280 



ANNALS NEW YOHK ACADEMY OF SCIENCES 



"MOMENT OF RESISTANCE AND "DIMINISHING LOAD" 



In every lever, whether of the first, second or third order, the "power" 

 and the "resistance," acting along parallel lines, but in opposite direc- 

 tions, are in equilibrium when the power multiplied by its effective dis- 

 tance from the fulcrum is equal to the resistance multiplied by its effect- 

 ive distance from the fulcrum. The "effective distance" is measured by 

 a line passing through the fulcrum and perpendicular to the line of direc- 

 tion of the force. The product of a force multiplied by its effective 

 distance from the fulcrum is called its "moment." 



m 

 M W 



Fig. 3. — 1. Hindfoot of an extremely cursorial type (Neohipparion) showing at the in- 

 stant of greatest extension of the foot a low moment of power of the calf 

 muscles (M X BB') and a very high moment of resistance (W X B' A') 

 of the pressure of the tibia upon the ankle. 

 II. Hindfoot of an extremely graviportal type (Mastodon) showing at the in- 

 stant of greatest extension of the foot a much higher moment of power of 

 the calf muscles (m X bo') and a relatively lower moment of resistance 

 (w X b' a') of the pressure of the tibia upon the ankle. 



In Pig. 3, I, it would appear natural to assume that the point A, on 

 the ground, is the fulcrum, and that the "resistance" is the pressure of 

 the tibia upon the ankle joint at B', while the "power" is the contractile 

 force of the muscles of the calf, applied at B. Similarly, Eduard 

 Weber 38 described the human foot as a lever of the second order and gave 

 for the relations of the forces and movements of the foot in raising the 



39 Cf. Haycraft, op. cit., p. 251. 



