THE PRINCIPLES OF MYODYNAMICS. 67 



wrist-joint; Fig. 19 is a front view of the 

 wrist-joint: — By a simple inspection of the 

 figures it can be seen how the retentive compon- 

 ents of the muscles that span the wrist-joint pre- 

 ponderate over the displacing components of 

 these muscles. 



50. The retentive pressure of the muscles 07t 

 the fore-arm is expended on the base of the 

 radius. And sometimes in old age and after 

 contusions and sprains the base of the radius is 

 shortened and otherwise deformed by interstitial 

 absorption. A condition of this kind will more 

 or less resemble the results of a fracture of the 

 base of the radius. 



THE RADIUS AND THE RADIO-ULN AR-JOINT. 



5 1. The base of the radius turns about the 

 head of the ulna as a wheel turns about its axle, 

 while the head of the radius turns on its own 

 axis in a concavity of the base of the ulna. The 

 radius turns inward and outward. 



(i.) The inward turn of the radius is called 

 in-rotation. 



