NUTRITIVE VALUE OF DIFFERENT CARBON-COMPOUNDS 383 



their conjoint properties are such as to render molecular dissociation 

 possible. Fischer 1 has shown that even in simple hydrolytic decom- 

 position by an enzyme more marked differences may often exist between 

 the behaviour of the optical varieties of the same sugar, than between 

 sugars of different chemical composition. 



Nutritive value and chemical constitution. Pasteur first cultivated fungi in 

 solutions of known composition, and this method has been largely employed by 

 Nageli and Reinke to determine the nutritive value of different carbon-compounds, 

 while at the same time the requirements of certain plants have been more or less 

 accurately indicated 2 . A few works chiefly upon fungi are mentioned beneath, and 

 Fliigge has obtained many interesting results with different bacteria 3 . Nageli paid 

 special attention to the requirements of a few common mould-fungi (Penicillium, 

 Aspergillus), but more recent researches have shown that these results are by no 

 means of general application, and that very marked specific peculiarities exist 

 among different fungi, not only as regards the most appropriate compounds of 

 carbon, but also those of nitrogen (Sect. 70). 



Both nutritive and non-nutritive carbon-compounds are found among groups 

 of substances widely differing in constitution and properties from one another. Thus 

 the food-material may comprise many mono- and poly-basic organic acids (acetic, 

 citric, benzoic, gallic acids), alcohols (ethyl alcohol, glycerin, resorcin), esters (fats, 

 ethyl acetate), aldehydes and aldehyde alcohols (glucose, galactose), ketones and 

 ketone acids (fructose, acetone), various nitrogen-containing compounds, amides 

 (ethylamine, tetraethylammonium hydroxide), amido-acids (glycocoll, acetamide), 

 ureides (allantoin, parabanic acid), nitriles (benzene nitrile, methylcyanide). 



Hence Nageli erred in supposing (1. c., p. 401) that compounds in which carbon 

 and oxygen were directly associated together could not be assimilated, or that the 

 CH-group could only be used as food when two or more atoms of carbon were 

 united together. Certain plants grow when supplied with formic acid or methyl 

 alcohol, both of which contain one atom of carbon only. According to Reinke 

 the CO-radicle of parabanic acid may be used as a source of carbon, while many 

 lower organisms can obtain carbon from oxalic acid, urea, or even from carbon 

 dioxide by chemosynthetic assimilation. Different plants are able according to their 

 specific properties to assimilate the most varied substances and to produce from 



1 E. Fischer, Ber. d. Chem. Ges., 1894, pp. 2992, 3228, &c. Cf. Pfeffer, I.e., p. 248. 



3 Pasteur, Ann. d. chim. et d. phys., 1860, Hi. se'r., T. LVIII, p. 323, and 1862, iii. se>., T. 

 LXiv, p. 106; Nageli, Bot. Mitth., Bd. in, Ober die Fettbildnng niederer Pilze, 1879; Emahrung 

 d. niederen Pilze, 1879; Unters. iiber d. niederen Pilze, 1882; Reinke, Unters. a. d. Bot. Lab. in 

 Gottingen, 1883, III, p. u, where a summary of the facts known up to 1883 is given. 



3 Elfving, Einwirkung d. Lichtes auf Pilze, 1890; R. H. Schmidt, Flora, 1891, p. 300 (oil); 

 Wehmer, Bot. Zeitung, 1891, p. 233 ; Linossier, Centralbl. f. Bact., 1892, Bd. xn, p. 162 ; Beyerinck, 

 ibid., 1892, xi, p. 70, and 1894, Bd. xvi, p. 57 ; Bruhne, in Zopfs Beitragen z. Physiol. u. Morph., 

 1894, Heft 4, p. i ; Raciborski, Flora, 1896, Bd. LXXXII, p. 118; Thiele, Die Temperaturgrenzen 

 d. Schimmelpilze, 1896; Laborde, Ann. d. 1'Inst. Pasteur, 1897, T. xi, p. i; Fliigge, Mikro- 

 organismen, 1896, 3. Aufl. 



