TISSUES OF THE BODY. 



255 



quence of its deposition in successive portions. This is the beginning of 

 the laminated formation of bony tissue. 



We are still in uncertainty as to the mode of formation of the canali- 

 culi during these processes. 



The characteristic peculiarity 

 of osseous substance soon makes 

 its appearance now, namely, 

 its calcification ; not in granules 

 moreover, but by a more dif- 

 fused deposit of bone earths, 

 communicating to the whole to 

 a certain extent a translucent 

 appearance. The organic sub- 

 stratum of these layers is pro- 

 bably from the very commence- 

 ment collagenous matter. 



Naturally enough, the irregu- 

 lar form of the medullary sinuses, Fig. 246. Osteoblasts from the parietal bone of n 

 and Continuous re-Solution of h uman embryo thirteen weeks old (after Gegenbatir). 



. bony septa, with the cells of the lacunas; b, layers 

 the Still remaining portions OI of osteoblasts; c, the latter in transition to bone cor- 



cartilage, give rise to very dif- P" sclcs - 



ferent appearances in the osseous tissue first formed, as we may see in 



fig. 241, or more strongly marked still in fig. 242. 



A transverse section, also, through the middle portion of the femur, 

 discloses the same irregular struc- 

 ture, the bone consisting principally 

 of longitudinal septa connected by 

 means of transverse bridges (fig. 

 243). 



Here, then, we have a contrast 

 to the regular texture of completed 

 bone. 



Those points are of special in- 

 terest, as explaining the former 

 error of supposing a direct transi- 

 tion of cartilage cells' into bone 

 corpuscles, where the ruptured 

 cavity of a cartilage cell has been 

 made use of as a receptacle for the 

 deposit of one or more bone cor- 

 puscles with the accompanying 

 ground-substance. Here one, two, 

 or three of the latter elements may 

 appear to be contained in the in- 

 terior of a closed capsule, owing 

 to the ease with which the open- 

 ing of the latter may be over- 

 looked (fig. 242, h,f; fig. 241, e.) 



But sometimes almost all the 

 septa of a preparation of osseous tissue have this same extraordinary 

 appearance, so difficult of description, which may be better understood 

 by a glance at fig. 242 (to the left, below). 



By the gradual liquifaction of the remaining portions of cartilaginous 



Fig. 947. Section of the frontal protuberance of 

 the calf (after Gegenbaur). a, hyaline, and 6, calci- 

 fied cartilage; c, bone corpuscles. 



