Natural Sources 



On the other hand, the work of the school of Schreiner and 

 Shorey seems to bear with some directness on the question of 

 the relation of protein-decomposition products and soil 

 fertility. The studies of Schreiner and Shorey on nitrogenous 

 compounds were more concerned with bodies related to the 

 purine group than those of the indole group and phenylic 

 amino-acids. After their preparation of creatinine from soil, 

 they broke new ground in two respects (Schreiner et al., 

 1 911): by trying the effect of creatinine on wheat-plants in 

 water-cultures both with and without nitrate, and by demon- 

 strating the presence of creatinine in stale extract of farmyard 

 manure and in fresh cowpea vines. 



Creatinine, and its relative creatine, which was also tested 

 on wheat-plants, may have acted simply as nutrients. Creat- 

 inine is the anhydride of creatine, which is methyl-guanid- 

 ino-acetic acid. 



H 



N CO 



HN:C 



\ 

 H3C-N CH, 



creatinine 



The experiments of Schreiner et al. were not fine enough 

 for it to be possible to say that the increases of plant yield 

 observed with creatinine and creatine in presence of small 

 amounts of nitrate showed that creatinine, or creatine, is a 

 growth-substance. The importance of the work of Schreiner 

 and Shorey in the present connexion is rather that it focuses 

 attention on the organic constituents of soils. As Schreiner 

 and Brown wrote, in 1912, "the purely mineral-requirement 

 theory of soil fertility has proven itself inadequate to cope with 

 the accumulated facts." 



A re-reading of the paper by Schreiner and Lathrop (191 2) 

 suggests in the light of present-day knowledge that decomposi- 

 tion products of protein (not necessarily of nucleo-proteins 

 only) may be associated with the phenomena of "sickness" of 



63 



