20 



ANIMAL LOCOMOTION^ 



P.AFurW.BF, and the pressure on the fulcrum is both the 

 power and resistance, or P-j-W. 



In the second order of levers (fig. 2), the resistance is be- 

 tween the fulcrum and the power ; and, as before, P : W : : 

 BF : AF, but the pressure of the fulcrum is equal to W—P, 

 or the weight less the power. 



In the third order of lever the power acts between the prop 

 and the resistance (fig. 3), where also P : W : : BF : AF, and the 

 pressure on the fulcrum is P— W, or the power less the weight. 



In the preceding computations the weight of the lever 

 itself is neglected for the sake of simplicity, but it obviously 

 forms a part of the elements under consideration, especially 

 with reference to the arms and legs of animals. 



To include the weight of the lever we have the following 

 equations : P. AFjf AF.JAF = W. BF + BF. J BF ; in the 

 first order, where AF and BF represent the weights of these 

 portions of the lever respectively. Similarly, in the second 

 AF 



order P. AF = W. BF + AF. , and in the third order 



Fig. 2. 



Fig. 3. 



P.AF=AV.BF + BF.— . 



