230 OUTLINES OF BACTERIOLOGY 



Bitter Cheese is an abnormality which is due to the predominance of 

 Bitter-soft-cheese-bacillus (Tyrothrix geniculatus), or Bitter cheese- 

 coccus (Micrococcus casei amari), or Weigmann's bitter-milk-bacillus, or 

 Conn's bitter-milk-micrococcus, or some other microbe with similar 

 properties. They all belong to the casein-digesting bacteria : they 

 fortunately do not under normal circumstances obtain a chance of 

 multiplying extensively. 



Colour in Cheese. Red Cheese may be due to bacteria or to yeasts. 

 Two species of bacteria belonging to the micrococcus group, and pro- 

 ducing red decomposition-products when fed on cheese, have been 

 isolated. Also the yeast, Saccharomyces ruber, is known to affect 

 cheese in the same way. A thorough disinfection of the cow stalls 

 whence the milk has been derived was found to be a sufficient guarantee 

 against the ravages of the yeast, and there can be little doubt that 

 general cleanliness will also prevent the bacterial pests from multi- 

 plying extensively in the cheese. 



Black Cheese may be due to the presence of iron in the milk, as, if 

 the milk be slightly sour and rusty buckets be used, some of the iron 

 will be dissolved, and if, as often happens, traces of sulphuretted 

 hydrogen are present, then the black sulphide of iron will be produced 

 and impart its colour to the cheese. Certain moulds and yeasts, 

 however, by feeding on the cheese and giving rise to black decom- 

 position-products, may be responsible for this colouring. 



Blue Cheese is due to the activity of a bacillus, but very little is 

 known about it. 



Putrid Cheese is undoubtedly due to the capture of the cheese by 

 saprophytic bacteria and other microorganisms. When one remembers 

 that the byre contains many millions of these bacteria, derived from 

 excrement and other filthy matters, it is a simple deduction to affirm 

 that want of cleanliness is the cause of this malady in cheese. 



Poisonous Cheese is a more serious matter. In 1883 arid 1884 the 

 intrusion of a disease-germ into cheese in Michigan, U.S.A., caused an 

 outbreak of cheese-poisoning affecting in all about 300 persons. This 

 microbe gave rise in the cheese to a poisonous decomposition-product 

 to which the name tyro-toxicon was given. In 1901 a similar outbreak 

 occurred in London. This was caused by a Dutch cheese, and about 

 17 persons were affected. In the latter case no deaths were reported, 

 and the symptoms disappeared after 48 hours. 



