C. A. WATKINS ON YEAST AND OTHER FERMENTS. 159 



I shall have a few words to say on M. Aceti, or the Vinegar 

 Plant as some call it, which, although included by many among the 

 Ferments, is not so considered by chemists, for reasons I will here- 

 after explain. 



When a saccharine solution is left in contact with casein either 

 in the form of fresh curd or cheese, the sugar is slowly transformed 

 into lactic acid, according to the following equation : — ■- 



Cane Sugar CHO + HO = 2CHO Lactic Acid. 



12 11 11 6 6 6 



In this fermentation water is assimilated, but no gas is evolved. 



A solution of lactic acid, similarly treated, is transformed into 

 Butyric acid thus : — 



Butyric Acid. Carb.Acid. Hydrogen. 



Lactic Acid 2CHO= CHO + 4CO + 4H 



6 6 6 8 8 4 2 



In this fermentation, both carbonic acid and hydrogen gases are 

 evolved. It is a question not yet answered, whether these chemical 

 changes are induced by mere contact with the decomposing casein 

 which is regarded as the ferment, or whether the minute organisms 

 developed in these solutions are the real ferments living on the 

 matters therein. One thing is quite certain, that in both fermenta- 

 tions living organisms abound, and they cannot grow without 

 chemical changes taking place. 



" M. Pasteur considers that a specific ferment is concerned in the 

 production of the lactic acid fermentation, which spreads itself out 

 as a grey substance over the surface of the sediment ; and he 

 asserts that this organism when once obtained, and a small quantity 

 added to a solution of sugar, very rapidly converts it into lactic 

 acid, provided the solution contain a small quantity of some nitro- 

 genous substance. When this grey matter is examined by the 

 microscope it is seen to consist of very small globules or very short 

 articulations, either isolated or in threads, much smaller than Yeast, 

 and to exhibit very rapid gyratory motion." 



I have not succeeded in obtaining this grey matter, but as the 

 lactic acid fermentation goes on very slowly, and as this season of 

 the year is not favourable for experiments on fermentation, it may 

 not have had time to make its appearance. 



In order to observe the organisms which accompany the trans- 

 formations of sugar, I watched the progress of the lactic acid 



m 2 



