ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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produced by acetic acid. (3) With certain ferments the total acidity 
increases, while the fixed acidity continually decreases, and finally only 
acetic acid remains. (4) After a certain day, which varies with the 
ferment and the cultivation medium, the total quantity of acid produced 
per diem regularly decreases. 
(C.) Influence of age. (1) The age of the ferment has a great in- 
fluence on the progress of fermentation. (2) Ferments sown on neutral 
media preserve for a long time their special properties, but on solid or 
acid media they degenerate. (3) Ferments a month old are more 
vigorous than those quite young ; but afterwards they lose more or less 
rapidly their power, according to the medium on which they are sown. 
Thus they degenerate more quickly on onion juice without chalk than on 
turnip juice without chalk. 
(D.) Influence of air. There are aerobic and anaerobic lactic fer- 
ments, and also indifferent (potential) ferments. 
(E.) Influence of the superficial and deep culture. (1) The super- 
ficial culture produces volatile acid (acetic). (2) The fixed acidity 
may be considerable in deep cultures, and may attain 85, 90, or even 
95 per cent, of the sugar lost, while in surface cultures it is as a rule 
much less. 
(F.) Influence of nitrogenous matter. (1) Lactic ferments prefer 
pepton to other nitrogenous matter. (2) The fixed acidity increases pro- 
portionally, up to a certain limit, with the richness of the medium in 
pepton ; the differences becoming so much the more pronounced as the 
ferment is exacting. (3) The volatile acidity depends but little on the 
richness of the medium in nitrogenous matter. (4) The lactic ferments 
can produce lactic acid from mere nitrogenous matter. (5) The relation 
between the quantity by weight of ferment and the quantity of sugar lost 
may be very high. (6) The same weight of ferment can transform into 
fixed acid more sugar by deep than by superficial culture. (7) The 
lactic ferments may be so rich in nitrogen as* to resemble albuminous 
substances (15 per cent.). (8) This richness is proportional to the 
amount of nitrogen in the medium. (9) A deep-cultivated ferment 
is less rich in nitrogen thau when cultivated on the surface, other 
things being equal. (10) After a certain period the ferment ceases 
to multiply ; its richness in nitrogen increases with the length of the 
fermentation. 
(G.) Influence of the amount of sugar. (1) The addition of sugar 
to a cultivation medium acts less energetically than the addition of 
pepton. (2) Each ferment seems to prefer certain sugars to others. 
(H.) Salts. (3) The same ferments may give different acids with 
the same sugar. (4) There are ferments which give with different 
sugars the same acid (left, right, or inactive). (5) The same ferment 
may produce different lactic acids. (6) C 5 sugars [sic] may be attacked 
by vigorous lactic ferments. (7) The age of the seed and the successive 
cultivations in different media exercise an influence on the acid produced. 
(8) The same ferment produces the same acid, whether it be cultivated 
deeply or superficially. (9) There are lactic ferments which seem able 
to attack the inactive lactate of lime. 
(I.) Diastase. A lactic diastase does not seem to exist. 
1895 
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