410 MICRO-ORGANISMS AND FERMENTATION. 



of Mycoderma vini. Greater or less distinctions were noted 

 in the shape of the cells, their content in glycogen, the presence 

 of oil drops, and in their giant colonies. The film-formation 

 also showed distinct differences with different species, both 

 with regard to the time required for their appearance, their 

 character, and colour (white, cream, yellowish-brown, and 

 yellowish-olive-green). When covered with the film, the 

 liquor remains clear in certain cases, whilst in others a turbidity 

 takes place of a permanent or temporary character. 



Will believed that the decolorisation of the liquid may be 

 referred to the formation of acid brought about by the film 

 cells, whereas Heinze thought that it was caused by the removal 

 of acid. Meissner confirmed the fact that a more or less marked 

 decolorisation takes place, but showed that afterwards a. 

 reversal of the colour tints may come about, so that must 

 which had turned pale assumed by degrees a dark brown 

 colour. Not only is the total amount of acid destroyed, but 

 the must at last acquires an alkaline reaction. Meissner 

 succeeded in proving experimentally both with large and 

 small amounts of must, that one and the same race may 

 appear, first as a producer, and then as a destroyer of acid. 

 It is, therefore, necessary to forego the division of film yeasts, 

 into acid-destroying and acid-forming species. Once the sugar 

 in the must is destroyed, all so-called acid ferments will act 

 as destroyers of acid. With regard to this question of the 

 formation and destruction of acid, Meissner also states that 

 when an increase of acid takes place it must be regarded as a- 

 result of two simultaneous processes of construction and 

 destruction of acid, and that production has exceeded destruc- 

 tion. If, on the other hand, a reduction of acid takes place, 

 the destructive action must be regarded as exceeding the 

 constructive. 



Butyric acid is formed amongst others, and ammonium 

 compounds are also produced. 



Meissner's experiments regarding the reaction of the 

 Mycodermas with organic acids gave the following results : 

 Malic acid is only very slightly attacked by certain races, 

 but strongly attacked by others. Tartaric acid is slightly 

 decomposed. Lactic, citric, and succinic acids are in some 



