766 



PHYSIOLOGY. 



to the transformation of the acids,' cellulose, lignine, starch, 

 dextrin, gum, and matters of a like nature. According to 

 M. Buignet's recent investigations, the cause of the change of the 

 primarily formed cane sugar into interverted sugar is not the 

 acids of the fruits, but that it appears to depend on the influence 

 of a nitrogenous body playing the part of a glucosic ferment, 

 analogous to that which M. Berthelot has extracted from yeast. 

 M. Buignet adds, that "the abundance in which starch is found 

 distributed through the vegetable kingdom, leads to the supposi- 

 tion that it is the true source of the saccharine matter in fruits. 

 Its presence cannot, however, be detected in green fruits, either 

 by the microscope or by iodine, excepting in green bananas, 

 which contain a notable quantity of starch." M. Buignet also 

 notices that green fruits contain a particular principle resembling 

 the tannins, which is capable of being converted into a sugar 

 identical with the sugar from starch, under the influence of 

 dilute acids and a proper temperature. The proportion of this 

 tannin diminishes in fruits in the same ratio that the proportion 

 of sugar increases. 



The changes which take place in the composition of fruits 

 during ripening are well exhibited in the following table founded 

 upon Berard's observations : — 



The pericarp of some fruits has developed in it during the pro- 

 cess of ripening fixed and essential oils, as well as other sub- 

 stances of an aromatic nature. According to Fremy, the inner 

 walls of the cells of succulent fruits in an unripe state, consist 

 of a substance called pectose, which is insoluble in water. This 

 is converted in ripe fruits into pectinc, which is soluble in water. 

 Pcctine is afterwards transformed into pcctic acid. Frcmy has 

 also noticed, that at the ])eriod of maturation the thickness of 

 the cell-walls diminishes rapidly; hence, it would api)ear that 

 these transformations of the pectic compounds play an important 



