Nomenclature Relating to Cranial Volume. Anomalies.—(In regard to the method of directly measuring or calculating the cranial capacity, and of taking and estimating the measurements of the skull, see the section on Technique.)
Limits.—The cranial capacity, according to Deniker, has normally such a wide range of oscillation that the minimum is fully doubled by the maximum, the limits being respectively 1,100 and 2,200 cubic centimetres—these figures, however, including men of genius. Furthermore, the mean average capacity oscillates between limits that change according to race—not only because the cerebral volume may of itself constitute an ethnic characteristic (superior and inferior races) with which the form of the forehead is usually associated, but also because the cranial volume bears a certain relation to the stature, which is another factor that varies with the race.
Deniker gives the following mean averages of oscillations:
| Europeans | from 1,500 to 1,600 cu. cm. |
| Negroes | from 1,400 to 1,500 cu. cm. |
| Australians, Bushmen | from 1,250 to 1,350 cu. cm. |
The average difference of cranial capacity is 150 cubic centimetres less in woman than in man.
The following nomenclature for oscillations in cranial capacity was established by Topinard, based upon the figures and methods of Broca:
| Macrocephalic crania | from 1,950 cu. cm. upward |
| Large crania | from 1,950 to 1,650 cu. cm. |
| Medium or ordinary crania | from 1,650 to 1,450 cu. cm. |
| Small crania | from 1,450 to 1,150 cu. cm. |
| Microcephalic crania | from 1,150 cu. cm. downward |
To-day, however, the terms macrocephalic and microcephalic have come to be reserved for pathological cases. Virchow has introduced the term nanocephalic to designate normal crania of very small dimensions; while Sergi has adopted a binomial nomenclature, calling them eumetopic microcephalics, which signifies possessed of a fine forehead: since, as we have seen, it is precisely the shape of the forehead which determines normality. And in place of macrocephalic, we have for very large normal crania the new term megalocephalic.
Pathological terminology includes the following nomenclature: macrocephaly, sub-macrocephaly, submicrocephaly, microcephaly.
Microcephaly may fall as low as 800 cubic centimetres; macrocephaly may rise as high as 3,000 cubic centimetres, and at these extremes the volume alone is sufficient to denote the anomaly. But in many cases the volume may fall within the limits of normality; in such cases it is the pathological form and an examination of the patient which lead to the use of the term submicrocephalic in preference to that of nanocephalic, etc.