i8 Natur c of Hiwiiis [Oct. 



drates and their disintegration products were comparatively few 

 (which was also true of the protein products) ; and last, but not 

 least, that the methods of research in organic and biological chem- 

 istry were inadeqnate. 



Recent investigations have thrown enough light upon the chem- 

 ical natiire of humus or hiimus organic matter in the soil to demon- 

 strate that it is a very complex material, which, in addition to dark 

 colored hiimin substances, contains a large number of organic Com- 

 pounds displaying acid, basic, neutral and amphoteric characters. 



The development of the idea of the chemical nature of humus 

 Stands in a certain relation to the development of the chemistry of 

 carbohydrates and proteins out of which humus is formed in the 

 soil. 



Of the carbohydrates, mankind for centuries knew only cane 

 sugar, which was originally obtained exclusively from the sugar 

 cane. The same sugar was later discovered in the sugar beet 

 (Marggraf, 1747), sorghum, maple tree and other plants. In addi- 

 tion to this sugar there were discovered, also, lactose (Bartoletti, 

 1615), glucose (Lowitz, 1792), fructose (Dubrunfaut, 1847), ^^^^ 

 so forth. At present we know a considerable number of sugars in 

 the form of bioses, trioses, tetroses, etc., up to nonoses, i. e., sugars 

 which contain in their molecules from two to nine carbon atoms, 

 respectively, and which occur, in part as such, in nature ; the pentoses 

 and hexoses and the corresponding Polysaccharides being the most 

 important. 



As was demonstrated by many researchers, such sugars and, 

 generally speaking, carbohydrates,^ when treated with acids or alka- 

 lies, yield brown or black humin substances, whose physical and 

 chemicarproperties remind one of soil humus to such a degree, that 



«Malaguti: Ann. (Liebig), 17, 52 (1836) ; Berzelius, Lehrbuch d. Chemie, 3. 

 Aufl. 8 (1839) ; Conrad and Guthzeit, Ber. d. d. ehem. Ges., 18, 439 (1885) ; 19, 

 2850 (1886) ; Sestini, Gas. ehim. iL, 10, 121, 355. 



Grote and Tollens, Ann. (Liebig), 176, 181 (1875) ; 202, 226 (1880) ; Peligot, 

 Ann. chim. phys. [2], 73, 208; Mulder, Ann. (Liebig), 36, 243 (1840); Chemie 

 der Ackerkrume; O. Schmiedeberg: Arch. expt. Path. und PharmakoL, 39, l 

 (1897); Hoppe-Seyler : Zeit. f. physiol. Chetn., 13, 66 (1889); Samuely: Beitr. 

 ehem. Physiol. und Path., 2, 355 (1902). 



