FEKMENTED MILKS. 3 
come established there in large numbers. In the normally nourished 
infant the bacterial varieties are limited in number and for the most 
part consist of acid-forming types which by the active fermentation 
of the milk sugar furnished in large quantities in the food produce 
conditions under which bacteria of the putrefactive type are unable 
to multiply to any extent. The predominance of an acid fermenta- 
tion in the large intestine produces an acid stool with a characteristic 
but comparatively unobjectionable odor. As the child gets older the 
variety of food is greater and the relative proportion of carbohy- 
drates to protein is much reduced. In place of the acid fermentation 
there is a decomposition of the protein by other bacteria, intestinal 
gas is produced, and the stools become alkaline and frequently have a 
very objectionable odor. In the bacterial decomposition of the predi- 
gested protein it is supposed that products of a more or less toxic 
nature are produced. When the quantity of these products is rela- 
tively small they are disposed of through the normal channels and 
have no appreciable effect. If the excretory system fails to do its 
normal work, or if the protein decomposition is unusually active, 
toxic substances accumulate and the symptoms of autointoxication 
are produced. The production of toxic substances in abnormal 
amounts may be caused by a combination of circumstances promot- 
ing an unusual activity of putrefactive bacteria normally present, or 
it may be because the bacterial flora of the intestines changes and new 
bacteria are introduced. 
The method of treating this condition by the use of sour milk is 
based on three conditions which may be stated as follows: (1) It 
assumes as correct the theory of the production of toxic substances 
in the intestine by the action of bacteria in quantities sufficient to 
cause the symptoms of autointoxication; (2) the putrefaction or 
fermentation through which these toxic substances are produced can 
be suppressed by other bacteria; and (3) the bacteria which it is 
proposed to use in suppressing the putrefactive bacteria may be 
introduced into the intestines and will be able to establish conditions 
there under which they will multiply and persist, while the objec- 
tionable types are driven out. 
The standing of the theory of autointoxication mentioned under 
the first condition can not be discussed in detail in a paper of this 
nature. It may be said, however, that the question of autointoxica- 
tion, in its broader sense, is not nearly so simple as it is stated here. 
It is at best only a theory, and much investigation of details will be 
necessary before its position can be determined. 
The second condition is easily demonstrated, not only by scientific 
observation, but also by many instances in our daily life. Vinegar, 
which is used in pickle making, owes its preservative action to the 
