Fearon — Pasteur Centenary Celebration. 53 



It was impossible for a great observer like Pasteur to contemplate the 

 phenomena of fermentation and of micro-organic life without thinking of the 

 problems of human life itself, of pain and disease, and the bitterness of 

 apparently useless suffering. But the way of approach to the scientific 

 study of human ailments was extraordinarily hard for Pasteur. He was not 

 qualified (in the academic sense) to practise medicine. His presence, as a 

 mere chemist, was acutely resented by the physicians and surgeons of Paris. 

 Greater than all these was the almost complete lack of knowledge about the 

 immediate cause of diseases themselves. Indeed, it was sometimes doubted 

 if diseases had a definite cause ; they may have arisen spontaneously, or as 

 the result of a vast number of indefinable conditions. " Treat the patient 

 and not the distemper " was a catch-cry of the period. 



Before approaching the study of diseases, Pasteur had carried out an 

 original and startling experiment on the fermentation of ammonium salts of 

 tartaric acid. This fermentation he found to be due to the growth of a mould, 

 penicillium glaumim. When he added some of this mould to a solution of the 

 racemic acid, which he had previously shown to be a mixture of two substances, 

 the mould grew, and fermented the solution just as if it were simple tartaric 

 acid. However, on examining the mixture, he found that the organism had 

 somehow separated the racemic acid into its two constituents, and had 

 fermented or eaten up one of them, leaving the other form untouched. In 

 other words, this minute vegetable had, in the course of some hours, 

 performed the chemical operation of analysing or resolving racemic acid into 

 its two constituents — an operation which had taken Pasteur several years of 

 research to accomplish and explain. 



This work has been extended and amplified by many subsequent inves- 

 tigators ; and fermentation by living organisms, or their eouivalents. enzymes, 

 is now widely employed in biological chemistry as a means of separating 

 sugars and other substances. 



The power of the mould to attack one component of the racemic acid in 

 preference to the other was shown by Pasteur to be due to the fact that the 

 component destroyed was of frequent natural occurrence, and hence more 

 familiar to the mould. This was one of the first examples of an intentional 

 bacteriological operation. Pasteur also brought about the formation of 

 butter-milk by inoculating fresh milk with the lactic bacillus, which he had 

 previously isolated from sour milk. In this he reproduced the change that 

 takes place everywhere in the dairies of the world, only instead of the lac lie 

 bacillus being borne to the milk by the uncertain winds, it was brought by 

 the more certain test-tube. The rule of man had been extended into the 

 reahu of the invisible. Another Gulliver had come to Lilliput, but instead 



