XIV. 



BONE AND ITS DEVELOPMENT. 



I8 5 



of the bone the epiphysis (E) and the future shaft or diaphysis 

 of the bone (Z>). 



(<.) In the epiphysial cartilage (EG) the vertical rows of carti- 

 lage-cells, smaller above, and larger and more quadrilateral below 

 (fig. 158 and iig. 159, C). 



(d.) The shaft with longitudinal spaces the primary medul- 

 lary spaces (fig. 158, MS) bounded by trabeculse of calcined 

 cartilage partly covered by bone (fig. 159, b). The spaces con- 

 tain young marrow (c). 



(e.) (H) Study specially the cells of the epiphysial cartilage 

 (fig. 159, 0), and notice that the cells and capsules are smaller 

 above and larger below zone of enlarged cartilage-capsules. Some 

 of the enlarged cartilage- 

 capsules of the lowest row 

 may be seen opening into 

 the primary medullary 

 spaces. The line of ter- 

 mination of these spaces is 

 called the line of ossifica- 

 tion. The bone grows in 

 length by the proliferation 

 of the epiphysial cartilage- 

 cells. 



(/'.) Bounding the pri- 

 mary medullary spaces, 

 directive trabeculse of cal- 

 cified cartilage (//) with a 

 deposit of bony matter on 

 them. Note specially the 

 osteoblasts (p) partially em- 

 bedded in the osseous matter which they themselves secrete or 

 form. When they become embedded in the osseous products 

 of their own activity, they are then called bone-corpuscles. Note 

 also that the bone on the cartilage is bounded by convex surfaces 

 which fit into corresponding depressions in the cartilage. On 

 the larger trabecnlse may be found osteoclasts 

 cavities Howship's lacunae which they have 

 spares themselves are filled with red marrow 

 vessels (v). 



4. Intra-Membranous Formation of Bone (H and L). Take the 

 parietal bone of a foetus when the parietal bone is only partially 

 ossified; scrape off the periosteum from a part near the periphery 

 of the ossified part; stain in picro-carmine and mount in Far- 

 rant's solution. 



(a.) Observe at one part the fibrous matrix, and shooting from 



FIG. 158. V.S. Head of Tibia of a Young Rabbit, 

 greatly reduced to show details. C. Encrust- 

 ing cartilage ; E. Epiphysis ; EC. Epiphysial 

 cartilage ; D. Diaphysis ; p. Periosteum ; MS. 

 Primary medullary spaces. 



lying in little 

 eroded. The 

 (c) and blood- 



