431 
through gravel or any other device, while it looks clean, always con- 
tains more bacteria than before it has been purified.’’ This is due 
to the fact that, while the visible particles of dirt are held back, the 
particles of manure, dirt, and bacterial clusters are broken up. Fur- 
I ther, unless the most painstaking technical precautions are taken, 
i milk receives fresh bacterial contamination every time it is poured 
from one vessel to another or is handled in any other way. 
THE INITIAL CONTAMINATION OF MILK. 
1 1 Now that we know that milk freshly drawn from the udder under 
^ordinary circumstances always contains bacteria, it is of practical 
importance to determine their number and kind. 
Sedgwick and Batchelder,® 1892, found that with moderate pre- 
cautions on the part of the milker the number of bacteria in fresh 
I milk may not exceed 500 to 1,000 per cubic centimeter, but when 
the ordinary flaring milk pail is used, with more or less disturbance 
■ of the bedding and shaking of the udder, as many as 30,000 bacteria 
have been counted in one cubic centimeter. 
MacConkey,^ however, finds that with ordinary care and cleanli- 
, ness it is possible to obtain milk winch when freshly drawn contains 
; less than 1,500 organisms per cubic centimeter; and, further, that 
' such milk should not contain gas-forming organisms in less than 50 
cubic centimeters. 
Comparing these results with the work of others, we find that 
Park,*" 1901, found the average bacterial content of the milk from 
six separate cows examined five hours after collection to be 6,000 
per cubic centimeter, the lowest count being 400, and of 25 cows of 
which the milk was tested immediately after drawn it was 4,550. 
Burr,*^ 1902, also taking every reasonable precaution, found 500 
organisms per cubic centimeter in the milk of a single cow. 
Von Freudenreich,^ 1902, thought it would be easy to carry out 
strict asepsis and thus obtain a bacteria-free milk; but he soon came 
to the conclusion that this was impossible. He found that milk 
always contained 250 to 300 organisms per cubic centimeter, even 
« Sedgwick, William T., and Batchelder, John L.: A bacteriological examination of 
the Boston milk supply. Boston Med. and Surg. Journ., vol. 126, 1892, p. 25-28. 
^MacConkey: A contribution to the bacteriology of milk. Journ. of Hyg. vol. 
6, 1906, p. 385. 
cPark, William H.: The great bacterial contamination of the milk of cities, can 
it be lessened by the action of the health authorities? Journ. Hyg., vol. 1, 1901. 
p. 391. 
<^Burr, Rollin H.; The source of the acid organisms of milk and cream. Cent. f. 
Bakt., 2 Abt., vol. 8, 1902, p. 236. 
«Von Freudenreich, Ed.: Milchsaurefermente und Kasereifung. Cent. f. Bakt., 
2 Abt., vol. 8, 1902, p. 674. 
