8o THE PRINCIPLES OF M VOD VNAMICS. 



and outward across the quadrangle of the fore- 

 arm. 



67. The muscles that span the elbow joint 

 may be divided into three groups : 



(k) The rotators of the fore-arm have already 

 been enumerated. 



(2.) The flexors of the fore -arm are : (i.) The 

 supinator longus, the biceps brachii, and the 

 brachialis anticus. (ii.) The pronator radii teres, 

 and the flexors on the fore-arm, and the long 

 carpo-radial extensor. 



(3.) The extensors of the fore-arm are : (i) 

 The triceps brachii and the supinator brevis. (ii) 

 The extensors on the fore-arm. 



(a.) The flexors on the fore-arm and the ex- 

 tensors on the fore-arm have indirect moving 

 components acting on the radius and ulna. 



(b.) A muscle that spans two joints can make 

 the intermediate bone a fixed bone, and the 

 adjacent bones movable bones. One of the 

 adjacent bones may be the fixed bone, and the 

 other two movable bones. 



68. In the next place, the following proposi- 

 tion can be proved : 



