418 MILK AND MILK PRODUCTS 
exist between the groups of bacteria in milk. In an earlier paper (1910), 
these same authors found that pasteurized milk soured about the same as 
a clean, raw milk. Weigmann et al. (1916) found that, in milk which 
had been heated from 60° C. to 63° C. for thirty minutes, lactic acid 
bacteria were present in a much larger proportion to remaining organ- 
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Fig. 70.—The Hypothetical Relation of Bacteria in Raw and Pasteurized Milk 
(After Ayers and Johnson, 1913.) 
isms than in raw mulk. ‘lhe same was also found in milk which had 
been heated for ten to twenty minutes. Souring, however, was much 
delayed over that in raw milk, which the authors attribute to attenuation 
of the lactic acid organisms. With regard to the resistance of Bacillus 
colon to heat, Ayers and Johnson (1915) state that this organism would 
