All traces of the fontanelles have disappeared by the end of the fourth year. The angle of the jaw in infants and young children is obtuse; as dentition proceeds, the body becomes deeper and the angle alters so that towards adult life it approaches a right angle, the ramus is longer and the body has become well developed with a mental foramen midway between upper and lower borders. In the new-born, the mental foramen is low down as the body of the jaw is practically all alveolar. In old people the angle again becomes obtuse and the alveolus disappears as the teeth are shed, and the mental foramen is at the upper border. Table of the Eruption of the Teeth Age--Eruption of teeth. Lower central incisors, 7 months. } Upper “ “ 8 “ } “ lateral incisors, 7-10 “ } Lower “ “ 10-12 “ } Temporary. First molars, 12-14 “ } Canine teeth, 18 “ } Second molars, 22-24 “ } First molars, 6 years. } Middle incisors, 7 “ } Lateral incisors, 8 “ } First bicuspids, 9 “ } Second bicuspids, 10 “ } Permanent. Canines, 11-12 “ } Second molars, 12-13 “ } Wisdom teeth, 18-25 “ } Examine the lower jaw. The ramus forms an obtuse angle in full-grown fœtus, a right angle in adult life, obtuse in old age from loss of teeth. Table showing the Periods at which Points of Ossification appear after Birth Years of Life. Bones in which Centres of Ossification appear. 1. Fourth piece of the body of the sternum; coracoid process of scapula; head of humerus; os magnum (carpus); head of femur; upper end of tibia; external cuneiform (tarsus). 2. Lower end of radius; unciform (carpus); lower end of tibia; lower end of fibula. 3. Great tuberosity of humerus; patella; internal cuneiform (tarsus). 3-4. Upper end of fibula. 4. Great trochanter (femur); middle cuneiform (tarsus). 4-5. Scaphoid (tarsus); lower end of ulna. 5. Lesser tuberosity (humerus); internal condyle (humerus); trapezium and semi-lunar (carpus). 5-6. Upper end of radius. 6. Scaphoid (carpus). 7. Trapezoid (carpus). 10. Upper end of ulna. 12. Pisiform (carpus). 13-14. External condyle (humerus); small trochanter (femur). Periods of Union of Epiphyses with the Shafts of Bones, and of Bones with each other