CARTILAGE. 121 



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

 fibrous 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 

 (ha?mapophyses) to the ribs, connecting them distally with the 

 sternum; Membraniform, 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 

 always thickest in the young, 

 becoming thinner as the sub- ^. 

 jacent ossification proceeds. It ff 

 is thickest in the centre of v^ 

 convexities, thinnest in the 

 centre of cavities. In the adult 

 it is non-vascular, being nour- 

 ished by a vascular zone in 

 the sy no vial membrane, called 

 the circulus articuli vasculosus, 



e i i ,1 , Section of hyaline cartilaee. a, Four separating 



from which the nutritive ma- cel]8f 6 Two y cens in ap ^ tion ;. c c> uclei * 



terial is COUVeyed. The blood- d > Cavit >' in the matri * containing three cells. 



vessels of the bone underneath the cartilage also assist in 

 supplying nourishment to the latter. All hyaline cartilage, 

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

 perichondrium. 



Fibro-cartilage consists of cartilage cells and fibrous 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 pad is termed a 

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

 furnished with such. Circumferential, where it surrounds and 

 deepens an articular cavity, as the acetabulum. Cuiin<-ctinf/, 

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



