17 



ed from the soil that are related to proteins, it is well to discuss 

 some of the complex organic compounds such as nucleoproteins, 

 nucleic acids, and lecithins that find their way to the soil through 

 plant and animal remains. While the final decomposition products 

 are undoubtedly simple compounds or elements such as carbon 

 dioxide, methane, ammonia, nitrogen, and hydrogen, these products 

 are reached by fairly definite and well defined methods of cleav- 

 age. The process may be a rapid one, a slow one, or one entirely 

 arrested at certain stages, all depending on the factors present 

 in the soil. 



1. Nucleoprotein decomposition. The nucleoproteins are with- 

 out doubt the most complex compounds that enter the soil. They 

 are common constituents of plants, animals, bacteria, and molds, and 

 hence occur wherever these live or die. The chemical changes 

 through which these compounds go during decomposition may be 

 rendered clear by the following scheme presented by Lilienfeld 

 (1892): 



Nucleoprotein 



Protein Nuclein 



(Histone) I 



! I 



Protein Nucleic acid 



The products are then protein and nucleic acid, the latter of 

 which has been isolated from the soil (Shorey 1911 a, 1912, and 

 1913). 



2. Nucleic acid decomposition. Nucleic acids are constituents 

 of all nuclei and on decomposition yield a variety of compounds 

 composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus. 

 The acids occur in both plant and animal cells. 



Jones (1914) states that all plant nucleic acids contain a pen- 

 tose group, while on the other hand all animal nucleic acids yield 

 levulinic acid, which is formed from a hexose group in their mole- 

 cule. 



The hydrolysis products may be classified, according to Forbes 

 and Keith (1914) as follows: 



Nucleic acids 



Phosphoric acid Carbohydrates Bases 



Pentoses 

 Hexoses 

 Unidentified Purine Pyrimidine 



Guanine . Cytosine 

 Adenine Thymine 



Xanthine Uracil 



Hypoxanthine 



