THE SKELETAL S^'S'F'KM 



195 



face of the bone and with the central marrow cavity. Between the 

 Haversian canals most of the lamelUu run ])arallel to the canals. 



In a cross section through the shaft of a long bone (Fig. 117), three 

 distinct systems of lamella? are seen. These are known as Haversian 

 lamellcB, interstitial lamcllce, and circumferential lamellce. 





Fig. 117. — Cross-section of Hard (Undecalcified; Bone from Human Metatarsus. 

 X90. (Szymonowicz.) Haversian canals, lacunae, and canaliculi in black, a, Outer 

 circumferential lamellae; b, inner circumferential lamellae; c. Haversian lamellae; d, 

 interstitial lamellae. 



(i) Haversian Lamellae (Fig. 118). — These are arranged in a con- 

 centric manner around the Haversian canals. Between the lamellae, 

 their long axes corresponding to the long axes of the Haversian canals, 

 are the lacunos with their inclosed hone cells (page 105). The lacunae 

 of adjacent lamellae are usually arranged alternately. In a section 

 of ordinary thickness the lacunas are not nearly so numerous as the 

 lamellae, and are seen only between some of the lamellae. The 



