CHAPTER VIII 



BONE-BUILDERS AND THE MANNER IN WHICH THEY 

 CONSTRUCT LIVING LEVERS 



It has been your good fortune, I am sure, to peer through 

 the window of an experimental hive and watch bees 

 building the cells of their combs. They are noted as 

 skilful masons, arranging their habitations according to 

 the space at their disposal, and carrying out alterations in 

 their arrangements should such be found to be necessary. 

 Now, if we could peer into the substance of bone through 

 the eye-piece of a microscope, we should see the interior 

 of a hive of a different kind — a hive where minute cells 

 are occupied by living microscopic units known to anato- 

 mists and physiologists as bone corpuscles or osteoblasts, 

 but since they spend their lives in laying down and looking 

 after bone we may name them " bone-builders." Although 

 so minute these bone-builders are like bees in several 

 respects. The building materials of the honeycomb are 

 manufactured in the living tissues of the bee's body ; 

 the wax, when the bee is building, can be seen oozing 

 from between the rings of the builder's abdomen. Bone- 

 builders also employ materials which are formed in their 

 own bodies in the formation of the cells or spaces in 

 which they live. Perhaps it is when the honeycomb is 

 rilled with a brood of maggot bees that it most resembles 

 bone, excepting that the cells or spaces of bone in which 

 the osteoblasts live are so very small that they can be seen 

 only by the aid of a microscope. The walls of these cells 

 or spaces are enormously thick and strong, and are made 

 up of lime salts in place of wax. Each cell or space is 



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