Determining Cranial Volume

[cosmocreator]

Anyone know how it is estimated?

The only way I can think of, is to cut a skull in half, make a mold of this half. Then place the mold in water. The amount of water that is displaced is equal to half the cranial volume.

But how is it done on the living other than with some type of CAT scan?

[Glenlivet]

You can use the Lee-Pearson formulae (see Martin, Lehrbuch, II pp. 643-648). The interracial formulae is based upon maximum length of the skull, maximum breadth, and either basion-bregma height or auricular height. It is considered that the auricular height gives a better result than the basion-bregma height. The auricular ear-hole height is diffucult to measure though.

A rought approximation of auricular height is as follows, one prop the skull in the eye-ear plane and the mark the point on the saggital suture that lies in the same plane as poria (which is the middle point on the lower edge of the upper border of the tympanic bones). After that, a caliper is used to measure the distance across the skull base between the poria and half of it is taken. After that one measure the distance from each porion to the point marked on the saggital suture.

The Pearson formulae is:

Basion-bregma height
Males: Capacity = 524 + 0.000266 x L X B X H
Females Capacity = 812.0 +000.156 X L X B X H
Auricular Height
Males: Capacity = 359.34 + 0.000365 X L X B X H
Females: Capacity = 296.40 + 0.000375 X L X B X H

If the mean index of the left parietal bone exceeds 6 mm., one may obtain a better result by substracting 50 cc. from the total. If the mean thickness fall below 4 mm., it may be well to add 50 cc. to the total.

[cosmocreator]

That wouldn't be very accurate though. The method I suggested for a (dead) skull would be accurate. I think to determine volume accurately, you'd have to use multi-varible calculus and complex curves.