UNC1FORME. 



Fig. 38.f 



The UNCIFORME is a triangular-shaped bone, remarkable for a long 

 and curved process, which projects from its palmar aspect. It pre- 

 sents five surfaces ; three articular, and two free. One of the arti- 

 cular surfaces is divided by a slight ridge into two facets ; the other 

 two converge, and meet at a flattened angle.* One of the free sur- 

 faces, the dorsal, is rough and triangular ; the other, palmar, also tri- 

 angular, but somewhat smaller, gives origin to the unciform process. 



If the bone be held perpendicularly, so that the articular surface 

 with two facets look upwards, and the unciform process backwards 

 (towards the holder), the concavity of the unciform process will point 

 to the hand to which the bone belongs. 



Articulations. With five bones ; 

 by the two facets on its base, with 

 the fourth and fifth metacarpal 

 bones ; by the two lateral articu- 

 lating surfaces, with the magnum 

 and cuneiforme ; and by the flat- 

 tened angle of its apex, with the 

 semilunare. 



Attachments. To two muscles, 

 adductor minimi digiti, and flexor 

 brevis minimi digiti ; and by the 

 hook-shaped process to the annular 

 ligament. 



Development. The bones of the 

 carpus are each developed by a 

 single centre ; they are cartilagi- 

 nous at birth. Ossification com- 

 mences towards the end of the first 

 year in the os magnum and unci- 

 forme ; at the end of the third 

 year in the cuneiforme ; during the 

 fifth year in the trapezium and se- 

 milunare ; during the eighth, in 

 the scaphoides ; the ninth, in the 

 trapezoides ; and the twelfth in the 

 pisiforme. The latter bone is the 

 last in the skeleton to ossify ; it 



is, in reality, a sesamoid bone of the tendon of the flexor carpi ul- 

 naris. 



* When the unciforme does not articulate with the semilunare, this angle is 

 sharp. 



t The hand viewed upon its anterior or palmar 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 un- 

 ciforme. 10, 10. The five metacarpal bones. 1 1 , 1 1 . The first row of phalan- 

 ges. 12, 12. The second row. 13, 13. The third row, or ungual phalanges. 

 14. The first phalanx of the thumb. 15. The second and last phalanx of the 

 thumb. 



