PROXIMATE PRINCIPLES. 157 



corporated into their own substance. This constitutes 

 tion, and distinguishes living substances from dead matter. A 

 stone does not receive nourishment, although it may increase 

 by an external accumulation of matter. "Vegetable sub- 

 stances, analyzed by a chemical process, have been found to 

 contain carbon, oxygen, hydrogen, and sometimes nitrogen, sul- 

 phur, silex (a flint-like substance), the oxide of iron, soda, mag- 

 nesia, and chalk."* These different substances are by the 

 root, stems, and leaves of the plant, derived from the earth, 

 air, and water. 



Proximate Principles. 



Vegetation produces chemical combinations, which are dis- 

 tinguished by the name of proximate principles. Although the 

 proximate principles of plants are very numerous, but few of 

 them are well known ; they are the result of the action of the 

 vital forces of plants, and are, therefore, important subjects of 

 investigation to those who pursue the study of physiological 

 botany to any great extent. Carbon, oxygen, hydrogen, and 

 nitrogen, are the constituent parts of the proximate principles 

 of plants. These principles may be divided into two classes. 



I. Those principles which are composed of carbon, hydrogen 

 and oxygen, without any nitrogen. 



II. Such as contain, besides the substances belonging to the 

 other class, some nitrogen. There are few of this class. 



The first class of proximate principles is divided into three 

 orders. 



1st. Principles which have more oxygen than sufficient to form 

 water. 



2d. Principles in which oxygen and hydrogen exist in the 

 exact proportion to form water. 



3d. Principles where hydrogen is in excess. 



The 1st order includes vegetable acids : as, 



Acetic acid, or pure vinegar ; this is generally produced by 

 fermentation from wine, cider, and some other liquids ; it is 

 also found in a pure state in the campeachy wood, and the sap 

 of the elm. 



Malic acid may be extracted from green apples and the bar- 

 berry. 



Oxalic acid is found in several species of sorrel, belonging to 

 the genera OXALIS and RUMEX. 



Tartaric acid is obtained from the tamarind and the cran- 

 berry ; this acid, combined with potash, forms what is com- 

 monly called cream of tartar. 



* Mirbel, " Elemens de Botanique." 



Proximate principles Proximate principles divided into two classes First 

 class divided into three orders First order. 



14 



