THE CONNECTIVE TISSUES. I I 3 



Lamellae of bone are plainly visible throughout the ground-sub- 

 stance, and are arranged in the following general systems : 



First, there is a set of bone lamellae running parallel to the ex- 

 ternal surface of the bone, while another set is similarly arranged 

 around the marrow cavity. These are the so-called fundamental, 

 or outer and inner circumferential lamella (known also as periosteal 

 and marrow lamella). Around the Haversian canals are the con- 

 centrically arranged lamellae, forming systems of Haversian or con- 

 centric lamella. Besides the systems already mentioned, there are 

 found interstitial or ground lamella wedged in between the Haversian 



Fig. 80. Longitudinal section 

 through a lamellar system. 



Figs. 8 1 and 82. Lamellae seen from the surface ; 

 X4 (after v. Ebner 75). 



a y Primitive fibrils and fibril-bundles; r, bone-corpuscles with bone-cells; d, bone 



canaliculi. 



or concentric systems of lamellae. Some authors group the inter- 

 stitial lamellae with the systems of fundamental lamellae. 



Lying scattered between the lamellae are found spaces known as 

 bone corpuscles (Virchow) or lacuna. These are present in all the 

 lamellar systems. It is very probable that all the lacunae are in 

 more or less direct communication with each other by means of fine 

 canals called canaliculi (\ . I /J. to 1.8 // in diameter). It can be demon- 

 strated without difficulty that the lacunae of a single lamellar sys- 

 tem communicate not only with each other, but also with those of 

 8 



