29 



is very high when compared to the amounts in proteins ; (2) that 

 no typical class of organic compounds is extracted from the soil 

 by dilute alkali ; (3) that the amounts of amino acid and peptid 

 nitrogen in the soil are found to be very small compared to the 

 amounts of amino. acids formed by acid hydrolysis ; (4) (and this 

 is the most important for our purpose) that 



nothing very significant can be deduced from the variations in the different 

 soils, 



or in other words, the organic matter in the same soil type under 

 different fertilizer treatment, is essentially the same, and as I shall 

 show later in the experimental part of this paper, the organic mat- 

 ter (as distributed by Van Slyke's method) in different soil types is 

 essentially the same. 



Lathrop (1916) recently made a study of protein decomposi- 

 tion in the soil. He added a high grade nitrogenous fertilizer to 

 the soil and allowed decomposition to proceed at laboratory tem- 

 perature, and at different periods topk samples and subjected them 

 to Van Slyke's method o.f protein analysis in order to determine 

 how the different fractions were affected by bacteria and other 

 agencies present in the soil. 



From his \vork he concludes that the analysis obtained by the 

 Van Slyke method indicates that there is a formation of protein 

 taking place in the soil in the course of the decomposition of the 

 protein materials, and that apparently the new protein is somewhat 

 resistant to decomposition. He states, that 



this is indicated in (1) the unequal loss of mon-amino acids and hydroly/able 

 nitrogen from the soil during- the early stages, (2) by an increase in amide 

 nitrogen during the early stages, (3) by an increase in histidine nitrogen dur- 

 ing the early stages, (4) by an increase in the arginine nitrogen during the 

 later stages, and (5) by an increase in lysine nitrogen during the later stages. 



This view that the protein nitrogen in the soil was largely con- 

 tained in the bodies of bacteria and protozoa had been previously 

 advanced by Shmook (1914). 



It was stated by Loew and Aso (1906-08) that under favor- 

 able condition of growth protein material is excreted by yeast and 

 bacteria, and that soluble materials can pass through the cytoplasm 

 to the outside on death of the cell. They also state that the amount 

 of nitrogenous substances partly consisting of peptones excreted 

 by dead cells, is by no means inconsiderable. 



H. A Summary of the Nature of the Organic Matter of the Soil in 

 the Light of Our Present Knowledge. 



It has been pointed out, that the organic matter of the soil 

 was at first considered to be a very simple thing, that the alkali 

 extract contained the essential plant nutrients, and that the process 

 of "humification" was the necessary step through which the or- 

 ganic matter of the oil must pass in order to be converted into food 

 materials for plant life ; but as the knowledge of chemistry de- 

 veloped it became evident that the problem was more complex. 

 A definite knowledge of the forms of organic matter in the soil 

 can only be secured when we have a thorough understanding of 



