4 BULLETIN 148, U. S. DEPARTMENT OF AGRICULTURE. 
Jensen 1 advised the use of a streptococcus in connection with 
B. hulgaricus as a starter for suppressing undesirable bacterial 
growths in the cheese, but offered no proof of the efficiency of this 
combination of cultures. 
Though it is generally believed that it is the lactic acid produced 
by different bacteria that gives different varieties their value in pre- 
venting the growth of undesirable forms of germ life, this assump- 
tion is seriously questioned by some bacteriologists, who think it 
possible that the formation of lactic acid is incidental and is not the 
active inhibiting principle. 
"White and Avery 2 point out that cultures of B. hulgaricus grow at 
relatively high temperatures, forming acid as high as 50° C. (122° F.) . 
They also show that relatively high percentages of acid are formed 
in milk, reaching as high as 3.1 per cent. 
Hastings and Hammer 3 give 4.09 per cent as the maximum amount 
of acid found in milk. They find that B. hulgaricus is distributed 
very widely and generally in dairy products of all kinds. Mention 
is made especially of its presence in the milk and whey at Swiss- 
cheese factories. 
Heinemann and Hefferan 4 also noted the general distribution of 
B. hulgaricus, its high growing temperature and its ability to form 
acid in milk. 
The authors quoted found a very great difference in the maximum 
amount and the rapidity of acid formation of different cultures. 
Cultures also lose their ability to form acid to a great extent when 
carried under laboratory conditions. The growth of Mycoderma on 
the surface of the whey starter greatly facilitates the growth of the 
B. hulgaricus culture used. Thoni 5 in some tests with the Myco- 
derma found that while the whe} 7 culture of B. hulgaricus without 
the Mycoderma showed at the end"of 24 hours 7,000,000 and 18,000,000 
bacteria per cubic centimeter, with the Mycoderma the numbers 
were 136,000,000 and 200,000,000, respectively, and the increase of 
acid with the Mycoderma was more than one-half. 
In our own work we have found that B. hulgaricus can form as high 
as 2 per cent acid in whey, and we found that with the culture iso- 
1 Jensen, Orla. Leber die im Emmentalerkase stattfindende Milcksauregarung. Milch- 
wirtsehaftliches Zentralblatt, vol. 2, no. 9, p. 393-414. Leipzig, Sept., 1906. 
2 White, Benjamin, and Avery, Oswald T. Observations on certain lactic-acid bacteria 
of the so-called hulgaricus type. Centralblatt fur Bakteriologie, Parasitenkunde und 
Infektionskrankheiten, Abteilung 2, vol. 25, no. 5/9, p. 161-178. Jena, Nov. 30, 1909. 
3 Hastings, Edwin George, and Hammer, B. W. The occurrence and distribution of 
organisms similar to B. hulgaricus of yogurt. Centralblatt fur Bakteriologie, Para- 
sitenkunde und Infektionskrankheiten, Abteilung 2, vol. 25, no. 14/18, p. 419-426. Jena, 
Dec. 22, 1909. 
i Heinemann, Paul Gustav, and Hefferan, Mary. A study of Bacillus hulgaricus. Jour- 
nal of Infectious Diseases, vol. 6, no. 3, pp. 304-318. Chicago, June 12, 1909. 
5 Loc. cit. 
