742 THE SMALL-MAMMAL PROBLEM 
Britain. But such success would not bring with it the real 
fruits of victory; the small-mammal problem would still remain, 
demanding urgent solution from the inhabitants of this island. 
The problem in question has arisen in this, as in all other 
countries, as one of the many far-reaching consequences of 
human interference with the working of the “Balance of 
Nature.” Small mammals, like humanity, feel the pinch of 
cold and hunger, or the pain of heat and thirst ; accordingly 
they welcome shelter from the weather, food and drink in 
plenty, and security from their foes. Wherever man in the 
presence of a wild mammalian fauna, contrives a shelter for 
himself, his goods, or his domestic animals, there will always 
be a greater or less number of species quick, if not prevented, 
to enter into an uninvited partnership with him, sharing his 
joys and, it may be, increasing his sorrows. Among mammals, 
no doubt, murine rodents show the quickest appreciation of 
the benefits conferred by unintentional human benefaction ; 
and they are generally the first wild mammals to become 
commensal with man. But the power to force an undesired 
alliance upon careless humanity is not restricted to the Muride 
among rodents, nor to the rodents among mammals; it is 
shown in various degrees by such different Orders as the 
Chiroptera, Insectivora, and Carnivora. Individual species 
belonging to these other Orders like Pachyura gigantea, the 
Indian Musk Shrew, may become thoroughly parasitic, and 
acquire greatly extended distributions in consequence. 
Among Muridz, at the present time, three species alone 
claim so much attention because of their parasitic habits, that 
there is danger of our overlooking the claims of their rivals 
in such a connection. Two of the three, the House Mouse 
and R. rattus, had the good fortune to live originally in the 
cradle of civilization. Possessing habits which permitted a 
close association with humanity, they entered the earliest houses, 
and with civilized man they have spread over the greater part 
of the globe. The third species, A. norvegzcus, is a native of 
a more remote and desolate region; widely different in habits 
from either House Mouse or A. vatéus, and habitually shunning 
the presence of man, it had to wait long for an opportunity 
of invading Western Europe. Once introduced, it made rapid 
