DISCUSSION WITH LIEBIG 129 



light on the physiology of the cell. We shall not follow 

 the discourse in all its developments, which are some- 

 times digressions, but shall ask only what it had to reply 

 to the new doctrine on the fermentations. 



On this point his position became more and more 

 embarrassing. Already, at the time when he had first 

 developed his theory, he had been obliged to admit that 

 the yeast was a living organism which renewed and 

 destroyed itself continually, and it was only the products 

 of the destruction which made the sugar ferment. That 

 point had become difficult to maintain and support 

 after Pasteur had shown fermentation to be a cellular 

 phenomenon. It is curious to see how Liebig extricates 

 himself from this difficulty. He considers that life is 

 accompanied at every instant, in every cell, by a move- 

 ment of decomposition and reconstruction, and, naturally, 

 it is to the first that he has recourse. He admits then 

 the physiological phenomenon but he takes into con- 

 sideration only a part of it and, once more, the chemical 

 side, endeavoring "to reduce the chemical decomposition 

 of the sugar to a simple formula common to all analogous 

 phenomena." 



The attempt is bold, and we recognize in it the general- 

 izing mind of Liebig. We shall see how he succeeded. 

 Let us note in the beginning that, from a chemical point 

 of view, the vital phenomenon of Pasteur does not differ 

 essentially from the phenomenon of movement of Liebig, 

 and that it is possible to reconcile them. "I admit," 

 says Liebig, "that the yeast consists of vegetable cells 

 which come into existence and multiply in a liquid con- 

 taining sugar and an albuminoid substance (it is I who 

 underscore). The yeast is necessary in order that there 

 may be formed in its tissues, by means of the albuminoid 

 substance and the sugar, a certain unstable combination," 

 which alone is capable of undergoing dismemberment. 



