The _pelvic girdle_ consists of two large bones of irregular shape, called the _innominate_ bones. They connect behind with the sacrum and in front they connect, through a small pad of cartilage, with each other. On the inside of the girdle is a smooth, basin-shaped support for the contents of the abdomen, but on the outside the bones are rough and irregular and provide many places for the attachment of muscles and ligaments. Each innominate bone has a deep, round socket into which the end of the femur (the long bone of the leg) accurately fits. 5. _The Arm and Hand Groups._—A long bone, the _humerus_, connects the arm with the shoulder and gives form to the upper arm. In the forearm are two bones, the _radius_ and the _ulna_, which connect at one end with the humerus and at the other with the bones of the wrist (Fig. 102). [Fig. 102] Fig. 102—*Bone groups of arm and leg.* A group of eight small, round bones is found in the wrist, known as the _carpal_ bones. These are arranged in two rows and are movable upon one another. Five straight bones, the _metacarpals_, connect with the wrist bones and form the framework for the palm of the hand. Attached to the metacarpals are the bones of the fingers and thumb. These form an interesting group of fourteen bones, called the _phalanges of the fingers_ (Fig. 102). The bones of the hand provide a mechanical device, or machine, for grasping, and the arm serves as a device for moving this grasping machine from place to place. The work of the arm, in this respect, is not unlike that of a revolving crane upon the end of which is a grab-hook. The hand without the arm to move it about would be of little use. 6. _The Leg and Foot Groups._—These correspond in form and arrangement to the bones of the arm and hand. Since, however, the leg and foot are used for purposes different from those of the arm and hand, certain differences in structure are to be found. The _patella_, or kneepan, has no corresponding bone in the arm; and the _carpus_, or ankle, which corresponds to the wrist, contains seven instead of eight bones. The bones of the foot and toes are the same in number as those of the hand and fingers, but they differ greatly in size and form and have less freedom of motion. The _femur_, which gives form to the thigh, is the longest bone of the body. The _tibia_, or shin bone, and the _fibula_, the slender bone by its side, give form to the lower part of the leg (Fig. 102). The legs are mechanical devices (walking machines) for moving the body from place to place. The feet serve both as supports for the body and as levers for pushing the body forward. By their attachment to the legs they may be placed in all necessary positions for supporting and moving the body. The different bone groups are shown in Fig. 97 and named in Table IV.