82 THE TYPES OF MILK BACTERIA. 



in the dairy. It is one of the most common of the types of 

 unusual fermentations of milk, is .widely distributed and occa- 

 sionally is the cause of much bother to dairymen. Its general 

 characteristics are unfortunately too well known. The milk, 

 though apparently treated as usual, fails to sour and curdle 

 normally, but after a few hours begins to be somewhat slimy. 

 The trouble increases until, at the time when the milk should 

 normally sour, it has developed such an amount of slime that 

 it can be drawn out into long threads. At the same time it 

 has a sweetish taste. Such milk is practically worthless. It 

 cannot be used for butter-making, for the cream will not 

 separate. It will not be used for drinking or cooking pur- 

 poses, although there seems to be no reason for believing 

 that it is not perfectly wholesome. Most people, however, 

 do not wish to drink slime and will throw it away. Some- 

 times such an infection may spread through a whole farming 

 district, affecting many dairies and continuing for a long 

 time. Although not always easily explained, when such infec- 

 tions have been studied, the trouble has generally been traced 

 to some common source of distribution. For example, a cen- 

 tral creamery receiving such milk from a single patron, may 

 distribute it over the whole patronizing district by returning 

 to the farmers milk vessels not properly sterilized by live 

 steam. 



Wherever such slimy milk appears it may always be traced 

 to the action of bacteria. As in the case of other fermenta- 

 tions it is not a single species of bacterium which has the 

 power of producing slimy milk, but rather a somewhat large 

 class of organisms. More than a score of bacteria have been 

 described as possessing the power of producing a slime in 

 greater or less amount (see Fig. 16). Moreover it appears, 

 according to recent work, that some of the common dairy 

 bacteria (B. acrogenes lactis) are capable, under certain con- 

 ditions, of producing slime. But of this large number of 

 species probably only a few are concerned in the actual dairy 



