166 MICRO-ORGANISMS AND FERMENTATION. 



made in the author's laboratory point rather to the action 

 of bacteria. In distilleries and yeast factories, on the other 

 hand, moulds have been known to appear even during fer- 

 mentation. Growths of Oidium, Chalara, Dematium, etc., are, 

 for example, found on the surface of the yeast layer in the vat, 

 and the yeast-like cells which are produced by these fungi 

 and by certain species of Mycoderma, which bear a striking 

 resemblance to true yeast cells can frequently be observed 

 multiplying in the upper yeast layer. They may be skimmed 

 off along with the yeast, and thus the author has often found 

 a fine white deposit on the surface of pressed yeast, which 

 most frequently consists of a mould mycelium, belonging 

 principally to forms resembling Oidium, Chalara, and De- 

 matium. It is quite possible that when these plants form a 

 dense layer on the surface of the yeast-mass, they retain by 

 respiration a portion of the free oxygen which is necessary 

 to enable the quiescent yeast to remain alive. Even here, 

 without exception, bacterial growths were observed. 



Judging from practical observations, a growth of mould 

 nearly always serves to indicate that other organisms of a 

 more injurious and more active character are developing. 

 It is, therefore, of great importance that the walls of the 

 fermenting rooms should be smooth ; this is effected with 

 the greatest certainty by employing the enamel paint now 

 so much in use. 



The moulds are also of direct significance to the dairy 

 industry. The experience of recent years has shown that 

 amongst the great diversity of forms which make their appear- 

 ance in this industry, some of which are of the nature of 

 unbidden guests, many could contribute in no small measure 

 to the improvement of the quality of cheese if proper means 

 were adopted. Amongst the useful forms may be mentioned 

 Aspergillus oryzce from Japan, which, on account of its power- 

 ful diastatic enzyme, is used for the manufacture of sugar from 

 starch ; Amylomyces, introduced from Indochina, and employed 

 in European distilleries ; and Citromyces, similar in appearance 

 to Penicillium, used in the preparation of citric acid from 

 grape-sugar. 



The moulds, many of which represent stages in the life 



