VII.] BONE, OSSIFICATION, TEETH. 77 



sections and stain them with picrocarmine, and 

 mount in glycerine or Canada balsam. Observe 



a. The periosteum consisting externally of 

 coarse connective tissue, internally of fine 

 connective tissue with numerous cells. 



b. The trabeculae of the bone matrix, exter- 

 nally these give off numerous small projec- 

 tions into the inner layer of the periosteum. 



c. The osteoblasts forming a layer on the 

 outer surface of the bone matrix ; some will 

 also be seen on the trabeculse throughout the 

 section ; note the fine connective tissue and 

 the blood vessels in the trabecular spaces. 

 Many of the osteoblasts especially in the ex- 

 ternal layer are elongated and their smaller 

 ends appear to run into the matrix. 



d. Some osteoclasts as in 1 , e. may be seen. 



C. STRUCTURE OF TEETH. 



1. Examine under a low power longitudinal sec- 

 tions of teeth prepared in the same manner as 

 bone in B. Observe the dentine surrounding 

 the pulp cavity, the cement or crusta petrosa 

 covering the dentine of the fangs, and the 

 enamel covering the dentine of the crown. 

 Note the general arrangement of the dentinal 

 tubules. 



2. Examine under a high power the same section, 

 and study in detail 



