130 ELEMENTARY lilOLOGY. [CHAP. 



/?. T\\e periosteum ; a thin layer closely applied to 

 the outer face of d., and staining with great in- 

 tensity. 



y. The marrow ; composed of larger vacuolated 

 (fat-laden) cells, and smaller rounded deeply- 

 stained ones {red viarrow cells). 



h The nutrient vessels; in section as follows: — a 

 larger ovoidal and thin-walled vein^ and a smaller 

 cylindroidal and thick-walled artery, lying close 

 together near the middle of the marrow. 



€. Search your sections for any which may have 

 passed through a nutritive foramen ; if ])resent, 

 note the relations of the periosteum to the 

 marrow. 



c. Examine your thinnest section under a high 

 power. 

 a. The bo?iy shaft ; seen to consist of a number of 

 concentric layers or lamcllce, rendered distinct 

 under the action of the reagent. 



Find the middle lamella {b. a); it marks the 

 boundary line between an inner, more lightly 

 stained series {concentric or peri-medullary lamella;) 

 and an outer, more deeply stained series {circum- 

 ferential or subperiosteal lamella;). 



/?. The bone corpuscles ; minute fusiform or branch- 

 ing cells, set along the lines of the above la- 

 melhie. Each clear and little stained, with a 

 deeply stained nucleus. (Cf connective tissue 

 corpuscle.) 



y. The periosteum ; if the section ])e a good one, 

 its innermost layer will be seen to consist of a 

 row of small flattened cells (osteoblasts). 



