674 GASTRO-INTESTINAL BACTERIOLOGY 
For convenience of discussion this last group may be divided into 
three types: (o) Those cases in which products resulting from the 
action of bacteria upon proteins or their derivatives appear to be the 
prominent factors in the production of the morbid process; (b) those 
cases in which products resulting from the fermentation of carbohy- 
drates by the action of bacteria are the prominent substances concerned 
in the morbid process. A third group, practically unstudied at the 
present time, would include those cases in which symbiotic activities 
of proteolytic and fermentative bacteria would result in the production 
of substances derived both from proteins and from carbohydrates.^ 
The action of bacteria on fats is little understood at present and 
no statement can be made covering this type of abnormality. It is 
expressly understood that products of the nature of endotoxins result- 
ing from the dissolution of bacteria are not considered in this connec- 
tion, which relates exclusively to a discussion of the activities of living 
organisms. 
The symptomatology induced from the products arising from the 
decomposition of proteins or protein derivatives by the action of 
bacteria in the intestinal tract depends largely upon the organism or 
organisms concerned; it varies from the somewhat insidious, slowly 
progressing, so-called auto-intoxication, in which a marked increase 
of urinary ethereal sulphates may be a suggestive index, to the acute 
toxemias characteristic of bacillary dysentery, typhoid, paratyphoid 
or cholera. Of course, a variety of other bacteria than the few men- 
tioned specifically may be concerned, either alone or in symbiosis. 
Thus streptococci alone and streptococci in association with dysentery 
bacilli may be justly regarded as the etiological agents in their respec- 
tive syndromes. The important factor, from the viewpoint of this 
discussion, is to realize that the formation of aromatic residues from 
proteins or protein derivatives which are being utilized by various 
types of intestinal bacteria for energy may be injurious to the host. 
These substances are of unknown composition for the most part, but 
beyond doubt they are of nitrogenous origin. Some, as phenols, 
cresols, or indol are simple in structure and ordinarily harmless, or 
nearly so, although long-continued absorption may gradually lead to 
cumulative effects. Others, as beta imidazoleethylamine^ and other 
primary amines formed from amino-acids may be physiologically 
active. It is important to recall that certain but by no means all 
strains of the gas bacillus, and of B. coli produce this substance in 
relatively large amounts. The unknown poisons of the meat poisoning 
1 Thus, in occasional severe diarrheas of children strains of Bacillus coli and Bacillus 
mesentericus are not infrequently isolated, which grow symbiotically in milk, causing a 
deep-seated change both in the protein and carbohydrate (Content of the medium. The 
result of their mutual development is much greater than the sum of their separate 
activities. Ordinary strains of these organisms frequently do not exhibit this sj^mbi- 
otism. It is by no means improbable that similar symbiotic activity in the intestines 
if unrestrained, may lead to conditions incompatible with the well-being of the host. 
2 Guggenheim: Die Biogenen Amine, 2d cd., 1924. 
