THE ORIGIN OF ORGANIC MATTER 19 



demonstrate that higher plants are not capable of assimilating" atmospheric 

 nitrogen, but that when they are supplied with nitrogen from the nitrates 

 of the soil they develop normally. He further showed that plants can 

 develop in a soil in which all traces of organic substance have been removed 

 and that all of the carbon in such plants is derived from the atmosphere. 

 This was an experimental refutation of the humus theory and clearly 

 showed that the favorable effect of a soil rich in humus must be due to 

 other causes than those which were maintained by the proponents of the 

 humus theory. Boussingault's greatest service, however, probably was 

 in the demonstration of the fact that all of these questions are amenable 

 to experimental treatment, difficult and time-consuming though the method 

 may be. 



Great as the influence of Liebig's writings was in demonstrating the 

 application of organic chemistry to biological problems, the development 

 of organic chemistry was destined to follow a course which for a long 

 time neglected a consideration of the synthesis of organic substances by 

 the plant. Through the discovery by Wohler of the synthesis of urea from 

 ammonium cyanate the theory was refuted that the carbon compounds 

 found in plants and animals, the "organic" compounds, were the result 

 of a vital force peculiar to living things. Thereafter a continuously in- 

 creasing number of such organic compounds was synthesized in the 

 laboratory and it was concluded that the intermediary action of living 

 things was not essential to the production of most of the substances found 

 in nature. The chemist had devised a number of short cuts and could, 

 in fact, greatly improve on nature in the production of the multifarious 

 substances of use in industry and the arts. Under the leadership of men 

 like Dumas, Laurent, Gerhardt, Kekule, Hofmann and Baeyer the primary 

 interest was centered about considerations of constitution, structure and 

 synthesis. The tremendous development which the study of carbon com- 

 pounds has enjoyed since the middle of the nineteenth century together 

 with the stimulus of the commercial application of synthetic products and 

 the development of new processes, for a considerable time forced the study 

 of the chemistry- of living things into second place. At the same time, 

 however, the tremendous mass of information regarding carbon com- 

 pounds which was thus accumulated served as a logical prerequisite to a 

 rational study of the chemistry of living things and as the most valuable 

 tool in the unravelling of the tangle of chemical reactions which go to 

 make up the various life processes. 



It is, of course, true that the study of the chemical changes taking place 

 in living things has been assiduously pursued for many years. When, 

 with the development of organic chemistry this discipline became a sepa- 

 rate division of science, the study of biological chemistry also enjoyed a 

 rapid and fruitful development. Its efforts were, however, both in re- 

 search and teaching, very largely devoted to investigations on animals and 

 relatively little attention was devoted to the chemistry of plants. This 

 fact undoubtedly, to a large measure, accounts for the difficulty of en- 



