cviii 



BONE. 



contain, in some it is a pellucid substance strongly refracting the light, and nearly 

 filling the capsule ; in others it is faintly granular and light like ground glass, and 

 has a well-defined outline, and in these there is a very distinct nucleus, varying much 

 in size in different cells, but always most regularly circular, and inclosing one or 

 more nucleoli ; lastly, a good many cells may be seen, in which the contained mass 

 or cell-body has shrunk and does not nearly fill the capsule, and then it is usually 

 coarsely granular or grumous, with an uneven, and in some, a jagged outline. 



Fig. LIT. 



Fig. LTII. 



Fig. LIT. THIN LONGITUDINAL SECTION OP OSSIFYING CARTILAGE PROM THE HUMERUS 



OF A F<ETAL SHEEP. 



a, cartilage-cells uniformly diffused ; b, cells nearer the boundary of the ossification, 

 collected into piles and inclosed in oblong areolse of the clear matrix ; c, dark lines of 

 ossification extending into the matrix and forming the primary bony areolee. Magnified 

 about 70 diameters. 



Fig. LIII. TRANSVERSE SECTION OF THE OSSIFYING CARTILAGE REPRESENTED IN 



Fig. LIL, 



Made a little above c, along the surface of ossification, and including part of the new- 

 bone, magnified 70 diameters. The circular sections of the groups of cells and of the 

 osseous areolse are seen ; and the dark bone extending into the clear intercellular 

 matrix. 



It thus appears that the bony tissue, as it advances into the cartilage, 

 has at first a sort of alveolar structure, made up of fusiform areolce, or 

 short tubular cavities, with thin parietes, which are formed by calcifi- 



