THE PRINCIPLES OF MYODYNAMICS. 1 7 



components a and b. The velocity of the motion 

 must also be considered, according to the prin- 

 ciples above stated. 



8. The inclined plane involves the principle 

 of the rectangle of forces. For instance, when 

 two bones meet at their articulation at an acute 

 or an obtuse angle, one rests upon the other as 

 a body on an inclined plane. 



9. Let Fez Fig. j, be a movable bone, and o c 

 a fixed bone, c being the joint. The mnscle m has 

 its origin at o, and its insertion at i. The force 

 of the contracting mnscle is resolved into tJie two 

 compone7tts a and b \ a acts in the direction i c and 

 is a displacing component acting on the movable 

 bone. Bid b acts in the direction i P and contaiiis 

 a DISPLACING and a retentive component. Nozv 

 the force b acts at i and reacts at o i7i the di^'ection 

 0 c : The fixed bone rests on the movable bojie as 

 a body rests on an inclined plane : The fixed 

 bone tends to descend on the movable bone — which is 

 i^npossible : Hence the movable bone tends to go 

 upward under the fixed bone with the same force 

 that the fixed bone tends to descend: And this 

 force which is equal b is resolved into the compon- 



