CONNECTIVE TISSTJE 



43 



or lamellm, about central canals (the Haversian canals). 

 Further, the pits or lacunm ^¥hich contain the bone-form- 

 ing cells are connected by fine tubes {canaliculi). The 

 explanation of this difference of arrangement is found in 

 the fact that the cells can give off only substances which 

 they manufacture from the food brought to them. The 

 Haversian canals contain blood vessels which bring to the 





Fig. 14 — Bone tissue ; A, piece of Tjone under the low power of the microscope, 

 showing rings or lamellse ahout central cavities (Haversian canals); jB, piece of 

 bone highly magnified, showing the lacuna with the fine canalicuti radiating 

 from tliem. 



bone cells their food and lime. Food and lime ooze out 

 of the blood vessels and finally reach the cells by way 

 of the canalicuU. The protoplasm of the cells, then, manu- 

 factures from the food the cartilage material which it 

 throws out with the lime, so that it accumulates in layers 

 about the cells. The result of the similar action of many 

 cells means a great accumulation of this material, and 

 hence the production of supports for the soft parts of our 

 body. 



