THORACIC LIMBS 603 



The palmar surface appears as a downward and backward con- 

 tinuation of the proximal surface. Its upper border is curved and 

 rounded ; it forms part of the proximal facet for the ulna. The radial 

 border is nearly straight and parallel with the ulnar border ; botli 

 borders pass obliquely distally and to the ulnar side. The distal 



FIG. 463. 

 Dorsal Side. 



With Unciform. 



Radial Side. HT" ifi Ulnar Side. 



Ligament. 

 Palmar Side. 



LEFT CUNEIFORM, DISTAL SURFACE. 



border is straight. An articular facet occupies the entire surface, 

 except near the proximal and ulnar borders. The facet is concave 

 from the proximal to the distal margin, and articulates with the facet 

 on the dorsal surface of the base of the pisiform. 



Nomenclature. The word cuneiform is composed of cuneus, a 

 wedge, and forma, likeness. A similar idea is expressed in the 

 widely used synonym os triquetrum, the triangular bone. These 

 designations are translated into German by das Pyramidenbein and 

 das Dreieckigebein. The French use le pyramidale. In comparative 

 anatomy the cuneiform is known as the ulnare. 



Determination. If the proximal surface be held upward and 

 the dorsal surface toward the student, the produced palmo-ulnar angle 

 will point to the side to which the bone belongs. 



Articulation. The cuneiform articulates with the ulna, the unci- 

 form, the pisiform, and the scapho-lunar. 



Ossification. The cuneiform develops from one centre of ossifi- 

 cation. 



THE PISIFORM. 



General Description. With the exception of the scapho-lunar, 

 the Pisiform is the largest bone in the carpus. It may be recognized by 

 its oblong form and its swollen, hooked end. It is irregular in shape, 

 and is nearly twice as long as wide. When in its place in the carpus, 

 the long diameter is directed in a dorso-palmar direction. It may be 

 described as composed of three parts, a base, a shaft, and a head. 



The base is the end which bears the articular facets. It is oblong ; 



