Kaymond Pearl 
15 
quite different numerical appreciations of the relation existing between brain- 
weight and other characters. The very interesting question of variation in 
brain-weight has been scientifically investigated only by Pearson*, so far as is 
known to the writer. 
The reason which led me to undertake the present piece of work was primarily 
a desire to apply adequate statistical methods to a biometrical problem of peculiar 
intrinsic interest, and for which fairly large collections of reliable data were 
available. It was desired to determine as a part of a general plan of work 
outlined as exactly as possible from the data at hand, what were the actual 
conditions of variation and correlation in brain-weight. It was hoped that by 
such work some light might be thrown on the question of the evolution of man's 
brain. The work was originally planned to include the analysis of only one large 
collection of brain-weight data (see below p. 16) but when the constants for this 
material had been determined certain of the results were seen to be rather peculiar. 
Not being satisfied that these indicated the true state of affairs, but thinking that 
they might be caused by some hidden anomalies of the raw material, it was 
decided to extend the work to other data in order to test the first results. 
The specific problems to which attention has been directed in this work are : 
1. The amount of variation in the weight of adult male and female brains. 
2. The relation of brain-weight to age in the adult. 
3. The relation of brain-weight to stature and body-weight in the adult. 
4. The relation of brain-weight to skull characters. 
5. The nature of the regression of brain-weight on those other characters. 
6. The effect of natural selection on brain-weight. 
7. The value of brain-weight statistics from the anthropological standpoint. 
At this point I wish to acknowledge my indebtedness and express my thanks 
to the officials of the Carnegie Institution for a grant through which I obtained 
a large Brunsviga arithmometer and other necessary apparatus for statistical 
work. This aid enabled me to extend this work far beyond what would have 
been possible had I been restricted to " long-hand " methods of computation. The 
amount of arithmetical calculation necessary in any extensive biometrical in- 
vestigation is so great that it may almost be said that such work cannot profitably 
be undertaken on any large scale unless one has at command the various mechanical 
aids which reduce to a minimum the time necessary to carry out the computations. 
To my wife I am especially indebted for much aid in the computing, and for the 
diagrams which accompany the paper. To Prof H. H. Donaldson I am indebted for 
the loan of some unique and valuable manuscript records of brain-weighings, as 
well as for numerous helpful suggestions regarding the work as a whole. 
* Pearson, K.: " Variation in Man and Woman," The Chances of Death, Vol. i. pp. 319—32.3. 
