106 
As in other well-known cases of fermentation, a further production of 
acid may be obtained by precipitating that already formed. Thus, it is easy 
to convert as much as one-half of the sugar used into acid ; 30 grammes of 
dextrose yielded about 16 grammes of aci y this means, the conver- 
sion is also accelerated, and the breaking-up of the sugar, with which the 
formation of acid is evidently closely connected, proceeds more rapidly. 
Other ts may also act in a similar way, as for instance, the presence 
of saline compounds of chlorine, &c. The formation of acid continues 
as long as there is any vitality i in the fungus film and available material 
in the liquid. The acid, however, which is found in the fermenting 
fluid at a given time, is the atom "which results from the two parallel 
processes of acid formation and acid destruction; the latter eventually 
prevails, and finally every trace disappears in older eniin The 
destruction of the acid by the fungus is easy to prove by ex 
ous and uniform at different times, but its rate describes a 
rather ése mener. and descending curve, which is in close 
relation to the amount of the conversion of sugar effected by the 
growing fungus. 
The formation of the acid proceeds most actively at the time of 
maximum vitality of the fungus-film ; it increases before and decreases 
after this peri 
I may point to ‘the rather interesting comparison with the production of 
oxalic acid. In this, favourable conditions of fungus growth (heat and 
presence of chlorine compounds) promote the r apid destruction of the 
acid, and prevents its accumulation in the — Under 
similar gre? iiie the prodajni of citric acid is not only not check 
but even advanced. 'The difference may perhaps depend on ia lesser 
capacity of citric acid for being oxidised. 
The comparison is important also in other respects. As much as one- 
half of the sugar consumed can be converted into oxalic acid without 
impairing the fungus growth. In the prodnetion of citric a the 
withdrawal of very considerable quantities of this acid has actually no 
demonstrable vene _on the development of the fungus. We must 
decrease in quantity. In this instance this is the carbonic acid into which 
also under other conditions part of the citrie acid is converted. e 
eni now is whether the relation i isa direct tone. On the whole, I 
up ‘of the sugar r molecule results in a great deal of the citrie acid pro- 
duced, besides perhaps other compounds, yielding ultimately carbonic 
acid as a product of oxidation. Although we may thus consider the acid 
ermedia i 
back the totality of the material broken up by metabolism, especially 
the whole of the carbonic acid derived from respiration, to molecules of 
organised living substance. 
