120 PHYSIOLOGICAL VIEWS. 



Proximate Privciples. 



Vegetation produces chemical combinations, which are distir^ 

 gTiished by the name of proximate principles. Although the proxi- 

 mate 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 most important of 

 the ultimate elements of plants, and the constituent parts of their 

 proximate principles. These principles may be divided into two 

 classes. 



I. Those principles which are composed of carbon, hydrogen, and 

 oxygen, without any nitrogen. 



n. Such as contain, besides the substances belonging to the other 

 class, some «?Yroo-en. 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 fermen- 

 tation 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 barberry. 



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

 genera Oxalis and Rume.x. 



Tartaric acid is obtained from the tamarind and the cranberry; 

 this acid, combined with potash, forms what is commonly called 

 cream of tartar. 



Citric acid is found in the lemon ; it is mixed with the malic acid 

 in the gooseberry, the cherry, and the strawberry. 



Quinic acid is obtained from the Peruvian Bark, {Cinchona.) 



Gallic acid is obtained from the oak, and the sumach ; it is highly 

 astringent. 



Benzoic acid is found in the Laurus benzoin, and in the Vanilla; 

 this is highly aromatic; it is thought to give the agreeable odour 

 common to balms. 



Prussic acid ; this acid gives out a strong odour like bitter al- 

 monds ; it is an active poison ; it is obtained from peach-meats and 

 blossoms, from bitter almonds, &c. 



The 2d order includes gum, sugar, &c. 



The Gums. Of these there are many kinds; they have neither taste 

 nor smell ; dissolved in water, they form a mucilage more or less 

 thick. The principal gums are, 



Gum- Arabic, which flows from the plant Mimosa nilotica ;* 



Common Gums, such as issue from the peach-tree, the cherry-tree, 

 and many others. 



Sugar is a substance which dissolves in water, and Jias a sweet 

 taste ; it is obtained from the sugar-cane, the sugar-maple, from the 

 stalks of Indian-corn, pumpkins, beets, and sweet apples. All vegfr- 

 tables which have a sweet taste, may be made to yield sugar. 



* By some writers called Acacia Arahica. 



Proximate Principles— What are the most important uhirnate elements of plants?— 

 Proximate principles divided into two classes — First class divided into three orders— 

 First order— Second order— Third order. 



