Hip bone male), and one or more for the Y-shaped piece at the bottom of the acetabulum. The centers appear in the following order: in the lower part of the ilium, immediately above the greater sciatic notch, about the eighth or ninth week of fetal life; in the superior ramus of the ischium, about the third month; in the superior ramus of the pubis, between the fourth and fifth months. At birth, the three primary centers are quite separate, the crest, the bottom of the acetabulum, the ischial tuberosity, and the inferior rami of the ischium and pubis being still cartilaginous. By
Mastoid part of the temporal bone the innermost of the mastoid cells by a very thin lamina of bone, and even this may be partly deficient. The "superior border" of the mastoid part is broad and serrated, for articulation with the mastoid angle of the parietal. The "posterior border", also serrated, articulates with the inferior border of the occipital between the lateral angle and jugular process. Anteriorly the mastoid portion is fused with the descending process of the squama above; below it enters into the formation of the ear canal and the tympanic cavity. A section of the mastoid process shows it to be hollowed out