THE PRINCIPLES OF MYODYNAMICS. 87 



of energy in the biceps necessary to move the 

 weight acciinmlates in the weight. 



(2.) The simple fact is, that the molecular 

 motion of the biceps is correlated into the molar 

 motion of the radius and the weight; and, as 

 molar motion represents energy, there is no 

 loss of muscular force. 



THE HUMERUS AND THE SHOULDER-JOINT. 



79. The humerus may act as a lever of the 

 first, second, or third order : 



(1.) The transverse diameter of the tuberoci- 

 ties of the humerus acts as a lever of the first 

 order when moved by the rotators The in- 

 rotators of the arm may be the power, and the 

 out-rotators may be the weight. 



(2 ) The supraspinatus can act on the humerus 

 so as to make it a lever of the second order, 

 when the weight of the body is put more or less 

 on the head of the humerus, and consequently 

 on the outside of the elbow. 



