THE PRINCIPLES OF MYODYNAMICS. 47 



dynamic angle will give the most stable relations 

 to a joint. 



30. In myodynamics, when we have any order 

 of bony lever, the force of the weight may be 

 resolved into rectangular components. 



(i.) One component of the weight acts at 

 right angles to the long axis of the movable 

 bone : as this component resists the moving 

 component of the contracting muscle, it may be 

 called the Resisting component ; and as it aids in 

 holding the movable bone against the fixed bone, 

 it may also be called the Retentive component. 

 See a d. Fig. 1 5. 



(2.) The other component of the weight acts 

 in the direction of the long axis of the movable 

 bone : as this component tends to displace the 

 movable bone from the fixed bone, it may be 

 called the Displacing component. See a e, Fig. 1 5. 



31. The two lines which represent the com- 

 ponents of the weight are the base and perpen- 

 dicular of a right-angled triangle — that may be 

 called the dyiiamic triangle. One angle of this 

 triangle is important, and may be called the 

 dynamic angle. 



