THE PRINCIPLES OF MYODYNAMICS. Io5 



The dynamic relations of the muscles that span 

 the ankle-joint and move the foot accord with 

 the facts of observation. The backward dis- 

 placing components preponderate over the for- 

 ward displacing components. 



(b.) The foot is dislocated outward more 

 frequently than inward. The following dynamic 

 relations will explain this fact : The long axis 

 of the leo- at the tibio-fibular arch meets the 

 conjugate axis of the foot at a considerable 

 angle, going down to the supporting surface on 

 which the foot rests, near the inner side of the 

 foot, the conjugate axis of the foot deviating 

 outward from above downward. On account of 

 this outward obliquity of the foot, when the foot 

 forcibly meets a resisting surface, the force of 

 reaction will be resolved so as to afford a con- 

 siderable displacing component acting outward. 

 The deltoid ligament is apt to be ruptured, or 

 the internal malleolus may be broken off, and 

 the fibula may be broken above the ankle-joint. 



1 02. (A.) Fig. 22 represents the tibia, fibula, 

 astragalus, and os calcis, as seen from behind — 

 one-half natural size. The line a j b is in the 



