t62 BACTERIA IN MILK 
ITI. Bacillus bulgaricus.—A third radically different type of 
acid bacterium is one that has recently come into prominence in 
various forms of beverages composed of soured milk. In certain 
parts of Europe sour milk is commonly used as a beverage, and 
has been highly recommended as a healthful drink. It is claimed 
that the lactic acid, present in abundance in these sour milks, 
has a very beneficial action in the intestine, preventing the growth 
of the common putrefactive germs, and serving in general as a 
corrective for various intestinal disturbances. It is not ordinary 
sour milk that is especially recommended for this purpose, but a 
special form, found most common in Bulgaria, and used very 
widely as a drink in that country. Such milk contains a variety 
of lactic acid bacterium very different from the two above de- 
scribed, and deserving to be called a distinct type. It is in the 
form of a long, large rod (Fig. 33), which fre- 
rN quently forms long chains. It differs from the 
SY F—\ more common type in producing a much larger 
Pie 33-~B Bul- quantity of lactic acid. The ordinary sour milk 
garecus organisms produce from 1.2 per cent. to 1.5 per 
cent. of lactic acid, and then cease to grow; but 
this Bulgarian type produces as much as 3.0 per cent. of 
acid, double the amount produced by the common type. 
This type is very vigorous and when growing in milk will 
soon destroy other bacteria. Quite a number of commercial 
products containing this organism are now on the market, 
and are used somewhat widely in making a fermented milk. 
Though originally found in Bulgaria, bacteria that agree with it 
in all essential respects have been found elsewhere. It has been 
found in this country as well as in Europe, and is known to play 
an important part in the ripening of hard cheese. Several of the 
fermented milks found in different countries appear to contain 
representations of this type of lactic acid organism. 
Peptonizing and Rennet-forming Bacteria—Occasionally a 
dairyman is puzzled by a somewhat unusual phenomenon: his 
