CHAPTER VII. 



THE PREVENTION OF INFECTIOUS DISEASE BY 

 COMBATING THE CAUSE OF THE DISEASE. 



WHEN the devastating disease of cholera first 

 invaded Europe early in the present century 

 it caused great mortality. This destruction of 

 life led the authorities first in England and 

 later in France and Germany, to make accurate 

 record of the morbidity and mortality statistics 

 of infectious diseases, both independently and 

 in their relations to other diseases. The re- 

 form of medical statistics begun in England 

 at this time afforded science its first basis for 

 the comparison of the data of disease. 



Epidemiological observations upon cholera 

 made it probable that cholera is not strictly a 

 contagious disease but that it sustains rela- 

 tions with the outside world, especially with 

 the water and the soil. From this fact im- 

 partial observers deduced the probability that 

 the frightful havoc wrought by cholera might 

 be due to the unhygienic surroundings of city 

 dwellings which at that time were thoroughly 



bad, and they declared that all human sur- 



398 



