THE HYGIENE OF THE BUBBLE FOUNTAIN 



475 



been found for as long as 90 minutes. A column 7.5 cm. in 

 height has shown the presence of B. prodigiosus for 20 min- 

 utes although commonly no organisms have been found for 

 more than 2 minutes. Even with the column 10 cm. high, B. 

 prodigiosus has always been found in the plates poured one or 

 two minutes after the introduction of the suspension. 



Another type of experiment was tried more nearly approxi- 

 mating the ordinary use of the bubble fountain. The writers 

 washed out their mouths with suspensions of B. prodigiosus and 

 while the lips were still moist drank from a column 2 to 3 cm. in 

 height, exercising due care not to touch the metal portions of 

 the fountain. Samples of water were taken as before and plated. 

 In one instance the organisms were retained for 135 minutes, 

 and the average was 25 minutes. 



The following tables show the results of sample tests taken at 

 random from those made with the experimental fountain: 



TABLE 1 



Column 2 cm. high. Suspension of B. 

 ■prodigiosus introduced by pipette, 

 two twenty-Jour hours cultures 1 cc. 

 salt solution to each culture 



TABLE 2 



Column 2 cm. high. Suspension of B. 



prodigiosus introduced as in table 1 



