OBSERVATIONS ON WILD RATS IN ENGLAND, WITH 
AN ACCOUNT OF THEIR ECTO- AND ENDOPARASITES. 
Reported by ANDREW BALFOUR, C.B., C.M.G., M.D., B.Sc. 
Director-in-Chief, Wellcome Bureau of Scientific Research, London. 
(With Plates XXIII and XXIV, 1 Text-figure and 2 Charts.) 
CONTENTS. 
PAGE 
Introduction .......... 282 
1. Bacteriological examination of rats ..... 285 
2. Determination of parasites in rats ...... 288 
Collection and Technique ....... 289 
Ecto-parasites ......... 290 
Helminths 290 
Intestinal protozoa ........ 292 
Haematozoa ......... 292 
3. Incidence of Leptospira icterohaemorrhagiae and mechanism of its 
transmission ......... 293 
Technique .......... 293 
Culture of Leptospira ........ 295 
Mechanism of transmission ...... 295 
4. General pathology ......... 296 
5. Miscellany.297 
Summary .......... 297 
References .......... 297 
INTRODUCTION. 
It is generally recognised that the measures at present in vogue for the 
reduction of the rat population are far from satisfactory. A great deal can no 
doubt be done in the way of lessening the numbers of these destructive and 
dangerous rodents by poison, bacterial viruses, trapping, the use of natural 
enemies and so forth, but the rat is so prolific that the losses inflicted by these 
means are soon made good. The Rodier system attacks the problem from a , 
somewhat different aspect, inasmuch as it is primarily a method of interference 
with the reproductive life of the rat. Both sexes are trapped, the females 
destroyed and the males liberated. The relative number of males to females 
is thereby altered, with the result that the males wage warfare amongst each 
other, many being killed, while the female also frequently perishes in the 
struggle for possession. 
It would seem that in certain places and under certain conditions the 
Rodier system works well but it appears more adapted for use in limited areas. 
