CHAPTER XIV. 



( IIKoMol' AltOUS BACTERIA, PRODUCING BLUE, GREEN, AND 

 VIOLET COLOURING MATTERS. 



8 94. Blue Coloration of Milk 



is a phenomenon known from time immemorial. The opinions as to its cause 

 are widely divergent, but the earliest of them are at present only of historical 

 interest. They may be found in MARTINY'S (I.) useful handbook, which (it may 

 be parenthetically observed) affords a rich supply of information respecting the 

 literature published on milk, butter, and cheese up to the year 1871. 



The first to arrive at the opinion that the blue coloration of milk might 

 proceed from some external infection penetrating into the liquid, was STEINHOF (I.) 

 who, however, made no attempt to prove by experiment the correctness of his 

 hypothesis. This was only effected three years later, viz., in 1841, by 0. J. 

 FUCHS (I.), who inferred from the results obtained during numerous inoculation 

 experiments and much microsopic research that the blue coloration of milk is 

 induced by the development of a pigment microbe, which he first named Vibrio 

 cyanoyeiiKS and then Bacterium syncyaneum. 



Unfortunately, however, for the study of this question, Liebig just at this 

 time promulgated his theory of fermentation, and fetterad philosophers in his 

 dogmatic shackles. This explains why HAUBNER (I.) lost sight of the object for 

 which Fuchs had striven, and, by endeavouring in 1852 to adapt the result of 

 his numerous and careful experiments on this point to preconceived opinion, came 

 to the conclusion that the blue coloration of milk is not caused by vibrions, but 

 by a lifeless chemical ferment contained in the decomposing casein. If, then, this 

 work is mentioned now, it is not for the purpose of controverting its untenable 

 conclusions, but because it contains an instructive description of the development 

 of the milk disease in question. It runs verbally as follows : 



"Under ordinary domestic conditions blue milk occurs only in the warm season, 

 and persists from early summer to autumn. In small households where the milk 

 is not kept in a separate chamber, but in warmer apartments (living rooms), the 

 evil may be prolonged through the winter. A case of this kind is recorded by 

 St.einhof as lasting for twelve years, without interruption, in the house of a farmer. 

 The blue coloration appears from twenty-four to seven ty-two hours after the 

 milk is drawn from the cow, the process being accelerated by warm, close weather, 

 and retarded by cold. At a temperature of i5-2o R. (i8J-25 C.), it may 

 ensue in twenty hours the shortest limit of time observed by H. whilst, at 

 only a few degrees above zero, it may linger on to the seventh day. The colora- 

 tion always begins to form at the surface, never in the depths of the liquid, and 

 generally appears at first as isolated patches or dots, immovable, and increasing 

 in circumference and depth ; so that there are various stages, ranging from 

 single superficial patches to almost complete impregnation of the mass with blue 

 colour. " 



F. NEELSEN (I.), in 1880, took up the work commenced by Fuchs. Convenient 

 and reliable methods of pure cultivation were, however, lacking at that time, and, 

 in fact, the cultures prepared by Neelsen, when subsequently examined analytically 



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