144 PROCEEDINGS OF SECTION B. 
of enormous importance in all dairy fermentations, and of 
these I shall write subsequently. 
The Fermentation of Silage. 
Until quite recently it has been understood that the lactic 
bacteria played a most important part in the fermentation 
of silage. It was considered that the sour silage—in which 
the temperature never rises so high as in the sweet—was fer- 
mented by the lactic and butyric ferments, and the sweet 
silage by the lactic bacteria only. It has now been shown 
that the fermentation is not bacterial, but results from 
-the physiological acivity of the plant-cells. Silage can be 
made under conditions that exclude bacterial action. The 
acidity is due to the intra-molecular respiration, and the 
quantity is roughly proportional to the length of time that 
the vegetable-cells respire. Thus the greener the plant and 
the lower the temperature of fermentation, the more acid 
is produced. 
The Production of Butyric, Oxalic, and Citric Acids. 
The butyric fermentation is a later stage of the lactic, as 
the butyric bacteria first form lactic, which they then con- 
vert into butyric acid. Butyric acid is accordingly never 
solely produced by bacteria from starch or sugar, but is 
always mixed with lactic. In fact, a pure bacterial acidifica- 
tion of any kind is seldom if ever obtained, ¢.g., in the 
presence of air, lactic bacteria always produce some acetic 
acid. 
Fermentation butyric acid is used chiefly in the prepara-__ 
tion of alcoholic butyrates, which are flavouring essences. 
The writer recently separated a lactic-butyric bacillus from 
raw sugars, in which it is universally found, and it is possible 
that this organism was responsible for the original pine-apple 
odour of rum. I write “original,” for in these days of 
enlightenment the flavour is most easily imparted by the 
addition of the pure ethyl butyrate. Oxalic acid is always 
produced by the acetic bacteria in the presence of carbo- 
hydrates, and the crystals of oxalate of lime in culture media 
are familiar to every microscopist who has grown the 
commonly-occurring hyphomycetes. Aspergillus niger has 
been suggested as a source of oxalic acid, but it does not 
_appear to have advanced beyond the experimental stage. 
The production of citric acid by certain citromycetes from 
glucose at one time promised to become of some importance. 
_ The yield was good, six parts of acid being obtamed from 
