6 
Colorado Experiment Station 
(i) has shown the milk supply of Raleigh, N. C., to vary in bacterial 
content from 1,200 during November to 54,000,000 in May. 
A number of the bacteria which fall into milk are harmless in 
themselves, but during their growth they bring about certain changes 
which produce disagreeable odors and flavors, and frequently del¬ 
eterious substances. The natural souring of milk is accomplished by 
the lactic acid germ. However, Marshall (2) has shown that the 
lactic bacteria are favorably influenced by the presence of other 
bacteria, notably by germs of filth, which for the sake of the present 
illustration, let us call “B.” The lactic germ we shall designate “A.” 
By growing the lactic acid germ by itself and also by associating it 
with the germ B, Dr. Marshall has been able to show the increased 
number of lactic forms when associated with B in milk. At the time 
of loppering or curdling of culture A+B, the ratio of the lactic acid 
bacteria in the two cultures was: 
A :A+B: 127:1614. 
Again,' he has demonstrated that germ B produces stable products 
which withstand sterilization and exert the same influence over germ 
A in milk cultures as the living germ. The comparative number of 
lactic germs in culture A and in culture (A-{-products of germ B) 
was expressed by the ratio: 
A:(A+products of germ B) ::27:ioc>7. 
From this it follows that clean milk will keep sweet much longer than 
other milk. We see this same thing every day in a practical way when 
we notice that milk from certain dairies sours so much more quickly 
than that from other sources, and if we trace down this matter still 
further, we invariably find that the better milk comes from the cleaner 
stable. 
There are also those forms of microscopic life which produce 
bitter milk, ropy milk, and milk of different colors commonly desig¬ 
nated bloody milk, blue milk and yellow milk. If these bacteria are 
present in the milk, they will be present also in the cream and will 
impart their disagreeable properties to the butter made from it. 
A few suggestions along the line of clean milk may not be out 
of place at this time. The writer feels that while this topic has been 
treated upon thoroughly and exhaustively in many publications and 
by institute speakers, yet, not all of us who are in the dairy business, 
have understood fully and put into practice the principles and meth¬ 
ods advanced by the advocates of sanitary milk. 
No dairyman who pretends to produce clean milk should allow 
his cows to have access to muddy bayous, wading places and irrigating 
ditches. It is not through any preference, but as a last resort, that 
cattle in the summer time stand knee deep in mud and water to get 
(1) Market Milk, bacteriological data. Cant, of Bakt; II Abt. Bd. XX. 
No. 4-5. >1907, p. 114. 
(2) Special bulletin No. 33, 1905. Mich. Exp. Station. 
