PLAGUE, RATS AND FLEAS. 273 



then told you that I had noticed that on certain days I whs able to get 

 many ileus from the rats sent to the Laboratory, while on other days 

 none were obtained. As many as 53 rats on one day were examined 

 and not a single flea was obtained, while on another day 13 rats yielded 

 22 fleas. In seeking for an explanation for this I noticed that when 

 the rats were brought to the Laboratory in a dark iron cage, fleas were 

 plentifully found on the rats, while when they were brought in an open 

 wire caire no fleas were found on them. I also noticed that if the rats 

 were kept in open cages in a light place, all the fleas that were placed 

 on them disappeared. 



It would be possible thus to greatly enlarge upon this subject ; but 

 already I have occupied you far beyond the usual time devoted to a 

 paper. I had sketched out in my plan of this paper a heading which 

 was to deal with the lessons to be learned from the facts placed before 

 you. I cannot, however, do so to-day ; perhaps some other opportunity 

 may present itself. I will only say that it is obvious that any changes 

 which will free Bombay or India of plague can only be introduced 

 gradually, as the people become more educated and civilised, and learn 

 that rats are the most important factor in the spread of the disease. If 

 we cannot speedily place a distance between ourselves and rats, we 

 can at least protect ourselves from the danger of their propinquity by 

 acquiring immunity to plague by inoculation. This is to my mind the 

 only measure that offers any hope in combating the disease in the near 

 future. 



LIST OF REFERENCES TO LITERATURE. 



cl > I. Samuel VI. 5. 



« Quoted in " The Plague Inspector, " uy Lieut.-Ool. W. G. 



King, p. 157. 



< 3) Appendix XXV, Indian Plague Commission's Report, Vol. II, 



p. 335. 



< 4 > llankin, Atmales d l'Institut Pasteur, 1898. 



< 5) Simond, Annales d l'Institut Pastour, 1898. 



(6 > Report on the Second Outbreak of Plague in Sydney, 1902, p. 2. 



* 7 > Blackmore " Rats & Plague, " Lancet, 11th October 1902. 



^ 8 > Local Government Board Reports, 1901-1902, p. '621. 



< 9 > Local Government Board Reports, 1902-1903. 



^ lu > Annales d l'Institut Pasteur, October 1898. 

 11 



