BACTERIA IN MILK. 2O5 



teria is blue milk. This trouble is one of special interest, inas- 

 much as it was carefully studied and traced to its origin in a 

 certain species of bacterium, even before the beginning of the 

 modern study of bacteria. As long ago as 1841 blue milk 

 was investigated by Fuchs with the best methods at his com- 

 mand, and it was successfully traced to the growth of a micro- 

 scopic organism. This same organism has since been many 

 times isolated, and is one of the well-known bacteria, almost 

 the oldest definitely named species. It is known as B. cyano- 

 gcncs. It is an ordinary bacillus, readily killed by moderate 

 heat since it does not produce spores. Its effect upon the 

 milk is striking, but it does not commonly appear until the 

 milk is from one to three days old. At this time there appear 

 blue patches, which may spread through the milk as it becomes 

 sour, until the whole is a sky blue. The infection is by no 

 means a common one, although occasionally it has been known 

 to produce considerable trouble in certain localities. The 

 remedy against it is simply the ordinary one of thoroughly 

 sterilizing the milk vessels and cleaning the surroundings, 

 which have likely become badly infested with the germs in 

 dairies where the trouble has been noticed. In recent years 

 another species of bacterium has been described having the 

 same property of turning milk blue. 



Red Milk. Red milk is by no means uncommon in the 

 dairy, but the red milk ordinarily seen has nothing to do with 

 bacteria. It is generally the result of a mixture of some blood 

 with the milk, and is due to some injury to the udder, or 

 even to the cows having eaten sedges and rushes which have 

 a large amount of silica in their tissues. Rarely milk may be 

 colored red because the cows have been feeding upon madder 

 root or other plants with red pigment. These, which are the 

 ordinary causes of red milk, have nothing to do with bacteria. 



But occasionally the red milk is of the nature of a fermenta- 

 tion and is produced by bacteria. Such effects, of course, do not 



