B O N E. 



47 



that of the shaft of the long bones. It is more fluid, and of a 

 reddish color, and contains very few fat-cells. 



The surfaces of bones, except the parts covered with articu- 

 lar cartilage, are clothed by a tough fibrous membrane, the 

 periosteum ; and it is from the bloodvessels which are distrib- 

 uted first in this membrane, that the bones, especially their 



FIG. 16. 



Transverse section of compact tissue (of humerus) magnified about 150 diameters. 

 Three of the Haversian canals are seen, with their concentric rings; also the cor- 

 puscles or lacunae, with the canaliculi extending from them across the direction of 

 the lamellae. The Haversian apertures had got filled with debris in grinding down 

 the section, and therefore appear black in the figure, which represents the object as 

 viewed with transmitted light (after Sharpey). 



more compact tissue, are in great part supplied with nourish- 

 ment minute branches from the peri osteal vessels entering 

 the little foramina on the surface of the bone, and finding 

 their way to the Haversian canals, to be immediately de- 

 scribed. The long bones are supplied also by a proper nutri- 

 ent artery, which, entering at some part of the shaft so as to 

 reach the medullary canal, breaks up into branches for the 

 supply of the marrow, from which again small vessels are dis- 

 tributed to the interior of the bone. Other small bloodvessels 

 pierce the articular extremities for the supply of the cancellous 

 tissue. 



Notwithstanding the differences of arrangement just men- 



