738 THE SMALL-MAMMAL PROBLEM 
departments. The Ministry of Agriculture and Fisheries 
formed a special Rats Branch, and in 1919 the emergency 
legislation was embodied, extended, and permanently established 
by the Rats and Mice (Destruction) Act. 
In view of the importance of this matter, and of the expense 
and not infrequent hardship, which the proper administration 
of this Act will entail, it-will perhaps not be thought out of 
place if we discuss some scientific considerations bearing upon 
the rat and mouse problem. We will in the first place deal 
with some points of interest in connection with the destruction 
of rats and mice. Secondly, we will try to show that the 
problem of the rat and mouse is only one branch of a far greater 
problem involving not one or two species merely but all small 
mammals. That greater problem must be solved in the near 
future, for with the growth of civilisation it confronts us in all 
parts of the globe. Even so far as Britain is concerned, the 
Act does not solve the problem, although undoubtedly it is the 
first step in the right direction yet made by the legislature. 
The Act aims at bringing about a great reduction in 
the rat and mouse population, It imposes certain obliga- 
tions upon, and gives certain powers to, County and Local 
Authorities, the general administration of the Act being 
entrusted to the Ministries of Health and Agriculture. 
County Rat Officers have been appointed for the purpose of 
putting the Act into practice; and the owner or occupier of 
rat-infested premises is now compelled to free his premises 
from infestation and to put his house in order. All this is 
good and should lead to a rapid improvement in existing 
conditions ; and from the Rat Officers we may hope to obtain 
a great deal of information. 
The high fecundity of our parasitic rats and mice 
makes it very difficult or impossible to exterminate any one 
of these species by methods of active destruction alone. The 
best information, at present at our disposal, concerning the 
breeding rate of any of the three species inhabiting Britain 
is that furnished for A. xorvegicus by Petrie and Macalister.’ 
1 Petrie and Macalister in “ Reports and Papers on Suspected Cases of Human 
Plague in East Suffolk and on an Epizootic of Plague in Rodents.” Reports to the 
Local Government Board on Public Health and Medical Subjects, N.S., No. 52. 
London Ig1lI, p. 58. 

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