256 THE FLOATING-MATTER OF THE AIR. 



the common practices of life. Heat kills the bacteria, 

 colds nmnbs them. When my housekeeper has pheasants 

 in charge which she wishes to keep sweet, but which 

 threaten to give way, she partially cooks the birds, kills 

 the infant 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 con- 

 tinuing putrefaction. This is the whole philosophy of 

 the preservation of meat by cold. The fishmonger, for 

 example, when he siuTounds 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 

 remain 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 crevasses of Alpine glaciers 

 have come to the surface forty years after their in- 

 terment, without the flesh showing any sign of putre- 

 faction. But the most astonishing case of this kind 

 is that of the hairy elephant of Siberia which was 



