appostion ; c c, Nuclei ; 



terial is conveyed. The blood- ''■ ^"""'^y '° ^^^ "''"^'^j^ containing three ceii.s. 

 vessels of the bone underneath the cartilKge also assist in 

 supplying nourishment to the latter. All hyaline cartilage, 

 except the articular kind, is covered by a menrbrane called the 

 perichondrium. 



Fihro-cartilage consists of cartilage cells and librous tissue, 

 which may be white or yellow, the former being tough and strong, 

 the latter highly elastic. White fibro-cartilage is much the more 

 plentiful, and presents the following varieties ; — It is called Inter- 

 articular when it appears as a pad interposed between the two 

 articular cartilages which form a joint ; such a j^ad is termed a 

 meniscus, and the temporo-maxillary and femoro-tibial joints are 

 furnished with such. Circumfereiitial, where it surrounds and 

 deepens an articular cavity, as the acetabulum. Connecting, 

 when it is interposed between bones and firmly connects them, as 



