There are twenty-seven bones in the hand. Eight small bones form the wrist, two rows of four bones each.

Counting from the thumb, the bones of the first row are : 1. Scaphoid.

2.   Semilunar.

3.   Cuneiform. 4. Pisiform.

Those of the second row are :

5.   Trapezium.

6.  Trapezoid.

7.   Os magnum,

8.   Unciform.

They are called the carpal bones, and the wrist is called the carpus.

The radio-carpal, or wrist-joint, is formed by the articulation of the first three carpal bones, the scaphoid, semilunar and cuneiform, with the radius. The ulnar does not form part of the joint, a triangular fibro-cartilage being between its lower end and the carpal bones.

A fibrous membrane stretches across the space between the radius and ulna, which braces the bones together, and gives origin to some muscles. All the processes, tubercles and ridges on the bones are for the attachment of muscles. There is an intercarpal or transverse joint, formed by the articulation of the two rows of bones, which supplements the movements

of the radio-carpal joint, and gives greater flexibility to the wrist. It is a gliding joint. Five metacarpal bones form the palm, the bases of which articulate with the second row of bones of the wrist and the heads with the bones of the fingers.

Fig. 35.—Back of Hand (Right).

The metacarpal bone of the thumb is the first, and it articulates with the first bone—the trapezium ; it is articulated in such a way that the thumb has very free movement. It can be moved in every direction. There are fourteen phalanges.

three in each finger and two in the thumb. There are two sesamoid bones at the metacarpo-phalangeal joint of the thumb.