STRUCTURE OF OSSEOUS TISSUE. 121 



or Haversian lamellae ; the others, general or fundamental 

 lamellae. It is more important to distinguish the three series 

 of Haversian lamellae, intermediate lamellae, and peripheric 

 lamellae. 



The open or closed systems of rings seen in transverse sections 

 of bone, are the transverse sections of lamellae arranged around 

 longitudinal and anastomosing canals, the transverse sections of 

 which last constitute the spaces already described. Of this we 

 may convince ourselves by making longitudinal sections of the 

 long bones (fig. 9), in which the vessels may be seen to form elon- 

 gated meshes. They either branch at acute angles, or if the 

 branches are more divaricant, they soon follow a less diver- 

 gent direction, or, which is more usual, they communicate 

 by means of short oblique or rarely transverse branches, and 

 pursue a course that is but slightly inclined to the long axis 

 of the bone. The above-mentioned Haversian or medullary 

 canals, opening upon the external surface of the compact sub- 

 stance, or into the medullary spaces of the spongy substance, 

 are destined for the passage of blood-vessels. The spaces inter- 

 vening between the Haversian canals are occupied by the 

 ribbon-like longitudinal sections of the lamellae. Portions of 



O 



these lamellae of the compact substance of the long bones may 

 either be splintered off, or they may be obtained by sections 

 made parallel to the surface. With high powers and a good 

 microscope, a sharply defined punctation may be observed in 

 them, besides also an indistinct, dull, veiny appearance, the 

 whole substance being thus divided into a few bright islands. 



The punctiform appearance is the expression of small round 

 holes (sections of the bone canals to be hereafter described). 

 The regular rhombs represented by Sharpey,* and observed 

 also by Kolliker,-)- in his earlier preparations, appear to occur 

 only under quite special conditions. 



In complete analogy with the arrangement of the Haversian 

 canals and lamellae of the compact substance of the shaft of 

 the long bones, is that seen in the compact substance of the 



* An illustration of this, after a preparation of Sharpey, may be found 

 in the large Microscopic Anatomy of Hassall, Taf. 30, fig 4. 

 t Gewebelehre, 1867, p. 186. 



