86 MILK AND ITS HYGIENIC RELATIONS 



Their action is most easily detected if the substance used changes 

 colour as a result of the reduction. For this reason methylene 

 blue has been found satisfactory, and has been largely, although 

 not exclusively, used in the investigation of the presence of these 

 ferments in milk. Methylene blue has been used alone in which 

 case, if it is reduced, the ferment or body causing such reduction 

 is known as a ' direct reductase.' It has also been used with formalin, 

 and the resulting reduction is said to be brought about by an 

 'indirect reductase.' This last body has also been called ' aldehyde- 

 catalase/ 'aldehyde-reductase/ 'formaldehydase,' and it has also 

 been suggested by Bach (i, 2) that, following the general type of 

 nomenclature, ' redukase ' would be more appropriate. Further, in- 

 asmuch as the reaction was first discovered by Schardinger (i), it is 

 often known as ' Schardinger 's reaction/ and on the assumption that 

 the body is a ferment it is known as ' Schardinger's ferment.' 

 These two reactions are most frequently denoted by the letters 

 M.B. (methylene blue) and F.M.B. (formalin - methylene - blue) 

 respectively. 



In addition to these two substances some authors have dealt 

 with a third reducing agent, hydrogenase, which converts sulphur 

 into sulphuretted hydrogen. This action will be considered after 

 the direct and indirect reductases. 



The reducing power of milk was shown in 1897 by Vaudin using 

 indigo, and also by Neisser and Wechsberg (1900) for methylene 

 blue, and by Wynter Blyth (1901) using litmus. 



The literature dealing with the reducing ferments began on a 

 considerable scale about 1902, and since this date a vast number 

 of papers have been published dealing with various aspects of the 

 reducing power of milk. The question has been further complicated 

 by a considerable amount of controversy, which cannot be said to 

 be altogether closed at the present time. It will probably simplify 

 the consideration of the various issues which have been studied 

 in connection with this class of bodies in milk, if a short history of 

 the literature be given first. 



Schardinger (i) in 1902 published his first paper on the reducing 

 properties of milk. He showed that when milk was quite fresh it 

 did not reduce methylene blue unless formalin was added to the 

 solution. The solution used by him for this test was made up of : 



5 c.c. saturated solution of methylene blue, 

 5 c.c. formalin, 

 190 c.c. water, 



and is known generally as Schardinger's reagent or solution. 

 Schardinger concluded that (i) either an aldehyde substance was 

 necessary for the reduction of the methylene blue, which was 

 ordinarily formed gradually in the milk by the action of bacteria, 

 being replaceable in the early stages by formaldehyde or some other 



