October 14, 1921] 



SCIENCE 



349 



as they are broken down in the digestive 

 system of animals. The soil has the same 

 kind of bacterial, enzymatic and oxidation 

 processes as are common to the animals. It is 

 evident that soil through these digestive 

 agencies will take care of the excreta of 

 plants and the organic matter that accumu- 

 lates in the soil from various causes, redu- 

 cing the organic matter to lower and lower 

 forms of oxygenated bodies until they ap- 

 proach the hydrocarbon type of compounds in 

 our humus, which are stable, innocuous and 

 form the sewage disposal of the soil. 



In the animal under abnormal functional 

 conditions the too great accumulation of prod- 

 ucts of metabolism causes a fatigue of the 

 muscles or if the system can not eliminate 

 them the death of the animal. So under 

 abnormal conditions in the soil brought 

 about by adverse methods of cropping, of 

 tillage, of the selection of crops, or improper 

 methods of crop rotation the soil, as the 

 French put it. becomes fatigued and the plant 

 is unable to function. 



The second stage of soil investigations 

 therefore has developed the . fact that the soil 

 has a digestive system and is liable to fatigue 

 or exhaustion as regards its power to produce 

 crops and is dependent for its efficiency upon 

 normal conditions, much as the animal is 

 dependent upon normal functional activities 

 to maintain life energy. This is a great field 

 opened up for the organic and physiological 

 chemist and bacteriologist. It may be stated 

 more concisely that the chemistry of the soil 

 is running parallel to the chemistry of the 

 animal. 



Some of the organic compounds isolated 

 from soils and identified are as follows: 



Acrylic acid, 



Adenine, 



Agroeeric acid, 



Agrosterol, 



Arginine, 



Creatinine, 



Cytosine, 



Dihydroxystearic acid, 



Glyeerides, liquid, 



Guanine, 



Hentriacontane, 



Histidine, 



Hypoxanthine, 



Lignoceric acid, 



Lysine, 



Maunite, 



Monohydroxystearic acid, 



Nucleic acid, 



Oxalic acid, 



Paraffiuic acid. 



Pentosan, 



Pentose, 



Phytosterol, 



Picoline carboxylic acid. 



Resin, 



Resin acids, 



Resin esters, 



Rhamnose, 



Saccharic acid. 



Salicylic aldehyde, 



Succinic acid. 



Sulphur, 



Trimethylamine, 



Trithiobenzaldehyde, 



Xanthine. 



MINERAL CHEMISTRY OF THE SOIL SOLUTION 



The mineral particles that make up the 

 structure of the soil are bathed with a solution 

 containing both inorganic salts and organic 

 compounds. The circulation of this solution 

 is similar in purpose to the circulation of the 

 blood and it is upon this nutrient solution 

 that the plant depends for its nourishment. 

 It is particularly desirable, therefore, that the 

 constitution of this nutrient solution be under- 

 stood. By handling large quantities of soil 

 in our laboratories it has been possible to 

 obtain large quantities of this soil solution 

 in dilute form. This solution, if allowed to 

 evaporate quietly at ordinary temperatures 

 yields successive crops of crystals which are 

 found to be analogous to the salts found in the 

 Stassfurt deposits of Germany and to the in- 

 land lake and sea deposits throughout the 

 world. Silvite, kainite, and earnalite, the 

 three important potash salts of Stassfurt, are 

 commonly present in the nutritive solution 

 of our soils, and, when we come to think of 

 it, it appears to be the simplest thing in the 

 world to understand that the salts that we 

 value so highly in our mines are formed in 

 our soils, transported through the oceans, and 

 crystallized out 'again when the waters 

 evaporate. 



Our chemists have been expressing the re- 

 sults of their analyses in simple conventional 

 terms of single salts. This work shows that 

 the soil solution is most complex and that 

 there are besides single salts, double salts and 

 triple salts. In a complex salt solution 

 changes of temperature or additions of ma- 

 terial have a profound effect upon the charac- 

 ter of the double or triple salts especially. 

 ISTo correlation has yet been made between 

 these different complexes and the production 

 of crops, or between these different complexes 



