4 6 



ELEMENTARY TISSrES. 



fills the interior, while a thin shell of compact bone forms 

 the outside. The spaces in the cancellous tissue are filled 

 "by a species of marrow, which differs considerably from 

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

 of a reddish colour, and contains very few fat cells. 



The surfaces of bones, except the parts covered with 

 articular cartilage, are clothed by a tough fibrous mem- 

 brane, the periosteum ; and it is from the blood-vessels 

 which are distributed first in this membrane, that the 

 Fig. 1 6.* 



bones, especially their more compact tissue, are in great 

 part supplied with nourishment, minute branches from 

 the periosteal vessels entering the little foramina on the 

 surface of the bone, and finding their way to the Haversian 

 canals, to be immediately described. The long bones are 



* Fig. 1 6. Transverse section of compact tissue (of humeras) mag- 

 nified abput 150 diameters. Three of the Haversian canals are seen, 

 with their concentric rings ; also the corpuscles or lacuna?, with the 

 canaliculi extending from them across the direction of the lamella?. 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). 



