72 THE TYPES OF MILK BACTERIA. 



times bacilli, which are probably different species. Whether 

 they are of much importance in dairy processes is not yet 

 known. 



A fourth type consists of four or five species of bacteria 

 which agree in producing a kind of lactic acid different from 

 that produced by the common lactic organisms. Whereas 

 the common bacteria produce lactic acid which has com- 

 monly no rotary effect upon polarized light or rotates 

 it to the right, there are several species of lactic bac- 

 teria known which rotate the plane of polarization to 

 the left. These four or five species do not resemble 

 each other very closely, and are only grouped together 

 because of the character of lactic acid they produce. 

 Several species have been described as having this charac- 

 ter: B. acidi l&volactici (Schardinger), M. Icevolactici 

 (Leichmann), B. l&volacticus (Leichmann), B. acidi lavo- 

 lactici (Kozai) and others. Whether they are of much im- 

 portance in dairy processes cannot be stated, although one 

 of them has been found to be quite abundant, especially in 

 milk that has been kept at a moderately warm temperature ; 

 so much so that Kozai believes that at warm temperatures 

 this organism is the chief agent in the souring of milk (50). 



In addition to these there are some other lactic bacteria 

 which have characters different from any of these types. 

 But all of these other forms are so unusual that they can- 

 not be regarded as typical dairy organisms, and while they 

 are found in milk incidentally, and sometimes in consider- 

 able quantities, they must be put down as occasional visitors 

 and not as distinctively characteristic of the dairy. 



In general, then, it will be seen that, of the numerous milk 

 bacteria which have the power of producing lactic acid and 

 souring the milk, the first type here mentioned is almost 

 universal and, although not extremely abundant in any local- 

 ity, is so widely distributed that milk will, in the vast ma- 

 jority of cases, become contaminated with this type of bacil- 



