88 THE TYPES OF MILK BACTERIA. 



washing the teats of a cow with weak acetic acid. In Amer- 

 ica no examples of spontaneous blue milk infection appear 

 to have been recorded. The bacterium which produces this 

 trouble, however, has been found in this country, and is 

 capable of rendering milk blue under proper conditions. A 

 blue milk epidemic may sometimes break out, but it is not 

 one of the common dangers of dairying. 



Red Milk. A fermentation by which the milk becomes 

 red is as rare as that of blue milk. Milk is not infrequently 

 somewhat red when freshly drawn, but this is not due to a 

 fermentation. Milk is occasionally turned red by the pres- 

 ence of blood, which comes from some inflamed or irri- 

 tated condition of the udder. At times cows give milk of a 

 red color after they have fed upon madder root, or occasion- 

 ally some other plants. In all of these cases, ho.wever, the 

 red color to the milk is at its height at the moment 

 the milk is drawn from the cow. In the rare case 

 of milk turning red from fermentation the red color is 

 not visible at first, but appears after a few hours and 

 increases greatly as the microorganisms develop. A few 

 instances of such red milk have been described in literature 

 in the last fifty years, and two or three species of bacteria 

 have been described as capable of producing red milk (88, 

 etc.). B. ery thro genes has been most studied, but a species 

 of Sarcina has also been said to produce a spontaneous infec- 

 tion of red milk, 5\ aurantiaca. So rare is this trouble that 

 there is very little chance that one will run across it in com- 

 mon dairy experience, but if such trouble does arise it must 

 always be attributed to the growth of microorganisms, and 

 the remedy will be found along the general line of cleanli- 

 ness and disinfection of milk vessels and cow stalls. 



Yellow Milk, Green Milk, etc. Certain other colors are 

 sometimes imparted to milk by the growth of bacteria. 

 Yellow milk, green milk, black milk and chocolate milk 

 have been described. These phenomena, however, can hardly 



