2 BULLETIN 319, U. S. DEPARTMENT OF AGRICULTURE. 
In many large cities special fermented milk preparations can be 
obtained under various trade names, such as zoulak, vitallac, yogurt, 
matzoon, bacillac, kefir, kumiss, and lacto-bacilline. These are 
all soured milks which have been introduced from southern Russia, 
Turkey, and neighboring countries. They are sold as freshly pre- 
pared milk, or in the form of tablets or powders in capsules which 
may be taken as such or used to ferment milk. These preparations 
have been widely advertised and are the subject of very positive 
statements in regard to the benefits derived from their use. 
THERAPEUTIC VALUE OF FERMENTED MILK. 
Fermented milks have been used ever since very early times, but it 
is only within very recent years that physicians have become inter- 
ested in the possibilities of their use for therapeutic purposes. 
Within the past 20 years there has been an increasing number of 
papers in the medical journals on this subject, and at one time the 
widespread popular interest in fermented-milk therapy was reflected 
by the numerous magazine and newspaper articles on various phases 
of the subject. This interest was stimulated in a large measure by 
the work of Metchnikoff (58) 1 and his associates. His views, which 
are set forth in some detail in Chapter V, " Lactic acid as inhibiting 
intestinal putrefactions," of his book entitled " The Prolongation of 
Life,*' are looked upon by the more conservative investigators of this 
country as overdrawn and as unsupported b}^ experimental evidence. 
In this book great stress is laid on the longevity of the people of cer- 
tain countries in which fermented milks are an important part of the 
diet. 
In considering evidence of this kind it should be remembered that 
many other things may contribute to the general health and vigor of 
the people and that these factors can not be excluded in drawing the 
conclusions. The people who habitually consume large quantities of 
fermented milk usually live a simple life, largely in the open air, and 
we have no means of knowing how much this may have contributed 
to the vigorous old age frequently observed among them. 
The use of fermented milks as a therapeutic agent is based on the 
assumption that they are able to combat the so-called autointoxica- 
tion caused by the undue accumulation in the body of toxic sub- 
stances emanating from the intestinal tract. The theory of auto- 
intoxication may be stated briefly as follows : The digestive tract of 
the human being is at birth free from bacteria, but in various ways, 
chiefly through the food, many kinds of bacteria are introduced into 
the alimentary canal. In the intestines and particularly in the large 
intestine some of them find favorable conditions for growth and be- 
1 Figures in parentheses refer to the bibliography at the end of this bulletin. 
