THE PEST OF EATS 23 



rat-flea will bite and communicate the disease 

 from rat to rat, and an outbreak of plague 

 among men is usually preceded by an epidemic 

 among the rats. The rat-flea does not bite 

 man; but those which live on human beings 

 will thrive on rats and may return from an in- 

 fected rat to a human host if opportunity offers. 

 The fleas of dogs and cats will temporarily live 

 on the skin of both rodents and human beings, 

 and may thus take a part in the transmission 

 of plague. The fleas usually leave a rat or 

 other animal as soon as it dies, and, with their 

 stomachs full of plague-bacilli, with others 

 clinging to their proboscis and sucking lips, 

 they seek new hosts. The new host, whether 

 rat, or some other animal, or perchance a 

 human being, is soon bitten with these infected 

 mouths, and thus receives the germs of the 

 malady. 



Those who wish to pursue the study of this 

 matter in further detail will find a very full 

 exposition of it, and of the general relations of 

 insects to common diseases, in R. W. Doane's 

 Insects and Disease (New York, Holt, 1910). 



