BRAINS OF EUROPEAN AND AMERICAN RATS COMPARED 93 
From the foregoing data on cranial capacity, we therefore con- 
clude that there is no evidence that any of the European Norway 
series represent a small brained strain which might have been the 
source of the Albino variety. 
The studies on the cranial capacity lead then to the same con- 
clusion as was reached from the direct determinations of the 
weight of the central nervous system and thus the particular 
suggestion which we proposed to test is shown to be without 
support. There remain however some minor aspects of these 
results on cranial capacity which require further consideration. 
TABLE 20 
Showing the percentage values of the differences in brain weight between the Phila- 
delphia Albinos and the Philadelphia Norways of like body weight—using the 
body weights for the European Albinos as given in table 19. Data in column 3 
are calculated from the formula for the albino brain weight based on body weight 
(Donaldson ’08). Datain column 4 are calculated from the formula for the Norway 
brain weight based on body weight (Donaldson and Hatai, ’11) 
| MEAN BRAIN WEIGHT | fA a 
WEIGHT GROUP poe a =  TIGUHIgREANOENGR 
_ Albinos | Norways EUS) RRC 
SOO Rew. et eet: hese 90.0 * 1.640 | 1.827 | (114) * 
NOES SO Mes ae ake hc 130.4 1.740 1.965 12.9 
HIL—PA0 ORS ean lapere se eer 172.4 1.814 2.068 14.0 
PAU SPAS 0) Sa en en 217.1 1.873 2.152 14.9 
Dol UO maria Maire as oe 283 .0 1.941 2.249 | 13 om 
CE Rc VRE. AOR Pi ys Ss I NAR Rec OR CSE cree hee | 4. fe 
* This entry omitted in making the final average so that this BERNE may be 
directly compared with the final average in table 19. 
Before it was recognized that the amount of shrinkage of the 
skulls in the different series was dissimilar, I had expected to find 
the percentage differences between the cranial capacities of the 
European Norways and European Albinos approximately equal 
to the percentage differences between the brain weights of the 
Philadelphia Norways and Philadelphia Albinos. 
The data on brain weight which should be used for such a com- 
parison are given in table 20. 
