326 FKAGMENTS OF SCIENCE. 



Seeing its ability to nourish bacteria when once inocu- 

 lated 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. Through- 

 out Germany the ablest literature of the subject, even 

 that opposed to heterogeny, is infected with this error; 

 while heterogenists at home and abroad have based upon 

 it a triumphant demonstration 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 sterilised 

 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 whilst 

 the boiled saline solution is quite incapable of engen- 

 dering 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 develope bac- 

 teria; ' the inference is ' Therefore if a turnip infusion 

 similarly exposed develope bacteria, they must be spon- 

 taneously generated/ The inference, on the face of it, 

 is an unwarranted one. But while as matter of logic 

 it is inconclusive, as matter of fact it is chimerical. 

 London air is as surely charged with the germs of bac- 

 teria as London chimneys are with smoke. The in- 

 ference just referred to is completely disposed of by 

 the simple question: ' Why, when your sterilised or- 

 ganic infusion is exposed to optically pure air, should 

 this generation of life de novo utterly cease? Why 

 should I be able to preserve my turnip- juice side by 

 side with your saline solution for the three hundred and 



* ; Proceedings of the Royal Society,' vol. xxi. p. 180. 



