292 



SPECIAL HISTOLOGY. 



Fig. 125. 



As regards the intimate structure of the parts just described, the 

 articular cartilage, on completely formed bones (Fig. 125), and under 



normal conditions, presents throughout, a 

 finely granular, in part almost homogeneous 

 matrix, in which are lodged delicate cartilage- 

 cells, which towards the surface of the carti- 

 lage 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, easily dis- 

 tinguished from the matrix by the use of 

 acetic acid, clear, frequently granular con- 

 tents, containing, however, but little fat, and 

 a vesicular nucleus. They occur either 

 isolated or in groups, and present very fre- 

 quently 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 tem- 

 poral bone, until the bone is completely 

 formed, there is a . thick layer of very dis- 

 tinctly marked cartilage-cells, covered, to- 

 wards the cavity of the articulation, by a 

 layer of connective tissue. This cartilaginous layer disappears by de- 

 grees, as the bone approaches its completion, and at last there remains 

 beneath the layer of connective tissue, now become both relatively and 

 absolutely thicker, merely an excessively thin and transparent lamina, 

 the elements of which, although morphologically not true bone-cells, nor 

 as yet ossified, still seem to resemble the latter more closely than cartilage- 

 cells. % 



The cartilaginous lips of the joints consist principally of connective 

 tissue, always containing, however, isolated cartilage-cells of a roundish 

 or elongated form, with a moderately thick membrane, distinct nucleus, 

 and occasionally fat-granules. I have not as yet noticed parent cells in 



FIG. 125. Articular cartilage of a human metacarpal bone, cut perpendicularly : a, most 

 superficial, flattened cartilage cells; b, middle round cells; c, innermost cells, disposed per- 

 pendicularly in small rows; rf, outermost layer of the bone with ossified fibrous matrix and 

 thick- walled cartilage cells, in this instance appearing dark from their containing air ; e, true 

 bone-substance; /, ends of the cancelli of the apophyses; g, one of the cancelli. Magnified 

 90 diameters. 



