863 



and of European man 65 kilograms, i.e. 257o more. This ratio comes 

 nearer that of the average relative muscle weights, computed from 

 the data of Theile. 



Hence it may safely be assumed that for the human species, the 

 male body has higher relative weight of the muscles than the female 

 body in the same geometrical ratio as the former has already more 

 weight than the latter. In other words: Between Woman mid Afan 

 the absolute weight of the muscles varies in rate of the square of 

 the body weight. 



This now accounts for the fact that between Woman and Man 

 the brain weight, in function of the body weight, increases propor- 

 tionally with the square of the increase of the brain weight, in 

 function of the body weight, between the two sexes of most other 

 species, namely, proportionally to /^o.56 between Woman and Man, 

 and proportionally to 7^o.28 between the two sexes of most animal 

 species. 



When the exponent of relation of the brain weight between Woman 

 and Man is reailj' not calculated with i-espect to the average body 

 weight, but with respect to the absolute average muscle weight, it 

 is found to be equal to the exponent of relation of the brain weight 

 in function of the body weight, bet\veen individuals of identical 

 species, viz. about 0.28, instead of 0.56. 



There are only few direct data about the ratio of the muscle 

 weights between individuals of one sex of identical species, between 

 the two sexes and between different homoneuric species at our 

 disposal. From Wet.ckek's and Theile's determinations of the muscle 

 weights for the human species it is already clear that these weights, 

 between individuals of identical sex, vary proportionally to the 

 body weight. 



We find the same proportionality in other species of Vertebrates, 

 Of two almost adult dachshunds from the same litter, examined by 

 Fai-ck M, the somewhat older and heavier female had slightly higher 

 relative muscle weight (which rapidly increases with the age in both 

 sexes) than the male. Though the full-grown male of the albino rat 

 (Mus uorvegicus Erxl.) weighs on an average about 300 grams as 

 against the female about 200 grams, they are equally muscular, 

 judging from Jackson and Lowrey's determinations') on not yet 

 full-grown animals. Comparing six males of 150 days, with an 



') C. Ph. Falck, Beitrage zur Kenntniss der Wachsthumsgeschichte des Thier- 

 körpers. Archiv fur patliologische Anatomie und Physiologie (Virchow), Band VII. 

 Berlin 1854, d. 37 - 75. 



») H. H. Donaldson, The Rat. Philadelphia 1915, p. 76. 



56* 



