CHAPTER XIV. 



CHROMOPAROUS BACTERIA, PRODUCING BLUE, GREEN, 

 AND VIOLET COLOURING MATTERS. 



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 

 MARTIN Y'S (I.) useful handbook, which (it may be parenthetically 

 observed) affords a rich supply of information respecting the litera- 

 ture 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 C. J. FUCHS (I.), 

 who inferred from the results obtained during numerous inocula- 

 tion experiments and much microscopic research that the blue 

 coloration of milk is induced by the development of a pigment 

 microbe, which he first named Vibrio cyanogenus and then Bac- 

 terium syncyaneum. 



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

 just at this time promulgated his theory of fermentation, and 

 fettered 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 con- 

 tained in the decomposing casein. If, then, this work is mentioned 

 now, it is not for the purpose of controverting its untenable con- 

 clusions, 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 cham- 

 ber but in warmer apartments (living rooms), the evil may be 

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

 Steinhof as lasting for twelve years, without interruption, in the 



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