THE STRUCTURE OF THE ELEMENTARY TISSUES. 59> 



The lacunae are occupied by branched cells, which are called bone- 

 cells, or bone-corpuscles (fig. 62), which very closely resemble the ordi- 

 nary branched connective-tissue corpuscles; each of these little masses 

 of protoplasm ministering to the nutrition of the bone immediately sur- 

 rounding it, and one lacunar corpuscle communicating with another,, 

 and with its surrounding district, and with the blood-vessels of the 

 Haversian canals, by means of the minute streams of fluent nutrient 

 matter which occupy the canaliculi. 



It will be seen from the above description that bone is essentially 

 connective-tissue impregnated with lime salts : it bears a very close re- 

 semblance to what may be termed 

 ft )| ft . typical connective-tissue such as- 



the substance of the cornea. The- 

 bone-corpuscles with their pro- 



Fig. 62. Fig. 63. 



Fig. 62. Bone-corpuscles with their processes as seen in a thin section of human bone. (Rollett.) 

 Fig. 63. 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.) 



cesses occupying the lacunae and canaliculi correspond exactly to the 

 cornea-corpuscles lying in branched spaces. 



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 tracea- 

 ble just beneath the periosteum, and around the medullary cavity, form- 

 ing around the latter a series of concentric rings. Ac 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 system of Haversian 

 lamellae, filling the spaces between them, and consequently attaining 



