Biometry of the human occipital bone.

A biometric study of the occipital bone was carried out on 125 dissecting room skulls; it brought out the following points: 1. The occipital squama, despite its dual histological origin, constitutes a stable anatomical structure because its dimensions remain in correlation if the size factor is maintained constant. 2. The parts around the foramen magnum also show 'organic correlations', but these are virtually unrelated to the squama. 3. The pars basilaris is biometrically independent of the squama; it could well be described with, and regarded as an extension of, the body of the sphenoid if it were morphologically separated from the rest of the occipital bone; there is thus good cause to describe in Man a spheno-occipital 'clivus'. 4. The study of the curvatures of the squama shows that fossil Man agrees with present day Man in that when the occipital is rounded, the parietal is not, and the skull is low and elongated. 5. Sexual differences are more easily described than measured. The shape of the occipital condyles has greater value for sex determination than that of the nuchal crests. 6. Attempts were made to estimate cranial capacity from isolated occipital bones, but one had to be content with a fairly large margin of error. Several types of formulae are nevertheless offered to human palaeontologists in the hope that they might satisfy their need to get a rough indication of cranial capacity from occipital material.