THE PRINCIPLES OF MYODYNAMICS. 5 9 



entire force of the weight would be retentive 

 without the direct co-operation of the articular 

 ligaments, for instance, when a weight is lifted 

 nearly directly upward by the hand, having the 

 long axis of the fore -arm and hand in a perpen- 

 dicular position, the hand being above the fore- 

 arm. 



(E.) When the displacing component is gi^eater 

 than the resistance of the articular ligaments, these 

 ligaments 7mcst give zuay, ajid the movable bone 

 luill be dislocated. 



THE HAND AND THE WRIST-JOINT. 



42. The hand can act as a lever of the first, 

 second, or third order. 



(i.) When the hand is extended and sustains 

 a weight, it acts as a lever of the first order. 



(2.) When the heads of the metacarpal bones 

 rest on a solid surface, the hand acts as a lever 

 of the second order. 



(3.) When the hand is flexed and lifts a 

 weight, it acts as a lever of the third order. 



