SECT. 94.] 



OSSEOUS SYSTEM. 



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dissolved and abstracted cartilage-substance, and which may be said entirely 

 to agree with those of developing foetal bones, and may be readily observed 

 in the ossifying costal and laryngeal cartilages. 



B. Connection by Articulation. Diartkrosis. — The articular ex- 

 tremities of the bones, or such parts of their surface as enter into 

 the formation of a joint, are covered with a thin layer of cartilage, 

 which is firmly attached by a rough, depressed, or prominent 

 surface to the bone ; and, on the opposite side, is, in great part, 

 naked and directed towards the articular cavity, but in part covered 

 by a special coat — a perichondrium — which, as a 

 prolongation of the periosteum, extends over a 

 small part of the cartilage, and then gradually a 

 terminates without a well-defined border. In its 

 intimate structure, articular cartilage presents a 

 finely granular, in part, almost homogeneous ! - 

 matrix, and imbedded in this, thin-walled car- 

 tilage-capsules. These, at the surface, are nu- 

 merous and flat, and lie with their planes parallel 

 to it; further inwards, they become oblong or 

 roundish, and more scanty, and are disposed in c 

 various directions; and, finally, in the vicinity of 

 the subjacent bone, they are elongated and di- 

 rected perpendicularly to it. All these capsules 

 have distinct walls, which, especially on the addi- ^ 

 tion of acetic acid, are readily distinguishable 

 from the matrix, and contain in their interior, 

 viz., in the primordial utricle, or proper cartilage- 

 cell, a clear substance, often granular, but still <° 

 with little fat, and vesicular nuclei. They are 

 isolated or in groups, and very frequently contain 

 two, four, or even more secondary cells, which, in 

 the flat-cells, are disposed alongside each other, f "the ^rtievdar "carfc^ 

 but in the elongated ones, in linear series. On oa^ibonern^gSfied 

 the condyle of the lower-jaw and the glenoid pyfic?ai s 'flatcar°tnage- 

 cavity of the temporal bone, there is found, so 5?£taSK*S3£ 

 long "as the bone is not fully developed, a thick d^nd^'S 

 layer of well-marked cartilage capsules, covered 

 towards the joint by a layer of connective tissue. 

 This cartilage-layer shrinks away the more the 

 bone approaches its full development, and at last J.^StaSSSJ^SS " 

 there remains, under the layer of areolar tissue, 

 which has become relatively and absolutely thicker, only a very 



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rows ; d. outermost 

 layer of the bone with 

 ossified fibrous matrix, 

 and thick-walled car- 

 tilage-cells rendered 

 dark by included air ; 



