THE OSSEOUS SYSTEM. 



301 



which account they were termed " bone," or " calcareous corpus- 

 cles/' but simply to their being filled with air. In fresh bone, not 

 yet deprived of its watery constituents, nothing can be seen in 

 these bone-cells or lacunae but clear contents with a nucleus, 

 which may best be described as the nutritive fluid of the bone, 

 and consequently the designation above given to these cavities 

 is the most suitable. 



The lacuna? are elliptical, flattened cavities, having an average 

 length of 0-01"', 0001'" wide, and 0-003'" thick, which 

 give off both from the 

 borders, and particu- 

 larly from the surfaces, 

 a great number of very 

 fine canals, measur- 

 ing 0-0005 — 0-0008'" 

 in diameter — the bone- 

 canaliculi above-men- 

 tioned (figs. 115, 116, 

 and 117). The lacunas 

 are equally numerous 

 in both of the lamel- 

 lar systems before de- 

 scribed, and are placed 

 so close together, that, 

 according to Harting 

 (1. c, p. 78), from 709 

 to 1120, or, on the 

 average, 910 of them 

 occur within the space 

 of a square millimeter. 

 They lie for the most 

 part within the lamellae, 

 but also between them, 

 and are invariably placed with their broad sides parallel with the 

 surfaces of the lamellae. The canaUcitli proceeding from them 

 are much branched, and penetrate the osseous substance in all 



Fig. 115. From a transverse section of the shaft of the humerus, x 300 diam.: 

 a, Haversian canals ; b, lacunae with their canals, in the Haversian lamella; ; c, lacunae 

 of the interstitial lamella?; d, lacuna; with unilateral canaliculi proceeding 10 the 

 surface of the Haversian system. 



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