86 



HUiMAN ANATOMY. 



The compact bone in such preparations, when examined under low ampH- 

 fication (Fig. 114J, is seen to be composed of osseous layers arranged as three 

 chief groups : (a) the circumfcreyitial lamellce, which extend parallel to the external 

 and internal surfaces of the compact bone ; {^b) the Haversian la^nellcz, which are 

 disposed concentrically and form conspicuous annular groups, the Haversian systems, 

 enclosing the Haversian canals ; and (r) the interstitial or ground lamellce, which 

 constitute the intervening more or less irregularly arranged bony layers filling up 

 the spaces between the Haversian systems and the peripheral strata. 



Fig. 114. 



HIHjJfcWk -. i^t.,. } "7^ ''^ ~""' -^■^^ 



-^ 

 •^ '^' 











I- 





&lr:^#^'e 







%*^ >./. 



h:>? 



'2t^4> 



■External circumferen- 

 tial lamellae 



Haversian canal sur- 

 rounded by Haver- 

 sian lamellae 



Interstitial lamellae 



-Internal circumferen- 

 tial lamellae 



Transverse section of compact bone (metatarsal) ; the section has been ground and dried, hence the lacunae are 



filled with air. X 85. 



Each Haversian system consists of the concentrically disposed lamellae and 

 the centrally situated channel, or Haversian canal, enclosing the ramifications of the 

 medullary blood-vessels and associated marrow-tissue. Between the annularly 

 arranged lamellae are seen small spindle-shaped or oval spaces, the lacuna, about 

 .02 millimetre long, .01 millimetre wide, and .006 millimetre thick, from which ex- 

 tend minute radiating channels, the canaliculi, establishing communication between 

 the adjacent lacunae of the same Haversian system. The lacunae and the canaliculi 

 constitute an intercommunicating net-work of lymph-spaces similar to those encoun- 



