The outward ethnic differentiae of the Bantu are admittedly palpable and patent to everyone, but in the opinion of competent observers there is nothing in the anatomy of the black man to make him a lower beast than the man with the white skin.  It is now seen that there is no apparent relation between complexion or skull shape and intelligence, but while this is so there appears to be a correlation between the size of the brain and the number of cells and fibres of which it is made up, although this correlation is so weak as to be difficult of demonstration.[6]

The capacity of the normal human cranium varies from 1,000 cubic centimetres to 1,800 cubic centimetres, the mean capacity of female crania being 10 per cent. less than the mean of male crania.  On this basis skulls are classified in the text books as being microcephalic when below 1,350 cubic centimetres, such as those of the extinct Tasmanians, Bushmen, Andamanese, Melanesians, Veddahs, and the Hill-men of India; mesocephalic, those from 1,350 to 1,450 cubic centimetres, comprising Negroes, Malays, American Indians, and Polynesians; and megacephalic, above 1,450 cubic centimetres, including Eskimos, Europeans, Mongolians, Burmese and Japanese.  The mean capacity among Europeans is fixed at 1,500 cubic centimetres, and the average weight of the brain at 1,300 grams.

These figures show that the skull capacity of the average European is larger than that of the average Negro, and as it seems plausible that the greater the central nervous system, the higher will be the faculty of the race, and the greater its aptitude for mental achievements, the conclusion that the European is superior in this respect seems on the face of it to be well grounded.  There are, however, certain relevant facts which qualify this inference, and these must be briefly considered.

The anthropologist Manouvrier measured thirty-five skulls of eminent white men and found them to be of an average capacity of 1,665 cubic centimetres as compared to 1,560 cubic centimetres general average derived from 110 ordinary individuals.  On the other hand he found that the cranial capacity of forty-five murderers was 1,580 cubic centimetres, also superior to the general average.  Professor Franz Boas, in discussing this experiment, says that most of the brain weights constituting the general series are obtained in anatomical institutes, and the individuals who find their way there are poorly developed on account of malnutrition and of life under unfavourable circumstances, while the eminent men represent a much better nourished class.  As poor nourishment reduces the weight and size of the whole body, it will also reduce the size and weight of the brain.[7] Dr. Arthur Keith when dealing with the so-called Piltdown skull in his book “The Antiquity of Man” says to the same effect that the size of brain is a very imperfect index of mental ability in that we know that certain elements enter into the formation of the brain which take no direct part in our mental activity, so that a person who has been blessed with a great robust body and strong, massive limbs requires a greater outfit of mere tracts and nerve cells for the purposes of mere animal administration than the smaller person with trunk and limbs of a moderate size.[8]