Sacrum a lateral surface. The base of the sacrum, which is broad and expanded, is directed upward and forward. On either side of the base is a large projection known as an ala of sacrum and these alae (wings) articulate with the sacroiliac joints. The alae support the psoas major muscles and the lumbosacral trunk which connects the lumbar plexus with the sacral plexus. In the articulated pelvis the alae are continuous with the iliac fossa. Each ala is slightly concave from side to side, and convex from the back and gives attachment to a few of the fibers of the
The Singing Bone learns of the younger brother's adventure. They then set out to deliver the body to the king, but on passing a bridge, the older kills the younger and buries his body beneath it. He takes the boar himself to the king and marries the king's daughter as prize. One day a shepherd sees a bone under the bridge and uses it to make a mouthpiece for a horn, which sings of the brother's fate: "Ah! Dear shepherd, you are blowing your horn With one of my bones, which night and morn Lie still unburied, beneath the wave Where I was