818 SPECIAL HISTOLOGY. 



cartilage-cells of the ossifying border, which in this case are of larger 

 size, be traced from without to within, it will soon be found, that at 

 the point where the deposition of calcareous salts (which takes place 

 for the most part without the formation of the calcareous granules) 

 commences, they exhibit, instead of a membrane indicated by a single, 

 tolerably strong line, a thicker coat, which on the inner side presents 

 delicate indentations. Even when the thickness of this membrane 

 does not exceed 0*001 of a line (Fig. 132, d), it is obvious that the car- 

 tilage-cells are about to be transformed into bone-cells ; and this be- 

 comes still more evident, when, further on in the bone, the thickness 

 of the membranes in question, together with the simultaneous diminu- 

 tion of the cavity of the cell, is seen to be constantly increasing, the 

 indentations of the interior contour line to become more and more 

 marked, and, accompanying the progress of these changes, the walls to 

 become more and more dark from the addition of calcareous matter 

 (Fig. 132, e). The slow ossification of the matrix between the cells is 

 very favorable to the observation of these changes, allowing not only of 

 the accurate investigation of the first alterations in the cartilage-cells, 

 but also of their subsequent conditions, at a time when they must be 

 termed bone-cells and lacunce, being traced step by step. To this cir- 

 cumstance alone is also due the establishment of the interesting fact, 

 that cartilage-cells, enclosing secondary cells within them, are converted, 

 as a whole, into a single, compound bone-cell. Cells of this kind -are 

 very frequently met with, having two cavities, which cells, according to 

 their degree of development, are sometimes wide and furnished with 

 short prolongations, and sometimes from their contracted cavity and 

 long canaliculi, resemble in all respects perfect bone-lacunae. Com- 

 pound cells, with 3, 4, and 5 cavities, each with the remains of the 

 original contents and nucleus, occur more rarely, though even such are 

 occasionally to be found in almost every preparation. The cartilage- 

 cells lying free, and inclose apposition, though in a non-ossified matrix, 

 having thus evidently become transformed into bone-cells with nuclei 

 and other contents, the ultimate changes now take place from which the 

 rickety bone-substance acquires pretty nearly the nature of the sound 

 tissue. These changes, in as far as they effect the bone-cells, chiefly 

 depend, in the first place, upon the commencement of ossification in 

 the matrix, but without any primary formation of calcareous particles ; 

 and secondly, upon the continually increasing deposition of earthy mat- 

 ter in it, and in the thickened cell-walls, owing to which, the new bone- 

 substance, to the naked eye, becomes more and more white, and under 

 the microscope appears more and more dark and transparent ; it now, 

 also, becomes more homogeneous, and the abrupt limits of the bone-cells 

 gradually less and less defined, till at last they appear, not as cellular 

 organisms lodged in the matrix, but to be confused with it, being recog- 



