ORGANIC NITROGEN. ITS DECOMPOSITION. 53 
earlier form, and consequently its atoms must enter into new relations 
to form new bodies. These by-products have not been actually in the 
bacteria and are not the direct results of metabolism. The new 
products formed in the decomposing mass are partly gaseous. 
This is proved by the odor that commonly arises from putrefying 
bodies which are indications of the exhalation of volatile products. 
A chemical study has shown, in many cases, the actual nature of 
these gaseous products, indicating that the end-products are 
chiefly CO 2 , H, CH 4 , NH 3 , H 2 S, and N, in addition to others, present 
in much smaller amount, producing the peculiar and characteristic 
odors. Some of the new products are solids and may be either 
soluble or insoluble. If soluble they are dissolved in the course 
of time by the rain which falls upon the decaying mass and pass 
into the soil, perhaps to be drained away in the drainage-water. 
The insoluble bodies are also incorporated into the soil, becoming 
eventually mixed with the solid masses of the earth. 
The list of the by-products of such decompositions is a long one. 
A few of these are as follows: Carbon dioxid, hydrogen sulphid, 
marsh gas, hydrogen, nitrogen, calcium carbonate, propionic acid, 
valerianic acid, acetic and lactic acids, alcohol, succinic acid, 
phenol, indol, leucin, tyrosin, skatol, etc. 
This list is far from complete. It includes only a few of the 
products already known, and beyond question there are numerous 
bodies, formed as by-products or excretions, which still remain 
to be discovered. The actual products which appear will depend 
upon three factors: (i) The substance which is decaying; (2) 
the species of bacteria which produces the decay; (3) the conditions 
under which the decay occurs. 
The Ammoniacal Fermentation. One phase of these decom- 
position processes must be especially mentioned. After passing 
through an unknown series of intermediate stages, the nitrogen 
of the decaying mass assumes, in large part, the condition of 
ammonia. One of the first and easiest substances to undergo 
this ammoniacal fermentation is urea. Urine is always filled 
with bacteria, even while in the ducts from the bladder, and among 
them are several species that cause it to break down to form ammonia 
