208 HUMAN PHYSIOLOGY CHAP. 



prying up a stone by bearing down on one end of the 

 crowbar, it becomes a lever of the first class ; the power 

 is at one end, the load at the other, and the fulcrum 



Fu/cram Power 



i 



First C/ass. 



\ 



Power 



Weight 



3ecor?af 



\ 



_ . Power 



Fu/crum 



Third C/ass. 



FIG. in. Showing the three classes of levers (Zuppke). 



somewhere between the two. If one end of the crow- 

 bar is under the stone and an attempt is made to lift it 

 by pulling up on the other end, it is used as a lever of 

 the second class ; the power is at one end, the fulcrum 



