BRAINS OF EUROPEAN AND AMERICAN RATS COMPARED 73 
the Physiological Institute directed by Professor v. Exner. 
Through Dr. Przibram, Director of the Biologische Versuchsan- 
stalt, arrangements were made to get Norway rats and ultimately 
Dr. Przibram, beside presenting me with some of his own Albinos, 
kindly allowed his assistant, Dr. Megusar, to make for me the 
collection and first measurements of the animals needed to com- 
plete the Vienna series. My thanks are specially due to Dr. 
Megusar for the precision and care with which this work was 
done. 
In Paris, Professor Lapicque obtained for me-a table in the 
Physiological Laboratory at the Sorbonne, and in every way 
alded my plans. 
Finally, in London, Sir Victor Horsley courteously allowed 
me to work in his own laboratory and through his assistants 
arranged for the supply of animals. 
It may be noted in passing that rats in these several cities are 
most readily obtained through local dog fanciers who usually 
control a supply used for the higher education of their terriers. 
Norway rats were hard to get in Vienna. Possibly the war of 
extermination waged against them about 1898, when public inter- 
est was aroused by a laboratory outbreak of plague, has served to 
check their increase. 
In Paris the rats were easier to obtain, but bore evidence of 
having been caught in rather unsavory surroundings. In London 
they were very numerous. I was offered a thousand in three 
days, and moreover Mus rattus alexandrinus and Mus rattus, 
the old English black rat, were also to be had—both kinds in 
large numbers. 
The general plan of this investigation was the following: To 
collect at each of the three foreign cities about one hundred Nor- 
way rats—and a smaller number of Albinos; to record the body 
weight and body length of each individual, and in a few cases to 
remove and weigh the central nervous system on the spot. In 
the majority of cases however, it was planned to preserve the 
heads only. 
Later the skulls were to be prepared in this laboratory, the 
cranial capacity determined and the data from the several series 
