SPONTANEOUS GENERATION 343 



will, I think, see that there is no escape from it. He may, 

 if he prefers, hold the opinion, which I consider errone- 

 ous, 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 inac- 

 tive 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. See- 

 ing 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 hete- 

 rogeny, is infected with this error; while heterogenists at 

 home and abroad have based upon it a triumphant demon- 

 stration of their doctrine. It is proved, they say, by the 

 deportment of the mineral solution that neither bacteria 

 nor their germs exist in the air: hence, if, on exposing 

 a thoroughly sterilized turnip infusion to the air, bacteria 

 appear, they must of necessity have been spontaneously 

 generated. In the words of Dr. Bastian: "We can only 

 infer that while the boiled saline solution is quite inca- 

 pable of engendering bacteria, such organisms are able to 

 arise de novo in the boiled organic infusion." * 



I would ask my eminent colleague what he thinks of 

 this reasoning now? The datum is "A mineral solution 

 exposed to common air does not develop bacteria"; the 

 inference is "Therefore if a turnip infusion similarly ex- 

 posed develop bacteria, they must be spontaneously gen- 



1 "Proceedings of the Royal Society," vol. xxi. p. 130. 



