BOXE. 



cation of the matrix and partial calcification of the capsules of the cartilage- 

 cells. But this condition, which differs from that of perfect bone, is only transi- 

 tory, and at a short distance below the ossifying surface we see a change 

 taking place in the newly formed tissue ; the structure becomes more 

 open, the original cartilage-cells disappear from its interstices, and the 

 medullary spaces, with their lainellated parietes, as in the permanent cancel- 

 lated tissue, begin to be formed. This, which is the next step of the 

 process, takes place in the following manner. The primary areolce of the 

 bone above described open into one another 



both laterally and longitudinally by absorp- pj_ j^y 



tion of their intermediate walls, and by 



their confluence give rise to the larger or =^ S :== S, ^. ^ ^ ^, 

 secondary cavities, the medullary spaces of sSS^SM^^ 

 H. Miiller, which succeed them lower down. '\~k' = ^ = ?= "^"^S ^ 

 This is shown in a longitudinal section in IE =" jj^ Sf <H i 3>' = L 

 fig. LV., and in transverse section in fig. LVI., 

 A, which represents a thin section made 

 almost immediately below the surface of 

 ossification, and in which the primary cavi- 

 ties are seen to have coalesced into larger 

 ones. A transverse section somewhat lower 

 down, (fig. LVI., B,) shows that they go on 

 enlarging by further absorption and coales- 

 cence, and that their sides are thickened 

 by layers of new bone ; this soon begins to 

 be deposited, (fig. LV., 6, 6, in longitudinal, 

 and LVL, A, in cross section) and goes on 

 increasing, (fig. LVI., B). In the meantime 

 the cartilage-cells have disappeared, and the 

 bony cavities are filled with soft matter, 

 in which there are a few fibres and numerous 

 granular corpuscles resembling those seen in 

 the intrainembranous ossification (d, fig. 

 LV.) ; there are also many blood-vessels. 

 In the end 

 and open 



cancellated tissue, but much of this struc- 

 ture is afterwards removed by absorption, 

 to give place to the medullary canal of 

 the shaft. In many of these cavities the 

 walls of the coalesced primary areolae may 

 long be distinguished, like little arches, 

 forming by their union a sort of festooned 

 outline, within which the new bony laminae 

 are situated. 



, some of the enlarged cavities 

 structure remain to form the 



Fig. LIV. SMALL PORTION OF A 

 SECTION SIMILAR TO THAT IN FIG. 

 LIL, MORK HIGHLY MAGNIFIED 

 (ABOUT 140 DIAMETERS). 



a, b, two of the new-formed osse- 

 ous tubes orareolae, with a few car- 

 tilige-cells and granular corpuscles 

 lying in them ; c, c, cartilage-cells 

 near the ossifying surface, exhibiting 

 the appearance described in the text. 



The primary osseous matter forming the original thin walls of the areolse, and 

 produced by calcification of the cartilaginous matrix, is decidedly granular, and 

 has a dark appearance ; the subsequent or secondary deposit on the other hand is 

 quite transparent, and of an uniform, homogeneous aspect. This secondary deposit 

 begins to cover the granular bone a very short distance (about ^th of an inch) below 

 the surface of ossification, and, as already stated, increases in thickness further down. 

 The lacunae first appear in this deposit ; there are none in the primary granular bone. 

 The cartilage-cells do not become calcined. According to H. Miiller the capsules 



