280 HOW CROPS FEED. 
ily decompose, and cannot therefore themselves be consid- 
ered as ingredieuts of the soil. 
Among. the proximate products of their decomposition 
are organic acids (butyric, valeric, propionic) destitute of 
nitrogen, and the amides leucin (C, H,, NO,) and tyrosin 
(C, H,, NO,). These latter bodies, by further decompo- 
sition, yield ammonia. As has been remarked, it is proba- 
ble that the albuminoids, when associated as they are in 
decay with cellulose and other carbohydrates, may at 
once give rise to insoluble amide-like bodies, such as those 
whose existence in humus is evident from the consider- 
ations already advanced. 
Can these Organic Bodies Yield Nitrogen Directly to 
Plants 3—Those nitrogenous organic compounds that exist 
in the soil associated with humus, which possess something 
of the nature of amides, though unknown to us in a pure 
state, appear to be nearly or entirely incapable of feeding 
vegetation directly. Our information on this point is de- 
rived from the researches of Boussingault, whose papers 
on this subject (De la Terre végétale considérée dans ses 
effets sur la Veéegétation) are to be found in his Agronemie, 
etc., Vols. I and IL. 
Boussingault experimented with the extremely fertile 
soil of his garden, which was rich in all the elements 
needful to support vegetation, as was demonstrated by the 
results of actual garden culture. This soil was especially 
rich in nitrogen, containing of this element 0.26°|,, which, 
were it in the form of ammonia, would be equivalent to 
more than 7 tons per acre taken to the depth of 13 inches; 
or, if existing as nitric acid, would correspond to more 
than 43 tons of saltpeter to the acre taken to the depth 
just mentioned. 
This soil, however, when employed in quantities of 40 
to 130 grams (1} to 44 oz. av.) and shielded from rain 
and dew, was scarcely more capable of carrying lupins, 
beans, maize, or hemp, to any considerable development, 
