BRAINS OF EUROPEAN AND AMERICAN RATS COMPARED 89 
chart 4. This is calculated from formula (2). The observed 
value for the smallest weight group of the Philadelphia series 
was considered normal (see table 13) but that for the largest 
weight group was taken midway between the value for the Vienna 
series and that observed for the Philadelphia series. The inter- 
mediate determination, at a body weight of 175 grams, was also 
taken midway between the observed Philadelphia record and the 
corresponding record for the London series—which is here low. 
go PANIAL CAPACITY OF 
2. ALBINO RATS 20 
Gic: 
1.9 ye 1.9 
— PHILADELPHIA B ae 
18 RECORDS u : 18 
7 ee 7 
16 16 
15 15 
CHART 4. 
14 14 
/) BODY WEIGHT gms. 
0 100 120 140 160 180 200 220 240 260 280 300 "= 
Chart 4, showing the cranial capacity in cubic centimeters for the four albino 
series. The values for the Philadelphia series are represented by a curve com- 
puted from formula (2). The values for the European series are entered separ- 
ately. O = Paris series, 0 = London series, VY = Vienna series. 
Using these three points, Dr Hatai has kindly devised the follow- 
ing formula: 
y = 1202 log z= 0:00027) 2 = 0.596.428 bens. (2) 
where x is the body weight and y the cranial capacity. 
The curve thus obtained is the one entered in chart 4 and used 
as the standard from which to compute the deviations of the 
records for the European series.. The European albino records 
follow in about the same order as the records for the Norways, 
1.e., the Paris series give the highest mean value, being above the 
standard, while the London and Vienna series are slightly below 
it. 
These relations suggest that the conditions in the three Euro- 
pean stations which act to modify ultimately the cranial capaci- 
