THE METACARPUS. 267 



with the trapezoid by a small facet at its anterior inferior angle, behind which is 

 a rough depression for the attachment of an interosseous ligament. Above this 

 is a deep and rough groove, w,hich forms part of the neck and serves for the 

 attachment of ligaments, bounded superiorly by a smooth, convex surface, for 

 articulation with the scaphoid. The internal surface articulates with the uncifonn 

 by a smooth, concave, oblong facet which occupies its posterior and superior 

 parts, and is rough in front, for the attachment of an interosseous ligament. 



Hold the bone with the broader, non-articular surface toward you, and the 

 head upward. The small, articular facet at the anterior inferior angle of the 

 external surface will point to the side to which the bone belongs. 



Articulations. With seven bones : the scaphoid and semilunar above ; the 

 second, third, and fourth metacarpal below; the trapezoid on the radial side; and 

 the unciform on the ulnar side. 



Attachment of Muscles. Part of the Adductor obliquus pollicis. 



The Unciform (uncus, a hook ; forma, likeness) may be readily distinguished 

 by its wedge-shaped form and the hook-like process that projects from its palmar 

 surface. It is situated at the inner and lower angle of the carpus, with its base 

 downward, resting on the two inner metacarpal bones, and its apex directed 

 upward and outward. The superior surface, the apex of the wedge, is narrow, 

 convex, smooth, and articulates with the semilunar. The inferior surface articu- 

 lates with the fourth and fifth metacarpal bones, the concave surface for each 

 being separated by a ridge which runs from before backward. The posterior or 

 dorsal surface is triangular and rough, for ligamentous attachment. The anterior 

 or palmar surface presents, at its lower and inner side, a curved, hook-like pro- 

 cess of bone, the unciform process, directed from the palmar surface forward and 

 outward. It gives attachment by its apex to the annular ligament ; by its inner 

 surface to the Flexor brevis minimi digiti and the Flexor ossis metacarpi minimi 

 digiti : and is grooved on its outer side, for the passage of the Flexor tendons 

 into the palm of the hand. This is one of the four eminences on the front of the 

 carpus to which the anterior annular ligament is attached, the others being the 

 pisiform internally, the oblique ridge of the trapezium and the tuberosity of the 

 scaphoid externally. The internal surface articulates with the cuneiform by an 

 oblong facet cut obliquely from above, downward and inward. The external sur- 

 face articulates with the os magnum by its upper and posterior part, the remaining 

 portion being rough, for the attachment of ligaments. 



Hold the bone with the hooked process away from you, and the articular sur- 

 face, divided into two parts, for the metacarpal bones, downward. The concavity 

 of the process will be on the side to which the bone belongs. 



Articulations. With five bones : the semilunar above, the fourth and fifth 

 metacarpal below, the cuneiform internally, the os magnum externally. 



Attachment of Muscles. To three : the Flexor brevis minimi digiti, the Flexor 



a metacarpi minimi digiti, the Flexor carpi ulnaris ; and to the anterior annular 

 ligament. 



The Metacarpus. 



The Metacarpal Bones are five in number: they are long, cylindrical bones, 

 presenting for examination a shaft and two extremities. 



Common Characters of the Metacarpal Bones. 



The Shaft is prismoid in form and curved longitudinally, so as to be convex in 

 the longitudinal direction behind, concave in front. It presents three surfaces: 

 two lateral and one posterior. The lateral surfaces are concave, for the attach- 

 ment of the Interossei muscles, and separated from one another by a prominent 

 line. The posterior or dorsal surface presents in its distal half a smooth, 

 triangular, flattened area which is covered, in the recent state, by the tendons of 

 the Extensor muscles. This triangular surface is bounded by two lines, which 

 commence in small tubercles situated on the dorsal aspect of either side of the 



