UNITED STATES DEPARTMENT OF AGRICULTURE 
ft BULLETIN No. 739 !■» 
\&Z flnntrihntinn from the Rureau of Animal Industrv «?klk>2<il^^ 
Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 
^V#*^&L 
Washington, D. C. 
PROFESSIONAL PAPER 
December 30, 1918 
THE SIGNIFICANCE OF THE COLON COUNT IN RAW MILK. 
By S. Henry Ayers and Paul W. Clemmer, Bacteriologists, Dairy Division. 
CONTENTS. 
Page. 
Present status of the question 1 
Do organisms of the colon-aerogenes group in- 
dicate the presence of manure in fresh milk? 3 
Can milk be produced commercially without 
contamination by organisms of the colon- 
aerogenes group? 9 
How many organisms of the colon-aerogenes 
group can be introduced into milk during 
milking? 12 
Why are high colon counts often found in raw 
milk? 19 
Are both the B. coli and B. aerogenes types 
present in milk; and if so, is their relative 
proportion of any value? 27 
Has the colon count any significance in raw 
milk? 31 
Significance in fresh milk 31 
Significance in milk that has been held. . . 31 
Summary 32 
Literature cited 33 
PRESENT STATUS OF THE QUESTION. 
For many years the organisms of the colon-aerogenes group have 
occupied a position of very great importance in the eyes of sanitarians. 
From the public-health standpoint the quality of water supplies has 
been determined by means of the number of these organisms present; 
not because they are considered pathogenic but rather because they 
are present in fecal material in large numbers, and therefore their 
presence in any considerable number in water may indicate the 
presence of pathogenic organisms of fecal origin. 
Investigations have shown, however, that the colon bacillus is by 
no means confined to the human intestines, but is often the pre- 
vailing form in the intestines of many animals, including cows. It 
would seem at first thought, therefore, that the presence of colon 
organisms in milk might afford a valuable means for determining 
pollution by cow feces. In fact, the determination of colon bacilli 
in milk as a means of indicating manurial pollution has become quite 
general on account of the value of the colon test as an index of the 
purity of water and the apparent analogy between the contamination 
of water by fecal material and the contamination of milk by cow 
feces. 
75649°— lS-Bull. 739 1 
