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Biometric Constants of Etiglish Brain-weights 
(ii) They are, allowing for the differentiation of a general hospital population, 
consonant with what we know of other English anthropometric and craniometric 
material. 
(iii) They show that a general hospital population differs in mean from other 
groups of the general population, but that the difference in variability and 
correlation is not very marked. 
(iv) Important results would be reached if the change in physical characters 
with age were more completely studied ; especially if the human prime for various 
physical measurements were more adequately determined. 
(v) Allowance can be made for the effect of age and stature on brain-weight, 
but neither of these factors is nearly as important for brain-weight prediction as 
the knowledge of diametral product or horizontal circumference. 
(vi) The probable brain-weight of an individual can be determined from 
stature, age, diametral product, and horizontal circumference with a mean error 
of about 50 grs. The mean deviation in brain- weight from the mean of the 
group is about 80 grs. In other words, we improve our prediction in the ratio of 
8 to 5 by taking into account these characters. Nothing better can probably be 
achieved (see Figures 3 to 6) by introducing further external characters, or by 
considering regression as curved instead of plane. 
(vii) Generally Pearl's conclusion that brain-weights for homogeneous material, 
uniformly measured, can be dealt with as satisfactorily as any other anthropometric 
characters is confirmed. We would add that the material ought to be restricted 
so that the highest prime of any character dealt with is the minimum age 
included in the data. 
(viii) The apparent shrinkage of the diameters of the head with age is 
probably peculiar to general hospital material. Its absence in criminal data is 
significant. The subject, however, is at present being directly investigated by one 
of the present writers. 
(ix) There is no sensible relative difference between the brain-weights of 
man and woman, when proper allowance is made for the relative difference in size 
of man and woman. 
