THE CONNECTIVE TISSUES. 69 



stance prevent the preparation of sections by means of the knife, 

 and, unless they be removed, specimens of bone must be made by 

 grinding. This can best be accomplished after the bone has been 

 dried. But drying the bone destroys the corpuscles, which appear 

 as little desiccated masses, devoid of structure, within the lacunae. - 

 Ground sections of bone can, therefore, give only an idea of the 

 intercellular substance and the arrangement of the lacunae, eanal- 

 iculi, Haversian canals, etc. (Fig. 54). Sections may be cut if 



FIG. 54. 



Ground section of dried bone. Human femur, a, Haversian canal in cross-section ; a', Ha- 

 versian canal occupied by debris ; a", anastomosing branch from a', in nearly longitud- 

 inal section; b, lacuna belonging to the Haversian system, of which a! occupies the 

 centre ; c, lacuna in excentric laminse of bone between the Haversian systems. The 

 delicate lines connecting the lacunae are the canaliculi. 



the bone be first decalcified i. e., if the earthy salts be dissolved 

 through the action of acids. This treatment not only removes the 

 earthy constituents of the intercellular substance, rendering it soft 

 and pliable, but causes the organic constituents to swell. The 

 effect of this swelling upon the appearance of the bone is very 

 marked. The fine canaliculi are closed and the lacuna diminished 

 in size, so that the structure of the bone appears much simplified, 

 being reduced to a nearly homogeneous mass of intercellular sub- 

 stance in which there are spaces arranged in definite order and 

 enclosing the somewhat compressed bone-corpuscles. The delicate 

 processes of the latter are not discernible within the canaliculi, but 

 blend with the swollen intercellular substance forming the walls of 

 those minute channels. It is important that the student should 

 learn to recognize these mutilated preparations of bone, since it is 



