

BONE 



89 



vessel anastomose with the arteries of the cancellous and compact tissues. In most 

 of the flat, and in many of the short spongy bones, one or more large apertures are 

 observed, which transmit to the central parts of the bone vessels corresponding to 

 the nutrient arteries and veins. The veins emerge from the long bones in three 

 places (Kolliker) : (1) one or two large veins accompany the artery; (2) numerous 

 large and small veins emerge at the articular extremities; (3) many small veins 

 pass out of the compact substance. In the flat cranial bones the veins are large, 

 very numerous, and run in tortuous canals in the diploic tissue, the sides of the 

 canals being formed by thin lamella? of bone, perforated here and there for the 

 passage of branches from the adjacent cancelli. The same condition is also 

 found in all cancellous tissue, the veins being enclosed and supported by osseous 

 material, and having exceedingly thin coats. When a bone is divided, the vessels 

 remain patulous, and do not contract in the canals in which they are contained. 

 Lymphatic vessels, in addition to those found in the periosteum, have been traced 

 by Cruikshank into the substance of bone, and Klein describes them as running in 

 the Haversian canals. Nerves are distributed freely to the periosteum, and accom- 

 pany the nutrient arteries into the interior of the bone. They are said by Kolliker 

 to be most numerous in the articular extremities of the long bones, in the vertebrae, 

 and in the larger flat bones. 





FIG. 73. Transverse section of compact tissue bone. Magnified. (Sharpey.) 



Minute Anatomy. A transverse section of dense bone may be cut with a saw 

 and ground down until it is sufficiently thin. 



If this be examined with a rather low power the bone will be seen to be mapped 

 out into a number of circular districts each consisting of a central hole surrounded 

 by a number of concentric rings. These districts are termed Haversian systems; 

 the central hole is an Haversian canal, and the rings are layers of bony tissue 

 arranged concentrically around the central canal, and termed lamellae. More- 

 over, on closer examination it will be found that between these lamella?, and 

 therefore also arranged concentrically around the central canal, are a number of 

 little dark spots, the lacunas, and that these lacunae are connected with each other 

 and with the central Haversian canal by a number of fine dark lines, which radiate 

 like the spokes of a wheel and are called canaliculi. Filling in the irregular intervals 

 which are left between these circular systems are other lamellae, with their lacunae 

 and canaliculi running in various directions, but more or less curved (Fig. 73); 

 they are termed interstitial lamellae. Again, other lamellae, found on the surface 

 of the bone, are arranged parallel to its circumference; they are termed circum- 



