igoo-i.] The Ripening of Cheese. 109 



a species of Tyrothrix, was an example of the conversion of a lactic 

 acid bacterium into a peptonizing organism. T. urocephalum and T. 

 tenuis were found to aid the ripening of cheese, and there were grounds 

 for believing that in this ripening, peptonizing bacteria played the 

 principal part. A bacteriological examination of hard cheese always 

 shewed a greater preponderance of lactic acid bacteria, and this might 

 possibly be explained in this way, that certain peptonizing bacteria 

 changed in the cheese to lactic acid bacteria, especially strongly 

 developing the property of producing lactic acid. Aside from the 

 behaviour of T. tennis and T. nrocephaluni that of Bacillus xvi, Adametz 

 in Emmenthaler cheese confirmed this view." 



These results of Winkler were subsequently made the subject of a 

 special research by Wittlin working under von Freudenreich. The 

 experiments were made with a culture obtained originally from 

 Duclaux, and after many cultivations on gelatin, no evidence was 

 forthcoming to support the conyersion contended for. Wittlin failed to 

 be convinced that Tyrothrix tenuis could be converted into a lactic acid 

 bacterium ; and the author supposed that Winkler's results were due to 

 contamination. 



By making emulsions of various cheeses and inoculating milk 

 therewith, De Freudenreich was able to obtain absolutely anaerobic 

 bacilli. These bacilli probably formed butyric acid. One of the two 

 isolated, formed spores and from its shape, it was evidently a Clostridium 

 form. He named it Clostridium foetid2i7n lactis. This germ, as its name 

 implied, imparted a disagreeable odour to the milk, did not grow on 

 gelatin, but on agar developed slowly giving rise to a cheesy odour. It 

 apparently entirely dissolved the casein of milk, this medium turning 

 yellow, only a slight sediment remaining. Later de Freudenreich 

 became convinced that this Clostridium was identical with the bacillus 

 of malignant oedema. I have also found this bacillus in two small 

 experimental cheese, made from Swiss milk, its pathogenicity and 

 cultural characteristics leaving no room to doubt its identity. 



In a Holland cheese, Weigmann found two aromatic bacilli. These 

 gave the milk cultures a cheese aroma. When pasteurised milk was 

 inoculated with these forms, and cheese made, it ripened and resembled 

 Swiss cheese. These germs were gelatine liquefiers and digested the 

 casein of the milk. 



A very systematic study of the rise and fall of the bacteria in 

 Cheddar cheese was made by Russell and Weinzirl. Six cheeses were 

 analysed at various periods, and the qualitative distribution of the 



