MODERN BIOLOGY 449 



of the century. The son of a colour-man at Darmstadt, he acquired in his 

 father's shop even as a child an interest in chemistry and its practical applica- 

 tion. At one time he endeavoured to follow his bent as an apprentice to an 

 apothecary, but did not get on well there, and he then studied for a couple of 

 years at German universities, during which time he associated himself with 

 Schellingianism; he soon wearied of this also and went to Paris, where he 

 eventually found the training he sought for in the laboratory of the famous 

 Gay-Lussac. On the recommendation of Humboldt he was called to the chair 

 of chemistry at Giessen, and after struggling for years against jealousy and 

 hostility he succeeded in bringing into being the first chemical university- 

 laboratory in Germany. As a teacher he resembled J. Miiller in his capacity 

 for gathering around him and educating numbers of pupils; indeed, the re- 

 vival of chemistry in Germany is attributable to him. Towards the close of 

 his life he became a professor at Munich. He was a pioneer in his purely 

 chemical discoveries, especially in the field of organic chemistry; he gave 

 to organic elemental analysis the form that it has retained ever since, while 

 his investigations into organic acids were of epoch-making importance, as 

 were also his discoveries in the sphere of zymurgy. These latter discoveries 

 made him the foremost supporter of the chemical fermentation theory, and 

 Pasteur's stubborn opponent. He is of greatest importance, however, as the 

 creator of practical agricultural chemistry; hitherto it had been thought 

 generally that plants absorbed their principal nourishment out of the sur- 

 face-soil, but he proved that the surface-mould was rather augmented by 

 cultivation, that carbonic acid was the plants' sole source of carbon, and 

 ammonia its source of nitrogen, and to prove his theory he instituted experi- 

 ments with manure on an expensive scale. As a result of these experiments he 

 placed agricultural economy on a natural-scientific basis, but he certainly 

 shot far beyond the mark — partly owing to his ignorance of vegetable 

 anatomy — and he gained many enemies on account of his overbearing 

 polemic, especially against the plant-physiologists. These in their turn ex- 

 posed a number of Leibig's inaccuracies; he denied the value of nitrogenous 

 manures, he wanted to supply the earth with insoluble instead of soluble 

 phosphoric acid and potassic salts, and he entirely ignored the respiration of 

 plants. On many points he received sharp criticism at the hands of Schleiden 

 and Mohl. As an animal-physiologist Liebig also acquired fame for his pio- 

 neer studies of the preparation and utilization of foodstuffs; he ascertained the 

 chemical compounds that are conveyed to the body through the food, but 

 here, too, he often went wrong, as when he divided food-substances into 

 "plastic" and "respiratory," including albuminous substances among the 

 former, and fats and carbohydrates among the latter. 



In this sphere Liebig was opposed by a young Dutch physiologist, 

 Jacob Moleschott (18x2.-93). The son of a physician, he studied physiology 



