56 PRACTICAL DAIRY BACTERIOLOGY 



proper handling of soft cheeses, since it may choke out other 

 organisms, whose growth is desired. (See page 250.) Oidium 

 lactis has no appreciable action upon milk, neither souring nor 

 curdling it, nor making any change in its flavor in the short 

 period before the milk would ordinarily be consumed. 1 Upon 

 further growth, however, it gives rise to chemical decomposition, 

 the result of which is the development of strong flavors, and 



FIG. 29 OIDIUM LACTIS, FROM A SURFACE COLONY ON GELATIN 



these are of significance in certain types of soft cheese and 

 probably also in rancid butter. The organism is extremely 

 abundant, and found practically in all dairies. It does not, 

 however, ordinarily appear in milk or in the gelatin plates made 

 from fr.sh milk, but it is almost certain to be found in old 

 milk. It is almost always present in old butter, and may be 

 found practically in all soft cheeses during the early process of 

 their ripening. While, therefore, the organism has no important 

 bearing upon milk, it is one of extreme importance in cheese 

 making, as will be noticed later. There are several varieties of 

 it, differing only slightly from each other. 



1 Lang and Freudenreich. Land. Jahr. d. Schw., 1893. 



