THE PREVENTION OF INFECTIOUS DISEASE. 425 



already set forth, may prove also of value 

 through their action upon the disease germs. 

 By improvement of air, water and soil and by 

 control of the food supply the dissemination of 

 disease germs can be restricted and even pre- 

 vented. In this respect bacteriology has often 

 led to a correction of the practice of earlier 

 times and has especially strengthened in es- 

 sential points the simple methods of pro- 

 cedure in vogue in England. 



Disease germs that have somehow found 

 their way to the deeper layers of the soil may 

 probably maintain their vitality for years since 

 they are there withdrawn from competition 

 with saprophytes, and the absence of air to- 

 gether with the presence of moisture favors the 

 continued existence of the germs without per- 

 mitting their multiplication. In this way 

 may be explained the fact that, according to 

 the statement of Donitz, cholera at one time 

 broke out in Japan among soldiers who were 

 reinterring properly the bodies of their fellows 

 who had died from cholera the year previously 

 and had been buried in a common grave. 

 Similarly cholera broke out in a single street 

 in a small city of Nassau when excavations 

 were going on in the street the year after a 

 cholera epidemic. In cases of this kind proper 

 sanitary measures at the outset would have 



