EXPERIMENT STATION BULLETINS. 



509 



TABLE XXVIII. 



Name of organism. 



Bad. bnlgaricum 



Bad. ladis acidi (from sour milk) 

 Bod. ladis acidi, No. 4 



Maximum average acidity. 



Milk. 



314° 



113° 



89° 



Broth. 



80° 

 52° 

 52° 



Whey. 



101° 

 39° 

 33° 



Percentage of maximum acidity 

 produced in 



Milk. 



100 

 100 

 100 



Broth. 



25.5 



40 

 58 



Whey. 



32 



34.5 



37 



CONCLUSIONS. 



The minimum acidity produced by Bad. lactis acidi (from sour 

 milk) which will destroy B. tijpliosus is -(-37° in lactose broth. This 

 corresponds to 80° acid in milk and 28° acid in whey. 



The minimum inhibitive acidity produced by Bad. hulgai'icum is -)-53° 

 in lactose broth. This corresponds to 4-208° acid in milk and to 66>° 

 acid in whey. 



The above amounts of acid in milk corresponding to the acidity pro- 

 duced in whey and lactose broth by the same organism: are theoretically 

 the minimum acidities at which the typhoid bacteria will be killed. 



However, in raw milk, the medium of natural infection, many factors 

 enter which are never constant, e. g., the character of the initial microb- 

 ial flora, the flora gained by the necessaiw exposure to sources of con- 

 tamination, and the temperature conditions under which the milk is 

 kept after being strained. 



If certain species of microorganismvS are present in milk, they may, 

 either by growing in association with the lactic bacteria, or by some 

 of their own metabolic products cause a more rapid destruction of the 

 typhoid organisms than the lactic bacteria are capable of causing alone. 

 Or, on the contrary, certain species of bacteria may predominate which 

 will check the production of acid by the lactic bacteria, some even living 

 in symbiotic relatioL'-hip with B. typhosus. 



It is very probable that some one of these conditions will occur in the 

 greater number of infected milk samples since milk infected with typhoid 

 bacteria must have been subjected to sources of contamination from 

 which a varied flora would be acquired. 



Thus, while this series of experiments brings out some very interesting 

 facts in regard to the influence of fermentation lactic acid upon typhoid 

 bacilli, the many factors entering under natural conditions prevent any 

 definite conclusions being made when these natural conditions exist. 



BIBLIvXJRAPHY. 



1. Bacteriology of Milk, Swithinbank and Newman, p. 314. 



2. Bakteriologie des Meiereiwesens, Chr. Barthel, p. 116. 



3. Herkunft der Bakterien der Milch, von Prof. Dr. H. Weigmann, 



Handbuch d. Technischen Mykologie, Bd. II, Lafar, pp. 36-39. 



4. Experimentelle Beitrage z. Frage der Tvphusverbreituug durch But- 



ter, C. Burck, Cent. f. Bakt. I, Referate, Bd. XXXIV, p. 778. 



