THE OSSEOUS SYSTEM. 



297 



In many joints there ai-e firm, •whitish-yellow, fibrous plates, the 

 so-termed interarticular carti- 

 lages or ligaments, Avhich, either '°' ^~^' 

 projecting in pairs from the syno- 

 vial capsule, are interposed be- 

 tween the bones constituting the 

 articulation (knee), or form a 

 single diaphragm transversely 

 across the joint (articulations of 

 the jaw, clavicle, sternum, and 

 wrist). These processes consist 

 of a firm, fibrous tissue, the fibres 

 of which usually cross each other 

 in various directions, and are in 

 all respects closely allied to con- 

 nective tissue, but presenting less 

 distinct fibrils ; and, besides this, 

 of cartilao;e-cells and fine elastic 

 fibres.* The cartilage-cells, in the 

 most superficial layers, are more 

 solitary, in the deeper, disposed 

 more in roivs and smaller, ultimately being replaced by fine elastic fibres, 

 a certain number of which, at all events, appear to originate from cells 

 resembling the cartilage-cells. The interarticular ligaments, which, 

 from what has been said respecting them, must be enumerated among 

 the fibro-cartilages, are not covered by synovial membrane, though they 

 probably have an epithelial investment at the attached border, but only 

 for a small extent, — never over the entire surface. The articular liga- 

 ments, with the exception of the softer ligamentum teres, are composed 

 of the same firm connective tissue (in the costal ligaments containing 

 cartilage-cells), as that of which the tendons and the fibrous ligaments, 

 elsewhere, are constituted. The internal ligaments (lig. cruciate^), how- 

 ever, present softer connective tissue, containing vessels, and covered 

 with epithelium. 



Fig. 127. — From the synovial membrane of a phalangeal articulation : ^, two non-vascular 

 appendages of the synovial processes, magnified 250 diameters: a, connective tissue in its 

 axis; 6, epithelium (in the peduncle of the larger process not distinctly cellular) continuous 

 with that on the free borders of the process; r, d, cartilage-cells; B, four cells from the 

 epithelium of the synovial membrane of the knee, one with two nuclei; magnified 350 dia- 

 meters. 



* [Tliese interarticular fibro-cartilages lose in old persons their distinct filirous structure, 

 and assume a yellow or brownish color. Yet they never, according to \'ircliow (Arcliiv. f. 

 Path. Ariat.), become entirely homogeneous, since a careful examination will always permit 

 two directions of their fibres to be recognized, viz. : one parallel to the free edge, and the 

 other running vertically towards it. — DaC] 



