BACTERIA IN FOODS 



193 



been detected by several observers and classified as slime 

 fermentation bacteria. The Bacillus lactis pituitosi, a 

 slightly curved, non-liquefying rod, which is said to produce 

 a characteristic odour, in addition to causing ropiness, brings 

 about some acidity. B. lactis viscosus is slow in starting its 

 fermentation, but maintains its action for as long as a 

 month. Many of the above organisms, with others, pro- 

 duce " slimy " fermentation in alcoholic beverages as well 

 as in milk. 



(6) Soapy Milk. This is still another form of fermenta- 

 tion, the etiology of which has been elucidated by Weig- 

 mann. The Bacillus saponacei imparts to milk a peculiar 

 soapy flavour. It was detected in the straw of the bedding 

 and hay of the fodder, and from such sources may infect 

 the milk. There is little or no coagulation. 



(7) Chromogenic Changes. We have already remarked 

 that colour is the natural and apparently only product of 

 many of the innocent bacteria. They put out their strength, 

 so to speak, in the production of bright colours. The chief 

 colours produced by germs in milk are as follows : 



Red Milk. Bacillus prodigiosus, in the presence of oxy- 

 gen, causes a redness, particularly on the surface of milk. 

 It was the work of this bacillus that caused " the bleeding 

 host," which was one of the superstitions of the Middle 

 Ages. B. lactis erythrogenes produces a red colour only in 

 the dark, and in milk that is not strongly acid in reaction. 

 When grown in the light this organism produces a yellow 

 colour. There is a red sarcina (Sarcina rosed] which also 

 has the faculty of producing red pigment. One of the 

 yeasts is another example. 



It must not be forgotten that redness in milk may actually 

 be due to the presence of blood from the udder of the cow. 

 In such a case the blood and milk will be inextricably mixed 

 together, and not in patches or a pellicle. 



Blue Milk is due to the growth of Bacillus cyanogenus. 



