METACARPUS. 



83 



Fig. 32 * 



the insertion of tendons and ligaments. The base presents three 

 articular surfaces, one at each side, for the adjoining metacarpal 

 bones; and one at the extremity for the 

 carpus. 



The metacarpal bone of the thumb is 

 one-third shorter than the rest, flattened 

 and broad on its dorsal aspect, and convex 

 on its palmar side; the articular surface 

 of the head is not so round as that of the 

 other metacarpal bones ; and the base has 

 a single concavo-convex surface, to arti- 

 culate with the similar surface of the tra- 



pezium. 



The metacarpal bones of the different 

 fingers may be distinguished by certain 

 obvious characters. The base of the 

 metacarpal bone of the index finger is the 

 largest of the four, and presents four arti- 

 cular surfaces. That of the middle finger 

 may be distinguished by a rounded pro- 

 jecting process upon the radial side of its 

 base, and two small circular facets upon 



its ulnar lateral surface. The base of the metacarpal bone of the 

 ring-finger is small and square, and has two small circular facets to 

 correspond with those of the middle metacarpal. The metacarpal 

 bone of the little finger has only one lateral articular surface. 



Devdopement. By two centres ; one for the shaft, and one for the 

 digital extremity. 



Articulations. The first with the trapezium ; second, with the 

 trapezium, trapezoides, and os magnum, and with the middle meta- 

 carpal bone ; third, or middle, with the os magnum, and adjoining 

 metacarpal bones; fourth, with the os magnum and unciforme, and 

 with the adjoining metacarpal bones ; and fifth, with the unciforme, 

 and with the metacarpal bone of the ring-finger. 



The figures resulting from the number of articulations which each 

 metacarpal bone possesses, taken from the radial to the ulnar side, 

 are 13121. 



Attachment of Muscles. To the metacarpal bone of the thumb, 

 three the flexor ossis metacarpi, extensor ossis metacarpi and first 

 dorsal iriterosseous ; of the index finger, five the extensor carpi 

 radialis longior, flexor carpi radialis, first and second dorsal interos- 

 seous, and first palmar interosseous ; of the middle finger, four 

 the extensor carpi radialis brevior, adductor pollicis, and second 



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

 2. The sernilunare. 3. The cuneiforme. 4. The pisifbrme. 5. The trapezium. 

 C. 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 meta- 

 carpal bones. 11, 11. The first row of phalanges. 12, 12. The second row. 13, 13. 

 The third row, or ungual phalange?. 14. The first phalanx of the thumb. 15. The 

 second and last phalanx of the thumb. 



