THE OSSEOUS SYSTEM. 



317 



Fig. 132. 



by period or situation, although there is no doubt that they are fre- 

 quently, in one place, of uniform minuteness, and in others uniformly 

 of coarser character, but rather by some change occurring in the supply 

 of plastic material to the ossifying border. If this earthy deposit be 

 traced in microscopical sections, from the margin of the ossification into 

 the interior of the young bone, it will be apparent, that it is to it, for 

 a certain distance, although with diminishing distinctness, that the 

 granular and opaque aspect of the margin itself is due ; the substance 

 gradually becomes more homogeneous, clearer, and more transparent, 

 ultimately acquiring the aspect of perfect bone. According to all 

 appearance, the primordial earthy granules or particles become gradu- 

 ally fused together, and thus impregnate the whole tissue of the matrix 

 of the cartilage, instead of, as 

 before, separate portions, and 

 thenceforth disappear as iso- 

 lated, distinguishable parti- 

 cles. 



With respect to the forma- 

 tion of the bone-cells, I believe, 

 that owing to the discovery 

 of an excellent subject for 

 their observation, viz., rachitic 

 bone, I have put the matter, 

 as regards the most essential 

 particulars, in a clear point 

 of view. The bone-cells are 

 formed, as Schwann thought 

 possible, and Henle supposed, 

 from analogy with the ligni- 

 fied vegetable cell with pores 

 or dotted canals, from the 

 cartilage-cells, by the thick- 

 ening of their wall, with the 

 simultaneous formation of 

 canalicular vacuities in it, 

 and its ossification. In the 

 ossifying shaft of a rickety 

 bone (Fig. 132) the morpho- 

 logy of this process may be most beautifully observed. If the rows of 



FIG. 132. From the ossifying border of the condyle of the femur of a rachitic child, 

 two years old, a, cartilage cells, simple and parent cells in series ; 6, more homogeneous j 

 c, striated matrix between them; d, cartilage-cell.s at the commencement of their trans- 

 formation into bone-cells ; e, the same further advanced, with very much thickened walls, 

 indication of canaliculi, commencing deposition of calcareous matter in the walls, whence 

 their darker color, though still with distinct nuclei ; /, bone-cells still more developed and 

 more ossified, in an equally ossified, matrix. Magnified 300 diameters. 



