THE OSSEOl'S SYSTEM. 



32] 



Fig. 125. 



border of the articular cartilage by a wider basis, immediately 

 to the bone or partly to the cartilage. They thin oft" to an 

 acute edge, and for the most part free and uncovered by the 

 synovial membrane, or any epithelium, project into the articu- 

 lation, being exteriorly in relation with the periosteum and 

 synovial capsule. 



As regards the intimate structure of the parts just de- 

 scribed, the articular cartilage, on completely formed bones 

 (fig. 125), and under normal condi- 

 tions, presents throughout, a finely 

 granular, in part almost homo- 

 geneous matrix, in which are lodged 

 delicate cartilage-cells, which to- 

 wards the surface of the cartilage 

 are numerous and flattened, and lie 

 parallel to it ; more deeply they are 

 oval or rounded, more rare, and 

 disposed in various directions; and 

 lastly, close to the bone they are 

 elongated, and placed vertically with 

 respect to the surface of the bone. 

 These cells all have distinct walls, 

 easilv distinguished from the matrix 

 by the use of acetic acid, clear, fre- 

 quently granular contents, contain- 

 ing, however, but little fat, and a 

 vesicular nucleus. They occur either * /. L * n$m 

 isolated or in groups, and present 

 very frequently two, four or even 

 more secondary cells, which in the 

 flat cells are placed close together, 

 and in the elongated are disposed 

 in rows. On the condyle of the 

 lower jaw, as on the corresponding surface of the temporal 



§1411 



m 

 w 



a ' 



*w% 



'**' 



'■ 



■ t 



I 



■ 



Fig. 125. Articular cartilage of a human metacarpal bone, cut perpendicularly, 

 x 90 diam.: a, most superficial, flattened cartilage cells ; b, middle rounded cells ; 

 c, innermost cells, disposed perpendicularly in small rows ; d, outermost layer of the 

 bone with ossified fibrous matrix and thick-walled cartilage cells, in this instance ap- 

 pearing dark from their containing air ; e, true bone-substance ; /, ends of the can- 

 celli of the apophysis; g, one of the cancelli, 



i. 21 



