3 



Physiology. 



locating a bullet or other solid body, which probing often 

 fails to discover. 



Levers. The main facts to be learned about a lever are 

 that it is a rigid bar ; the point about which the lever turns 

 is called the fulcrum ; the place where the power is ap- 

 plied is called the power ; and the part to be moved is 

 called the weight. In the body, the fulcrum is some joint, 

 the power is the place where the muscle is attached, and 

 the weight is the part to be moved. 



Kinds of Levers. There are three kinds of levers. In 

 the first class the fulcrum is between the power and the 

 weight, as in prying over a block with a crowbar. In 

 the second class the weight is between the power and 

 the fulcrum, as in a wheelbarrow. In the third class the 



(I) Tapping on Floor. 



(2) Rising on Toe. 



(3) Lifting Weight. 



Fig. 19. Three Kinds of Levers as shown by the Foot. 

 P Power. W Weight. F Fulcrum. 



power is between the fulcrum and the weight, as in rais- 

 ing the forearm (see upper part of Fig. 19). We may 

 find many examples of levers in the body if we look for 

 them. 



Kinds of Levers shown by the Foot. The different 



