RIPENING OF FRUITS. 303 



3. Parapecti rie/when treated at a boiling heat with dilute acids, 

 is converted into metapectine. 



4. Pectase converts pectine into pectic acid. 



5. By long-continued action of pectase upon pectine pectic 

 acid is formed. 



6. Pectic acid is transformed by boiling water into parapectic 

 acid. 



7. An aqueous solution of parapectic acid is quickly converted 

 into metapectic acid. 



All these bodies are derived from pectose, which through all 

 these transformations has not even suffered a change in the pro- 

 portion of weight of its constituents (carbon, hydrogen, and 

 oxygen ) ; hence all have the same qualitative and quantitative 

 composition. This may, perhaps, sound odd, but chemistry pre- 

 sents numerous analogies for such cases, and hence the term 

 isomeric has been applied to bodies which with the same quanti- 

 tative composition exhibit very different chemical properties. 



The changes pectose undergoes by the influence of heat, a 

 peculiar ferment, acids and alkalies, and the resulting combina- 

 tions mentioned above, have of course been artificially effected by 

 chemical means. They resemble, however, so closely the state of 

 fruits in the course of their growth and ripening, and the influ- 

 ences and conditions to which fruits are exposed in nature are 

 sufficiently similar to those artificially induced, that their action 

 may be reasonably supposed to be the same. We know from 

 daily experience that heat promotes the development and ripening 

 of fruit ; fruits contain pectose and acids, and alkalies or bases are 

 conducted to them from the soil ; hence in fruit in a normal state 

 of development none of the chemical agents are wanting which the 

 chemist uses for the production of derivatives of pectose. 



If the transformation of substances under the influence of others 

 be considered as dependent on chemical processes, the develop- 

 ment of a fruit from its first formation to complete ripeness, and 

 even to its decomposition, rotting, and putrefaction, is a chemical 

 process in the widest sense of the word. This is evident, not 

 only from what has been said in the preceding, but has also 

 been plainly shown by special chemical researches into the changes 



