no™ 0F SciENCEal MEASUREMENTS 39 



Brief resume as to head size. — Both the absolute size of the bead, and the head size in relation 

 to stature, are appreciably larger in the academicians than they are even in the educated and 

 cultured old Americans at large ; and this excess holds good even in those of 60 years of age and 

 less. In addition, the general regularity and smoothness of the vault in the members of the 

 Academy, with on the average but moderately developed muscles of mastication, suggest strongly 

 that the skull is thinner and hence more spacious, for all sizes, than it is in even the old American 

 population at large. The excess in the size of the head appears to be limited to its length and 

 breadth, the height remaining unaffected. The increase thus observed can only be attributed 

 to interstitial augmentation in the brain, which in turn is doubtless caused by long-continued 

 greater than ordinary supply of blood to the brain. The excess of blood supply may, it would 

 seem, be either primary, due to favorable endowment as to the circulatory system of the brain; 

 or secondary, induced by long-continued greater demands. In all probability the two agencies 

 in most cases cooperate. 



HEAD SHAPE 



The shape of the head, especially the skull, is also always of interest, though its value has 

 often been ill-understood and still suffers frequently from unwarranted exaggeration. As already 

 partly stated the shape of the skull or head, under normal conditions, has but little to do with 

 the development and nothing whatsoever with the quality of the brain ; it is of hereditary osteo- 

 genetic nature; that is, inherent in the bones themselves and their trophic nervous centers, 

 modifiable more or less by ontogenetic mechanical conditions. It is of value in determining 

 group or racial affinities, but by itself can tell but little in addition. 



Under the influence of progressive civilization with its accompanying weakening of the 

 muscles and structures that serve mastication, there has been noticed what appears to be a 

 general tendency toward broadening and shortening of the skull. There are individual and 

 familial exceptions to this, but the general trend has been as stated. In no known case of a 

 human group has there been found a tendency in the opposite direction. So much in the way 

 of an introduction to this item and its allure. 



The most used, though by no means sufficient, representation of head shape is that by the 

 cephalic index, which is the expression of the percentage of the breadth of the head as compared 

 with its length. Tbe data on this index in the academicians follow: 



167689°— 40- 



