TABLE OF CONTENTS. 



Page 

 I. Introduction: Our present knowledge of the organic matter of 



the soil 7 



A. Early investigations ^ 7 



B. The humus theory of Grandeau 12 



C. The complexity of the ammonia soluble material 14 



D. The presence of definite organic compounds in the soil.. 15 



E. The origin of organic compounds in the soil 16 



1. Nucleoprotein decomposition 17 



2. Nucleic acid decomposition 17 



3. Lecithin decomposition 18 



F. Bacterial processes which influence the form of soil 



nitrogen 19 



1. Deamination or reduction , 20 



2. Decarboxylation or amine formation 20 



3. Hydrolysis 20 



4. Oxidation 21 



G. 'Nitrogen distribution in the soil . . . . 21 



H. A summary of the nature of the organic matter of the 



soil in the light of our present knowledge 29 



II. Experimental: A study of the nitrogen distribution in different 



soil types 31 - 



A. The problem 31 



B. The material : 31 



1. Calcareous black grass-peat 31 



2. Sphagnum-covered peat 31 



3. Acid "muck" soil 31 



4. Fargo clay loam 32 



5. Fargo silt loam 32 



6. Carrington silt loam 32 



7. Hempstead silt loam 32 



8. Prairie-covered loess 32 



9. Forest-covered loess 32 



10. Hempstead silt loam subsoil 32 



C. The method 33 



1. The method in detail for a peat soil 34 



2. The method in detail for a mineral soil 36 



3. The method for determination of "Jodidi num- 



bers" ; 37 



4. The determination of nitrogen 38 



4. The analytical data 38 



1. The analysis of "fibrin from blood" hydrolyzed in 



the presence of 100 grams of ignited subsoil 38 



2. Calcareous black grass-peat 41 



3. Sphagnum-covered peat 42 



4. Acid "muck" soil.. 42 



