Liebigs Organic Chemistry applied to Agriculture. 573 



of which is completely unknown to him ? The thing is impossible ! 

 Matters containing nitrogen are among the essentials requisite for 

 the formation of yeast. In what state are those matters when in 

 the wort ? What changes do they undergo in forming yeast ? And 

 how are we to explain the remarkable fact, that ferment, which is 

 entirely exhausted, much resembles woody fibre, and is therefore 

 destitute of nitrogen ? Whence is derived this woody fibre met with 

 thus unexpectedly ? Here now we, poor, ignorant vegetable physio- 

 logists apply to chemistry for assistance. Since you cannot answer 

 us, permit me to read you a short physiological lecture : — Cells in 

 plants are only formed where sugar or gum occur, and a substance 

 containing nitrogen ; this nitrogen forms nuclei, and afterwards 

 changes the sugar or gum altogether into fibrous matter (faserstofF) ; 

 the cell being completed, it afterwards grows only by distention. 

 In wort exist all the material conditions required for the formation 

 of cells ; the other conditions we are unacquainted with. When the 

 yeast, which originates in the wort, is examined by a microscope, 

 cells are found somewhat large, and frequently connected with each 

 other ; with care, the whole process of their increase may be per- 

 ceived. Such cells, at first, always consist of the nucleus containing 

 nitrogen ; besides which, there frequently appear other smaller ker- 

 nels in the interior of the cells, which are otherwise filled with 

 clear, watery juice. Such cells may easily be broken by pressure ; 

 when their contents come out, a small empty bag remains. As 

 soon as the wort no longer contains matter capable of maintaining 

 vegetation, the formation of yeast ceases. When much alcohol has 

 been formed, this renders vegetation impossible, and wine ceases 

 to ferment. When beer-yeast is well washed with distilled water, 

 and rubbed to a powder in an agate mortar, and then treated with 

 water, alcohol, ether, &c., there remains fibrous matter (faserstofF) 

 as a residuum, and the dissolving agents extract from the yeast a lit- 

 tle gum, matter resembling wax or fat, and a substance containing 

 nitrogen. My purposes are sufliciently served by this chemical 

 analysis, which was not made for the purpose of publication ; besides, 

 I am only a poor physiologist, whose art of making laboratory ex- 

 periments was learned from the deceased Stromeyer, my venerable 



