r 90 



BONE. 



Magnified 350 diameters. 



Portion of a transverse section of the shaft of the hu- 

 merus, treated with oil of turpentine. a, Haversian 

 canals ; b, their laminae, each lamina with a lighter and 

 darker portion and radiating striae in the latter ; c, darker 

 lines, probably indicating greater interruptions in the de- 

 position of the osseous substance; d, lacunae without 

 evident canaliculi. 



merous dark spots, with fine lines branch- 

 ing from them on all sides ; the former are 

 the lacuna, bone-corpuscles, or bone-cells 

 (fig. 68 c, b), and the latter are the canali- 

 culi or calcigerous canals (fig. 69 b, c, d}. 

 They derive their dark appearance in dried 

 bone from containing air; if this be displaced 

 by immersion in oil of turpentine, they be- 

 come so transparent as to be scarcely di- 

 stinguishable (fig. 67) ; and when examined 

 by reflected light, they appear white. The 

 lacunae are generally longer than broad, and 

 flattened. They are about 1-1 100" in length, 

 1-2000 to 1-2800" in width, and 1-3800 to 

 1-6000" in thickness; but their dimensions 

 are subject to great variety. The canaliculi 

 vary in breadth from 1-20,000 to 1-60,000", 

 and at their narrowest part, which is furthest 

 from the lacunas, they anastomose with those 

 of the adjacent lacunas. 



In a transverse section of bone, the lacunae 



Magnified 100 diameters. 



Section of the surface of the shaft of the femur, a, Ha- 

 versian canals ; b, side view of the lacunae in the 

 Haversian laniiuie ; c, surface view of lacunae. 



of the laminae surrounding the Haversian 

 canals are seen to be placed tangentially to 

 the orifices of these canals, as in figs. 67 and 

 69; whilst those of the laminae near the 

 surfaces are parallel with these surfaces (fig. 

 64). 



In a longitudinal section made through 

 the Haversian canals, they appear arranged 

 in numerous longitudinal rows running par- 

 allel with the Haversian canals (fig. 68). 

 The general arrangement is, that the long 

 axis of the lacunae is parallel with the laminae 

 in which they are contained, or between 

 which they are situated. 



When the section coincides with the sur- 

 faces of a set of the lacunae, they present a 

 very elegant round or oval form (fig. 72), 

 irregularly surrounded by a perfect tuft of 

 canaliculi, which, being turned directly to- 

 wards the observer, appear more or less 

 shortened, and a small number of others, 

 which are diffused through the surface of the 

 lamellae. Here and there, in the thinnest 



