INTERARTICULAR CARTILAGES. 



107 



less connective tissue of one kind or another. The carti- 

 lages of the ear and nose and some others have their matrix 

 pervaded by fine branching fibres of yellow elastic tissue, 

 "which form networks around the groups of cartilage cells. 

 Such cartilages are pliable and tough and possess also con- 

 siderable extensibility and elasticity. They are known as 

 elastic 01% from their color, as yelloiv cartilages. Elsewhere, 

 especially in the cartilages which lie between the bones in 

 some joints, we find forms which have the matrix pervaded 

 by white fibrous tissue and known as fibro-cartilages. For 

 example the articular cartilage on the end of the lower jaw 



FIG. 45. Section through the joint of the lower jaw showing its interarticular 

 fibro-cartilage, x, with the synovial cavity on each side of it. 



does not come into direct contact with that covering its socket 

 on the skull, but lying between the two in the joint (Fig. 45) 

 is an interarticular fibro-cartilage : similar cartilages exist 

 in the knee- joint; and the intervertebral disks arc also made 

 up of this tissue. Both elastic cartilage and fibro-cartilage 

 often shade off insensibly into pure elastic or pure white 

 fibrous connective tissue. 



Homologies of the Supporting Tissues. Bone, cartilage, 

 and connective tissue all agree in broad structural charac- 

 ters, and in the uses to which they are applied in the Body. 

 In each of them the cells which have built up the tissue, 



