No. 375.] REVIEWS OF RECENT LITERATURE. 209 
distinguishable, one due to the presence of acids, the other to the 
lack of air and the resultant production of alcohol. 
(3) The quotients of acids occur whenever fruits containing these 
acids (citric, tartaric, malic, etc.) are exposed to a sufficiently high 
temperature, — 30° C. and upwards for fruits containing citric and 
tartaric acid, 15° C. and upwards for fruits containing malic acid. 
Quotients of acids are also found in fatty plants. 
(4) The quotients of fermentation are produced whenever the oxy- 
gen of the air fails to reach the cells in sufficient quantity to furnish 
the energy necessary for vital activity. 
(5) The quotient of fermentation differs from the quotient of acids 
in the following ways : 
(a) By the time it appears, — end of maturity. 
(2) By the lower temperature at which it can take place, —even at 
o° C. in case of some fruits. 
(c) By its value,—often above 3, while that of acids is always 
below 2 and generally less than 1.5. 
(d) By the corresponding respiratory intensity,—the amount of 
oxygen absorbed after the quotient of fermentation appears is much 
less than before, while the quantity of oxygen absorbed after the 
quotient of acids appears is much greater than before. 
(e) By the change which takes place when sections are made, — 
sectioning slightly diminishes the quotient of respiration and scarcely 
increases the corresponding respiratory intensity, while it consider- 
ably raises the quotient of acids and at the same time greatly in- 
creases the respiratory intensity. 
Since the acids and tannins disappear rapidly at high tempera- 
tures, the ripening of sweet fleshy fruits containing acids (apples, 
grapes, oranges) or tannins (persimmons) or a mixture of acids an 
tannins (sorbs, medlars, pears) may be hastened by exposure to 
warmth. The ripening of fruits containing much acid and not sub- 
ject to fermentation due to asphyxiation (certain apples, grapes, 
cherries, oranges, etc.) may be retarded by exposing them to tem- 
peratures approaching o° C., since at low temperatures the acids 
are not oxidized. On the contrary, fruits containing tannin, and 
which present at the close of ripening a quotient of fermentation 
(sorbs, medlars, persimmons, bananas), cannot be preserved much 
longer at low temperatures than at high ones, since the tannin is 
oxydized as well at one temperature as at another, and immediately 
after its disappearance the pectose is transformed into pectin, oxy- 
gen is excluded, the period of fermentation sets in, and the fruit 
