544 FRAGMENTS OF SCIENCE. 
it will remain forever sweet. Thus we begin to see that 
within the world -of life to which we ourselves belong, 
there is another living world requiring the microscope for 
its discernment, but which, nevertheless, has the most 
important bearing on the welfare of the higher life- 
world. 
And now let us reason together as regards the origin of 
these bacteria. A granular powder is placed in your hands, 
and you are asked to state what it is. You examine it. and 
have, or have not, reason to suspect that seeds of some 
kind are mixed up in it. To determine this point you 
prepare a bed in your garden, sow in it the powder, and 
soon after find a mixed crop of docks and thistles sprout- 
ing from your bed. Until this powder was sown neither 
docks nor thistles ever made their appearance in your 
garden. You repeat the experiment once, twice, ten times, 
fifty times. From fifty different beds after the sowing of 
the powder, you obtain the same crop. What will be your 
response to the question proposed to you? " I am not in 
a condition," you would say, " to affirm that every grain 
of the powder is a dock-seed, or a thistle-seed; but I am in 
a condition to affirm that both dock and thistle-seeds form, 
at all events, part of the powder. " Supposing a succession 
of such powders to be placed in your hands with grains 
becoming gradually smaller, until they dwindle to the size 
of impalpable dust particles; assuming that you treat them 
all in the same way, and that from every one of them in a 
few days you obtain a definite crop it may be clover, it 
may be mustard, it may be mignonette, it may be a plant 
more minute than any of these, the smallness of the par- 
ticles, or of the plants that spring from them, does not 
affect the validity of the conclusion. Without a shadow 
of misgiving you would conclude that the powder must 
have contained the seeds or germs of the life observed. 
There is not in the range of physical science an experi- 
ment more conclusive nor an inference safer than this one. 
Supposing the powder to be light enough to float in the 
air, and that you are enabled to see it there just as plainly 
as you saw the heavier powder in the palm of your hand. 
If the dust sown by the air instead of by the hand 
produce a definite living crop, with the same logical 
rigor you would conclude that the germs of this crop 
must be mixed with the dust. To take an illustration: 
