ffiSTOLOGY OP BOflE. 



53 



Around each Haversian canal is a series of plates or 

 ^ each canal and its lamellae forming an Haversian 

 system; the entire bone is made up of a -number of such 

 systems, with the addition of a few lamellae lying in the 

 corners between them, and some which run around the 

 whole bone on its outer surface. In the spongy bone the 

 Haversian canals are very large, containing red marrow as 

 well as blood-vessels, and the lamellae around each are few 

 in number. 



FIG. 24. A small piece of bone, ground very thin and highly magnified. 



If a bit of bone be still more magnified (Fig. 24) we 

 find that very small cavities lie between the lamellaB ; they 



"What lies around each Haversian canal? What is an Haversian 

 system? Of what does a bone consist in addition tc Haversian sys- 

 tems? Are the Haversian canals comparatively large or small in 

 spongy bone? What do the spaces of spongy bone contain in addi- 

 tion to blood-vessels? 



What spaces lie between the lamella} of an Haversian system? 



