678 GASTRO-INTESTINAL BACTERIOLOGY 
reduce or even prevent the formation of toxin or indol respectively 
when iitilizal)le carbohydrates are present. 
There are a number of intestinal conditions of bacterial causation 
in which available evidence points strongly to the formation of pro- 
ducts arising from the metabolism of protein or protein derivatives 
by specific organisms as important etiological factors in the morbid 
process. Thus cholera, bacillary dysentery, typhoid, paratyphoid and 
many less acute infections are associated definitely with the develop- 
ment of these organisms within the body and, to some degree at least, 
at the expense of the body tissues. 
All of these organisms produce lactic and other acids when suitable 
carbohydrates are available ; the products of fermentation of those 
bacteria, chiefly lactic and other acids, are almost certainly no more 
harmful to the host than are those formed by B, bulgaricus, B. coli or 
B. acidophilus produced under like conditions. In other words, 
available evidence points strongly to the view that cholera vibrios, 
typhoid, dysentery and paratyphoid bacilli and similar organisms pro- 
duce their characteristic and harmful effects when they are developing 
in media free from utilizable carbohydrate; when utilizable carbohy- 
drates are added to these media, non-characteristic, harmless products 
are formed. It is frankly admitted that the chemistry of the products 
of nitrogenous metabolism of pathogenic bacteria is wholly unknown, 
and a rigorous proof of a relation between nitrogenous metabolism 
and disease is yet to be elucidated; the significant fact that the pro- 
ducts of fermentation of these organisms are almost certainly innocuous 
to the host cannot be disregarded. 
A comparative study of the nitrogenous metabolism of the composite 
intestinal bacteria from selected cases in plain broth, glucose and starch 
fermentation media, and in milk, illustrates both the differences in 
chemical activity of the flora of the nursling, the adolescent and the 
adult on the one hand, and the effect of diet upon these several floras 
on the other hand. Very few observations of this character have^ 
been made and only the more general features, therefore, can be con- 
sidered here. A few significant facts seem to stand out very plainly. 
First; the composite intestinal flora of the nursling exliibits slight action 
upon protein when carbohydrate is excluded from the medium in which 
are cultivated the composite bacteria of the intestines. The nature and 
extent of this action is essentially that of pure cultures of Micrococcus 
ovalis^ or B. acidophilus.^ In glucose, starch and milk cultures (and 
the same is equally true for lactose and saccharose), the process is 
1 Kendall, Day and Walker: Chemistry of the Intestinal Flora of Nurslings, Jour. 
Infec. Dis., 1926, 38, 200; ibid.: Chemistry of the Intestinal Flora of Artificially-fed 
Infants, p. 205; ibid.: Chemistry of Intestinal Flora of Normal Adults, p. 211; ibid.: 
Chemistry of the Intestinal Flora of Man Containing Abnormal Numbers of Gas Bacilli, 
p. 217; ibid.: Bacteriology and Chemistry of Adult Duodenal Contents, Jour. Infec. 
Dis., 1927, 40, 677. 
2 Kendall and Haner: Jour. Infec. Dis., 1924, 35, 67. 
3 Ibid.: Page 89. 
