THE HYGIENE OF THE BUBBLE FOUNTAIN 



477 



TABLE 5 



Column 10 cm. high. Suspension of B. 



prodigiosus introduced as in table 1 



TABLE 6 

 Column 2 cm. high. B. prodigiosus 

 introduced by rinsing m,outh with 

 suspension and then drinking while 

 lips were still moist. 



flushed off at once, whereas others ''dance" for varying periods 

 of time until they finally fall outside the column and disappear 

 in the waste pipe. Doubtless other factors are concerned, such 

 as variation in pressure due to excessive use elsewhere on the 

 same line and subsequent cessation of this unusual consumption 

 of water. Indeed a control series of plates of water samples taken 

 at five minute intervals from a bubble fountain shows wide vari- 

 ation in bacterial count due partly to variation in pressure. 

 When the pressure is suddenly increased the pipes are vigorously 

 flushed and the bacterial count is higher. Keith^ (2) has sug- 

 gested a modified form of fountain which automatically regu- 



2 Keith, S. C, Jr. Amer. Jour, of Public Hygiene, 1910, 20, 163. 



