322 SPECIAL HISTOLOGY. 



bone, until the bone is completely formed, there is a thick 

 layer of very distinctly marked cartilage-cells, covered, towards 

 the cavity of the articulation, by a layer of connective 

 tissue. This cartilaginous layer disappears by degrees, as 

 the bone approaches its completion, and at last there re- 

 mains beneath the layer of connective tissue, now become 

 both relatively and absolutelv 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 this situation, whilst 

 cells of the kind already described in the muscular system 

 (§ 82), arranged in series, are not unfrequently met with, and 

 might perhaps be regarded as cartilage-cells, although their 

 nuclei exhibit the most evident indications of a transition 

 into nuclear fibres. The articular cartilages, moreover, during 

 their development, which will be entered into more particularly 

 afterwards, have no nerves or vessels, as is the case also with 

 the cartilaginous lips. 



[The condition of the bone beneath the articular cartilages, 

 requires special notice. It consists, in almost all joints, in 

 immediate contiguity with the cartilage, of a layer of in- 

 completely formed bone-substance, and, more internally, of that 

 tissue in its usual form (fig. 125). The layer in question, 

 which is 004 — 0T6'", or on the average 0T2"' thick, is 

 composed of a yellowish, mostly fibrous, hard, and truly 

 ossified matrix, containing, however, not a trace of Haversian 

 canals or medullary cavities, nor of any perfectly formed 

 lacunae ; instead of which it presents roundish or elongated 

 corpuscles, aggregated into little masses or rows, the larger of 

 which are 0-016— 0-024" in length, and 0006— 0-008"' in 

 breadth, and the smaller 0006 — 0-008'" in length, and 

 0-004 — 0-005'" in breadth, which give thin sections of 

 the bone a perfectly opaque aspect, and consequently might 



