A method for the comparative study of the human skull, and its application to Homo sapiens and Homo neandertalensis

In a previous study of the Gibraltar skull I was so deeply impressed by the impossibility of discovering any fixed points of reference that I proposed to regard the comparison of cranial outlines, especially of the so-called sagittal sections, as a purely geometrical problem. A recent application of this method thus suggested has revealed some facts which appear to be of sufficient interest to justify a short note as a preliminary to more detailed exposition. Confining our attention for the present to a sagittal section we begin by determining its centre of figure or (what is the same thing) its centre of gravity; a diameter is then obtained by drawing through the centre a line which bisects the angle formed by two radii drawn to the basion and opisthion respectively. A second diameter is drawn at right angles to the first and in this way the section is divided into four quadrants, a frontal, parietal, occipital and facial quadrant. The semi-diameters or radii cut the periphery in the vicinity of the nasion (ν ), bregma (β ), lambda (λ ) and the middle of the occipital foramen, and thus we may term the points of intersection the nasion (N), bregma (B), lambda (L) and foraminal (F) poles. The position of any anatomical point on the periphery may then be indicated by the length of the radius meeting it and its angular distance from the nearest pole, the angle being regarded as positive or negative according as it lies right or left of the pole counting counter-clockwise (fig. 1).