SPONTANEOUS GENERATION. 589 
months the pure mineral solution and the pure turnip 
infusion side by side, I drop into each of them a small 
pinch of laboratory dust. The effect here is tardier than 
when the speck of putrid liquid was employed. In three 
days, however, after its infection with the dust, the turnip 
infusion is muddy, and swarming as before with bacteria. 
But what about the mineral solution which, in our first 
experiment, behaved in a manner undistinguishable from 
the turnip-juice? At the end of three days there is not a 
bacterium to be found in it. At the end of three weeks it 
is equally innocent of bacterial life. We may repeat the 
experiment with the solution and the infusion a hundred 
times with the same invariable result. Always in the case 
of the latter the sowing of the atmospheric dust yields a 
crop of bacteria" never in the former does the dry germinal 
matter kindle into active life.* What is the inference 
which the reflecting mind must draw from this experi- 
ment? Is it not as clear as day that while both liquids are 
able to feed the bacteria and to enable them to increase 
and multiply, after they have been once fully developed, 
only one of the liquids is able to develop into active 
bacteria the germinal dust of the air? 
I invite my friend to reflect upon this conclusion; he 
will, I think, see that there is no escape from it. He may, 
if he prefers, hold the opinion, which I consider erroneous, 
that bacteria exist in the air, not as germs but as desiccated 
organisms. The inference remains, that while the one 
liquid is able to force the passage from the inactive to the 
active state, the other is not. 
But this is not at all the inference which has been drawn 
from experiments with the mineral solution. Seeing its 
ability to nourish bacteria when once inoculated with the 
living active organism, and observing that no bacteria 
appeared in the solution after long exposure to the air, the 
inference was drawn that neither bacteria nor their germs 
existed in the air. Throughout Germany the ablest 
literature of the subject, even that opposed to heterogeny, 
is infected with this error; while heterogenists at home 
* This is the deportment of the mineral solution as described by 
others. My own experiments would lead me to say that the develop- 
ment of the bacteria, though exceedingly slow and difficult, is, uot 
impossible. 
