296 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 gum of Peas, placed with oxalic 

 acid, in a temperature of 1*25° (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 witli 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 blets.* 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." 



" Bietting 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 1 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 ? 



