IMPORTANCE OF ALKALINE BASES. 65 



into beer along with barley. The bran of flour contains a large 

 quantity of ammoniacal phosphate of magnesia. This salt forms 

 large crystalline concretions, often amounting to several pounds 

 in weight, in the ccecum of horses belonging to millers ; and 

 when ammonia is mixed with beer, the same salt separates as a 

 white precipitate. 



Most plants, perhaps all of them, contain organic acids of very 

 different composition and properties, all of which are in combina- 

 tion with bases, such as potash, soda, lime, or magnesia ; plants 

 containing free organic acids are few in number. These bases 

 evidently regulate the formation of the acids, for the diminution 

 of the one is followed by a decrease of the other : thus in the 

 grape, for example, the quantity of acid contained in its juice is 

 less when it is ripe than when unripe ; and the bases, under the 

 same circumstances, are found to vary in a similar manner. 

 Such constituents exist in the smallest quantity in those parts of 

 a plant in which the process of assimilation is most active, as in 

 the mass of woody fibre ; and their quantity is greatest in those 

 organs whose office it is to prepare substances conveyed to them 

 for assimilation by other parts. The leaves contain more inor- 

 ganic matters than the branches, and the branches more than the 

 stem (Saussctre). The potatoe plant contains more potash before 

 blossoming than after it (Mollerat). 



The acids found in the different families of plants are of vari- 

 ous kinds ; it cannot be supposed that their presence and peculi- 

 arities are the result of accident. The fumaric and oxalic acids 

 in the lichens, the kinic acid in the Rubiacece, the rocellic acid 

 in the Rocella tinctoria, the tartaric acid in grapes, and the nu- 

 merous other organic acids, must serve some end in vegetable 

 life. But if these acids constantly exist in vegetables, and are 

 necessary to their life, which is incontestable, it is equally cer- 

 tain that some alkaline base is also indispensable, in order to enter 

 into combination with the acids ; for these are always found in 

 the state of neutral or acid salts. All plants yield by incineration 

 ashes containing carbonic acid ; all, therefore, must contain salts 

 of an organic acid.* 



* Salts of organic acids yield carbonates on incineration, if they contain 

 cither alkaline or earthy bases. 



