XI] ELASTIC CARTILAGE. BONE. TEETH 87 



Observe (h. p.) the osteoblasts, covering the trabe- 

 culse and in the spaces ; they are larger than ordinary 

 leucocytes, with a single ovoid or spherical nucleus, and 

 finely granular cell substance. The spaces also contain 

 blood vessels and some jelly-like connective tissue. 



Osteoclasts may be seen here and there in contact 

 with the bone matrix; they are large multinuclear 

 cells, and where they touch the bone are often striated 

 at right angles to the surface. 



10. Transverse section of the shaft of the bone used 

 in 9, stained with hsematoxylin and eosin. Note 



The spongy periosteal bone beneath the periosteum, 

 the osteoblasts especially numerous in the lower layer 

 of the periosteum, and in the peripheral bone spaces. 

 Many of the osteoblasts are elongated and their smaller 

 ends appear to run into the matrix. 



The spongy endochondral bone in the centre ; there 

 may be the beginning of a central space but no fat- 

 cells are present. 



11. Structure of Teeth. Longitudinal sections 

 of teeth prepared as bone, 4. a. Examine under 

 a low power. 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. 



b. Examine under a high power, and study in 

 detail 



The Dentine. In the matrix, apparently homo- 

 geneous, are numerous dentinal tubules which run in a 



