CIRCUMFERENCE OF THE HEADS OF
| Boys of the age of | Rich | Sons of small tradesmen and clerks | Poor |
|---|---|---|---|
| 11 years | 534.9 | 529.7 | 524.8 |
| 12 years | 537.1 | 530.3 | 524.9 |
| 13 years | 537.8 | 532.4 | 528.6 |
| 14 years | 545.4 | 533.3 | 528.4 |
In short, there is a gradation of cranial volume corresponding to the economic status in society. This is a condition easy to understand: we simply find repeated in this particular the same thing that we have already seen happen to the body as a whole; the organism in its entirety and consequently each separate part of it—if it is to develop in accordance with its special biological potentiality and so attain the limits of finality set for it—must receive nourishment. It is only natural that children who, during their period of growth, are deprived of sufficient and suitable nutrition should remain inferior in development to those who had the advantage of an abundance of the proper kind of food. The influence of the economic factor is indisputable. Consequently, reverting once more to the studies above cited, may we not conclude that the man of letters, the physician, the person of distinction have a greater development of head than the manual labourer, the hospital attendant, the illiterate, simply because it was their good fortune to obtain better nutriment, through belonging to the wealthy social classes?
The Influence of Exercise upon Cerebral Development.—The second interesting question is in reference to the influence which exercise may have upon the development of the brain. As early as 1861 Broca investigated this question in a classic work: De l'influence de l'éducation sur le volume et la forme de la tête ("The influence of education on the volume and form of the head"), in which he arrived at the following conclusion: that a suitable exercise (intellectual culture, education, hygiene) does have an influence on the development of the brain, in the same way as with any other organ, as, for example, the striped muscles, which gain in volume and strength and beauty of form through gymnastic exercise. "Consequently," exclaims Broca enthusiastically, "education not only has the power of rendering mankind better; it has also the marvellous power of rendering man superior to himself, of enlarging his brain and perfecting his form!"
"Popular education means the betterment of the race."
Accordingly we might say, relying on the above-mentioned studies, that the man of letters, the physician, the person of distinction have a more highly developed head than the manual workman, the hospital attendant and the illiterate, because they exercised their brain to a greater extent, and not because they were more intelligent. This, however, is a question which differs profoundly from that which we were previously considering, nutrition, because in this case exercise, in addition to developing the organ, gives its own actual and personal contribution to the intelligence.
Therefore, we are able to be creators of intelligence and of brain tissue, which in turn becomes the creative force of our civilisation. A system of instruction which, in place of over-straining the brain, should aid it to develop and perfect itself, stimulating it to a sort of auto-creation, would truly be, as Broca says, "capable of rendering man superior to himself." This is what is being sought by scientific pedagogy, which has already laid the foundation of "cerebral hygiene."
We are still very far to-day from realising this highest human ambition! We do not yet know the basic laws of the economy of forces that would lead to a stimulation of the human activities to the point of creation; on the contrary, we are still at a primitive period, in which many of the environing conditions interfere, to the point of preventing the human germ to attain its natural biological finality. In short, we know how to obtain artificially an arrest of development; but we have not yet learned the art of aiding and enriching nature!
The Influence of the Biological Factor upon Cerebral Development.—What conclusion ought we to reach from what has been said up to this point? Upon what does the cerebral volume depend, in all its individual variations, resting on the common biological bases of race, normality and sex? Is individual variation due solely to causes of environment, such as nutrition and exercise? And does it follow that it is not dependent upon biological potentialities more or less pronounced in separate individuals—in short, upon different degrees of intelligence?
In the presence of such a multiplicity of questions we must proceed, not to a selection but to a sum. Every biological phenomenon is the result of a number of factors. The development of the brain depends in precisely the same way as the development of the whole body or of a single muscle, upon the combined influence of biological factors determining the individual variability, and of factors of environment, principal among which are nutrition and exercise. A suitable diet aids growth, and so also does a rational exercise; but underlying all the rest, as a potential cause, is the biological factor which mysteriously assigns a certain predestination to each individual. The environment may combat, alter, and impede what nature "had written upon the fertilised ovum;" but we cannot forget that this scheme, pre-established by the natural order of life, is the principal factor among them all, the one which determines the "character of the individual."