240 INTESTINAL BACTERIA 
Fermentation in the Intestinal Tract. Putrefaction is used in this 
case to indicate the bacterial decomposition of proteins. There has 
been much discussion with regard to the definition of the terms putre- 
faction and fermentation. Kendall (1911) has given a good discussion 
of these terms in their relation to the digestive tract. He quotes therein 
the definitions which have been given to the processes of putrefaction 
and fermentation by various workers and accepts the definition for 
fermentation which was given by Alfred Fischer. Fischer defines fer- 
mentation as the biochemical decomposition of nitrogen-free, organic 
compounds, especially the carbohydrates induced by fermenting organ- 
isms. If this definition is accepted there may then be different types 
of the process, depending on the main product: lactic acid, butyric acid, 
alcoholic fermentations, etc. With regard to putrefaction more confu- 
sion exists. The term has been used in so many different ways that it is 
difficult to correlate thom. Kendall states that the phenomena grouped 
together as putrefaction ‘‘ represent a scries of symbioses, in which the 
initial superficial breakdown is brought about by the anaerobes, while 
the process is brought to its lowest terms by the facultative anaerobes.” 
The Germans have made a distinction between “‘ Faulniss”’ putrefaction 
in the popular sense and ‘ Verwesung’”’ eremecausis. This latter is 
supposed to be an aerobic process carried on by many bacteria. That 
fermentation should mean decomposition of carbohydrates and putre- 
faction, decomposition of proteins are the opinions of the biological 
chemists. 
Certain microbiologists, however, have not accepted this definition. 
They define fermentation as an intracellular process which furnishes 
energy to the cell and pay no attention to the products which are decom- 
posed. The decomposition of soluble nitrogenous compounds within 
the cell protoplasm is regarded as fermentation. This seems to be the 
best definition for the term as has been suggested by Fischer (1902). 
He gives the following points as characteristic of such a conception of 
the term: 
1. Fermentation is an intracellular process. 
2. The products of the fermentation are essentially different from 
those in the substract and are not mere parts of these original substances. 
8. The products are useless to the cell and may be harmful. 
4, Vital energy is produced. 
According to this definition, then, and as it is stated by Fischer, the 
hydrolysis of starch to soluble sugars is not a fermentation, because it 
does not take place within the cell to yield energy to the cell. The 
burning of the sugar within the cell protoplasm, however, does consti- 
