THE OSSEOUS SYSTEM. 349 



in roivs. This is most distinctly seen, as has been long well 

 known, in the extremities of the diaphyses of the larger 

 cylindrical bones, where the Fi 130 



rows of cells arc very prettily 

 arranged in parallel lines close 

 together, and are of considerable 

 length; it is also evident in the 

 other long bones, as well as in ili 

 many others where the cartilage 



ossifies only on one side, as in n 



the connecting surfaces of the 

 vertebral. "Where, however, the 



ossific nuclei in the centre of a & 



cartilage enlarge on all sides, 



the cartilage-cells are confusedly ; . , / , ,./ \-;/ . ; 'j c 

 grouped in roundish, or oval, }V\ 



irregular little masses, as in EwOll f^yT^ %*' r \~\ v 

 the short bones at their first \\ 1 



formation, and in the epiphyses. ■ U !' : -. | %} e 

 An accurate comparison of the : , JvMy. 



cells which are closer to the ^^^a^^FYLJLJa 

 ossifying margin, with those \ j "\ -'• , ; /" ,. 



more remote from it, and of hLAmmI' <r^ 



the groups formed by them, \> ra R 



at once shows that their par- ' ' 



ticular disposition is directly related to their mode of increase, 

 Each iudividual group (or even two of them) corresponds, in a 

 certain measure, with a single primordial cell, and represents all 

 the descendants which in course of development have proceeded 

 from it. In the one case, all these newly-formed cells are 

 disposed, one behind the other, in a single or double, linear 

 series; and in this way are produced, by their further increase, 

 the rows of cells above described, whilst in the other they con- 

 Fig. 130. Perpendicular section from the ossifying border of the shaft of the femur 

 of a child a fortnight old, x 20 diam.: a, cartilage, in which the cells the nearer 

 they are to the ossifying border are placed together in more extended longi- 

 tudinal rows; b, ossifying border, the dark streaks indicate the progressive ossifica- 

 tion in the intercellular substance, the clearer lines the cartilage cells which ossify 

 subsequently; c, compact layer of bone near the ossifying border ; d, the substantia 

 spongiosa formed in the osseous substance by resorption, with cancclli, the contents 

 of which are not shown. 



a 



