474 DOROTHY F. PETTIBONE, F. B. BOGART AND P. F. CLARK 



through four perforations in the top of a cylinder which screws 

 into the center of a hollow metal bulb. Uniform suspensions of 

 B. prodigiosus were made by emulsifying each of two twenty-four 

 hour cultures of the organism in 1 cc. of salt solution. This emul- 

 sion (2 cc.) was then dropped slowly from a pipette into the top 

 of the bubble, care being observed not to touch the metal por- 

 tions of the fountain. Ten cubic centimeter samples of the 

 water were then taken at frequent intervals and plated in tripli- 

 cate on agar, 1 cc. to each plate. After incubation the plates 

 were allowed to stand at room temperature for several days in 

 order to allow the B. prodigiosus colonies to develop their char- 

 acteristic red pigment. Red colonies and total colonies were 

 then counted. In all cases control samples of the water were 

 taken before introducing the organisms. In a total of over 100 

 control plates, only one red pigment producer was found. This 

 formed colonies quite different from B. prodigiosus colonies 

 macroscopically and could never be mistaken for that organism. 

 Between each two experiments the bubble fountain was removed, 

 washed and sterilized. 



The experiments were repeated several times with the column 

 of water at different heights, varying from about 3 to 4 mm. 

 (approximately the height of column prevailing in the women's 

 dormitory at the time of the epidemic) to 10 cm., a column much 

 higher than we have ever observed in use. The results obtained 

 with the column at each level were somewhat variable. So 

 many factors are involved that this is to be expected. The rela- 

 tively small amount of water sampled as compared with the 

 volume flowing during the period of sampling, the variation in 

 the column caused by variation in water pressure, chance con- 

 ditions such as the position of the pipettes both in introducing the 

 organisms and in withdrawing the samples, together with un- 

 known factors, must all play a part in the results observed. 



In brief, when the bubble is extremely low (3 to 4 mm.) some 

 of the introduced organisms are found in repeated experiments 

 for as long as 135 minutes. With a column 2 to 3 cm. high, the 

 average height of the jets in the University, B. prodigiosus or- 

 ganisms are retained frequently for 10 to 20 minutes and have 



