BRAINS OF EUROPEAN AND AMERICAN RATS COMPARED 79 
This technique is essentially that which was used by Hatai (07) 
but has been given here in detail because in the determination of 
cranial capacities, concordant results can be obtained only by the 
strictest adherence to a uniform procedure. 
The various measurements made by the foregoing methods have 
been recorded and tabulated in detail and the individual records 
are on file at the Wistar Institute where they are at the service 
of other investigators. In the presentation which follows how- 
ever, we shall use only mean values, grouping the records for 
each series by mean body weights within weight groups differing 
by 50 grams. The smallest weight group includes the individuals 
betsveen 51 to 100 grams in body weight, and the largest those 
between 351 to 400 grams. The higher body weights appearing 
in the Philadelphia Norway series have not been considered be- 
cause there are no European records with which to compare them. 
BODY FORM 
Before taking up the records touching the central nervous sys- 
tem, it is important to know whether the several series to be 
examined are composed of animals having a like body form. The 
most general test for likeness in form is the relation of body length 
to body weight. The data for such a test are contained in tables 
12and13. For our present purpose therefore we select from these 
tables the records giving the mean body weights and mean body 
lengths for each weight group of each series. 
In chart 1 these data for body length both for the Norways and 
Albinos are entered in relation to the standard curves for body 
length based on Philadelphia material (Donaldson ’09 and Don- 
aldson and Hatai, 711). A study of chart 1 shows that the Euro- 
pean series of both forms agree fairly with the standard records 
as represented by the continuous curves in the chart. 
The records for the European Norways run somewhat below 
the standard. This is especially noticeable in the case of the 
Vienna and Paris series. The records for the European Albinos 
agree very closely with the standard curve based on the Phila- 
delphia Albinos. On the whole, the accordance between the 
