DISSECTING MANUAL. 



half oval, for the trapezoid; and the lower, circular, for the 

 second metacarpal. [205] 



Trapezoid. The palmar surface is much smaller than the 

 dorsal. The superior surface has a small facet for the scaphoid, 

 and the inferior a saddle-shaped one for the second metacarpal. 

 The outer surface has a facet for the trapezium ; and the inner 

 a deeply curved facet for the os magnum. [206] 



Os Magnum. The palmar and dorsal surfaces are rough. 

 The superior part forms a rounded head which has convex 

 facets, separated by a ridge, for the scaphoid and semilunar. 

 The inferior surface is widest behind and divided by two 

 antero-posterior ridges into three facets, for the second, third, 

 and fourth metacarpals. The outer surface has a facet for the 

 trapezoid; and the inner a facet, which may be subdivided, 

 for the unciform. [207] 



Unciform. The palmar surface is triangular and, at its 

 lower and inner part, presents a hook-like process ; the dorsal 

 surface is triangular. The superior and internal surfaces form 

 a long facet for the cuneiform. The outer surface has a facet, 

 sometimes two, for the os magnum ; the inferior has two facets, 

 separated by a ridge, for the fourth and fifth metacarpals. At 

 the junction of the superior and external surfaces is a narrow 

 facet for the semilunar. [207] 



Metacarpal Bones. There are five, lying side by side; 

 each has a shaft and two extremities. The shafts are slightly 

 curved ventrally; on the dorsal surface two divergent lines 

 run from the base to tubercles placed on each side of the head ; 

 on the palmar surface is a sharp longitudinal ridge; the sides 

 are grooved. The bases (carpal extremities) are wedge-shaped. 

 The heads (phalangeal ends) are rounded and have a pit on 

 each side ; behind each pit is a tubercle. Each head has a pha- . 

 langeal articular surface which is convex, widest anteriorly, 

 and extends farthest on the palmar aspect, where it is notched, 

 its edges forming tubercles. [209] 



The first (thumb) is the shortest and stoutest; the head is 



[148] 



