40 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



dinger's reagent, and a little of this solution is added to 

 milk, the mixture will also be colored blue, but the color 

 will disappear more rapidly. At first the difference in 

 the time of reduction was attributed to the difference in 

 the composition of the solution, but further research 

 demonstrated the presence in milk of two different re- 

 ducing agents. The ferment which reduces themethylene 

 blue solution is called " M-reduetase," while the one 

 which reduces the formalin-methylene blue solution has 

 been named " FM-reductase." 



M-Reductase. This ferment is not secreted in the 

 udder with the milk. It is generally regarded as of 

 bacterial origin, although the opinion has been expressed 

 (Burri and Kursteiner) that the cellular elements of 

 milk, like all living protoplasm, have a reduction power 

 and that the high reduction power of colostrum during 

 the first day after parturition and of mastitis milk is due 

 to the rich cellular content of these secretions. It has 

 been well established, however, that the capacity of milk 

 to reduce methylene blue increases with the number of 

 bacteria. 



The different species of bacteria vary in their reduc- 

 tion power. Reduction power appears to depend first 

 upon the species, then upon the number of bacteria, and, 

 finally, upon the media in which the organisms are grow- 

 ing. The anaerobic organisms usually have a greater 

 reduction power than the aerobes, while the facultative 

 anaerobes act more powerfully in the absence of oxygen 

 than when it is present. The colon bacilli belong to the 

 facultative anaerobes of high reduction power. On the 

 other hand, the reduction power of the lactic acid bacteria 

 is weak. Different samples of fresh milk containing 

 about the same number of bacteria may differ greatly in 



