40 BONE. 



On the inner surface of the shaft are the cancellous lamella?, 

 forming a spongy network of greater richness the nearer 

 the origin of the section is to the end of the bone. 

 (Jf) The Haversian canals and the lacunse intercommunicate 

 freely by means of fine channels, the canaliculi, and the latter 

 form at the periphery of the systems closed loops "recurrent 

 canaliculi" Search for well-defined lamellae in the Haversian 

 systems. 



Shaft of long bone. L.S. Similarly prepared. (L) The 

 Haversian canals form a longitude system of anastomosing 

 channels, which open both upon the outer and inner surfaces 

 of the bone. 



(H ) The grouping of the lamellae into systems is less recog- 

 nisable. The Haversian spaces may be traced in favour- 

 able positions to be expansions of Haversian canals. 



Cranial bones. The plate-like bones (L) exhibit an inner and an 

 outer layer (table) of dense osseous material, separated from each other 

 by cancellous tissue (Diploe). 



Sharpey's fibres. In the outer lamellae of dense bone fibres 

 occur which traverse them vertically from the surface. These are some 

 of the more obvious fibres of periostea! origin which have become 

 included in the lamellae during the growth of the latter. Some of them 

 are elastic fibres. 



Softened bone. (p. 14, c. G., s. 19, m. F.) The lime salts are 

 removed and the soft parts preserved. (L) Externally is the 

 periosteum, dense in its outer (fibrous) layer, and more open 

 in its inner (osteognetic) layer. The latter is attached to the 

 subjacent bone itself. These subdivisions are more striking in 

 the growing stage. (//) Observe the fusion of the periosteal 

 fibres to the bone matrix, especially where the tendons are 

 inserted. The lacunae, less sharply defined, each accommodate 

 a bone corpuscle. The canaliculi being filled with fluid, do 



