320 
PHYSIOLOGICAL VIEWS. 
Proximate Principles. 
Vegetation produces chemical combinations, which are distin¬ 
guished 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. 
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 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 barberrv. 
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 cranberrv; 
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 has 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 vege¬ 
tables which have a sweet taste, may be made to yield sugar. 
* By some writers called Acacia Arabica. 
Proximate Principles—What are the most important ultimate elements of plants 7 — 
Proximate principles divided into two classes—First class divided into three orders— 
First order—Second order—Third order. 
