OSSEOUS TISSUE 



331 



d' 



Various forms of lacunae and their pores, a. Simple regular cavities without pores, from an ossi- 

 fication of the pleura. &. From healthy human bone. 6'. One of the outer lacunae of an Haversian 

 system, with pores all bending down towards the Haversian canal, c. Other forms from human 

 bone, showing the lateral connecting pores, d. From the Boa, external lacunae of an Haversian sys- 

 tem with unusually large pores dipping towards the vascular surface, d'. Cavity intermediate be- 

 tween a lacuna and a pore. e. Another variety from the same reptile. (Mr. Tomes.) 



posed, and with their sides parallel to those of the lamellae. The 

 pores of these lacunae communicate with each other, and with those 

 of the surrounding Haversian rods, and thus their nutrition is pro 



Fig. 220. 



Transverse section of human clavicle, showing the orifices of the Haversian canals, and the con- 

 centric arrangement of the laminae of bony matter and of the lacunae around them ; and the inter- 

 stitial osseous substance. (Magnified 85 diameters.) 



