Justus Von Liebig

Animal and Vegetable Physiology.

These and other stud ies in pure chemistry mainly occupied his attention until about 1838, but the last thirty-five years of his life were devoted more particularly to the chemistry of the processes of life, both animal and vegetable. In animal physiology he attempted to trace out the operation of chemical and physical laws in the maintenance of life and health. To this end he examined such vital products as blood, bile and urine; he analysed the juices of flesh, establishing the composition of creatin and investigating its decomposition products, creatinin and sarcosin ; he classified the various articles of food in accordance with the special function performed by each in the animal economy, and expounded the philosophy of cook ing. In opposition to many of the medical opinions of his time he taught that the heat of the body is the result of the processes of combustion and oxidation performed within the organism. A secondary result of this line of study was the preparation of his food for infants and of his extract of meat.

Vegetable physiology he pursued with special reference to agri culture. His first publication on this subject was Die Chemie in ihrer Anwendung oaf Agricultur and Physiologie in 1840, which was at once translated into English by Lyon Playfair. Rejecting the old notion that plants derive their nourishment from humus, he taught that they get carbon and nitrogen from the carbon dioxide and ammonia present in the atmosphere, these compounds being returned by them to the atmosphere by the processes of pu trefaction and fermentation, while their potash, soda, lime, sul phur, phosphorus, etc., come from the soil. Of the carbon dioxide and ammonia no exhaustion can take place, but of the mineral con stituents the supply is limited because the soil cannot afford an indefinite amount of them ; hence the chief care of the farmer, and the function of manures, is to restore to the soil those minerals which each crop is found, by the analysis of its ashes, to take up in its growth. On this theory he prepared artificial manures containing the essential mineral substances together with a small quantity of ammoniacal salts, because he held that the air does not supply ammonia fast enough in certain cases, and carried out systematic experiments on ten acres of poor sandy land which he obtained from the town of Giessen in 1845. But in practice the results were not wholly satisfactory, and it was a long time before he recognized one important reason for the failure in the fact that to prevent the alkalis from being washed away by the rain he had taken pains to add them in an insoluble form, whereas, as was ultimately suggested to him by experiments performed by J. T.

Way about 185o, this precaution was not only superfluous but harmful, because the soil possesses a power of absorbing the sol uble saline matters required by plants and of retaining them, in spite of rain, for assimilation by the roots.

Liebig's literary activity was very great. The Royal Society's Cata logue of Scientific Papers enumerates 318 memoirs under his name, exclusive of many others published in collaboration with other investi gators. In 1832 he founded the Annalen der Pharmazie, which became the Annalen der Chemie und Pharmazie in 1840 when Wohler be came joint-editor with him, and in 1837 with \Willer and Poggendorff he established the Handworterbuch der reinen und angewandten Chemie. After the death of Berzelius he continued the Jahresbericht with H. F. M. Kopp.

The following are his most important separate publications, many of which were translated into English and French almost as soon as they appeared: Anleitung zur Analyse der organischen Kbrper Die Chemie in ihrer Anwendung auf Agrikultur and (1840) ; Die Thier-Chemie oder die organische Chemie in ihrer Anwen dung auf Physiologie und Pathologie (1842) ; Handbuch der orga nischen Chemie mit Riicksicht auf Pharmazie (1843) ; Chemische Briefe (1844) ; Chemische Untersuchungen ober das Fleisch and seine Zube reitung zum Nahrungsmittel (1847) ; Die Grundsdtze der Agrikultur Chemie (1855) ; Ober Theorie und Praxis in der Landwirthschaft (1856) ; Naturwissenschaftliche Briefe iiber die moderne Landwirth schaft (1859). A posthumous collection of his miscellaneous addresses and publications appeared in 1874 as Reden and Abhandlungen, edited by his son George (b. 1827). His criticism of Bacon, Ober Francis von Verulam, was first published in 1863 in the Augsburger allgemeine Zeitung, where also most of his letters on chemistry made their first appearance.

See also The Life Work of Liebig (London, 1876), by his pupil A. W. von Hofmann, which is the Faraday lecture delivered before the Lon don Chemical Society in March 1875, and is reprinted in Hofmann's Zur Erinnerung an vorangegangene Freunde; also W. A. Shenstone, Justus von Liebig, his Life and Work (1895) ; and Tilden's Famous Chemists ( 1921) .