SPONTANEOUS GENERATION. 589 



months the pure mineral solution and the pure turnip 

 infusion side by side, I drop into each of them n 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 uiidistinguishable 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 hy 

 others. My own experiments would lead me to say that the develop- 

 ment of the bacteria, though exceedingly slow and difficult, is not 

 impossible, 



