Blue Milk. 177 



cum grows similarly. It is not supposed to liquefy gelatin. The 

 nutritive media become fluorescent. 



The propagation of butyric acid bacteria causes rancidity of 

 milk, as does likewise the multiplication of bacteria which spilt up 

 fats, for instance the Bacterium lipolyticum. 



The appearance of the milk defects here mentioned may 

 sometimes be confined to the product of a single individual in the 

 stable. The milk of one or of several co\vs may manifest these 

 defects which may be retained persistently in spite of changing 

 the feed and disinfecting the stable. 



Weigmann mentions a case in which, with uniform feeding and care of the animals, 

 the milk of only one cow developed a fishy odor, and to such a marked extent that the 

 milk of the entire herd became fishy (possibly the udder of this cow was diseased). 



The same author mentions another case which occurred on an estate in northern 

 Germany. In that instance the milk of the Montavania cows in the stable was constantly 

 rancid, whereas the milk of the Holstein cows was faultless, although the animals were 

 all kept under the same conditions. The Bacillus lipolyticum was found to be the dis- 

 turbing bacterium. It is noteworthy that the milk of the Montavania cows was frequently 

 bloody at the same time. Therefore it is possible that the elimination of the aroma 

 bacteria took place from the affected udders, that is, the same bacterium was also the 

 cause of the inflammation of the udder. However, it is more likely that through the 

 secretion of the affected udders conditions were established in the milk from the Mon- 

 tavania animals which favored the propagation of the Bacterium lipolyticum in the 

 milk, or probably the bacteria were present in the milk cisterns of these cows as harmless 

 saprophytes, and the blood content of the milk may be attributed to some affection of 

 the udder (yellow garget), which had no connection with the cause of the rancid milk. 



It has also been proved that other changes in milk may per- 

 sistently occur in the secretion of certain individuals so that it 

 appears as if the causative agents of the changes in the milk may 

 at times exist as saprophytes in the cistern (Schultze), or that 

 they have at least multiplied in the excretory duct of the cistern. 



Thus Schultze proved that in the appearance of "blue milk" 

 the defect can only be removed by a thorough cleaning of the sta- 

 ble, animals, milk vessels, and all creamery utensils, and the milk 

 cisterns of the animals must also be treated by antiseptic infusions 

 of the udder. 



The "blue milk" is produced by the Bacillus cyanogenes, a Gram-negative, aerobic, 

 actively motile, unipolar, flagellated bacillus, with rounded ends, about 0.4/ci thick and 

 2.4/i long. It is also known as the Bacterium syncyaneum Hueppe (Heim). Growing 

 in sour milk the bacillus produces sky-blue to indigo-blue spots which gradually become 

 confluent. The bacillus attacks the casein, and produces alkali besides a coloring 

 substance, the triphenylrosanilin (Erdmann), which, depending on the reaction of the 

 nutritive media, appears greenish or pale blue, violet or indigo-blue, or blackish-brown. 

 The Bacillus cyanogenes in itself is colorless. 



The coloring is less typical in sterile milk; a dirty bluish-gray discoloration with 

 a reddish hue of the cream occurs, the color gradually diminishing in the deeper parts. 

 Indigo-blue spots develop only in sour milk (Heim). 



The changes which occur in milk appear to be especially fre- 

 quent in certain localities ; in others they are more rare and appear 

 to have a connection with the properties of the soil. Pastures rich . 

 in clover are supposed to favor the appearance of the defects while 

 in woodland pastures they have not been observed, or at least only 

 exceptionally. This would explain why the defects occur in cer- 



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