RELATION OF BACTERIA TO DAIRY INDUSTRY. 73 



satisfactorily the connection of all these infec- 

 tions with different species of the bacteria. A 

 large number of species have been found to cur- 

 dle milk without rendering it acid, several render 

 it bitter, and a number produce a 

 " tainted " and one a " soapy " 

 taste. A score or more have been 

 found which have the power of 

 rendering the milk slimy. Two 

 different species at least have the 

 power of turning the milk to sky- FIG. 20. Dahybac- 

 blue colour; two or three pro- ^1^1^"^ 

 duce red pigments (Fig. 20), and 

 one or two have been found which produce a yel- 

 low colour. In short, it has been determined be- 

 yond question that all these infections, which are 

 more or less troublesome to dairymen, are due 

 to the growth of unusual bacteria in the milk. 



These various infections are all troublesome, 

 and indeed it may be said that, so far as concerns 

 the milk producer and the milk consumer, bac- 

 teria are from beginning to end a source of trou- 

 ble. It is the desire of the milk producer to 

 avoid them as far as possible a desire which is 

 shared also by everyone who has anything to do 

 with milk as milk. Having recognised that the 

 various troubles, which occasionally occur even 

 in the better class of dairies, are due to bacteria, 

 the dairyman is, at least in a measure, prepared 

 to avoid them. The avoiding of these troubles 

 is moderately easy as soon as dairymen recog- 

 nise the source from which the infectious or- 

 ganisms come, and also the fact that low tem- 

 peratures will in all cases remedy the evil to a 

 large extent. With this knowledge in hand the 

 avoidance of all these troubles is only a question 



