VJ2 Mammals of Eastern Asia 
old-timer replied, ''but I guess he didn't like me too well. He 
named a damned rat after me." 
"What is the difference between a Rat and a Mouse?" is a 
question frequently asked. The trouble with this poser is that it 
refers only to domestic Rats and Mice. In the mind of the 
public, a Rat is a very large Mouse, and a Mouse is a very tiny 
Rat. On the other hand, those who are on more intimate terms 
with these rodents know that the murids (Rats and Mice) that 
make themselves known to man by living in his cellar or in the 
closet where he stores food amount to the merest handful out of 
literally hundreds of distinct kinds of rarely seen wild Rats or 
Mice, whose sizes intergrade completely and which reveal an 
immense variety of small but appreciable differences. So the sup- 
posed distinction of "rat" and "mouse" has no real application 
when the whole family of these rodents is considered, and no 
one can indicate the precise point where one of the many species 
of Mice is considered large enough to be called a Rat, or the 
reverse. The difference between a horse and a pony does not 
present, as one might think, a strictly comparable case, because 
horses and ponies are merely large and small varieties of the 
same horse species. The House Mouse, however, is an animal 
entirely different from any of the several kinds of House Rats. 
Some scientists believe that commensal Rats, namely, those 
that live right in houses with man, have darker underparts than 
wild Rats of the same identical kind. They claim that the two 
can be distinguished visually, and imply that life in man's 
houses and feeding upon his food affects the colors. 
With such large numbers of generally similar species of 
murids needing to be arranged and systematically studied, it can 
readily be understood that their classification presents a difficult 
problem. The system of classification employed in zoology has 
already been explained (pp. 7-9). The Rat family is divided into 
subfamilies, genera, species, and subspecies in just the same way 
as the cattle family or the kangaroo family, but many more 
