The chapter discusses the relationship between dysentery bacilli and potable water, based on experiments conducted by Vincent. Vincent tested the vitality and persistence of dysentery bacilli (Bacillus dysenteriae) in sterilized water and contaminated water. In sterilized distilled water, the bacilli died within a few hours to a day. In sterilized spring water, they survived from 7 to 16 days at 16° to 20°C and from 7 to 10 days at 38°C. In ice-chest conditions (2° to 4°C), they survived up to 38 days. The number of bacilli rapidly decreased in sterilized spring water. In contaminated water, the survival of B. dysenteriae was shorter than that of B. typhosus and B. coli, which could survive longer in impure water. Vincent found that sunlight rapidly killed B. dysenteriae, and their resistance to sunlight was less than that of B. typhosus and B. coli. The presence of saprophytic organisms in water also influenced the survival of B. dysenteriae, with more contaminated water leading to faster disappearance of the bacilli. Vincent concluded that ice can preserve B. dysenteriae for up to two months, suggesting it may be a means of transmission. He also noted that the role of drinking water in the etiology of dysentery is limited by the short persistence and rapid decline of the bacilli in water. The chapter highlights the importance of soil and privy contents in the spread of dysentery and the impact of temperature and light on the survival of B. dysenteriae.The chapter discusses the relationship between dysentery bacilli and potable water, based on experiments conducted by Vincent. Vincent tested the vitality and persistence of dysentery bacilli (Bacillus dysenteriae) in sterilized water and contaminated water. In sterilized distilled water, the bacilli died within a few hours to a day. In sterilized spring water, they survived from 7 to 16 days at 16° to 20°C and from 7 to 10 days at 38°C. In ice-chest conditions (2° to 4°C), they survived up to 38 days. The number of bacilli rapidly decreased in sterilized spring water. In contaminated water, the survival of B. dysenteriae was shorter than that of B. typhosus and B. coli, which could survive longer in impure water. Vincent found that sunlight rapidly killed B. dysenteriae, and their resistance to sunlight was less than that of B. typhosus and B. coli. The presence of saprophytic organisms in water also influenced the survival of B. dysenteriae, with more contaminated water leading to faster disappearance of the bacilli. Vincent concluded that ice can preserve B. dysenteriae for up to two months, suggesting it may be a means of transmission. He also noted that the role of drinking water in the etiology of dysentery is limited by the short persistence and rapid decline of the bacilli in water. The chapter highlights the importance of soil and privy contents in the spread of dysentery and the impact of temperature and light on the survival of B. dysenteriae.