IN HUMAN PHYSIOLOGY. 145 



12. Ought a boot to have a heel-piece ? 



A low and broad heel-piece probably aids in walking : 

 a narrow or high one weakens and enlarges the ankle, 

 produces bunions, corns, etc., by throwing the weight for- 

 ward upon the toes, and makes the gait exceedingly 

 ungraceful. 



13. Why should one always sit and walk erect ? 



Because then all the organs are in their natural 

 position. 



14. Why does a young child creep rather than walk ? 



(See Physiology, page 50.) 



Its bones not yet being fully ossified, nature teaches it 

 not to bear its weight upon them. Besides, it has not yet 

 learned the difficult art of balancing itself. 



56. i. What class of lever is the foot when we lift a 

 weight on the toes ? 



The third class. The ankle-joint is the fulcrum, the 

 weight is at the toes, and the power is in front of the 

 ankle, where the muscle which lifts the toes (the extensor 

 digitorium) is attached to the foot. 



2. Explain the movement of the body backward and for- 

 ward, when resting tipon the thigh-bone as a fulcrum. 



The weight is at the center of gravity of the head and 

 trunk, high above the hip joints, where the fulcrum is 

 situated. The flexor muscles of the thigh are the power, 

 and act close to the fulcrum. The weight is sometimes 

 directly over the fulcrum, and may be on any side of it. 



