242 



THE SKELETON 



the canals as centers. (For location of these parts, see 

 Fig. 97.) In these lacunse are the hving bone cells 

 which absorb the food and transform it into bone mate- 

 rial. The lime part of this secretion forms in concentric 

 rings about these lacunae and the layers of this material 





\z 



,^ ^^ 



Fig. 97 — a, transverse section of bone (X 150) a, a. Haversian canals, 6, 6, lacunar : 

 B, longitudinal section of bone (x 100) ; a, a, Haversian canals ; &, 6, lacunar ; C, 

 bone lacunar (X 600) ; c, lacunar ; d, canaliculi. 



are called lamellse. When the bones are young, the secreted 

 matter from the cells is largely cartilage; later, the mineral 

 part is given off more freely and the structure becomes 

 more rigid. In the marrow, as already mentioned, are 

 formed the red corpuscles which are added to the circu- 



