[ 109 ] 



Magnified 250 diameters. 



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

 merus, treated with oil of turpentine, a, Haversian 

 canals ; 6, their laminae, each lamina with a lighter and 

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

 darker lines, probably indicating greater interruptions 

 in the deposition of the osseous substance ; d, lacunae 

 without evident canaliculi. 



distinctly in bone from which the inorganic 

 matter has been removed by digestion in 

 dilute muriatic acid. In this the laminae 

 are easily separable. They frequently ex- 

 hibit a fibrous appearance ; and near the 

 surfaces of the bones they run parallel with 

 these surfaces (fig. 63 , 6) ; but in the other 

 portions they mostly surround the Haver- 

 sian canals concentrically (fig. 63 d}. 



When a section of bone is examined with 

 a somewhat high j>ower, it exhibits nume- 

 rous dark spots, with fine lines branching 

 from them on all sides ; the former are the 

 lacuna, bone-corpuscles, or bone-cells (fig. 

 67 c, 6) ; and the latter are the canaliciili or 

 calcigerous canals (fig. 68 6, c, cT). They 

 derive their dark appearance in dried bone 

 from containing air : if this be displaced by 

 immersion in oil of turpentine, they become 

 so transparent as to be scarcely distinguish- 

 able (fig. 66) ; and when examined by re- 



BONE. 



Fig. 67. 





w 



Magnified 100 diameters. 



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

 Haversian canals ; 6, side view of the lacunas in the 

 Haversian laminae ; c, surface view of lacunae. 



fleeted light, they appear white. The la- 

 cunae are generally longer than broad, and 

 flattened. They are about 1-1100" 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" j and at their narrow- 

 est part, which is furthest from the lacunae, 

 they anastomose with those of the adjacent 

 lacunae. 



The walls of the lacunae and canaliculi 

 consist of a homogeneous calcified mem- 

 brane. 



In a transverse section of bone, the lacunae 

 of the laminae surrounding the Haversian 

 canals are seen to be placed tangentially to 

 the orifices of these canals, as in figs. 66 

 and 68 ; whilst those of the laminae near 

 the surfaces are parallel with these surfaces 

 (fig. 63). 



In a longitudinal section made through 

 the Haversian canals, they appear arranged 



