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 jj> 

 development. The milk, when drawn, tastes as vj ^^C\ 

 usual, and the bitterness appears after standing a a Q ^ 

 few hours, increasing in intensity until, in a short FIG. 37. Organ- 

 time, it is at its maximum. In these instances 



the bitterness is produced by microorganisms b, a yeast Toruia 



i , ,, -11 rr- .1 j.- r amari (Harrison), 



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 



