XI] ELASTIC CARTILAGE. BONE. TEETH 85 



6. Examine under a high power. The individual 

 lacunae are much as in the transverse section, but 

 rather longer; observe the arrangement of the canali- 

 culi (cp. 4, 6). 



6. Transverse sections (in paraffin) through the 

 shaft of a decalcified and stained adult long bone 1 , as 

 femur of rat. Mount in balsam. Note 



The periosteum formed of connective tissue closely 

 attached to the bone. 



In the bone, each lacuna is occupied by a cell, the 

 bone corpuscle, probably shrunken from the walls of 

 the lacuna. The canaliculi are scarcely visible. 



The Haversian canals are chiefly occupied by small 

 blood vessels, the Haversian spaces by blood vessels 

 and leucocytes. 



The -white marrow, consisting mainly of fat-cells 

 (cp. Less. IX. 14). Small clumps of marrow cells are 

 seen, most of them are either leucocytes or resemble 

 leucocytes, and here and there giant cells, large cells 

 with irregularly lobed nucleus. 



7. Remove the periosteum from a decalcified parietal bone 

 (nitric acid) ; tear oft' from the surface thin strips of the bone 

 matrix and mount them with the inner side uppermost in water. 

 Under a high power note the perforating fibres projecting from 

 the surface and the apertures through which similar fibres have 

 passed. Examine carefully the thinnest part of the strip (con- 

 taining fewest lamella}) for the fine decussating fibres of the 

 matrix ; add acetic acid, both the perforating and decussating 

 fibres swell up and become indistinct or lost to view. 



1 For methods of decalcification cp. Notes at end of Lesson. The 

 tissue may be stained in bulk with picrocarmine, but it is better 

 to stain the sections on the slide (Less. vi. 5). 



