DECAY OF NITROGEMOUS BODIES, 291 



in absence of free oxygen may remove this element fruin 

 reducible bodies (Traiibe, Fermentwirkungen, pp. G3-78). 



In a mixture of cellulose, sugar, and albuminoids, ere- 

 mecausis, fermentation, and putrefaction, may all proceed 

 simultaneously. 



When the albuminoids decay in the soil associated with 

 carbohydrates and humus, the final results of their altera- 

 tion may be summed up as folloMs : 



1. Carbon unites mainly with oxygen, forming carbonic 

 acid gas, Avhich escapes into the atmosphere. With im- 

 perfect supplies of oxygen, as Avhen submerged in water, 

 carbonic oxide (CO) and marsh gas (CIIJ are formed. A 

 portion of carbon remains as humus. 



2. Hydrogen, for the most part, combines with oxygen, 

 yielding water. In deficiency of oxygen, some hydrogen 

 escapes as a carbon compound (marsh-gas), or in the free 

 state. If humus remains, hydrogen is one of its con- 

 stituents. 



3. a. Nitrogen always unites to a large extent with 

 hydrogen, giving ammonia, which escapes as gaseous car- 

 bonate in considerable quantity, unless from presence of 

 carbohydrates much humus is formed, in which case it 

 may be nearly or entirely retained by the latter. Lawes, 

 Gilbert, and Pugh, {Phil. Trans. 1861, II., p. 501) made 

 observations on the decay of wheat, barley, and bean 

 seeds, either entire or in form of meal, mixed with a large 

 quantity of soil or powdered pumice, and exposed in vari- 

 ous conditions of moisture to a current of air for six 

 mouths. They found in nine experiments that from 11 to 

 58" |„ of the nitrogen was convei'ted into ammonia, al- 

 though but a trifling proportion of this (on the average 

 but 0.4"! J escaj^ed in the gaseous form. 



b. In presence of excess of oxygen, a portion of nitro- 

 gen usually escapes in the free state. Reiset proved the 

 escape of free nitrogen from fermenting dung. Boussm- 



