356 
PHYSIOLOGY. 
BOOK II. 
thus, Couverchel found that, if we treat Apple jelly with a 
vegetable acid dissolved in water, we obtain a sugar analogous 
to that of Grapes ; that the gurn of Peas, placed with oxalic 
acid, in a temperature of 125° Reaum., changed to sugar; 
that gum extracted from starch, if mixed with the juice of 
green Grapes, rendered the latter saccharine ; and finally that 
tartaric acid will produce the same effect by aid of heat : this 
' is the reason why most fruits become sweet when cooked. ' 
Other matters offer remarkable disparities between one 
fruit and another: thus malic acid keeps diminishing in 
Apricots and Pears, augmenting in Currants, Cherries, Plums, 
and Peaches. Gum keeps diminishing in Currants, Cherries, 
Plums, and Pears, and augmenting in Apricots and Peaches. 
Animal matter keeps diminishing in Apricots and Plums, 
and increasing in Currants, Peaches, Cherries, and Pears. 
Lime, which never exists except in small quantity, seems 
generally to diminish, probably because evaporation becomes 
less with maturity. 
After the period which is generally called that of ripeness, 
most fleshy fruits undergo a new kind of alteration ; their 
flesh either rots or hlets* These two states of decomposition 
cannot, according to Berard, take place, except by the action 
of the oxygen of the air, although he admits that a very small 
quantity only is sufficient to cause it. He succeeded in pre- 
serving for several months, with little alteration, the fleshy 
fruits which were the subjects of the foregoing experiments, 
by placing them in hydrogen or nitrogen gases. All fruits 
at this extreme period of their duration, whether they decay 
or whether they blet, form carbonic acid with their own car- 
bon and the oxygen of the air, and moreover disengage from 
their proper substance a certain quantity of carbonic acid. 
“ Bletting is in particular a special alteration. I have re- 
marked, in another place, that this condition is not well cha- 
racterised in any other fruits than those of Ebenaceae and 
Pomaceae ; that both these natural orders agree in having the 
calyx adherent to the ovary, and that their fruits are austere 
* May I be forgiven for coining a word to express that peculiar bruised 
appearance in some fruits, called blessi by the French, for which we have 
no equivalent English expression ? 
