142 THE POPULAR SCIENCE MONTHLY. 



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 vigor- 

 ous 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 retransferred 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 preservation of meat by cold. 

 The fish-monger, for example, when he surrounds his very assailable 

 wares by lumps of ice, stays the process of putrefaction by reducing 

 to numbness and inaction the organisms which produce it, and in the 

 absence of which his fish would continue sweet and sound. It is the 

 astonishing activity into which these bacteria are pushed by warmth 

 that renders a single summer's day sometimes so disastrous to the 

 great butchers of London and Glasgow. The bodies of guides lost in 

 the crevices 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 necklaces. Each of these organisms 

 produces a fermentation and a flavor peculiar to itself. Keep them 

 out of your beer and it remains forever unaltered. Never without 

 them will your beer contract disease. But their germs are in the air, 

 in the vessels employed in the brewery, even in the yeast used to im- 

 pregnate the wort. Consciously or unconsciously, the whole art of the 

 brewer is directed against them. His aim is to paralyze if he cannot 

 annihilate them. 



For beer, moreover, the question of temperature is one of supreme 

 importance; indeed, the recognized influence of temperature is caus- 

 ing on the Continent of Europe a complete revolution in the manu- 

 facture of beer. When I was a student in Berlin, in 1851, there were 

 certain places specially devoted to the sale of Bavarian beer, which 

 was then making its way into public favor. The beer is prepared by 

 what is called the process of low fermentation ; the name being 



