FERMENTATION. 125 



substance, invertin, which has the power of materially 

 altering the carbo-hydrates to which it is added, and from 

 our knowledge of the functions of other cells we should be 

 led to expect that these cells may exert some influence on the 

 fermenting fluid without the whole of the sugar actually be- 

 coming part of the cell ; or perhaps that, on the other 

 hand, the protoplasm may set up such molecular motion in 

 its immediate neighbourhood, especially at certain tempera- 

 tures, that a certain area of the sugar present is so acted 

 upon that some of its molecules are set free for the use of 

 the yeast-cell, and that the others can only rearrange them- 

 selves in a definite manner ; and that, as a result, we have 

 hydration and the formation of alcohol, carbonic acid gas, 

 and water, the most stable elements that can be formed 

 under the existing conditions, and out of the molecules of 

 oxygen, hydrogen, and carbon that are available. There 

 may be slight modifications giving rise to the formation of 

 succinic acid or other bye products, as a greater or less 

 number of accidental or superfluous molecules are set free 

 to become converted into the superfluous or additional 

 substances. 



It is a well-known fact, that when yeast is placed under 

 conditions of moisture and warmth suitable for its develop- 

 ment, if there be sufficient nutriment present, but sugar 

 be withheld, or even if nitrogenous elements be kept from 

 from it, it becomes soft, and certain marked changes go on in 

 the substance of the cell. 



Bechamp found under such conditions leucine and tyrosine, 

 both of them products of protoplasmic metamorphoses, a 

 soluble albuminous substance coagulable by heat, an enzyme, 

 a peculiar gummy substance, phosphates and acetic acid, 

 along with which there was of course the production of a 

 certain amount of alcohol, some carbonic acid gas, and pure 

 nitrogen. 



Schiitzenberger, repeating the experiments, found other 

 products, such as xanthine, hypoxanthine, carnine, and 

 guaine, that pointed most distinctly to a process of meta- 

 morphoses of the protoplasm, and by a series of most inge- 

 nious experiments he found that yeast in distilled water 

 lost in five days about 9 per cent, of its protoplasm. That is, 

 in yeast there are certain soluble elements that can be re- 

 moved by washing with distilled water, leaving the insoluble 



