74 EXPERIMENT STATION RECORD. 



Gas-producing- bacteria and their effect on milk and its products, F. C. 

 II \i;i;isoN | Ontario Agr. Col. and Expt. Farm Bui. 141, pp- '<,f"J*- <?).— Practical noints 

 brought out in connection with a study of 66 varieties of gas-producing bacteria 

 isolated from milk are discussed briefly in this bulletin. 



Bacteriological examinations of the milk from a number of farms showed on an 

 average the presence of nearly 15,000,000 bacteria per cubic centimeter, of which 

 over 235,000 were gas producing. The percentage of gas-producing bacteria in 27 

 examinations made varied from 0.04 to 34.2 per cent. In studying the source of 

 these gas-producing organisms in milk it was ascertained that they were occasionally 

 present in the udders of certain cows, on the hair of the animals, in clean, dry milk 

 cans, in watering troughs, on flies present in the stable, and in manure. 



The gas-producing bacteria were found to be readily killed at temperatures of 137 

 to 140° F. for 10 minutes. While they were destroyed by immersion for 10 minutes 

 in a 2 per cent solution of ammonia or soda washing powders kept at 140°, it is 

 believed that these powders are scarcely more effective than hot water, except as 

 they help to remove the dirt in washing. 



It was found that by continued growth in milk the gas-producing bacteria increased 

 their pi >wer « if fermenting milk sugar. In one instance the increase in gas production 

 noted was from 26 to 62 per cent. In general the development of lactic-acid bacteria 

 tended to check the growth of the gas-producing forms. 



The injurious effects of the gas-producing bacteria were shown in butter and cheese 

 making experiments. 



A comparative study of sixty-six varieties of gas-producing bacteria found 

 in milk, F. C. Harrison {Rev. Gen. La it, 4 {1905), Nos. 12, pp. 265-275; 13, pp. 

 289-297; 14, pp. 315-328; 15, pp. 337-351; Centbl. Bakt. [etc.], 2. abt., 14 {1905),, Nos. 

 12-13, pp. 359-374; 15-16, pp. 472-480).— This is a detailed report of the bacteri- 

 ological investigations upon which the above bulletin is based. 



The author proposes a classification of the different varieties which were stated to 

 show every imaginable modification between Bacillus coli and B. lactis aerogenes, 

 which were taken as extremes. The neutral red test did not appear to be of value 

 in separating members of the coli group, and the agglutination test showed only a 

 limited value in the identification of closely related varieties. A bibliography is 

 appended. 



On the preservation of milk with hydrogen peroxid, E. Baumann (Munchen. 

 Med. Wchnschr., 52 {1905), No. 23, pp. 1083-1088) .—After citing objections which 

 have been raised to the pasteurization and sterilization of milk for infant feeding 

 and reviewing briefly some of the literature relating to the use of formalin and 

 hydrogen peroxid for this purpose, the author reports several series of experiments 

 with the latter substance. 



In no instance were all the bacteria in market milk destroyed by hydrogen peroxid 

 added in quantities ranging from 0.35 to 2 parts per thousand, the milk being heated 

 to 45 to 50° C. and kept at that temperature for 2 to 3 hours. The number of bac- 

 teria, however, was always greatly reduced and spontaneous curdling of the milk 

 delayed for several days. The reaction for hydrogen peroxid was usually absent at 

 the end of treatment unless the quantity added exceeded 0.54 part per thousand, 

 when a positive reaction was obtained for days. 



Market milk treated with hydrogen peroxid in the proportion of 0.42 : 1,000 showed 

 00, 2,220, and 26,400 bacteria per cubic centimeter at the end of 2, 5, and 7 days, 

 respectively, while milk which had been obtained under rigid aseptic precautions 

 was completely sterilized by the same treatment. 



Typhoid, cholera, and dysentery bacilli added to milk sterilized by heating were 

 destroyed in all cases by hydrogen peroxid in the proportion of 0.35 : 1,000, the milk 

 being heated to 45 to 50°. Typhoid bacilli were not all destroyed by hydrogen 



