Composition of Cheese. 
47 
high, thfi alcohol, in trickling over these shavings when in con- 
tact with abundance of air, undergoes a complete transforma- 
tion, and collects rapidly at the bottom of the cask as vinegar. 
But such a change does not take place if the alcoholic lifjuid is 
left for ever so long in a clean cask filled -witii such a liquid. 
Contact with air, subdivision of the liquid into drops, and the 
presence of the porous wood-shavings, are necessary for the 
transformation. These casks do not at first produce vinegar 
as rapidly as after they have been in use for some time and 
become thoroughly soaked with vinegar-ferment. And this is 
another peculiarity of all ferments, that, under favourable cir- 
cumstances, they reproduce themselves from other materials in 
immense quantities. Thus fresh and active yeast is generated 
in great abundance in fermenting malt-liquor, whilst the original 
yeast employed in brewing is more or less decomposed and be- 
comes what is called inactive yeast. These chemical facts, well- 
known to the manufacturers of vinegar and to the intelligent 
brewer, have a direct bearing on cheese-making. 
At the very beginning of her operations a good dairywoman 
unconsciously carries on a steady and constant battle with these 
remarkable ferments, and it is very interesting to the chemist to 
see her proceed in the most rational and philosophical manner. 
No milk is admitted into the cheese-tub before it has been 
carefully strained through a cloth, lest a little bit of a dead leaf or 
any similar matter, accidentally blown into the milk in its pas- 
sage from the milking-place to the dairy, should spoil the flavour 
of the cheese. No sooner has the cheese left the tub than she 
begins to pour scalding Vv ater into it, to scrub it, and to make it as 
clean and sweet as possible. In good dairies no utensil is allowed 
to remain for a moment dirty, but hot water and clean brushes 
are always close at hand to scrub the pails and make them 
almost as white as snow. The dairywoman probably knows 
nothing about the nature of the ferment, which is rapidly formed 
when a little milk is left at the bottom and adhering to the sides 
of the wooden milk-pails ; she is unconscious that here, as in 
the vinegar process, the conditioris most favourable to chemical 
change are present, and that the sugar of the milk, in contact 
with plenty of air and porous wood, is rapidly changed into 
lactic acid, whilst at the same time a peculiar milk-ferment is 
produced ; all this may be a perfect mystery to her, but, never- 
theless, guided by experience, she thoroughly avoids everything 
that favours the production of ferment, or taint, as she calls it, by 
leaving no vessel unclcaned, by scalding all that have been in use 
Avith boiling water, and if ever so little milk be accidentally spilt 
on the floor of the dairy, taking care that it is at once removed, 
and the spot where it fell washed with clean water. 
