226 THE RISE AND FALL OF DISEASE 



Europe was in the INIiddle Ages and even in later 

 times devastated by epidemics of the plague or black 

 death, the pestilence wliich wiped out entire populations 

 and which wc have every reason to believe was 

 plague. To-day, the homes of plague have to be 

 sought in the East and in India, to a less extent 

 in Egypt ; and it also bursts out sporadically in those 

 ^ parts of the world having intercourse with the East 



and which are not on tlie alert and are dirty, viz. 

 the Pacific coast of the United States of America, 

 and Australia, the Pacific seaboard of Central and 

 South America, JMauritius, Madagascar, South-AVest 

 Africa, South Africa, then finally the larger seaports 

 in Europe. 



If every now and then a few sporadic cases are 

 found in Liverpool or Glasgow, or London, they are 

 not feared, for they cannot spread, as the conditions 

 for their spreading are not at hand ; formerly they 

 were, but now they have ceased to exist. Of course 

 this is not the case in all parts of the world. Those 

 places which have not come into line with these 

 cities as regards modern hygiene are, as Europe was 

 in the Middle Ages, still vulnerable. If we inquire 

 into the reasons why plague has to so large a degree 

 disappeared from countries where once it was pre- ^ 

 valent, and why to-day it is i)eing confined to narrower I 

 areas, we must first recall what we have already 

 learnt about malaria and yellow fever. We have seen 

 how these diseases have steadily fallen back before 

 improved water supplies and drainage — that is, before 

 the destruction of the agents, the mosquitos, which 



