82 



preliminary decrease in the proportion of Fact, aerogenes, after 24 hours, 

 followed by an increase. An initial incidence of 46 percent Bact. aerogenes 

 rose to 71 percent after 60 days' storage. 



Savage and Wood, in studies on the vitality and viability of Strepto- 

 cocci in water also report a number of interesting observations on the rela- 

 tive incidence of the capsulated and non-capsulated members of the colon 

 group as affected by storage. The following experiment is illustrative of 

 their results. 



To a liter of water which was not sterilized but which was known 

 to be free from the colon group, were added 0.03 c. c. of a 24 hour peptone 

 water culture of non-capsulated and capsulated colon organisms were add- 

 ed. The non-capsulated form (Bact. coli) with an initial count of 4,000 

 per c. c. fell to 25 per c. c., after 31 days, and 3 per c. c. after 33 days' 

 storage and was entirely absent in 50 days. The capsulated form (Bact. 

 aerogenes), on the other hand, was reduced from an initial count of 7,440 

 to 440 in 31 days, to 122 in 50 days, and living organisms were still pres- 

 ent in this water at the end of 14 weeks. In another instance, an initial 

 count of 8,000 non-capsulated organisms (Bact. coli) dropped to less than 

 1 per c. c., whereas the capsulated strain, with an initial count of 4,920, 

 was still present to the extent of 540 per c. c. after 28 days' storage. 



TABLE XLV. ON THE VIABILITY OF COLON GROUP IN UNSTERILE TAP 

 WATER. (After Savage and Wood 1917). 



They also observed that when sewage was stored the Bact. coli strains 

 gradually disappear the ultimate colon survivors being all capsulated strains 

 (Bact. aerogenes). 



Clemesha in India reports that Bact. aerogenes is relatively rare in 

 waters recently polluted but becomes extremely common 5 to 15 days after 

 contamination. He found the Bact. aerogenes more prevalent in rivers and 

 lakes shortly after rains but was later supplanted by another member of 

 the aerogenes section, Bact. cloacae, which was found to be the predom- 

 inating type during dry seasons. 



