104 SCIENCE AND PRACTICE OF DAIRYING. 



detected, sometimes in larger and sometimes in smaller quantities. 

 It is without doubt formed directly from milk-sugar by butyric acid 

 fermentation. It is indirectly formed for the most part from other 

 substances, which vary according to the kind of cheese and the kind 

 of organism active in the ripening process. Such substances are 

 hydrated milk-sugar, salts of lactic acid, albuminous bodies of milk, 

 milk-fat, or glycerine, formed in the saponification of milk-fat. 



The organisms which interfere with the processes of ripening, 

 and which influence the products of ripening, have also been inves- 

 tigated. A very objectionable, and, at the same time, very commonly 

 occurring disturbance is the inflation of cheese. Many kinds of 

 lower organisms are already known which, under certain conditions, 

 are able to excite a kind of fermentation in ripening cheeses which 

 is associated with a strong evolution of gaseous bodies. Such are 

 the various kinds of micrococci, the saccharomyces lactis, the yeast 

 discovered by Duclaux, and other kinds of yeast, tyrothrix uro- 

 cephalum, the masticis cocci, bacterium lactis aerogenes, bacterium 

 coli commune, and others. In cheeses, on the surface or inside of which 

 red patches are developed, the presence of moulds, which in the con- 

 dition of sporulating produce a brick-red colour, have been detected, 

 as well as several kinds of micrococci, and also very probably a kind 

 of torula. A peculiar kind of disease cheese is subject to, in which 

 it becomes blue, has been probably traced to a kind of bacteria 

 which only flourishes in the absence of air (de Vries); while the 

 production on parts of the surface of cheese of black patches which 

 easily become sticky have been traced also to several different kinds 

 of fungoid growth. 



44. Characteristics of Milk which Owe their Origin to Micro- 

 organisms. That milk which has been standing for some time 

 owes its peculiar properties to bacteria, is known, although little 

 is known as yet regarding their nature. In a similar way the 

 organic ferments which yield the purest and best koumiss still 

 await investigation. 



Kephir, a slightly effervescing spirituous beverage, prepared 

 from milk, contains the common chief constituents of milk in a 

 slightly altered condition, in addition to minute quantities of car- 

 bonic acid, lactic acid, alcohol, and peptones. It also contains 

 caseous matter in a firm but very finely divided condition, well 

 known as kephir grains. In this beverage, several different kinds 

 of yeasts and bacteria have been identified. The yeasts differ from 



