MICRO-ORGANISMS IN CHEESE. 103 



a very complicated one, from the fact that the proper ripening of 

 cheese is the result of the co-operation of different kinds of micro- 

 organisms; a symbiosis or metabiosis in which certain kinds of 

 bacteria partly favour and partly retard the simultaneous develop- 

 ment in the same medium of other kinds of bacteria, or in which 

 one kind first prepares the way for and renders possible, to a certain 

 extent, the action of another kind. 



As has been already pointed out, there are fission fungi which 

 produce peculiar ferments, which exercise a solvent effect on the 

 coagulated caseous matter. Probably no kind of cheese can do with- 

 out the action of these fungi for its ripening, by means of which the 

 original white and friable or fragile cheese is converted into a yellow- 

 coloured, soft, pasty mass. For all cheeses which are soft, arid which 

 have a tendency to become liquid, the fission fungi are without doubt 

 of first importance. In the ripening of some cheeses, for example 

 Roquefort, Gorgonzola, Brie, Stilton, &c., certain fungoid organisms 

 cannot be dispensed with, since they, as has been explained, check 

 the action of the lactic bacteria, and gradually diminish the acid 

 reaction of the mass to such an extent that the bacteria which pro- 

 duce the decomposition of the albumin are permitted to develop. 



Long before bacteriological investigation had thrown light on 

 the subject, practice had instinctively sought the help of fungoid 

 organisms for producing certain peculiar characteristics of certain 

 cheeses. In the preparation of Roquefort cheese, for example, the 

 cheese-makers were in the habit of mixing the fresh cheese with 

 fungoid organisms, and in the preparation of other kinds of cheese 

 they had endeavoured so to arrange the treatment of the cheese that 

 the colonizing and development of fungoid growths should take place 

 as quickly as possible on its surface and in its inside. On the other 

 hand, in the ripening of other kinds of cheese, the action of the 

 albuminoid destroying bacteria has been held in check by the lactic 

 bacteria, since the cheese would otherwise be liable to premature 

 decay. 



In Holland, in the preparation of the Edam cheese, practice has 

 likewise preceded theory. In that country, when milk which has to 

 be used for churning is treated with sour milk, there is added to it, 

 if not a pure cultivation, yet one in which the growth of colonies 

 of such bacteria (cocci) predominates, as experience has shown these 

 cannot be dispensed with in the ripening period. 



In all ripened cheeses the presence of butyric acid can be 



