PUTRID POISONS. 385 



state of decomposition from the yeast just mentioned. 

 Thus, when sugar is acted on by rennet or putrefy- 

 ing vegetable juices, it is not converted into alcohol 

 and carbonic acid, but into lactic acid, mannite, and 

 gum. 



Again, it has been shown, that yeast added to a 

 solution of pure sugar gradually disappears, but that 

 when added to vegetable juices which contain gluten 

 as well as sugar, it is reproduced by the decomposi- 

 tion of the former substance. 



The yeast with which these liquids are made to 

 ferment, has itself been originally produced from 

 gluten. 



The conversion of gluten into yeast in these veg- 

 etable juices is dependent on the decomposition 

 (fermentation) of sugar ; for, when the sugar has 

 completely disappeared, any gluten which may still 

 remain in the liquid does not suffer change from 

 contact with the newly-deposited yeast, but retains 

 all the characters of gluten. 



Yeast is a product of the decomposition of gluten; 

 but it passes into a second stage of decomposition 

 when in contact with water. On account of its being 

 in this state of further change, yeast excites fermen- 

 tation in a fresh solution of sugar, and if this second 

 saccharine fluid should contain gluten, (should it be 

 wort^ for example,) yeast is again generated in con- 

 sequence of the transposition of the elements of the 

 sugar exciting a similar change in this gluten. 



After this explanation, the idea that yeast repro- 

 duces itself as seeds reproduce seeds, cannot for a 

 moment be entertained. 



From the foregoing facts it follows, that a body 

 in the act of decomposition (it may be named the 

 exciter)^ added to a mixed fluid in which its constit- 

 uents are contained, can reproduce itself in that 

 fluid, exactly in the same manner as new yeast is 

 produced when yeast is added to liquids containing 

 gluten. This must be more certainly effected when 

 the liquid acted upon contains the body by the met- 

 33 



