104 INFECTION AND IMMUNITY 



fever through the agency of contaminated water or 

 milk that certain other modes of transmission were 

 overlooked, or at least underrated. I refer to the 

 transmission by insects, or as dust by currents of air. 

 I have for many years insisted upon the part played 

 by flies as carriers of infectious material from moist 

 masses of excreta from cases of cholera and typhoid 

 fever. There is good reason to believe that the 

 bacillus of bubonic plague may be transmitted in the 

 same way. 



Certain of the lower animals, including rats and 

 mice, are very susceptible to infection, and they play 

 an important part in the propagation of the disease. 

 The germs are found not only in the blood and in 

 pus from suppurating buboes, but also in the dis- 

 charges from the bowels of the sick and of infected 

 rats. This being the case it can readily be seen how 

 important a strict sanitary police is in arresting the 

 spread of an epidemic. 



Dr. James A. Lowson, who has written an excel- 

 lent account of the epidemic in Hong Kong, says : 



" Filth and overcrowding must be recorded as two of the 

 most important factors. The district of Torpingshan supplied 

 these factors in a marked degree at the beginning of the out- 

 break, the majority of the houses being in a most filthy con- 

 dition, as, owing to the uncleanly habits of the people, the 

 amount of what is generally termed rubbish accumulates in a 

 Chinese house in a crowded city to an extent beyond the imagi- 



