36 Physiology, 



individuals never, with any amount of practice, work so 

 in unity as the parts of the individual ? 



Let us seek the answer to these questions in the follow- 

 ing lessons. 



Reading. " How to Get Strong and How to Stay So," Blaikie-, 

 " Sound Bodies for Our Boys and Girls," Blaikie. 



Summary. i . In the limbs the muscles are spindle-shaped and have 

 their greatest diameter opposite the central, or narrower, portions of the 

 bones, concealing the fact that the bones are largest at the ends, as is 

 so evident in the skeleton. 



2. The bones serve as levers by which the muscles exert their force. 



3. The bones of the limbs are hollow cylinders combining lightness 

 and strength. 



4. The joints have a smooth motion due to the cartilage and synovia. 



5. Locomotion is brought about by reaction. 



Questions. i . Find other examples of levers in the body. 



2. Find examples of the three kinds of levers, not in the body, which 

 we use often. 



3. Why is it easier to sit with one leg crossed over the other ? 



4. How may the arms be used to illustrate the three kinds of levers ? 



5. Analyze and explain jumping, hopping, etc. 



