CHAP. III.] 



CARTILAGE. 



19 



straining force is withdrawn. By reason of these mechanical 

 properties it serves important purposes in the construction of 

 some parts of the body. 



Hyaline cartilage occurs chiefly 

 in two situations ; viz. covering 

 the ends of the bones in the 

 joints, where it is known as 

 articular cartilage, and forming 

 the rib cartilages, where it is 

 known as costal cartilage. In 

 both these situations the carti- 

 lages are in immediate connec- 

 tion with bone, and may be said 

 to form part of the skeleton. 

 The articular cartilages, in cov- 

 ering the ends or surfaces of 

 bones in the jomts, provide these 

 harder parts with a smooth and 

 yielding surface, the smoothness 

 giving ease to the motion of the 

 joint, and the elastic yielding sur- 



ce breaking the force of con- 

 cussions. The costal cartilages, 

 in forming a considerable part of 

 the solid framework of the thorax or chest, impart elasticity to 

 its walls. Cartilage also enters into the formation of the nose, 

 ears, larynx, and windpipe. It strengthens these parts without 

 making them unduly rigid, maintains their shape, keeps them 

 permanently open, and gives attachment to moving muscles and 

 connecting ligaments. 



Elastic or yellow fibre-cartilage is tougher and more flexible 

 than hyaline cartilage ; it occurs only in parts of the throat 

 and ear. 



White fibro-cartilage is found wherever great strength com- 

 bined with a certain amount of rigidity is required ; thus we 

 find it joining bones together, the most familiar instance being 

 the flat round plates or disks of fibro-cartilage connecting the 

 bones of the spine and the pubic bones. White fibro-cartilage 

 very closely resembles white fibrous tissue. 



Cartilage is not supplied with nerves, and very rarely with 



Fio. 13. ARTICULAR HYALINE 

 CARTILAGE FROM THE FEMUR OF AN 

 Ox. , intercellular substance; p, 

 protoplasmic cell ; n, nucleus. (Kan- 

 vier.) 



