426 MILK 



B. coli may increase slightly." In fresh milk the same authors 

 found that B. coh far exceeds B. aerogenes in nimibers. 



Bacillus aerogenes must come from a different soiurce. Rogers, 

 Clark, and Evans studied 166 cultures of the coli-aerogenes group 

 obtained from grain, of which 151 were of the B. aerogenes type. 

 Hunter isolated bacteria of this group from silage, alfalfa, and 

 kafir corn, and classified 79 per cent, as B. aerogenes. Johnson 

 and Levine found "aerogenes-cloacse" organisms abundant in soil. 



It is clear from these findings that the "presumptive Bacillus 

 coli test" when applied to milk does not shed the desired fight on 

 conditions. 



Ayers and Clemmens made coimts of the cofi-aerogenes group 

 in milk obtained under conditions ranging in variety from those 

 so cleanly as to equal methods practised in certified milk dairies 

 to those involving conditions of filthiness beneath the meanest 

 dairy. They found fresh milk did not contain more than 2000 

 cofi-aerogenes bacteria per cubic centimeter, with but one excep- 

 tion, and naturally concluded that when a larger munber than 

 2000 per cubic centimeter is present, this is due to growth rather 

 than to initial pollution. Unfortunately, there is no method 

 known by which the descendants can be distinguished from those 

 present in freshly drawn milk. 



By carefully efiminating one factor after another, the same 

 authors determined that bacteria of the cofi-aerogenes group in 

 milk are chiefly derived from neglected utensils. 



Prescott and also Barthel have stated that Bacifius cofi grows 

 slowly at 10° C. Race foimd no growth at 7.2° C, and Ayers 

 and Clemmens observed that there is some indication of a slight 

 growth at 10° C. But as the temperature increases multiplication 

 becomes more rapid. This is shown clearly in the following table: 



GROWTH OF ORGANISMS OF COLI-AEROGENES GROUP AT 10° AND 70° C. 



Colon count. 



Sample No, Total count. 



Fresh. 



1 225,000 



2 1,140,000 



3 270,000 



4 680,000 



5 1,080,000 



6 490,000 



7 850,000 



8 840,000 



9 1,4,50,000 



10 2,400,000 



11 1,950,000 



12 260,000 



13 610,000 



14 340,000 



15 6,30,000 



16 179,000 



17 366,000 



18 304,000 



19 460,000 



20 620,000 



