THE PRINXIPLES OF MYODYNAMICS. 97 



force, tending to put the head of the humerus 

 into the axilla. Such a result takes place from 

 time to time. 



91. The conformation and the muscular rela- 

 tions of the shoulder-joint above and behind are 

 eminently conservative. The conformation and 

 the muscular relations of the shoulder-joint 

 below and partly in front are notably non-con- 

 servative. These conclusions agree with the 

 observations of surgeons in regard to disloca- 

 tions of the humerus. 



THE FOOT AND THE ANKLE-JOINT. 



92. The foot acts as a lever of the second 

 order. 



In the first place, the following points are to 

 be noted : (i.) The ankle-joint is a hinge -joint. 

 The foot has flexion downward and backward, 

 and extensio7i upward and forward. (2.) The 

 lateral motion of the foot (which is principally 

 inward) takes place at the subastragaloid joint. 



