OSTCOGENETIC 

 CELLS 



LAMELL/C 



LACUN/E 



CANALICUL 



HAVERSIAN 



CANAL 



COMPLETE 

 AVEHSIAN 

 SYSTEM 



Fig. 20. — Diagram of the Structure of Osseous Tissue. A small part of a 

 transverse section of the shaft of a long bone is shown. At the uppermost part 

 is the periosteum covering the outside of the bone ; at the lowermost part is the 

 endosteum lining the marrow cavity. Between these is the compact tissue con- 

 sisting largely of a series of Haversian systems, each being circular in outline 

 and perforated by a central canal. In the first one is shown only the area occupied 

 by a system ; in the second is seen the concentric arrangement of the lamellae ; 

 in the others, respectively, canaliculi ; lacunae ; lacunae and canaliculi ; the contents 

 of the canal, artery, vein, lymphatic, and areolar tissue ; lamellae, lacunae, and 

 canaliculi ; and finally all of the structures composing a complete system. Between 

 the systems are circumferential and intermediate lamellae, only a few of which are 

 represented as lodging lacuna>, though it is to be understood that lacunae are in all 

 parts. The periosteum is seen to be made up of a fibrous layer and a vascular 

 [ayer, and to have upon its attached surface a stratum of cells. From the fibrous 

 layer project inward the rivet-like fibres of Sharpey. (Gerrish.) 



45 



