146 



Messrs. E. C. Grey and E. G. Young. 



(3) The two most variable products are lactic acid and acetic acid. And 

 it is remarkable that whereas on the left-hand side of the figure these curves 

 do not cross one another, on the right they do so very frequently. From 

 this it is clear that there is much more constancy between the products 

 derived from glucose by anaerobic than by aerobic fermentation. With 

 aerobic fermentation it would appear that slight variation in the conditions 

 may very greatly affect the resulting proportions between lactic and acetic 

 acid. Bearing in mind what has already been ^stated in §3 of this series, 

 that variation in the proportions of the products is often to be correlated 



Experiments arranged From left to right in order of 

 decreasing values oF Carbon dioxide + Formic acid. 



Fig. 1b.— Products of decomposition of glucose by B. coli communis. 



with variation in the proportion between living and dead or dying cells, it 

 would seem that the most probable explanation of this intercrossing of the 

 curves on the right of the figure is that oxygen has altered this proportion 

 between living and dying cells. And that either the oxygen has caused a 

 multiplication of the cells added in the emulsion, or else at least that it 

 has prevented them dying as rapidly as in the anaerobic fermentations. 

 This is all equivalent to saying that the aerobic fermentations are more 

 complicated by the factor of bacterial life than are the anaerobic fermentation. 

 (4) The figure shows fairly clearly that there are three main lines of 



