CARPUS. 



195 



Fig. 44.* Two bones of the first row, viz., the 



scaphoides and lunare, form an oblong 

 convex surface, which has a transverse 

 position with respect to the arm, and 

 applies to the concave surface at the 

 end of the radius. These surfaces are 

 particularly calculated for flexion and 

 extension, and also for a considerable 

 motion to each side ; and by a suc- 

 cession of these flexures, in different 

 directions, the hand performs a cir- 

 cular motion, although it cannot 

 perform at this joint a rotation, or 

 revolution, on the axis of the car- 

 pus. 



The under surface of the bones has a deep concavity, which 

 is composed by the scaphoides, lunare and cuneiforme, and 

 receives a prominence of the second row. It also presents a 

 convex surface, formed by the scaphoides, which is received 

 by the second row. 



The upper surface of the second row, which is concerned in 

 this articulation, is very irregular ; it has a head formed by the 

 magnum and unciforme, which penetrates deeply into the 

 cavity of the first row. On the outside of this head the tra- 

 pezium and trapezoides form a surface, which receives the 

 projecting part of the scaphoides ; so that the first row receives, 

 and is received by the second, and the two surfaces are well 

 calculated for moving, to a certain extent, in the way of flexion 

 and extension, upon each other. I 



The lower surface of the second row, which is connected to 



* The hand viewed upon its anterior or palmer aspect. 1. The scaphoid bone. 

 2. The semilunare. 3. The cuneiforme. 4. The pisiforme. 5. The trapezium. 

 6. The groove in the trapezium that lodges the tendon of the flexor carpi 

 radialis. 7. The trapezoides. 8. The os magnum. 9. The unciforme. 10, 10. 

 The five metacarpal bones. 11, 11. The first row of phalanges. 12, 12. The 

 second row. 13, 13. The third row, or ungual phalanges. 14. The first phalanx 

 & the thumb. 15. The second and last phalanx of the thumb. 



