68 Dairy Bacteriology. 



affected in this way foams readily, and is abnormally 

 slow in souring. They traced the cause of the trouble in 

 one case to the infection of the milk from the straw that 

 was used for bedding; in another, it was present in the 

 hay. Marshall 1 in this country has also isolated an or- 

 ganism of this sort that acts upon casein and albumen. 



66.. Bloody or red milk. This condition often arises 

 from the actual presence of blood in the milk due to 

 some wound in the udder. The ingestion of certain plants, 

 as sedges and scouring rushes, is said to cause a bloody 

 condition in milk; madders impart a reddish tinge on 

 account of a coloring matter absorbed. These instances 

 can always be separated from bacterial troubles, because 

 if due to these sources the color will be noted at the time 

 of milking. 



There are several chromogenic or pigment-bearing bac- 

 teria that have been isolated from milk, that have the 

 power of turning milk red, although this change is so 

 slow that it does not amount to much in dairy practice. 

 The most widely known form able to bring about this 

 change is Bacillus prodigiosus, the so-called "bleeding 

 bread ' ' bacillus. It is interesting from a historical stand- 

 point, inasmuch, as it has been found to be the cause of 

 the bloody bread that has been the source of much super- 

 stitious fear. Its growth in milk is marked by the pro- 

 duction of a coloring matter that is diffused throughout 

 the milk, especially near the upper surface. Free con- 

 tact with oxygen is required to produce the characteristic 

 pigment. Bacillus lactis erythrogenes (bacillus of red 

 milk), is another form that grows easily in milk, produ- 

 cing a red color, but it has the curious property of being 

 able to form the color only in the dark, and in milk 



1 Marshall, Mich. Expt. Stat., Bull. 146, p. 16. 



