FERMENTED MILKS 6 
bacteria, intestinal gas is produced, and the stools become alkaline 
and frequently have a very objectionable odor. In the bacterial 
decomposition of the predigested protein it is supposed that products 
of a more or less toxic nature are produced. When the quantity of 
these products is relatively small they are disposed of through nor- 
mal channels and have no appreciable effect. If the excretor}^ system 
fails to do its normal work, or if the protein decomposition is un- 
usually active, toxic substances accumulate, and the symptoms of 
autointoxication are produced. The production of toxic substances 
in abnormal quantities may be caused by a combination of circum- 
stances promoting an unusual activity of putrefactive bacteria nor- 
mally present, or it may be because the bacterial flora of the intestines 
changes and new bacteria are introduced. 
The method of treatment 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 suppress- 
ing the putrefactive bacteria may be introduced into the intestines 
and will be able to establish themselves there and to multiply and 
persist, and the objectionable types are suppressed or driven out. 
The standing of the theory of autointoxication mentioned under 
the first condition can not be discussed in detail in this bulletin. It 
may be said, however, that the question of autointoxication, in its 
broadest sense, is not nearly so simple as 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 
observations, but also by many instances in daily life. For example, 
vinegar, which is used in pickle making, owes its preservative action 
to the acetic acid produced by bacterial fermentation ; and when milk 
sours spontaneously, the acid-forming bacteria develop acid so rap- 
idly that in a short time all other bacteria are inhibited. Observa- 
tions of this kind could be multiplied almost indefinite!} 7 . In fact, in 
the bacterial world, as among the higher plants in their natural 
state, there is a constant struggle for mastery, in which the types best 
suited to their environments, or, perhaps more correctly, less sensi- 
th T e to the unfavorable conditions which they themselves produce, 
gain the ascendancy and more or less completely suppress other forms. 
The question of implantation is most important. Unless the bac- 
teria to be used in sour-milk therapy are adaptable to the complex 
conditions obtaining in the human intestinal tract, their implantation 
is obviously impossible. 
Metchnikoff (61) proposed to combat intestinal putrefaction and 
its attendant disorders by the acid produced by the lactic-acid bac- 
teria found in milk. In an endeavor to make his results more certain 
he chose the bacterium Lactobacillus oulgaricus because of its ability 
to produce a high acidity. L. hulgaricu-s has since been found to be 
an active member of the microflora of all curdled milks. Attempts to 
demonstrate the successful implantation of L. bulgaricus in the intes- 
