50 BACTERIOLOGY 



the laboratory, where it is soaked out with water and 

 added to the culture. 



Prevention of Infection. A vaccine has been prepared 

 from dead cultures of the bacillus which raises the 

 opsonic index for this germ, and gives so high a degree of 

 immunity that it is coming into universal use. 



The best means of combating the spread of the in- 

 fection is absolute sterilization of all excreta from ty- 

 phoid patients by thoroughly mixing with formaldehyd 

 and allowing to stand for several hours, stirring in the 

 meantime. Pure water- and milk-supply or steriliza- 

 tion of same. Extermination of flies and vaccination. 



