g6 THE PRINCIPLES OF MYODYNAMICS. 



In this case the acromion will be the fulcrum. 

 Let the force applied to the distal end of the 

 humerus equal lOO pounds. Then, 



2 : lo = loo : 5oo. 

 Hence, so far, the strain on the capsule will 

 equal 5oo pounds. 



(2.) Again, let the power-arm of the lever be 

 ten inches longr — the distance from the elbow- 

 joint to the insertion of the adductors of the 

 arm. Let the weight-arm of the lever be two 

 inches lone — the distance from the inner and 

 lower portion of the capsule to the insertion of 

 the adductors of the arm. In this case the in- 

 sertion of the adductors of the arm will be the 

 fulcrum. But the force, as supposed, applied to 

 the distal end of the humerus, equals 100 

 pounds. Then, again, 



2 : 10 = 100 : 5oo. 

 Hence, also, so far the strain on the capsule will 

 equal 5oo pounds. 



(3.) Therefore, under the circumstances, the 

 capsule of the shoulder-joint receives a strain 

 equal to 1000 pounds. And it may happen that 

 the greater part of this strain acts as a displacing 



