424 THE POPULAR SCIENCE MONTHLY 



composed mainly of carbon, hydrogen and oxygen, and sometimes 

 nitrogen. 



The foundation and elaboration of organic chemistry was mainly the 

 great achievement of the illustrious chemist Justus Liebig (1803- 

 1873). After studying chemistry at Paris under Gay-Lussac, he was 

 professor of chemistry at Giessen 1824-1852, and at Munich from 1853 

 until his death in 1873. About 1837 he began epoch-making investiga- 

 tions of physiologic and organic chemistr}^, and in works published from 

 1840 he laid down the main lines of our knowledge of the chemistry of 

 food and nutrition. He first, for instance, sharply differentiated the 

 foodstuffs albumen, fat and carbohydrate, and recognized the tissue- 

 forming function of albumins and the heat-producing properties of fats 

 and carbohydrates. 



Since the time of Liebig many workers have brought our knowledge 

 of the chemistry of food to its present state. Among important investi- 

 gations of this character now being actively prosecuted are those on the 

 molecular structure of the complex foodstuffs, such as the studies of 

 Emil Fischer, Emil Abderhalden and others on the proteins. Some of 

 the sugars have been artificially sjTithesized, and a beginning has been 

 made even on the proteins. 



Crude attempts at food analysis date back for centuries, as in con- 

 nection with governmental measures to prevent adulteration of foods 

 and beverages. In the modern era George Pearson, of England, in 1795 

 reported an analysis of potatoes; in 1805, Einhoff analyses of potatoes 

 and rye. Eeliable analyses of milk were reported by Peligot in 1836, 

 and of feeding stuffs and milk by Boussingault and Le Bel 1836-1839. 

 From about 1840, through the work of Liebig a great impetus was 

 given to food analysis; and with the further advances of chemistry 

 came the development of reliable analytic methods and the accumula- 

 tion of data. From about 1860 the standard methods of food analysis 

 now employed were developed by Wilhelm Henneberg (1825-1890), of 

 the agricultural experiment station at Weende, near Gottingen; these 

 methods soon came into general use and have greatly facilitated and 

 S3'stematized this line of work. 



Possibly the earliest analyses of food made in the United States were 

 of some cereals by C. U. Shepherd published in 1844. Analyses of 

 various foods were published by Salisbury in 1848, Beck in 1848-1849, 

 Emmons in 1849, Jackson in 1857. One of the most prolific workers 

 in this field in this country was Atwater, who, employing the Weende 

 methods, made analyses of maize in 1869, and commenced an extended 

 series of analyses of fish and other foods in 1877. 



Dietary studies — investigations of the amounts of foodstuffs actually 

 consumed by different classes of people under various conditions — 

 furnish an important part of the data underlying the science of dietetics. 

 Among the earliest investigations of this sort were those conducted by 



