THE NUMBER OF BACTERIA IN MILK AND THE VALUE OF 
BACTERIAL COUNTS. 
By Milton J. Rosenaf. 
Director , Hygienic Laboratory , Public Health and Marine-Hospital Service. 
Milk delivered in cities contains a vast number of bacteria. For 
instance, the general milk supply of Washington averaged 11,270,000 
per cubic centimeter in the summer of 1907; and 22,134,000 during 
the summer of 1906. The milk of many other cities also is exces- 
sively rich in bacteria. 
Such enormous numbers mean but little to our minds. If we 
make comparisons we find that few substances contain such myriads 
of germ life as is often found in milk. Compared with sewage, for 
instance, a fluid which is popularly and rightly supposed to teem 
with germ life, it will almost always be observed that milk when it 
is consumed is richer in bacteria by far than the sewage of our large 
cities.® 
Sewage of — 
Average for— 
Bacteria per cubic 
centimeter. 
Boston, Mass. a 
London, England b 
London, England c (crude sewage) 
Lawrence, Mass.d 
St. Mary’s, Ohio « . 
Westerville, Ohio e 
Marion, Ohio « 
1894 to 1901 
1894 to 1901 
1898 
i Sept. 24 to Oct. 24, 1890*. . . 
16 samples, 1907 
16 samples, 1907 
16 samples, 1907 
2,800,000 
2, 000, 000 to 11,000,000 
3, 500; 000 to 4,000,000 
3.034.000 
5.600. 000 
2.350.000 
239,000 
a Winslow and Belcher: Changes in the bacterial flora of sewage during storage. 
b Laws and Andrews : Report on the result of investigations of the micro-organisms of sewage. Rep. 
London Co. Council, Dec. 13, 1894. 
c Clowes, F.: Report on the bacteriological examination of London crude sewage. First Rep. Lon- 
don Co. Council, June 16, 1898. 
State Board Health Mass., Rep. 1890, p. 35. 
« Kellerman, Pratt and Kimberly: The disinfection of sewage effluents for the protection of public 
water supplies. U. S. Bur. Plant Industry, Bull. 115, 1907. 
So far as numbers are concerned, they need not greatly alarm us, 
for we know that disease is due to agencies and conditions other 
than merely the presence of enormous numbers of bacteria. By 
universal consent, however, milk containing excessive numbers of 
bacteria is unsuitable for infant feeding. The tender mucous mem- 
a Russell, H. L. Outlines of Dairy Bacteriology, 1896. 
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