THE SKELETON OF THE ANTERIOR LIMB. 
radii) is immovably articulated with 
the ulna. It bears an extensive 
articular surface, meeting both the 
trochlea and capitulum of the hum- 
erus, and thus forming a considerable 
portion of the elbow-joint. The body 
‘of the bone is solidly united with the 
ulna by the interosseous ligament 
of the forearm. The distal extremity 
is largely formed by an epiphysis, 
which is well-marked even in older 
animals. It bears a grooved, carpal 
articular surface (facies articularis 
carpea), for articulation with the 
navicular and lunate bones. 
The ulna (Fig. 68) is a somewhat 
S-shaped bone, the shaft of which is 
vertically flattened, so that it pos- 
sesses two main surfaces, respectively 
anterodorsal and posteroventral. The 
former, in conjunction with the 
related surface of the radius, continues 
the area of origin of the extensor 
muscles of the hand from the lateral 
epicondyle of the humerus distad on 
to the forearm, while the latter has a 
similar function with respect to the 
flexor muscles. The proximal portion 
of the bone is laterally compressed. 
It bears a crescentic depression, the 
semilunar notch (incisura 
lunaris), the articulating surface of 
which continues that of the medial 
portion of the head of the radius, and 
is received into the trochlea humeri. 
Behind the elbow-joint the 
forms the large projecting portion 
of the elbow, the olecranon, which is 
astrong process for the insertion of 
the extensor muscles (anconaei) 
semi- 
bone 



Fic. 68. Skeleton of the fore- 
arm and hand from the dorsal 
surface: R, radius; U, ulna; C, 
carpus; M, metacarpus; P, pha- 
langes; I-V, metacarpal bones; c., 
central bone; cp., capitate; c.r., 
head of radius; f.a.c., carpal artic- 
ular surface of radius; h., hamate 
bone; i.s., semilunar notch of the 
ulna; 1., lunate bone; mi., lesser 
multangular; mj., greater multang- 
ular; n., navicular; ol., olecranon; 
p.s., styloid process of the ulna; 
tr., triquetral bone; u., ungual 
phalanges, 
