3o8 



CARV. 



[Vol. VII. 



Antero-posterior section 

 through radius and lunar. 



surfaces guide the parts in flexure ; they do not bear the weight 

 of the body. 



Systematic examination of the articular surfaces, bearing in 

 mind the two functions of weight-bearing and flexure, gives the 

 following results : — 



Cubito-carpal Joint. — The complication of surface here is 

 evident from the figures. The proximal faces of scaphoid and 

 cuneiform are nearly plane, while the 

 proximal surface of the lunar in vertical 

 antero-posterior section is a double 

 curve, corresponding to another in the 

 lower end of the radius. With the fool 

 on ground, the radius and ulna are 

 bearing on the anterior portion of all 

 these surfaces. In flexure the radius, by 

 reason of the curvatures, retains a firm 

 bearing on the back part of the lunar, 

 while contact with scaphoid and cuneiform is practically that 

 between a plane and a cylinder. At all times a slight twist 

 seems to be possible here. Motion in this joint is a rolling 

 one, and it is evidently considerable. 



Intcr-carpal Joint. — The position of the axis of movement in 

 this joint has been indicated in the woodcut. However, as the 

 articular surfaces are convex upward, the axis is really beneath 

 those surfaces and within the body of the bones. During 



plantation the scaphoid and lunar 

 are well forward, and the contact 

 between the posterior surfaces of 

 these bones and the magnum is 

 very slight. In flexure the lunar 

 and scaphoid slip back on the mag- 

 num, bringing the posterior sur- 

 faces to bear; the joints open at 

 their anterior face, and movement 

 takes place by sliding between the 

 posterior surfaces. The scaphoid at 

 the same time slips back, down, and medially across the long 

 axis of the trapezoid, while the unciform revolves in place. 

 The last-named bone, in accordance with the general plan of 

 weight-bearing in the foot, lies in an angle between the lunar 



(a) During plantation. 



(J)) During flexure. 



Relation of scaphoid to 

 magnum. 



