STRUCTURE OF BONES. 59 



to the presence of blood? Is the 

 marrow hard or soft? Dig out a 

 bit of it and rub it on a piece of 

 paper. Hold the paper to the 

 light. Of what nutrient is mar- 

 row largely composed? 

 B. Structure of a soup-bone (long bone). 



1. What is the general form of the bone ? How 



does it differ from a rib? How do the 

 two heads at the end of the bone differ 

 from the shaft ? Can you suggest the 

 use of the heads? 



2. What kind of tissue covers the end of each 



head? Suggest a reason for this. 



3. Where is periosteum found and where is it 



absent? 



4. In the longitudinal section of the long bone 



distinguish periosteum, cartilage, hard 

 bone, spongy bone, and marrow. State 

 the region or regions of the bone in 

 which each is found. 



5. Compare the cross-section of the shaft of a 



long bone with the cross-section of a rib. 

 In what respects do the two resemble 

 each other? How do they differ? 

 C. Summary. 



1. Name all the kinds of tissue found in 



bones. 



2. Suggest, as far as you can, the use of each. 



3. Can you give any reasons to explain why 



bones are not solid throughout? (Com- 

 pare with the frame of a bicycle.) 



