CENTRAL NERVOUS SYSTEM. 721 



the other hand, in those groups possessing the smallest weight not only the size, 

 but more probably also the number, of elements may be reduced below that 

 found in normal persons. These statements are of course to be applied for the 

 present to members of the same race. We know that the mammals with 

 smaller nervous systems than that of man have a far smaller number of nerve- 

 cells composing them. 



It is probable that the wider variations in the number of cells composing the 

 nervous system in man occur among the different races, and that here, as well 

 as among the microcephalies, in which development has been early arrested, 

 differences in the number of cells are most marked. 



Weights of Different Portions. A study of the proportional weights of 

 the several subdivisions of the encephalon according to the sex, stature, and 

 age shows that there is very little difference caused by variations in these con- 

 ditions. This too, so far as it goes, suggests that the absolute weight is depend- 

 ent rather on variations in the size than in the number of the elements, since 

 a harmonious variation in number would be less probable than a harmonious 

 variation in size. 



Social Environment. It is not to be expected that the weight of the 

 brain among the least-favored classes in any community will be the same as 

 that of those who, during the years of growth, are under favorable conditions. 

 All extensive series of observations which we possess relate to the least-favored 

 social classes, and hence it is not improbable that the figures in the foregoing 

 tables, which are based on data obtained mainly at the Marylebone workhouse 

 in London are decidedly below those which would be obtained from the more 

 fortunate classes in the same community. We have a list of brain-weights 

 which contains the records for a number of men of acknowledged eminence, 

 and also for others who attained recognition* as able persons without being 

 exceptionally remarkable. It shows the men in this list to have brains on the 

 average heavier than the usual hospital subject. 1 



Comparison of the brain-weights of eminent men with the weights taken 

 from the classes used to furnish the standard has been made by Manouvrier. 

 The table on page 722 gives the brain-weights occurring among eminent men 

 compared with those found among Parisians of the lower classes, these latter 

 being subdivided according to stature (Manouvrier). The figures express the 

 number of brains in each group of 100 that would fall within the limits of 

 weight opposite to which the entries stand. 



There is a wide range in the weights given in these tables, but at the same 

 time their average is high as compared with the figures of Boyd and other 

 observers. Since even those who are undoubtedly distinguished present 

 brain-weights having a wide range, and since any long series of observations 

 would furnish a fair number of cases of high brain-weight without any 

 suggestion of superior mental ability, it is evident that the high brain-weight 

 and unusual mental capability are by no means necessarily linked a conclu- 

 sion in harmony with common observation. Whether, however, high brain- 



1 Donaldson : The Growth of the Brain, 1895. 

 46 



