370 MILK 



Mason, in Camembert and Roquefort cheese; Dotterer and Breed 

 found them in enormous numbers in the raw and pasteurized 

 whey from cheese factories. This last discovery is of special 

 interest, inasmuch as it shows that the thermal death-point of the 

 bacilli must be above* pasteurization temperature, since in pas- 

 teurized whey they were present almost in pure culture. White 

 and Avery, however, claim that a minimum exposure of fifteen 

 minutes to 60 C. was necessary to kill all strains. 



Pathogenicity to man or animals has never been observed. 



Lactobacilli produce chiefly lactic acid. Hefferan and the 

 writer found that 5.8 to 6.1 per cent, of the total acid formed 

 consisted of volatile acid. The nature of the volatile acid was not 

 determined. According to Bertrand and Weisweiller and Ber- 

 trand and Duchacek acetic, formic, and succinic acids are formed. 

 White and Avery state that all strains observed by them produced 

 small amounts of volatile acid, the nature of which was not deter- 

 mined. The same authors found small but appreciable amounts 

 of alcohol in the distillates from whey of ten-day-old cultures, 

 but neither acetone nor aldehyd. They state further that the 

 casein and fat are slightly decomposed so that a bitter acrid taste 

 is produced. 



The influence of oxygen pressure on acid formation by lacto- 

 bacilli has been studied by Koestler. Working with Bacillus 

 casei of Freudenreich, the author determined that more acid is 

 formed when the surface of the culture-medium exposed to the 

 air is reduced. The author also found that more acid is produced 

 when the quantity of peptone is increased, and that acid is not 

 produced exclusively from the carbohydrate, but that part of it is 

 derived from the peptone. When all conditions as to composition 

 of the medium, the temperature, and the oxygen pressure were 

 equal, Koestler always found that the same amount of acid was 

 produced. 



The lactic acid formed by those lactobacilli which produce 

 large amounts of lactic acid is of the inactive variety according 

 to Heinemann and Hefferan and White and Avery, while accord- 

 ing to the latter authors the low acid producers form levorotatory 

 acid. This is in agreement with the findings of Heinemann and, 

 Ecker that the Boas-Oppler bacillus, wjiich belongs to the class of 

 low acid formers, produces levorotatory acid. Currie found 

 dextrorotatory acid formed by lactobacilli isolated from human 

 saliva, human feces, malt, kraut, cheddar cheese; he found d-acid 

 with a small admixture of i-acid in strains from cheddar cheese; 

 from another strain from cheddar cheese he found pure 1-acid; 

 and in milk soured at 38 C. he found 1- and i-acid mixed. 



Currie's results are not entirely in harmony with those of 



