Anatomy. — ''Comparison of the Brain Weight in Function of the 

 Body Weight, betioeen the Two Sexes.'' By Prof. Eug. Dubois. 

 (Communicated by Prof. H. Zwaahdemakkk). 



(Communicated in ttie meeting of November 30, 1918) 



The general relation of tlie brain weight in function of the body 

 weight, between honionenric species of Vertebrates could be accurately 

 determined, because between iheni there often exist important differ- 

 ences in size. Tlius it is known that their brain weight is i)i'oportional 

 to the power 0.5B of their body weight, to P^-^^ (more accurately 

 po555..y 



Between individuals of the same species and of the same sex, 

 however, the brain weight of each is on an average proportional 

 to a powei' of the body weight that has only half that value, but 

 with the available data it could not yet be ascertained whether this 

 is P^'^'^, P^"^^ or P^"^^. The differences in the size of the body within 

 a species are generall}' small, and when they become more consider- 

 able, as is the case with the Dog, we have to deal with such 

 dissimilar material, that the relation in question can only be deter- 

 mined in approximation. For the human species we have, indeed, 

 the advantage of having at our disposal a great number of deter- 

 minations of weight, but here the brain weight has mostly been 

 somewhat modified by the illness preceding death ; in general it has 

 soniewhat diminished, but not to the same degree for all individuals. 

 We may, indeed, make use of an indiiect method of determining 

 the brain weight, but it is clear that there are also objections to be 

 alleged to this. There are as yet too few data available about normal 

 individuals that have died a sudden death. 



On the strength of the relations that appear to be valid between 

 the cellular dimensions aiul volumes in the nervous system, I have 

 become more and more inclined to consider /^o'^ (more accuiately 

 po277..) as the correct interindividnal factor, and to look upon my 

 earlier attempts to interpret ^^22 as superfluous. ') 



With regard to the determination of the intersexual exponent of 

 relation the difficulties are, indeed, somewhat less, because it is 



1) These Proceedings. Vol. XVI (Meeting of December 27, 1913), p. 664—665. 



