THE PREVENTION OF INFECTIOUS DISEASE. 399 



roundings must be made sanitary and whole- 

 some. Under the pressure of events, which gave 

 to cholera the titleof " the police force of nature," 

 not only a complete and thorough organization 

 of the English public health service was effect- 

 ed, but those sanitary reforms in sewerage 

 and water-supply that were then thought to be 

 necessary, were introduced upon a larger scale 

 and the carrying out of such measures was 

 often made compulsory. The result justi- 

 fied the endeavors, and when cholera broke 

 out anew its violence was greatly diminished 

 and it was altogether suppressed in those locali- 

 ties where sanitary measures of this sort had 

 been adopted. The favorable effect of these re- 

 forms was shown not merely in the case of in- 

 fectious diseases of the character of cholera and 

 typhoid fever. We soon learned to regard 

 those infectious diseases which furnished the 

 larger part of all cases of sickness and death as 

 " preventable " diseases. Simon, Parr, Parkes, 

 Pettenkofer, and Stamm were the men who 

 were foremost in furthering this work. But 

 in spite of the great improvement, all diseases 

 were not prevented. The influence of sanitary 

 measures made itself felt chiefly in respect to 

 those infectious diseases which, from their 

 method of dissemination, required us to assume 

 their connection with the outside world, while 



