One hundred twenty adult skeletons, equally divided among white and Negro skeletons of both sexes were ashed. The weight of the ash in terms of per cent of the dry, fat-free weight of the bones was determined for the total skeleton and for twenty subdivisions of each skeleton (mandible, cranium, humeri, radii, ulnae, femora, tibiae, fibulae, clavicles, scapulae, hand bones, patellae, foot bones, hip bones, ribs of both sides; four segments of the vertebral column, and sternum). The resultant determinations of percentage ash weight were analyzed statistically to determine possible effects of age, sex, race, and type of bone (that is, ratio of compact to cancellous substance).

It was found that:

1. The percentage ash weight of neither the total skeleton nor any of its twenty subdivisions was affected by age in any sex-race group;

2. The individual percentage ash weights of each bone series did not vary symmetrically around the mean but had an excessive scatter of low values with the scatter increasing as the means decreased;

3. The twenty subdivisions had approximately the same rank order of percentage ash weight among the thirty skeletons of each sex-race group;

4. The ratio of inorganic to organic substance within the bones was constant except for random variation in the cranium, humeri, fibulae, radii, ulnae, femora, tibiae, patellae, and foot bones; this ratio showed an increase with increasing organic weight in the mandible series and a decrease with increasing organic weight in all other Series;

5. The mean percentage ash weight of all subdivisions except mandible, eranium, humeri and ulnae, and possibly the total skeleton, was significantly higher in males than in females;

6. The mean percentage ash weight of eight of the twenty bone series (clavicles, scapulae, hand bones, ribs, thoracic vertebrae, lumbar vertebrae, sacrum, and sternum) was significantly higher in Negro than in white skeletons;

7. The order of the skeletal subdivisions arranged according to decreasing means of percentage ash weight and according to decreasing ratios (estimated) of compact to cancellous substance was very nearly the same in each sex-race group;

8. In all sex-race groups the means percentage ash weight of the mandible was significantly higher than that of any other subdivision of the skeleton; the mean of the femora series was the lowest of the long-limb bones and was significantly lower than the means of the ulnae, radii, and fibulae; the mean percentage ash weights of the hip bones, ribs, and cervical vertebrae were higher than those of time other vertebral segments; and the mean of the sternum (except in the Negro male group) was lower than that of any other subdivision of the skeleton.