354 SPECIAL HISTOLOGY. 



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 OOOT" (fig. 132, d), it is 

 obvious that the cartilage-cells are about to be transformed 

 into bone-cells; and this becomes still more evident, when, 

 further on in the bone, the thickness of the membranes in 

 question, together with the simultaneous diminution 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 obser- 

 vation 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 circumstance alone is also due the establish- 

 ment 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 fre- 

 quently 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- 

 lacunse. Compound 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 in 

 close 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 affect the 

 bone-cells, chiefly depend, in the first place, upon the com- 



