XIIL] 



BONE, OSSEOUS TISSUE, ETC. 



175 



f i. External layer, fibrous, with the larger blood- 

 vessels. 



Periosteum J \ 2. Internal or osteogenic layer, with finer blood- 

 vessels, numerous elastic fibres, and 

 blasts, and sometimes osteodasts. 

 Osteodasts or myeloplaxes of Robin. 

 Blood-vessels, nerves, and lymphatics. 

 , . ( i. Endochondral in cartilage. 



* \ 2. Intra-membranous or periosteal. 



1. T.S. of Dense or Compact 

 Bone. It is better to buy a pre- 

 pared transverse section of the 

 shaft of a small, dry, long bone. 

 In it most of the smaller spaces, 

 being filled with air, appear 

 black. 



(a.) (L) Observe the medullary 

 cavity, bounded by a ring of bone, 

 less dense internally. 



(b.) Sections of tubes which 

 appear round, or oval Haver- 

 sian canals surrounded by con- 

 centric lamellae (fig. 145, c), and 

 between these lamellae are lacunae 

 (e), with fine channels passing 

 from them the canaliculi. Some 

 lamellae are arranged parallel to 

 the circumference of the bone 

 the peripheric (a) while others 

 of larger radius are incomplete, 

 and jnmmed in between the 

 Hayersian system : they are inter- 

 mediary (jl). Around the medul- 

 lary canal are the perimedullary 

 lamellae (b). 



(c.) (H) Observe the shape of 

 the lacunae flattened branched 



spaces with their numerous ' * -~" " - 1^ 



wavy branching canaliculi, and ^^^^^^^ ^-^* 

 how adjoining canaliculi anasto- *^ 



IM< iso by traversing the lameike FlG - MS- T.S. Human Metacarpal Bone. 

 /(> \ A , ,, o. Peripherie lamelle ; A. Perimedullary 



(fig 8 - r 45> I47> e )' Afc tne 0ter lamelhu; ft Ilaversian canals snr- 



part of each Hayersian system roded ^r their Hftrerriwi tanelto ; 



,. , " ' '' Intermediary lamella?; e. Lacuiiai, 



some 01 the canaliculi of the x 20. 



