FERMENTATION. 547 
bacteria, and thus postpones the evil day. By boiling her 
milk she also extends its period of sweetness. Some weeks 
ago in the Alps I made a few experiments on the influence 
of cold upon ants. Though the sun was strong, patches 
of snow still maintained themselves on the mountain 
slopes. The ants were found in the warm grass and on 
the "warm rocks adjacent. Transferred to the snow the 
rapidity of their paralysis was surprising. In a few seconds 
a vigorous ant, after a few languid struggles, would wholly 
lose its power of locomotion and lie practically dead upon 
the snow. Transferred to the warm rock, it would revive, 
to be again smitten with death-like numbness when retrans- 
ferred to the snow. What is true of the ant is specially 
true of our bacteria. Their active life is suspended by 
cold, and with it their power of producing or continuing 
putrefaction. This is the whole philosophy of the preser- 
vation of meat by cold. The fishmonger, for example, 
when he surrounds his very assailable wares by lumps of 
ice, stays the process of putrefaction by reducing to numb- 
ness and inaction the organisms which produce it, and 
in the absence of which his fish would remain sweet and 
sound. It is the astonishing activity into which these 
bacteria are pushed by warmth that renders a single sum- 
mer's day sometimes so disastrous 'to the great butchers of 
London .and Glasgow. The bodies of guides lost in the 
crevasses of Alpine glaciers have come to the surface forty 
years after their interment, without the flesh showing any 
sign of putrefaction. But the most astonishing case of 
this kind is that of the hairy elephant of Siberia which 
was found incased in ice. It had been buried for ages, but 
when laid bare its flesh was sweet, and for some time 
afforded copious nutriment to the wild beasts which fed 
upon it. 
Beer is assailable by all the organisms here referred to, 
some of which produce acetic, some lactic, and some 
butyric acid, while yeast is open to attack from the bacteria 
of putrefaction. In relation to the particular beverage the 
brewer wishes to produce, these foreign ferments have 
been properly called ferments of disease. The cells of the 
true leaven are globules, usually somewhat elongated. 
The other organisms are more or less rod-like or eel-like in 
shape, some of them being beaded so as to resemble neck- 
laces. Each of these organisms produces a fermentation 
