Feaeon — Pasteur Centenarij Celebration. 56 



metaphysical disputes about the immortality of animals and the origin of 

 life. 



Linnaeus, on his part, simplified the whole problem by grouping all germs, 

 infusoria, and the like into the class Cliaoa in his great treatise " Systema 

 JVatura." He also displayed a marked lack of confidence in the results of 

 microscopical observation. 



Before micro-organisms could be studied with satisfaction it was necessary 

 to obtain a clear notion as to their limitations. Did they only arise from 

 other living organisms or did they spring up from dead material under 

 favourable conditions ? There was a wide-spread belief in the spontaneous 

 generation of life. 



Organic fluids such as milk, meal -broth, hay-infusion, when exposed to 

 air or when closed up in flasks were found after a day to be full of a variety 

 of living organisms. The problem of the origin of life in some way resembled 

 the problem of fermentation, but it was infinitely more complicated. The 

 friends of Pasteur advised him to avoid it. " You will never find your way 

 out of it," said Biot, " and will only waste your time." 



All the same, Pasteur solved the problem, as far as it can be solved by the 

 methods of physics and chemistry. He employed the same weapons of 

 research as he had successfully used in the work on fermentation ; these 

 were : a systematic use of the microscope, a patient and exquisite skill in 

 manipulation, the establishment of the fact before the theory, and, lastly, 

 a love of the truth for its own sake and not for any fame that might 

 chance to come with it. 



Pasteur, suspecting that the air carried the infections which manifested 

 themselves as living organisms in the flasks of the upholders of the 

 spontaneous generation theory, began his research by a bacteriological 

 examination of the atmosphere. If it were the primary source of micro- 

 organisms, it should be possible to remove them by filtering through wool or 

 other material. If the organisms already existed in the culture-fluids, it 

 should be possible to destroy them by heat without altering materially the 

 nutrient material in the fluid. Eesults from experiments carried out in towns 

 where the air is impure should differ from experiments carried out in 

 mountain air. 



He devised a series of experiments which completely refuted the 

 claims of the spontaneous generation school, and at the same time marked 

 out the boundaries of the modern science of bacteriology. He demonstrated 

 the almost universal distribution of germs, and the impossibility of keeping 

 any material free from infection, unless by a systematic process of steriliza- 

 tion and isolation. In the Pasteur Institute at Paris are still preserved flasks 



