58 LABORATORY EXERCISES. 



30. STRUCTURE OF BONES. 



Materials (for each two pupils): A complete rib of sheep, care- 

 fully separated from its attachment to a vertebra; a piece of a rib of 

 beef, an inch long, sawed lengthwise in halves; a leg-bone of sheep, 

 from which meat has been removed; one-half leg-bone like the pre- 

 ceding, sawed lengthwise ; a piece of the shaft of a leg-bone of sheep, 

 sawed cross-wise; dissecting-needle and scalpel. (After completing 

 the study of the structure, lay aside the bones for the next experi- 

 ment.) 



A. Structure of a rib (flat or tabular bone) . 



1. What is the general form of the bone? 



2. Try to bend it. What do you conclude? 



3. Cut off a thin slice of the covering of the 



enlarged end of the rib. Give some 

 characteristics of this cartilage. 



4. Stick the point of the dissecting-needle into 



the surface of the bone where it is free 

 from muscle. Peel off some of the thin 

 membrane of connective tissue. This 

 membrane is per-i-os f -te-um. 



a. What are some of the characteristics 



of periosteum? Try to tear it. 



b. Where is periosteum found on the 



rib? Where is it wanting? 



5. Study the section of the rib, pricking the 



different parts with the dissecting-needle. 



a. In what respects does the outside 



layer of hard bone differ from the 

 spongy bone in the interior? 



b. Describe the color of the marrow. 



What does this color suggest as 



