Brachycephaly

BRACHYCEPHALY (from Greek brachys- short and kephale- head), or short-headedness, represents a form of human head in which the length-width index, i.e., the index expressing width as a percentage of length, is 80.0-81.9; if this index equals 85.0-89.9, it is called hyperbrachycephaly, with an index of more than 90.0- ultrabrachycephaly. According to V. Vorob'yev's data, the greatest transverse diameter of the skull in a modern Great Russian is 152.9 mm, the greatest longitudinal diameter- 185.5 mm (in the skeleton, the greatest transverse diameter- 141 mm, the greatest longitudinal- 176 mm); the length-width index for a living Great Russian is thus 100×152.9/185.5, or 81, for the skeleton it is 100×141/176, or 80; the modern Great Russian is thus a moderate brachycephal, or mesocephal.

The short brachycephalic skull (according to Huxley).

Hyperbrachycephaly occurs in certain tribes as a racial trait, as well as in the disease known as "mongolism" or "mongoloid idiocy"; ultrabrachycephaly is an anomaly and is also observed in patients with hydrocephalus, when the length-width index equals (according to Weber) 100.4, etc. The inheritance of skull shape apparently follows Mendelian laws.