NO. 1521. MEASUREMENTS OF CRANIAL FOSS.E—HRDLICKA. 187 



development of the frontal cavities, therefore, lags behind the devel- 

 opment of the re.st of the skull in the same direction throughout 

 growth. This harmonizes well with the relatively small frontal fosste 

 in many of the largest adult crania. A remarkable diminution in the 

 relative length of the anterior fosste takes place during fetal growth 

 itself. Thus, in the six smallest fetuses and the six largest children," 

 the mean lengths of the fossse were toward the greatest external length 

 of the skull, respectively as 32.9 (28.6-35.0) and 30.1 (28.0-33.1) to 

 100. Individual variation is quite pronounced at all stages of life. 



The differences, in man and lower mammals, between the length of 

 the anterior fossre as related to the greatest external length of the 

 skull are much like those between human adults and 3'oung. In all 

 the species of animals examined, the anthropoid apes included, the 

 relative length of the frontal cavities is greater than that in human 

 adults; in a few instances it is even greater than in the human young. 

 If the anterior lobes of the brain correspond in dimensions to the ante- 

 rior fossfe, as we believe, the facts shown by the figures relating to 

 the young, and especially to the other mammals than man, mean a 

 striking change in our notions concerning the relative size of those 

 parts of the cerebrum in the beings involved. There are differences 

 between the various species of anthropoid apes and monkeys, but from 

 the small number of specimens it is impossible to conclude how far 

 these differences are characteristic of definite groups. 



As to sexes, the females, both among the whites and negroes, show 

 on the whole, relatively longer anterior fossae than the males. This 

 difference is not large and agrees with the smaller size of the female 

 skull. The female sex appears in this, as in so man}" other features, 

 slightly nearer the infantile conditions. 



The racial differences in the frontal cavities are of a peculiar nature. 

 In whites and negroes the relative proportions of the anterior fossa?, 

 as contrasted with the length of the skull, are practically alike, but in 

 the Indian they are decidedly smaller. The latter condition is not due 

 to a large development of the Indian skulls ; in fact these are smaller 

 than either those of the whites or those of the negroes of the same 

 sex. 



There are certain differences in the relative length of the anterior 

 fossffi between dolichocephalic and brachycephalic crania, the pro- 

 portion being in all the groups slightly higher in average in the 

 latter than in the former. No clear reason for this has been arrived 

 at. The series overlap to a considerable extent through individual 

 irregularities. 



The familiar greatest antero-posterior (glabello-occipital) diameter 

 has proved very serviceable for contrasting the dimensions of the 



« For sizes see detailed tables at the end of the paper. Only one of the children 

 reached as high as about the sixth year of age. All the others were much younger. 



