Raymond Pearl 
81 
as well as brain-weight. In comparison witii the present series of brain-weighings 
a Series which should record the following facts would be almost ideal. 
1. Brain-weight; by the standard method. 
2. Race. In this the more essential detail given the better. 
3. Country of residence during adult life. 
4. Occupation (as an index of social status). 
5. Immediate cause of death. 
6. Chronic diseases of adult life. 
7. Stature. 
8. Body-weight. 
9. Head length. ^ Measurements all made be- 
10. Head breadth. | fore skull is opened, and 
11. Head height. j with hair removed at points 
12. Maximum horizontal circumference of headj of contact. 
13. Age. 
14. Sex. 
Such a list at first sight appears formidable from the practical standpoint, but 
evidently the things which would give the greatest difficulty are 2 to 6 inclusive. 
The head measurements could be made with little trouble, and a relatively small 
expenditure of time. This list is presented with the hope that any future workers 
who ma}} be about to undertake the great labour involved in obtaining a large 
mass of human brain-weight statistics will at least consider the points raised. 
The few additional facts would take but little more time in the collection, and they 
would greatly enhance the value of the completed series. I would especially call 
attention to the need for larger series of brain-weight statistics than those we now 
have. In order to do really "close" statistical work on the subject it is desirable 
that we have larger arraj's of individuals of given age and stature types in order 
that the regressions may be smoothed and the brain-weights in more absolutely 
homogeneous material may be investigated. 
Finally it should be said that the present paper is, from the biometi'ical stand- 
point, only a " first " study of the problems of brain-weight correlation. Much yet 
remains to be done, and as will have been appai'ent to the reader could be 
done with the present material. One thing especially which might be done is to 
separate the material into a third " old " group, comprising the individuals falling 
in age between 50 and 80, and treat this group separately. I very much doubt, 
however, in view of the apparent substantial linearity of the regression of brain- 
weight on age through the whole of adult life, and considering the statistically 
small number of individuals which in each case would have been available, whether 
the value of the results so obtained would have been in any way commensurate 
with the labour involved. Even a biometrician must stop somewhere. When we 
have much larger collections of .brain-weight statistics to work with an old age 
division of the material will be at least experimentally justified. 
Biometrika iv 
11 
