168 BACTERIA IN MILK 
especially 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 disinfec- 
tion 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: (1) The cow. 
€ She may give bitter milk because of improper 
& Osi food, such as lupines, which willimpart a bitter 
0) on (j} taste. Bitter milk is also quite common in a 
late stage of lactation. These types may be 
_ Fic 36—Organ- recognized by the fact that the milk is bitter as 
isms producing bitter o, 
milk. a, A coccus; soon as it is drawn from the cow, and the 
as iferrsom bitterness does not increase later. (2) Micro- 
organisms. In such cases the bitterness is a 
matter of slow development. The milk, when drawn, tastes 
as usual, and the bitterness appears after standing a few 
hours, increasing in intensity until, in a short time, it is at 
its maximum. In these instances the bitterness is produced 
by ‘microdrganisms 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. 36, 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 
