THE PRINCIPLES OF MYODYNAMICS. 1 5; 



140. The power of the dynamometer P — or 

 the force of the contracting muscle — is resolved 

 into a moving and a displacing component. The 

 moving component is a retentive component. 

 The displachig component is resisted by the ar- 

 tictdar ligaments, which put the stress of the 

 displacing co7nponent on the joint- surfaces in 

 addition to the stress of the moving component. 

 Hence, the residtant of the moving a7id displacing 

 comp07ients — tJiat is, the force of the co7itracting 

 mitscles — will appear as stress on the joint- 

 surfaces : 



(i.) For, if we could suppose that there is no 

 myodynamic angle, plainly the force of the 

 muscle and the force of the weight would be in 

 the same direction, and their sum would consti- 

 tute the pressure on the joint-surfaces. 



(2.) Make the myodynamic angle acute, and 

 it will be found, by the myometer, that the 

 weight, plus the indicated figures on the dyna- 

 mometer P will equal the indicated figures on 

 the dynamometer F. 



(3.) Make the myodynamic angle right, and 

 it will be found, by the myometer, that the 



