TYPES OF BACTERIA FOUND IN MILK. 155 
slimy milk, the dairyman should look first to his water-supply, es- 
pecially if the milk has been cooled by standing in cans in the water. 
Then he may turn his attention to the food of the cows to see if he 
has any special lot of hay or other food that holds the troublesome 
organisms. This may be tested by changing the food for a time. 
Lastly, he will do well to keep the milk of the different cows separate 
for a few days, to see if the trouble can be traced to any particular 
cow. Having once found the source, the remedy is simple: either 
by applying some method of disinfection at the source of infection, 
or seeing that infected water does not come in contact with the milk 
cans, or removing the milk of the cow that is at fault, or changing 
the food. 
Bitter Milk. Next to slimy milk, perhaps bitter milk offers the 
most trouble to the dairyman. Three quite different sources of 
bitter milk can be distinguished: i. The cow. She may give 
bitter milk because of improper food, such as lupines, which will 
impart a bitter taste. Bitter milk is also quite common in a late 
stage of lactation. These types may be recognized by the fact that 
the milk is bitter as soon as it is drawn from the cow, and the bitter- 
ness does not increase later. 2. Microorganisms. 
In such cases the bitterness is a matter of slow 
development. The milk, when drawn, tastes as %V C\ 
usual, and the bitterness appears after standing a a ^ 
few hours, increasing in intensity until, in a short FIG. 37. Organ- 
time, it is at its maximum. In these instances ^^"A^CU" 
the bitterness is produced by microorganisms &, a yeast Toruid 
which grow in the milk. Two or three varieties of 
bacteria have been described that have this power, and have been 
the cause of a troublesome bitter fermentation in milk (Fig. 37, a). 
The source of the trouble has been traced, in one case, to organisms 
in the udders of a single cow in a herd. Bitter milk is not of very 
common occurrence. In cheeses the development of a bitter taste 
is much more common, doubtless because, during the ripening, the 
bacteria have a longer time to develop their bitter products. A 
bitter taste in cheese has been in some cases traced to bacteria, and 
in one extended series of troubles, which affected the cheese-making 
