UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETLN No. 739 
Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 
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 indicate the presence of manure in fresh 
milk? 1 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 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1918 
