372 LOUIS PASTEUR 



about the decomposition of sugar into other organic mol 

 cules ; the physiological act, in this view, would be necessary 

 for the production of this substance, but would have nothing 

 else to do with the fermentation (page 10)." To this, again, 

 we have no objection to raise. 



Liebig, however, does not dwell upon these considerations, 

 which he merely notices in passing, because he is well aware 

 that, as far as the defence of his theory is concerned, they 

 would be mere evasions. If he had insisted on them, or 

 based his opposition solely upon them, our answer would 

 have been simply this: "If you do not admit with us that 

 fermentation is correlated with the life and nutrition of the 

 ferment, we agree upon the principal point. So agreeing, 

 let us examine, if you will, the actual cause of fermentation; 

 this is a second question, quite distinct from the first 

 Science is built up of successive solutions given to questions 

 of ever increasing subtlety, approaching nearer and nearer 

 towards the very essence of phenomena. If we proceed to 

 discuss together the question of how living, organized beings 

 act in decomposing fermentable substances, we will be found 

 to fall out once more on your hypothesis of communicated 

 motion, since according to our ideas, the actual cause of fer- 

 mentation is to be sought, in most cases, in the fact of life 

 without air, which is the characteristic of many ferments." 



Let us briefly see what Liebig thinks of the experiment in 

 which fermentation is produced by the impregnation of a 

 saccharine mineral medium, a result so greatly at variance 

 with his mode of viewing the question. 6 After deep consid- 

 eration he pronounces this experiment to be inexact, and the 

 result ill-founded. Liebig, however, was not one to reject 

 a fact without grave reasons for doing so, or with the sole 

 object of evading a troublesome discussion. " I have repeated 

 this experiment," he says, "a great number of times, with 

 the greatest possible care, and have obtained the same results 

 as M. Pasteur, excepting as regards the formation and in- 

 crease of the ferment." It was, however, the formation and 

 increase of the ferment that constituted the point of the 

 experiment. Our discussion was, therefore, distinctly limited 





See our Mtmoir of 1860 (Annales de Chimie et de Physique, vol. Iviii., 

 61, and f9llowing, especially pp. 69 and 70, where the details of the 

 :periment will be found). 





