THE CONXFXTIVE TISSUES 



105 



Fig. 51. — Bone Tissue showing Lacunae and 

 Canaliculi. X700. (Technic i, p. 106.) 



phosphate and the carbonate of calcium. These salts are not merely 

 deposited in the matrix, but are intimately associated and combined 

 with its histological structure. The intimacy of this association of 

 the organic and inorganic constituents of bone is shown by the fact 

 that, though the salts com- 

 pose two-thirds of bone by 

 weight, it is impossible to 

 distinguish them by the 

 highest magnification. Fur- 

 thermore, if either the lime 

 salts are dissolved out by 

 means of acids (decalcifica- 

 tion) or the organic matter 

 removed by heating (calcina- 

 tion), the histological struc- 

 ture of the bone still remains. 

 Like the other connective 

 tissues, bone consists morphologically of cells and intercellular 

 substance. 



Bone cells or bone corpuscles lie in distinct cell spaces or lacunce. 

 From the lacunae pass off in all directions minute canals — canaliculi — 

 which anastomose with canaliculi of neighboring lacunae (Fig. 51). 

 At the surface of bone these canaliculi open into the periosteal lym- 

 phatics. A complete system of canals is thus 

 formed, which traverse the bone and serve 

 for the passage of nutritive fluids. The bone 

 cells themselves (Fig. 52) are flat, ovoid, 

 nucleated cells, with numerous fine processes, 

 which extend in all directions into the can- 

 aliculi. In young developing bones the 

 Fig. 52.— Bone Cell and processes of adjacent cells anastomose. In 

 ^hTcS-bod^hlf shrunken, ^dult bone the processes extend but a short 

 allowing the outhne of the distance into the canalicuH, and probably do 



lacuna to be seen. 



not anastomose. 

 The basement substance or matrix has a fibrous structure, 

 closely resembling that of fibrillar connective tissue, and it is in this 

 fibrillar matrix that the lime salts are deposited. The fibrils are 

 held together by cement substance into bundles. In most bone the 

 bundles are fine and arranged in layers or lameUce. Less commonly 

 the fibre bundles are coarser and have an irregular arrangement. 



