226 BIOLOGY OF SPECIALIZED GROUPS 



and various gases, such as carbon dioxide, am- 

 monia, methane, and hydrogen. Ptomains, such 

 as cadaverin, ethyldendiamin, and putrescin. 

 (d) Phosphoric acid and purin bases (from nuclein). 



2. Fats: 



Glycerine and all the higher fatty acids. Ptomains, 

 such as cholin, neurin, etc., from the phosphorized 

 fat lecithin. 



3. Carbohydrates: 



The following fatty acids have been isolated and prob- 

 ably others occur which have not been isolated, 

 formic, acetic, propionic, butyric, valerianic, 

 succinic, oxybutyric. Gases, such as hydrogen, 

 carbon dioxide, methane in the case of cellu- 

 lose, and acetone. 



Most plants obtain their nitrogen supply from the nitrates 

 of the soil. The nitrogen of the soil is the key to soil 

 fertility. As a result of the action of the enzymes of various 

 species of saprogenic bacteria, ammonium salts are produced 

 after the ammonia which is formed during the process of de- 

 compositpn is combined with certain inorganic elements, such 

 as sodium and potassium. Only a small amount, if any, of 

 these ammonium salts can be used by plants as a source of 

 nitrogen supply. By the action of the nitroso bacteria which 

 are present in the soil, these ammonium salts are broken up 





