WHITE FIBRO-CARTILAGE. 249 



filaments in a piece of felt ; in such parts the matrix has a rough indistinctly granular 

 look, but sometimes this appearance is due to the fact that the elastic fibres are 

 incompletely developed, the granules which are to form them having not yet run 

 together into fibres. Sometimes the fibres are longer (fig. 291, c) but they still inter- 

 communicate at short distances. 



In large animals such as the ox, where the fibres of ordinary elastic tissue attain 

 a considerable size, those of elastic cartilage are also very large with comparatively 

 wide meshes, occupied of course by the hyaline ground-substance. 



WHITE FIBRO-CAETILAGE. 



This is a substance consisting of a mixture of the fibrous and cartilaginous 

 tissues, and so far partaking of the qualities of both. Like hyaline cartilage, it 

 possesses firmness and elasticity, bat these properties are united with a much greater 

 degree of flexibility and toughness. It presents itself under various forms, which 

 may be enumerated under the following heads : - 



1. Interarticular disks. These are interposed between the moving surfaces 

 of bones, or rather of articular cartilages, in several of the joints. In the 

 joint of the lower jaw and in that of the clavicle they have the form of round 

 or oval plates, growing thinner towards the centre ; in the knee-joint they 

 are curved in form of a sickle, and thinned away towards their concave free 

 edge. In all cases their surfaces are free ; while they are fixed by synovial or 

 fibrous membrane at their circumference or extremities. The synovial membrane 

 of the joint is prolonged for a short distance upon these fibro-cartilages, from 

 their attached margin. 1 



2. The articular cavities of bones are sometimes deepened and extended by 

 means of a rim or border of fibre-cartilage. Good examples of these marginal 

 fibro-cartilages are seen in the shoulder and hip-joints, attached round the lip of 

 the articular sockets. In the joint of the lower jaw, the cartilage lining the glenoid 

 cavity is also largely fibrous. 



8. Connecting fibro-cartilages are such as pass between the adjacent surfaces 

 of bones in joints which do not admit of gliding motion, as at the symphysis 

 of the pubis and between the bodies of the vertebras. They have the general 

 form of disks, and between the vertebrae are composed of concentric rings of 

 fibrous tissue with cartilage-cells and matrix interposed ; the fibrous tissue pre- 

 dominating at the circumference, the cartilaginous tissue increasing towards the 

 centre. The bony surfaces which they connect are usually encrusted with true 

 cartilage. 



4. The bony grooves in which tendons of muscles glide are lined with a thin 

 layer of fibro-cartilage. Small nodules of this tissue (sesamoid fibro-cartilages} 

 may also be developed in the substance of tendons, of which there is an example 

 in the tendon of the peroneus longus, and also in that of the tibialis posticus, where 

 it passes beneath the head of the astragalus. 



Fibro-cartilage appears under the microscope to be made up of wavy fibres, like 

 those of ordinary ligament, with cartilage-cells occupying the place, and often 

 simulating the arrangement, of the tendon-cells, As in elastic fibro-cartilage, the 

 cells are immediately surrounded by a part of the matrix which is free from fibres 

 (fig. 292). As a general rule they resemble the cells of ordinary cartilage, having a 

 rounded shape, although somewhat flattened where the bundles of fibres are closely 

 packed. 



1 It has been stated by several authors that the interarticular disks are formed of fibrous tissue 

 only, without any intermixture with cartilage. This statement is, however, incorrect. In all cases 

 (jaw, clavicle and knee), there are unmistakeable rows and groups of cartilage-cells enclosed in capsules, 

 between the bundles of white fibres. 



