On the basis of the skeletons in 103 Japanese, 100 American Whites and 97 American Blacks, the usefulness of the base-wing index for sexing the sacrum was ascertained by means of the size and shape distances, generalized distances and discriminant functions of the widths of base and lateral part (wing) of the sacrum, in addition to the distribution of the index, between the male and female series. In relation to sex differences of the sacrum, the shape component was more important than the size

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... for these measurements, at least. With the discriminant functions of these dimensions, the probability of sexing the sacrum was 75.32% in Japanese, 80.88% in American Whites and 82.70% in American Blacks. In the distribution of the base-wing index, the overlap samples between the mare and * were 26.2%, 22.0% and 16.5% in each population, respectively.