The presence ofBacillus colior of any other nonsporulating gas producer in pasteurized milk is usually taken to indicate either improper pasteurization or subsequent contamination of the milk. For according to most authorities the thermal death points ofB. coliand similar organisms are below the temperature of pasteurization. Thus Kolle and Wassermann1give the following summary of the various findings forB. coliup to the year 1903: However, more recently De Jong and De Graef2have described seven strains ofB. coliwhich survive 65 to 67 C. (149 to 152.6 F.) for thirty minutes in milk or broth. These strains would not be killed by the degree of heat commonly used in pasteurization and in consequence the presence ofB. coliin pasteurized milk could no longer be taken as an index of improper pasteurization or subsequent contamination. With the object of confirming these