RIPENING OF CHEESE: ABNORMAL MILK. 113 



Anaerobic bacteria also play a part in cheese fermentation, 

 and, amongst them, butyric acid bacteria. 



Amongst moulds which are of special importance in deter- 

 mining the character of different cheeses must be mentioned 

 the Mucor, Penicillium and Dematium species observed by O. 

 Johan-Olsen in Norwegian " Gammelost " (old cheese) ; a 

 white Penicillium (P. candidum, Rodger) in Camembert 

 cheese ; and a similar Penicillium album (Epstein) in Brie 

 cheese. Weigmann, Conn, and others, on the contrary, 

 attribute the special character of both these cheeses to the 

 action of a particular Oidium. O. Jensen assumes that the 

 peculiar flavour of Roquefort cheese is due to the symbiosis 

 of Penicillium glaucum and Oidium lactis. All these moulds 

 act partly by decomposing the acid contained in the cheese, 

 and partly by neutralising the acid with ammonia formed 

 by the breaking down of casein, and thus they prepare the 

 ground for the peptonising bacteria, whilst also decomposing 

 the milk fat, and liberating its volatile fatty acids. 



The abnormal characters of milk and milk products must 

 in an equal degree be attributed to micro-organisms.* Thus, 

 for instance, the bacteria introduced into milk from a diseased 

 udder, and the consequent changes in the character of the milk, 

 are accompanied, not only by a very great increase in the 

 bacterial contents, but also by the presence of characteristic 

 pus cells in the milk. 



" Soapy " milk, having a decided soapy taste and pro- 

 ducing a strong lather, owes these properties to the presence 

 of Bac. lactis saponacei, a short rod which forms slimy colonies 

 on ordinary nutritive gelatine, turning to a rusty yellow on 

 the surface. Other species may also produce this fault. 



Bitter milk may be the result of using certain food-stuffs, 

 but may also be produced by certain bacteria, as was shown 

 by Pasteur, Duclaux, Loftier, Weigmann, and others. In 

 practice, micrococci which liquefy gelatine and certain vari- 

 eties of aerobic, lactic acid bacteria appear to have this effect. 



* It is generally accepted that milk may act as a carrier of many dangerous 

 disease germs ; typhoid epidemics in particular appear to spread in this way. 

 Tubercular bacilli, capable of development, have frequently been found in raw 

 milk. 



