FERMENTATION AND PUTREFACTION 83 
In glucose broth diphtheria, colon, typhoid, cholera and other 
microbes produce potentially the same substances, namely lactic and 
acetic acids, together with smaller amounts of other acidic products. 
In plain, sugar-free media, of otherwise the same composition, the 
diphtheria bacillus produces its characteristic toxin, the colon bacillus 
produces indol, and the other organisms mentioned produce charac- 
teristic nitrogenous products of metabolism. 
It follows logically that the specificity of action of these pathogenic 
l)acteria depends upon their utilization of nitrogenous substances- 
proteins or protein derivatives— for energy. This is the real signifi- 
cance of the sparing action of utilizable carbohydrates for protein.^ 
IX. FERMENTATION AND PUTREFACTION. 
The terms "fermentation" and "putrefaction" have been confused 
and even used synonymously in bacteriological, chemical and even legal 
nomenclature, but the\' represent essentially distinct and generic types 
of bacterial activity. They indicate, or should indicate respectively, 
microbic decomposition of two quite distinct types of organic com- 
pounds, the carbohydrates and closely related nitrogen-free compounds, 
on the one hand (fermentation), and nitrogenous organic substances 
on the other hand (putrefaction). There are substances intermediate 
in character between carbohydrates and proteins, in which it would 
l)e difficult to predict a priori which term would be correct— glucose 
amine is such a substance. Glucose amine is an amino-aldose, con- 
taining both nitrogen and carbohydrate groupings. Such instances, 
however, are uncommon and do not militate against the correctness of 
the general theory that fermentation and putrefaction are distinct 
processes. - 
Fischer'' has defined fermentation in the broad sense in which it 
should be used in bacteriology, essentially in the following terms: 
"Fermentation is the biochemical decomposition of nitrogen-free 
compounds, chiefly carbohydrates, by the action of microorganisms." 
Similarly, putrefaction is defined as "The biochemical decomposition 
of nitrogenous organic compounds by the action of microorganisms." 
Fermentation and putrefaction are probably enzyme phenomena. 
Transposing the sparing action of utilizable carbohydrate for 
protein, which has been repeatedly emphasized in the preceding 
pages, it may be stated that in the catabolic phase of bacterial metab- 
olism "fermentation takes precedence over putrefaction," meaning by 
that that bacteria which can utilize carbohydrate derive their energy 
requirements from the utilizable carbohydrate when they are growing 
in media containing both carbohydrate and protein. The results of 
this sparing action of utilizable carbohydrate for protein have been 
indicated in the preceding pages, sections V to VIII, inclusive. 
1 Kendall: Am. Jour. Med. Sci., 1918, 156, 157. 
2 Kendall: Jour. Med. Res., 1911, 25, 117. 
3 Vorlesungen iiber Bakterien, 1903, II Aufl., 206. 
