THE PERIOSTEUM AND NUTRIENT BLOOD VESSELS 



43 



Yellow marrow fills the medullary cavity of long bones, and consists 

 chiefly of fat cells with numerous blood vessels. Many of its cells are in 

 every respect similar to lymphoid corpuscles. 



From these marrow cells, especially those of the red marrow, the red 

 blood corpuscles are derived. 



The Periosteum and Nutrient Blood Vessels. The surfaces of 

 bones, except the part covered with articular cartilage, are clothed by a 



FIG. 53. Transverse Section of Compact Bone (of humerus). Three of the Haver- 

 sian canals are seen, with their concentric rings; also the lacunas, with the canaliculi extending 

 from them across the direction of the lamellae. The Haversian apertures were filled with 

 debris in grinding down the section, and therefore appear black in the figure, which 

 represents the object as viewed with transmitted light. The Haversian systems are so 

 closely packed in this section, that scarcely any interstitial lamellce are visible. X 150. 

 (Sharpey.) 



tough, fibrous membrane, the periosteum, which is closely attached to the 

 surface of the bone. Blood vessels are distributed in this membrane, and 

 minute branches from these periosteal vessels enter the Haversian canals 

 to supply blood to the solid part of the bone. The long bones are supplied 

 also by a proper nutrient 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 distributed to the interior 

 of the bone. Other small nutrient vessels pierce the articular extremities 

 for the supply of the cancellous tissue. 



