Hip bone and ischium then become joined, and lastly the pubis and ischium, through the intervention of this Y-shaped portion. At about the age of puberty, ossification takes place in each of the remaining portions, and they join with the rest of the bone between the twentieth and twenty-fifth years. Separate centers are frequently found for the pubic tubercle and the ischial spine, and for the crest and angle of the pubis. Several muscles attach to the hip bone including the internal muscles of the pelvic, abdominal muscles, back muscles, all the gluteal muscles, muscles of the lateral rotator group, hamstring muscles,
Squamous part of the frontal bone are, however, occasionally associated with small air sinuses. Beneath each superciliary arch is a curved and prominent margin, the supraorbital margin, which forms the upper boundary of the base of the orbit, and separates the squamous part from the orbital portion of the bone. The lateral part of this margin is sharp and prominent, affording to the eye, in that situation, considerable protection from injury; the medial part is rounded. At the junction of its medial and intermediate thirds is a notch, sometimes converted into a foramen, the supraorbital notch or foramen, which transmits the supraorbital vessels and nerve. A