242 INTESTINAL BACTERIA 
Anaerobic Respiration. The products of anaerobic respiration are 
usually left in an incompletely oxidized condition. If dextrose is taken 
again to show this, any of the following equations might serve. 
CH20H(CHOH)4COH = CH3CHOH —COOH-+ 15 eal. 
CH20H(CHOH)4COH =38CH3COOH-+ 34 cal. 
CH2OH(CHOH)4COH = C2Hs50H+2C02+-22 cal. 
The main product in each of these equations may be further oxidized 
to yield more energy. 
The amount of energy secured by aerobic and anaerobic bacteria 
from the same amount of food is striking. Take, for instance, the 
following equation as a typical one for aerobes: 
CH20H(CHOH)4COH+ 602 = 12C0212H20 +674 cal, 
and the following as typical for anaerobic bacteria: 
CH2OH(CHOH)4COH = CH;CHOH COOH+15 cal. 
The proportion would then exist as follows: 
Aerobic : anaerobic = 674.15 
Aerobic : anaerobic =45.1 
That is, from the same amount of food the aerobes by complete 
oxidation will get forty-five times as much energy. Looking at it from 
the standpoint of energy, the anaerobes have to have forty-five times 
as much food as the aerobes. This explains why the anaerobic bacteria 
are so destructive in soil, sewage, etc. 
Putrefaction in the Intestinal Tract. As stated above the biological 
chemists have reserved this term for the decomposition of nitrogenous 
substances. According to the definition of fermentation which has 
been given above, some decompositions of nitrogenous substances would 
be regarded as fermentations. The combustion in the protoplasm of 
those peptones which are diffusible would be regarded as fermentation 
while the hydrolysis of the proteins and proteoses which goes on outside 
of the cell wall would not be regarded as fermentation. 
The chemistry of the putrefactive changes which take place in the 
intestines is fairly well known. Straight chain acids are among the first 
