ORGANIC MATTERS OF THE SOIL, 223 
Verdeil and Risler have made Similar observations on ten 
soils from the farm of the Institut Agronomique, at Ver- 
sailles. They found that the water-extract of these soils 
contained, on the average, 50°|, of organic matter, which, 
when strongly heated, gave an odor like burning paper or 
sugar. These observers make no mention of crenates or 
apocrenates, and it, perhaps, remains somewhat doubtful, 
therefore, whether their researches really demonstrate the 
presence in the soil of a neutral body identical with, or 
allied to, dextrin or sugar. 
Cellulose, starch, and dextrin, pass by fermentation into 
sugar (glucose) ; this may be resolved into lactic acid (the 
acid of sour milk and sour-krout), butyric acid (one of the 
acids of rancid butter), and acetic acid (the acid of vine- 
gar). It must often happen that the bodies of the cellu- 
lose group ferment in the soil, the same as in the souring 
of milk or of dough, thaugh they suffer for the most part 
conversion into humus, as will be shortly noticed. 
Vegetable Acids, viz., oxalic, malic, tartaric, and citric 
acids, become ingredients of the soil when vegetable mat- 
ters are buried in it. When the leaves of beets, tobacco, 
and other large-leaved plants fall upon the soil, oxalic and 
malic acids may pass into it in considerable quantity. 
Falling fruits may give it citric, malic, and tartaric acids. 
These acids, however, speedily suffer chemical change 
when in contact with decaying albuminoids. Buchner has 
shown (Ann. Ch. u. Ph., 78, 207) that the solutions of 
salts of the above-named vegetable acids are rapidly con- 
verted into carbonates when mixed with vegetable fer- 
ments. In this process tartaric and citric acids are first 
‘ partially converted into acetic acid, and this subsequently 
passes into carbonic acid. 
Volatile Organic Acids.—Formic, propionic, acetic, and 
butyric acids, or rather their salts, have been detected by 
Jongbloed and others in garden earth, They are common 
