THE PRINCIPLES OF MYODYNAMICS. 1 37 



lever P F. And by careful comparative meas- 

 urements and estimates of the lines and the 

 forces they represent, it appears that the head 

 of the femur is pressed into the acetabulum with 

 a force at least twice as great as the weight of 

 the lower limb, when that limb is freely sus- 

 pended as above indicated under the action of 

 the gluteus medius. 



1 34. When the long axis of the gluteus me- 

 dius is more vertical and runs in the direction 

 o' i, then the moving component will be greater 

 and the retentive component will be smaller. 

 Also when the femoral neck meets the femoral 

 shaft more nearly at a right angle, then, too, 

 the moving component will be greater and the 

 retentive component will be smaller. And, fur- 

 thermore, when the pelvis is tilted outward so 

 as to bring the origins of che glutei medius and 

 mJnimus more directly over the trochanter ma- 

 jor, any force acting downward in the long axis 

 of the femur will antagonize the retentive com- 

 ponents of these two muscles, and reduce the 

 -pressure between the femoral head and the 

 acetabulum to a minimum. These dynamic 



