SIGNIFICANCE OP COLON COUNT IN MILK. 3 



If the colon count were a direct measure of original contamination 

 during milking, it, would be a most valuable aid in determining the 

 purity of a milk supply. Can the colon count, however, be consid- 

 ered a direct measure of such contamination? This is a question 

 which seems to be unsettled. As has been shown there are opinions 

 on both sides of the question. While the test was formerly considered 

 of considerable importance, more recently it has lost some of its sig- 

 nificance because of the recognized ability of organisms of the colon 

 and aerogenes group to grow rapidly in milk when not properly cooled 

 and kept cold. 



A test which gives promise of indicating original contamination, 

 particularly fecal contamination, is worthy of attention, and it has 

 seemed desirable to study this subject under controlled conditions 

 with a view of determining the true value of the colon count in milk. 



Throughout this paper the expressions " colon-aerogenes group" 

 and "colon count" are used. The "colon count" means the number 

 of organisms belonging to the colon-aerogenes group, and the term 

 "colon-aerogenes group" as used includes both the Bacillus coli and 

 B. aerogenes types of organisms. When any differentiation is made 

 between the B. coli and B. aerogenes types it will be indicated in the 

 text. 



DO ORGANISMS OF THE COLON-AEROGENES GROUP INDICATE THE 

 PRESENCE OF MANURE IN FRESH MILK? 



If the organisms of the colon-aerogenes group are to be considered 

 evidence of external contamination it must first be known whether 

 or not they are present in the udders of cows. Both Savage (17) and 

 Race (13) believe that organisms of this group are derived from 

 sources outside the udder. Our results confirm this opinion, for in 

 an examination of four cows no organisms of the colon-aerogenes 

 group were ever found in milk drawn directly from the teats into 

 sterile tubes. While only a few cows were examined, the results 

 obtained, together with those of other investigators, seem to indicate 

 that in general organisms of the colon-aerogenes group are not de- 

 rived from the udder of the cow and therefore represent external 

 contamination. 



Haw market milk contains both the Bacillus coli and B. aerogenes 

 types of organisms, as has been shown by the work of Rogers, Clark, 

 and Evans (14),, who found the colon-aerogenes group in such milk 

 to be made up of nearly equal proportions of B. coli and B. aerogenes 

 types. This being the case, it becomes necessary to know the source 

 or sources of the B. coli and B. aerogenes types before they can be 

 accepted as an indication of manurial contamination. It has been 

 known for a long time that cow manure contains large numbers of 

 organisms of the colon-aerogenes group, and the authors last men 



