8 BULLETIX 319, U. S. DEPARTMENT OF AGEICULTUEE. 
THE VARIOUS FORMS OF FERMENTED MILK. 
If it is considered advisable to use cultures of acid-forming bac- 
teria, the form in which they are taken becomes an important ques- 
tion. In large cities one usually has a choice of lactic-acid bacteria 
from several sources. Buttermilk is usually available, although it is 
not always of good quality. Sometimes kumiss or kefir can be ob- 
tained, and at the present time milk coagulated with the so-called 
Metchnikoff bacillus is sold as yogurt or matzoon and under various 
trade names. 
CULTURES IN TABLET AND CAPSULE FORM. 
In addition to these freshly prepared preparations several tablets 
or capsules purporting to be pure and active cultures of the Bacillus 
bulgaricus are now offered for sale. These are for use in fermenting 
(miliinl 
Fig. 1. — Organisms causing fermentation of milk, 
a, Bacillus tulyarxcus ; &, lactic-acid bacteria. 
milk or are to be taken directly in place of buttermilk or yogurt. 
Herschell (39) in his little book on the therapeutic uses of soured 
milks recommends the use of these preparations in preference to 
fermented milk, but it should be noted that he is very explicit in his 
statement that great care should be taken to determine the abun- 
dance and purity of the desired organism. Bacillus bulgaricus seems 
to be particularly sensitive to desiccation. \YTien preparing the 
material in tablet form, therefore, a high percentage of the organ- 
isms is usually killed, whereas foreign organisms commonly retain 
their viability. Even when prepared with the best of care, such 
tablets lose their efficiency so quickly that unless such tablets are used 
within a time limit of efficiency guaranteed by the maker the results 
may be disappointing. 
It is very easy to test the purity and activity of these dried cultures. 
Thoroughly pasteurize a small quantity (about half a pint) of milk 
by holding it, in a bottle plugged with cotton, at or near the boiling 
point for an hour or more. When this has cooled add two or three 
of the tablets and keep in a very warm place overnight. It should 
