ORGANIC NITROGEN—ITS DECOMPOSITION 59 
relation to the bacteria. Some of them must be regarded as secre- 
tions or excretions from the bacteria and hence as the result of the 
active metabolism of the microdrganisms. These are probably 
rather small in amount, but of great significance in some connec- 
tions, Inasmuch as many of them are poisonous. Others must be 
looked upon as by-producis of decomposition. By this is meant 
that, as the bacteria take certain atoms from the complex mole- 
cules for their own use, the rest of the molecule can no longer re- 
tain its earlier form, and consequently its atoms must enter into 
new relations to form new bodies. These by-products have not 
been actually zm 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 exhala- 
tion 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 COs, H, CH1, NH, HS, 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, calclum 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 
