40 HANDBOOK OF PHYSIOLOGY. 



of the bone-lamellae, to be presently described, resembles the fibrillated 

 substance of the cornea in which the branching spaces lie. 



Lamellae of Compact Bone. In the shaft of a long bone three 

 distinct sets of lamellae can be clearly recognized. 



(1.) General or fundamental lamellae; which are most easily traceable 

 just beneath the periosteum, and around the medullary cavity, forming 

 around the latter a series of concentric rings. At a little distance from 

 the medullary and periosteal surfaces (in the deeper portions of the bone) 

 they are more or less interrupted by 



(2.) Special or Haversian lamellae, which are concentrically arranged 

 around the Haversian canals to the number of six to eighteen around 

 each. 



(3.) Interstitial lamellae, which connect the systems of Haversian 



FIG. 55. 



FIG. 56. 



FIG. 55. Thin layer peeled off from a softened bone. This figure, which is intended to represent 

 the reticular structure of a lamella, gives a better idea of the object when held rather farther off 

 than usual from the eye. X 400. (Sharpey.) 



FIG. 56. Lamellae torn off from a decalcified human parietal bone at some depth from the surface, 

 o, a lamella, showing reticular fibres ; 6, 6, darker part, where several lamellae are superposed; 

 , perforating fibres. Apertures though which perforating fibres had passed, are seen especially in 

 the lower part, a, a, of the figure. (Allen Thomson.) 



lamellae, filling the spaces between them, and consequently attaining 

 their greatest development where the Haversian systems are few, and 

 vice versa. 



The ultimate structure of the lamellce appears to be reticular. If a 

 thin film be peeled off the surface of a bone, from which the earthy 

 matter has been removed by acid, and examined with a high power of 

 the microscope, it will be found composed of a finely reticular structure, 

 formed apparently of very slender fibres decussating obliquely, but coa- 

 lescingrat the points of intersection, as if here the fibres were fused 

 rather than woven together (Fig. 55). (Sharpey.) 



