ACADEMY OF SCIENCES] MEASUREMENTS 29 



No. 3 



The Head 



In the scrutiny of any human group, the foremost interest, aside from the face, attaches 

 to the study of the head, respectively the skull, as the outward expression of the form and size 

 of the brain, the most important and distinctive organ of man. The numerous forms the head or 

 skull assumes, however, have also been found of value in group and race classification, which 

 became an added incentive for giving this part intensive attention. Regrettably, as so often 

 happens, some workers in their studies on the head or skull have gone to unnecessary and even 

 impeding minutiae which not only cannot tell more about the substantial problems the part 

 presents but tend to obscure these problems. 



The skull, particularly the head, as Arthur Tompson has long ago demonstrated, may be 

 regarded as comparable to a plastic bag filled with sometliing that can only behave as a near- 

 liquid and that, were other factors absent, would necessarily give the skull the shape of a simple 

 globe or near-globe, as can actually be observed in a large measure at certain embryonic and 

 fetal stages. If the skull, or that part of it which contains the brain, assumes any different shape, 

 the cause of this must lie essentially in factors outside of the brain. The skull may in fact be 

 defined, in its ultimate shape, as the result of a series of mechanical agencies comiected partly 

 with the hereditary endowments of the different cranial constituents, and partly with the action 

 of all such muscular, pressural, and other outside factors that have acted on it from its beginning. 

 How any derangements in the hereditary conditions, or any additions to the mechanical factors, 

 can affect the skull, may be seen in the large number of deformations to which it is subject. A 

 few weeks of incidental or artificial pressure will deform the skull of the newborn infant in directly 

 compensatory way and proportion, and the brain during all the rest of the life of the individual 

 will be incapable of any material restitution or alteration in these changes. And a premature 

 occlusion or other disturbance in any of the cranial sutures will lead to other permanent mis- 

 shapements. If these facts were clearly borne in mind in every study of the head or the cranium 

 they would obviate much unnecessary detail and confusion. 



Another fact of prime import but one often lost sight of, is that every feature of the head, 

 and every group of its correlated features, presents, under a universal biological law, a substan- 

 tial range of normal, that is, nonpathological or incidental, individual variation. This variation 

 reaches invariably over, and in some dimensions and indices considerably over, 10 percent of 

 the average; in other words, over 5 percent on each side of the mean, so that with individual 

 heads or skulls no deviation within this range can without other proof be regarded as significant. 



Another point that may profitably be touched upon in this connection is the choice and 

 methods of head measurements. Two of the main measurements of the vault, namely, those of 

 the greatest length and greatest breadth, are regulated by international anthropometric agree- 

 ments and involve no difficulty. The value of the third essential dimension, that of the height 

 of the head, has not been sufficiently appreciated in the earlier times of the development of 

 anthropometric techniques and, offering difficulties, has been largely neglected until recent years, 

 when independently several somewhat different methods for taking the measurement on the 

 living came into use. The method followed in these studies was that of the writer, developed 

 by him 40 years ago and used by him and those instructed by him ever since, in extensive studies 

 on both the American white and colored populations. It is the method used in the studies on 

 the old Americans at large and on a series of groups of immigrants to this country, which fur- 

 nished the indispensable and nowhere else obtainable material for comparison. The method 

 itself will be detailed later. 



It seemed necessary to state these facts so as to prevent possible unwarranted expectations 

 or misunderstandings. 



