26 ORGANIC EVOLUTION CONSIDERED 



remarkable example which shows the almost unlim- 

 ited possibilities of an element in helping to build 

 structures of the most wonderful and diverse kinds. 

 In its uncombined crystalline condition, it constitutes 

 the diamond, the hardest of all known substances. 

 In a second form it is known as graphite, or black 

 lead, and in other forms as charcoal and lampblack. 

 This hardest of all elements helps to form a countless 

 number of compounds, some of which are gases, 

 other liquids, and still others are solids. It is a neces- 

 sary constituent of every plant and animal. It is 

 found in the gas, carbon dioxide, which is a necessary 

 food of plants. The same gas unites with many 

 bases to form the many mineral carbonates that exist 

 in nature. It is a part of a vast number of organic 

 compounds which are of the highest importance to 

 man and in the economy of life. Among these com- 

 pounds are starch, cellulose, the various sugars, the 

 many organic acids, the alkaloids, such as those in 

 quinine, morphine and strychnine, the alcohols, the 

 different fats and oils, and the numerous essential 

 oils, and the long lists of hydrocarbons. These are 

 but a few of the great number of compounds which 

 carbon helps to form. So important is this element 

 that the great branch of organic chemistry is often 

 called the chemistry of the compounds of carbon. 



In many compounds carbon is combined with 

 hydrogen alone, in many" more with hydrogen and 

 oxygen, and in a large number it is united with hydro- 

 gen, oxygen and nitrogen. 



It is indeed marvelous [that these four elements, 

 which constitute the great bulk of the organic world, 

 can, by uniting in different ways, produce the vast 

 number of compounds that constitute the great 

 science of organic chemistry. 



Carbon and hydrogen alone unite to form several 



