Hand. The bones of the hand may be divided into three groups, viz. carpus, metacarpus, and phalanges. The bones of the carpus are eight in number, and may be divided into two groups containing four each. The first group consists of three bones, the scaphoid, semi-lunar, and cuneiform bones, which articulate with the radius and ulna, forming the wrist joint; and of a small additional bone on the outer side of the wrist called the pisiform bone. The second group consists of the remaining four bones (trapezium, trapezoid, os magnum, itnd unciform), which articulate with the first-named group of carpal bones on the one hand, and with the metacarpal bones on the other. The metacarpal bones are five in number, one for the thumb and one for each of the four digits; and in front of these are the phalanges, numbering fourteen bones in all, two for the thumb and three for each of the fingers. The bones of the hand are united to one another by ligaments. The chief movements of the hand are those of flexion and extension, and pronation and supination - pronation being the position in which the palm of the hand faces downwards, and supination that in which the back of the hand faces downwards with the palm upwards. Beneath the skin of the palm is a resistant fascia which serves to protect the underlying structures, and is known as the palmar fascia.