1098 



GENERAL ANATOMY OR HISTOLOGY. 



which accompany the artery ; (2) by numerous large and small veins at the artic- 

 ular extremities ; (3) by many small veins which arise in 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 a 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 structure and having exceedingly thin coats. 

 When the bony structure is divided, the vessels remain patulous, and do not con- 

 tract in the canals in which they are contained. Hence the occurrence of puru- 

 lent absorption after amputation in those cases where the stump becomes inflamed 

 and the cancellous tissue is infiltrated and bathed in pus. 



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 accompany 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 

 the larger flat bones. 



Minute Anatomy. The intimate 

 structure of bone, which in all essential 

 particulars is identical in the compact 

 and cancellous tissue, is most easily 

 studied in a transverse section from the 

 compact Avail of one of the long bones 

 after maceration, such as is shown in 

 Fig. 625. 



If this is examined Avith a rather 

 low pOAver the bone will be seen to be 

 mapped out into a number of circular 

 districts, each one of which consists 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 around are layers of bone-tissue 

 arranged concentrically around the cen- 

 tral canal, and termed lamella 3 . More- 

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

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

 little dark specks, the lacunce, and that these lacunae are connected Avith 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. All these structures 

 the concentric lamellae, the lacunae, and the canaliculi may be seen in any 

 single Haversian system, forming a circular district round a central, Haversian, 

 canal. Between these circular systems, filling in the irregular intervals Avhich are 

 left between them, are other lamellae, Avith their lacunae and canaliculi, running in 

 various directions, but more or less curved (Fig. 626). These are termed interstitial 

 lamellae. Again, other lamellae, for the most part found on the surface of the bone, 

 are arranged concentrically to the circumference of bone, constituting, as it were, 

 a single Haversian system of the whole bone, of Avhich the medullary cavity would 

 represent the Haversian canal. These latter lamellae are termed circumferential, 

 or by some authors primary or fundamental lamellae, to distinguish them from those 

 laid down around the axis of the Haversian canals, which are then termed secondary 

 or special lamellae. 



The Haversian canals, seen as round holes in a transverse section of bone at 

 or about the centre of each Haversian system, may be demonstrated to be true 



FIG. 625 From a transverse section of the shaft of 

 the huraerus. Magnified 350 times, a. Haversian 

 canals, b. Lacunae, with their canaliculi in the lamellae 

 of these canals, c. Lacunae of the interstitial lamellae. 

 d. Others at the surface of the Haversian systems, with 

 canaliculi given off from one side. 



