PLAGUE, HATS AND PLEAS. ■ 269 



the 2nd April, and died on the 8th April. Three other cases occurred 

 in the same house. " 



Captain Browning Smith remarks : " The above is a case where it 

 seems that infection was brought in the clothes of the man ; rats were 

 infected from this, and the man himself was infected from the rats. " 

 The cases speak for themselves. The explanation I offer is that a man 

 living in an infected village takes fright when he finds cases of plague 

 occurring among others in his own house. The infection of this 

 household was clearly brought about in the way I have described 

 above ; rats died, the remaining ones migrated, the hungry infected fleas 

 they left behind attacked man ; man became infected — some of these 

 fleas having got among the clothes of the fugitive man, he has carried 

 them to the village to which he has fled. The fleas may have in 

 the meantime attacked him and if so he died of the disease shortly 

 after his arrival ; but possibly the fleas may have failed to get through 

 his clothes, the man then remains unaffected. When transferred to 

 the new village in this manner, the floas find themselves in fresh rat- 

 infested premises, and are not long in scenting out their natural host 

 the rat. They infect the rats, the disease spreads among the rats 

 rapidly, they die ; the rest take fright and migrate; man becomes 

 infected. 



But why press this flea theory, you will say, when we know 

 perfectly well that the excreta from infected animals is capable of 

 infecting fresh animals. This is a gratuitous assumption. Have 

 you tried it? I have. Healthy rats can live in the same cage with 

 infected rats without acquiring the disease, if only fleas are 

 excluded. I told you of such experiments when I read a paper 

 before you in March last year. Since then other persons have 

 independently confirmed my observations, particularly Dr. Klein. 9 I have 

 here been able to prove that although susceptible animals do take plague 

 through the alimentary canal if fed on large quantities of grossly conta- 

 minated food, yet they can eat food which has been contaminated by a 

 relatively small quantity of plague without harm. Moreover, what is 

 more important, they are not infected with the insufficiently large 

 quantity of plague which is contained in the various excreta of plague- 

 infected man or animals. I have fed rats on such excreta, and kept 

 them in contact in a small cage with clothing which had been soiled by 

 dying plague patients, and they have not suffered from the disease. 



