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ELEMENTARY PHYSIOLOGY 



system the <analicnli, and the lacunae of the innermost 

 layer or that nearest the Haversian canal communicate 

 with it, while the canaliadi and the lacunct of the outer- 

 most layer communicate only with those of the next inner 

 layer. Hence the lacume and canaliculi compose a 



Fio. 95.— Transverse Section of Bonk, highly magnified (300 

 diameters). 



H, Haversian canals ; I, lacunae with canaliculi. 



meshwork of canals, which is peculiar to each Haversian 

 system, and by which the nutritive plasma exuded from 

 the vessels in the canal of that system irrigates all the 

 layers of bone which belong to the system. 



A very thin section of perfectly fresh bone exhibits no 

 dark bodies, inasmuch as the lacunte and canaliculi con- 



