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226 THE EVOLUTION OF LIFE 
out, that hard, dry seeds will stand an amount of 
heat which would utterly destroy them when they 
were once soaked through. Many persons would 
probably be able to confirm his experience, that a 
very dry pea may be boiled for hours before the 
moisture penetrates its hard coating; and it is com- 
mon knowledge nowthat a considerable amount of dry 
heat will not destroy the power of germination in 
seeds which would yield at once to a moist tempera- 
ture much below the boiling-point. Boiling a pea, 
therefore, seems a scarcely conclusive proof that 
bacterial germs, if there are any, can survive desicca- 
tion and induration, that theyare freely given off in this 
protected state from old hay, and that when they get 
into the air they have a special power, not possessed 
by their moister brethren, of resisting subsidence, 
penetrating cotton-wool, and enduring the contact 
of air calcined by red-hot platinum. All this may 
be worked out some day, but it will need something 
more than boiled peas or dried seeds to establish it. 
“The true inference to be drawn from the two 
series of experiments seems to me to be that the 
discrepancy has arisen from some cause which 
neither the public nor the Professor himself have as 
yet any trustworthy means of so much as guessing 
at. The wise course would be to abandon for the 
future the unsatisfactory and complicated machinery 
employed in Professor Tyndall’s mode of experi- 
mentation, and to resort to simpler means of exclud- 
in 1871 (Thirteenth Report of the Medical Officer of the Privy 
Council, p. 61); his view, however, subsequently required much 
modification, as I have indicated on p. 75. 
