STUDIES ON FEKMENTATIOX. 251 



solution, sho^\-ed that 1-04 grammes (16 grains) of sugar had 



disappeared. The weight of the yeast, dried at 100° C. (212° F.), 



was 0127 gramme (2 grains), which gives us the ratio between 



the weight of the yeast and that of the fermented sugar 



0"127 1 • 



= b 1 > which is considerably higher than the preceding 



ones. 



We may still further increase this ratio by making our 

 estimation as soon as possible after the impregnation, or the 

 addition of the ferment. It will be readily understood why 

 yeast, which is composed of cells that bud and subsequently 

 detach themselves from one another, soon forms a deposit at the 

 bottom of the vessels. 



In consequence of this habit of growth, the cells constantly 



covering each other prevents the lower layers from having access 



to the oxygen held in solution in the liquid, which is absorbed 



by the upper ones. Hence, those which are covered and 



deprived of this gas act on the sugar without deriving any vital 



benefit from the oxygen — a circumstance which must tend to 



diminish the ratio of which we are speaking. Once more 



repeating the preceding experiment, but stopping it as soon as we 



think that the weight of yeast formed may be determined by the 



balance {we find that this may be done twenty -four hcu:"s after 



impregnation with an inappreciable quantity of yeast) in this 



case the ratio between the weights of yeast and sugar is 



0s'--024 yeast 1 ^, . . , , . , . , 



A o^ nno =-,- I his IS the highest ratio that we have been 



0^-098 sugar 4 ° 



able to obtain. 



Under these conditions the fermentation of sugar is extremely 

 languid : the ratio obtained is very nearly the same that ordi- 

 nary fungoid growths would give. The carbonic acid evolved 

 is principally formed by the decompositions which result from 

 the assimilation of atmospheric ox^'^gen. The yeast, therefore, 

 lives and performs its functions after the manner of ordinary 

 fungi : so far it is no longer a ferment, so to say ; moreover, 

 we might exptct to find it cease to be a ferment at all if we 



