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 *times called, is not only the main connecting structure and support of the body, but it forms a channel through which passes the spinal cord.

Fig. 32 shows a vertebra, or one of the bones that compose the column. The three projecting points or processes are for the attachment of ligaments and muscles. The main body of each vertebra is for supporting the weight transmitted by the column above. Just behind this thick body is a half ring (Fig. 32), which with the half rings on the other vertebrae form the channel for the spinal cord. Between the vertebrae are thick pads of gristle, or cartilage, which act as cushions to prevent jars, and by compression allow bending of the spinal column in all directions.

The Chest (see Fig. 75).—The twelve pairs of ribs are attached to the spinal column behind, and extend around toward the front of the body, somewhat like hoops. The first seven pairs, called true ribs, are attached directly to the flat breastbone, or sternum. Each of the next three pairs, called false ribs, is attached to the pair above it. The last two pairs, called floating ribs, are free in front.

The Shoulder Girdle.—The collar bones (Fig. 28) can be traced from the shoulders until they nearly meet on the breastbone at the top of the chest. The collar bone is shaped like the italic letter f; it helps to form the shoulder joint and holds the shoulder blade out from the chest that the motions of the arm may be free.

The flat, triangular shoulder blade (Fig. 75) can be felt by reaching with the right hand over the left shoulder. It spreads over the ribs like a fan. Its edges can be made out, especially if the shoulder is moved while it is being