FIBRO-CAETILAGE. 



structure and outward characters, that they have been included in a 

 class apart, under the name of the "elastic," "yellow," or "spongy" 

 cartilages. These are opaque and somewhat yellow, are more flexible and 



tough than the ordinary cartilages, and 

 have little tendency to ossify. They 



Fig. XLII. are maf ] e U p O f ce iis and a matrix, but 



the latter is everywhere pervaded with 

 fibres (fig. XLTI.), except sometimes in a 

 little area or narrow zone left round each 

 of the cells. These fibres resist the 

 action of acetic acid ; they are in most 

 parts short, straight, and confusedly 

 intersecting each other in all directions, 

 like the filaments in a piece of felt ; in 

 such parts the matrix has a rough in- 

 distinctly granular look. Here and there 

 the fibres are longer and more fascicu- 

 F!g. XLII. SECTION OP THE EPI- lated, but still interlace at short distances. 

 GLOTTIS, MAGNIFIED 380 DIAMETERS j n thin sections the cells readily drop 

 (Dr. Baly). out from the ma t r i x> leaving empty the 



cavities which they occupied. 



In the foetus the matrix of elastic cartilage is at first homogeneous and hyaline, 

 and the elastic fibres are then produced in it, quite independently of the cells, and in 

 the same way as in the intercellular substance of growing elastic ligaments. 



FIBRO- C ARTILA GE. 



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 car- 

 tilage, it possesses firmness and elasticity, but 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. Inter articular fibro-cartilages. These are interposed between the 

 moving surfaces of bones, or rather of articular cartilages, in several of the 

 joints. They serve to maintain the apposition of the opposed surfaces in 

 their various motions, to give ease to the gliding movement, and to 

 moderate the effects of great pressure. 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 their 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, 

 or at least its epithelial coat, is prolonged for a short distance upon these 

 fibro-cartilages, from their attached margin. 



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

 by means of a rim or border of fibro- cartilage. A good example of one of 

 these circumferential or marginal fibro-cartilages is seen in the hip-joint, 

 attached round the lip of the cotyloid cavity. 



3. 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 pubes and between the bodies of the vertebrae. They 

 have the general form of disks, and are composed of concentric rings of 

 fibrous tissue with cartilage interposed ; the former predominating at the 



