CRANIAL MEASUREMENTS AT DIFFERENT AGES (According to BONNIFAY)
-------------------------------------------------------------------------- | Absolute figures | Amount of Increase |--------------------------+-------------------------- Age from -- to -- |Circum-| Antero- | Trans- |Circum-| Antero- | Trans- |ference|posterior| verse |ference|posterior| verse | | diameter|diameter| | diameter|diameter --------------------+-------+---------+--------+-------+---------+-------- Birth to 15 days | 343.9 | 116.3 | 93.4 | -- | -- | -- 15 days to 2 months| 368.7 | 126.3 | 99.1 | 24.8 | 10.0 | 5.7 3 months to 4 months| 388.8 | 132.7 | 106.0 | 20.1 | 6.4 | 6.9 6 months to 1 year | 429.8 | 145.4 | 118.2 | 41.0 | 12.7 | 12.2 1 year to 2 years| 459.7 | 154.3 | 129.3 | 29.9 | 8.9 | 11.1 2 years to 3 years| 473.5 | 161.9 | 133.3 | 13.8 | 7.6 | 4.0 3 years to 4 years| 487.4 | 166.2 | 136.3 | 13.9 | 4.3 | 3.0 4 years to 5 years| 495.7 | 169.9 | 138.3 | 8.3 | 3.7 | 2.0 5 years to 6 years| 497.8 | 171.9 | 140.4 | 2.1 | 2.0 | 2.1 6 years to 7 years| 504.4 | 172.8 | 141.1 | 6.6 | 0.9 | 0.7 7 years to 8 years| 511.6 | 175.2 | 143.7 | 7.2 | 2.4 | 2.6 8 years to 9 years| 514.1 | 176.1 | 144.3 | 2.5 | 0.9 | 0.6 9 years to 10 years| 514.7 | 176.4 | 144.2 | 0.6 | 0.3 | 0.9 10 years to 11 years| 519.8 | 177.1 | 146.6 | 5.1 | 0.7 | 2.3 11 years to 12 years| 521.1 | 177.5 | 145.7 | 1.3 | 0.4 | 0.1 12 years to 13 years| 529.7 | 180.1 | 147.8 | 8.6 | 2.6 | 1.2 13 years to 14 years| 533.1 | 178.1 | 148.5 | 3.4 | -- | 0.7 14 years to 17 years| 548.8 | 182.4 | 152.2 | 15.7 | 2.3 | 3.7 22 years to 27 years| 549.1 | 186.6 | 153.2 | 0.3 | 4.2 | 1.0 --------------------------------------------------------------------------
Among the linear measurements of the cranium, the one which serves to give the most exact index of volume is the _maximum_ _circumference_.
This index, nevertheless, is not a perfect one, in the same sense that the _stature_, for instance, is a perfect index in respect to the body, because in the case of the cranium another element enters in: the form. The cranial circumference of an extremely brachycephalic cranium (almost circular) may contain a larger surface (and consequently include a larger volume), than a maximum circumference of the same identical measure, which belongs to an extremely dolichocephalic cranium (approaching the shape of an elongated ellipse). This may be easily understood if we imagine a loop of thread laid out in the form of a circle: if we pull it from two opposite sides, the enclosed area diminishes until it finally disappears as the two halves of the thread close together, while the length of the thread itself remains unaltered.