GASTRO-IXTESTINAL FLORA OF NORMAL INFANTS 679 
essentially an intense lactic acid fermentation. The evidence of 
proteolysis induced by the mixed intestinal bacteria in the sugar-free 
medium is somewhat greater in artificially-fed infants, but in the 
fermentation media the general phenomenon is reminiscent chemically 
of those obtained from the normal nursling. The bacteria of the adult 
feces induced qualitative and quantitative changes in plain broth 
cultures that are the counterpart of those induced by pure cultures of 
B. coli under similar conditions.^ Some indol is formed, and the 
changes in the nitrogenous constituents of the medium are definitely 
but not profoundly altered. The action of the adult flora upon starch 
fermentation medium is not distinctive: some fermentation usually 
occurs, but it is rather less marked than that induced by either the 
normal nursling or the artificially fed child. In general, it appears to 
be a fact that the composite intestinal flora of the normal person, young 
or old, is without evidence of marked proteolytic power in the sugar- 
free media, and strongly lactic-acid-producing in fermentation mediums 
and milk. In this respect it follows the principles relating to diet 
mentioned above. 
The metabolism of the composite intestinal flora from certain cases 
of gas bacillus overgrowth,'- associated in two instances with rather 
definite symptomatology,'^ offers a striking contrast to that observed 
with normal composite intestinal floras. The outstanding quantitative 
change is found in the plain broth medium from which carbohydrate 
is excluded. Here the evidence of proteolysis is quite striking, both 
with respect to deamination, which occurs to the extent of a fifth or 
even a third of the total nitrogen of the medium, and also in respect 
to the rapid degradation of the more complex nitrogenous constituents 
of the medium. Qualitatively, physiologically large amounts of a 
histamine-like substance^ are formed in a fair proportion of such cases, 
during the fermentation of the carbohydrates. It is important to find 
that this histamine-like substance, which is produced both by certain 
strains of the gas bacillus and of B. coli, is not present in media where 
strongly lactic-acid-forming bacteria are growing vigorously. This 
points to one method of reducing the activity of these objectionable, 
but fortunately rather uncommon, strains of these bacteria. It 
should be remembered that these strains have never been detected in 
the normal nursling's intestinal tract where normal lactic acid bacteria 
develop in response to the continual flow of carbohydrate in the diet 
of the child. In the absence of gas bacilli, in infections caused by 
typhoid, cholera and dysentery bacilli, carbohydrate tends to change 
the metabolism of these intestinal infectants to the lactic acid producing 
type.5 
In the absence of any definite indication to the contrary it would be 
logical to attempt to maintain a sufficient concentration of carbo- 
1 Kendall and Bly: Jour. Infec. Dis.. 1922, 30. 239. 
2 Kendall, Day and Walker: .Jour. Infec. Dis., 1926, 38, 217. 
3 Kendall: Jour. Am. Med. Assn., 1926, 86, 7.37. 
* Kendall and Schmitt: Jour. Infec. Dis., 1926, 39, 250. 
* See Kendall and Haaer: Ibid., 1922, 30, 225 et seq. for details. 
