484 
On the Chemistry of Ensilage. 
time on exposure to the air, and soon turns mouldy, whilst 
well-made sour silage may be kept sound for six or nine months, 
and even longer, when freely exposed to air, without turning 
mouldy. Some of the best samples of sour silage which I 
analysed last January, and which I kept in the Society's 
Laboratory, without taking any particular care to exclude air, 
remain at the time of writing (August) still quite sound and 
perfectly free from mould ; in fact, even after the great heat of 
this summer, they are as good as they were when they first 
reached me. 
At the same time I must mention that sour silage does not 
always keep well, as I shall presently show. I am now engaged 
in investigating the circumstances under which sour silage keeps 
well for a reasonably long time, and those under which it 
rapidly turns mouldy and gets spoilt on exposure to the air. 
As far as I am able to judge, and, I must confess, from an in- 
sufficient number of not altogether conclusive facts, I think it 
likely that the whole difference in the keeping qualities of sour 
silage depends upon whether the silage has passed through the 
lactic acid fermentation (which takes place on the more or less 
complete exclusion of air), or through the alcoholic and subse- 
quent acetic acid fermentations (which proceeds with facility 
only if air has free access). In most cases I find that acetic 
acid fermentation precedes mouldiness ; and although ver}' 
mouldy silaged grass or clover is rarely very acid, and some- 
times has even an alkaline reaction, it does not follow from the 
absence of an acid reaction that the mouldy silage has not 
undergone acetic acid fermentation ; for it is well known that 
vinegar loses by degrees its acidity in measure as it becomes 
more and more mouldy. The fungus which causes the mouldi- 
ness in flat vinegar appears to consume the acetic or vinegar 
acid, and to live upon its constituent elements. That there 
are great differences in the quality of the silage made from 
different kinds of green food, or even from the same food made 
on different farms, or on the same farm in different seasons, 
admits of no doubt. These differences are attributable in a 
great measure to the quality of the original green food, as 
regulated by its composition, and more especially by its state 
of maturity. Generally speaking, well-ripened nutritious grass 
or clover, which is sweet to the taste and comparatively rich in 
sugar, when under conditions favourable to the production of 
either sweet or sour silage, makes a better, more nutritious, and 
more wholesome food than immature or over-ripe green food, 
which originally is either so immature as to contain hardly any 
sugar, or else so over-ripe as to have become insipid and woody. 
