3:20 SPECIAL HISTOLOGY. 



in part with those of the ribs ; and the osseous substance is 

 more that of normal bone, though almost always more opaque, 

 less homogeneous, and with imperfectly formed lacunse, which 

 frequently contain a calcareous deposit. Under the name of 

 cartilage-marrow, are understood the medulla-cells, fat-cells, 

 bundles of connective tissue and vessels, which are presented 

 instead of the detritus, afforded by the disintegration of 

 cartilage, and which may be said to correspond in all respects 

 with those of developing fcetal bone, and may be readily 

 observed in ossifying costal and laryngeal cartilages. 



§95. 



B. Moveable Articulation (Diarthrosis). — The articular ex- 

 tremities of the bones, or any other surfaces entering into the 

 formation of a joint, are invariably invested with a thin layer 

 of cartilage, which in the middle of the surfaces covered by it, 

 is of tolerably uniform thickness, gradually thinning as it 

 extends outwardly, and finally terminating with a very abrupt 

 edge. This articular cartilage is closely applied to the bone 

 with a rough, hollowed or raised surface, but is not united to 

 it by any interposed substance ; and, on the opposite surface, 

 it is in most joints usually quite bare, and directed towards 

 the cavity of the articulation. Sometimes, however, it is in- 

 vested with a special fibrous membrane, a perichondrium, which 

 is an immediate prolongation of the periosteum, and extends 

 most generally only over a small portion of the cartilage, 

 gradually ceasing without any defined margin. 1 In some 

 joints (shoulder, hip) the more secure lodgment of the articular 

 head of the bone is ensured by special cartilaginous lips. 

 These are firm, yellowish-white, fibrous rings, attached, at the 



1 [Reichert, who has paid particular attention to the question of the existence of 

 an epithelium upon the articular cartilages, says, that in the fcetal condition of Man 

 and the domestic Mammalia, an epithelium exists over the whole surface of the 

 synovial capsules, and, on the articular cartilage, lies in immediate contact with its 

 suhstance. It resembles the epithelium of the vessels. In adults, on the other hand, 

 he could discover an epithelium only on those parts of the articular capsules which 

 are not subject to friction ; and here it had the same appearance as in the fcetal con- 

 dition. It was wanting upon the articular cartilages and their immediate neighbour- 

 hood; but it was not uncommon to meet with fine desquamated flakes of cartilage in 

 the synovia, which fell readily into folds, and thus resembled a fibro-cartilaginous 

 tissue (Bericht, Muller's 'Archiv,' 1840, p. 16).— Eds.] 



