Cephalic index

The cephalic index is the ratio of the maximum breadth of the head to its maximum length (i.e., in the horizontal plane, or front to back), sometimes multiplied by 100 for convenience. It was defined by Swedish professor of anatomy Anders Retzius (1796-1860) and first used in physical anthropology to classify ancient human remains found in Europe. It has been generally discredited since a study Franz Boas made at the turn of the 19th/20th century; however, Boas's study has recently been itself heavily criticised (v. Sparks & Jantz, 2002, at Proceedings of the National Academy of the Sciences, USA).

In adults, the index is no longer used except for describing individuals' appearances, and has no correlation with behavior. It is, however, still sometimes used for estimating the age of fetuses for legal and obstetrical reasons, in which case the differences in skull shapes between different populations are still of interest.

Cephalic indices are grouped as

< 75% : dolichocephalic, or 'long-headed'
75%-80% : mesocephalic, or 'medium-headed' (sometimes mesaticephalic)
> 80% : brachycephalic, or 'short-headed'

The alternative terms mesocranial and brachycranial are also used.

Technically the measured factors are defined as the maximum width of the bones that surround the head, above the supramastoid crest (behind the cheekbones), and the maximum length from the most easily noticed part of the glabella (between the eyebrows) to the most easily noticed point on the back part of the head.

The terminology is also applied to animals, such as dogs and cats. Brachycephalic (snub-nosed) dogs and cats are very sensitive to high temperatures.

List of brachycephalic (snub-nosed) dogs:

List of brachycephalic (snub-nosed) cats:

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