A plating method was developed to enumerate psychrotrophic bacteria in raw and pasteurized milk. Standard Methods agar plates were prepared according to Standard Methods for the Examination of Dairy Products, and incubated at 21 C for 25 h (21 C-25 h). Counts obtained by this method were in very good agreement with those obtained by the standard psychrotrophic count. The correlation coefficients between counts obtained by the 21 C-25 h method and by the standard psychrotrophic count method for 132 samples of raw milk and 190 samples of pasteurized milk were 0.992 and 0.996, respectively.

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A line heat source thermal conductivity probe was used to measure the thermal conductivity of 28 dairy products and margarines at 0, 20, and 40†C. Water and fat contents and mass density of each sample were also measured and correlated to thermal conductivity. There was a strong positive correlation between thermal conductivity and water content, and an inverse correlation between thermal conductivity and fat content. Temperature did not appear to be a significant factor over the limited temperature range studied. Although there was some correlation between mass density and non‐fat solids fraction, no correlation was observed between mass density and thermal conductivity.

Owving to their very small size, bacteriophage particles were not observed or photographed until the advent of the electron microscope. Electron micrographs of club-shaped objects resulting from the lysis of Eschcrichia coli by phage were first reported by Ruska (1940) and Pfankuch and Kausche (1940). Ruska (1941) found the various phages with which he worked to measure 250 to 400 m, in total length and 60 to 100 mA in breadth of head. LUIia, Delbrtick, and Anderson (1943) reported the head of the a virus of E. coli was 45 to 50 m,u in diameter; that of they virus was 65 by 80 m,u, with a tail 120 m,u long. The phage affecting the motile E. coli is 50 to 60 m,u in diameter and apparently has no tail. The electron micrograph of Staphylococcus phage presented by Luria,