Work on the thermal death point of micro-organisms in milk has been carefully reviewed, the difficulties of the problem stated, and the possible sources of error pointed out by M. J. Rosenau,1 who investigated the thermal death point of a number of pathogenic microorganisms. He concluded that milk heated to 60 C. and maintained there for 20 minutes may be considered safe so far as conveying infections with the micro-organisms tested is concerned. These results were later confirmed by Schorer and Rosenau,2 using methods of actual pasteurization ; the micro-organisms studied did not include B. paratyphosus A or B. The first work on paratyphoid bacilli was by Bernhard Fischer in 1903.3 It was mainly epidemiologic, but he makes the statement that he established by oft repeated experiment that the paratyphoid bacilli isolated in the epidemic studied were not killed by exposure to 60 C. for 30 minutes, that in two experiments bacilli were still living after exposure at 70 C. for from 10 to 25 minutes. Five minutes at 75 C. killed most of the organisms, but a few were living even then. The methods of experiment employed are not given in the report. Friedel, Kutscher and Meinicke,4 working in Koch's laboratory, reported, all paratyphoid bacilli killed by 5 minutes' exposure to 58 C.