74 ELEMENTARY PHYSIOLOGY. [VII. 



5. Prepare transverse sections through the shaft of 

 a long bone which has been decalcified 1 . Stain 

 with picrocarmine (cp. Lesson IV. 6). Wash 

 with water and mount in glycerine. Observe 

 that 



a. Each lacuna is occupied by a cell or bone 

 corpuscle. 



b. The canaliculi are scarcely visible. 



c. The Haversian canals and spaces are occupied 

 by cells, connective-tissue fibres and blood- 

 vessels (red blood corpuscles if present will 

 be stained yellow). 



d. If the tissue of the central cavity has not 

 fallen out of the section, it will be seen to 

 consist of fatty tissue. 



e. The periosteum is closely attached to the out- 

 side of the bone; it consists externally chiefly 

 of white fibres, internally largely of small 

 elastic fibres some of which may be seen to 

 run into the bony matrix. 



G. Take a bone (e.g. the parietal) which has been 

 decalcified by nitric or hydrochloric acid, well 

 washed with water and preserved in spirit; 

 remove the periosteum, tear off 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 pro- 

 jecting from the surface and the apertures 

 through which similar fibres have passed. 



1 Cp. Appendix for methods of decalcification. 



