1. A nickel tube magneto-striction oscillator of 320 watts output producing sonic vibrations of 9,300 cycles per second frequency is described. Certain structural innovations contribute to operating efficiency and permit more convenient exposure of test materials than in earlier types.

2. The rate of phage inactivation by sonic waves proceeds logarithmically with time and serves as a satisfactory measure of energy output during operation of the generator. The curve for phage inactivation taking place in the presence of homologous staphylococci follows that for phage alone but soon reaches a plateau after which no further loss of activity is noted. In general higher concentrations of bacteria more effectively inhibit phage destruction than do lower concentrations.

3. Cells that have attained a resting state after a preliminary phase of rapid growth normally have the capacity of inducing a very rapid and marked increase in [phage] when added to phage. This effect has been attributed to the presence of intracellular phage precursor. The store of phage precursor in activated cells is destroyed by sonic waves in about 30 minutes. The number of cells (plate count) shows no reduction until after the precursor is entirely inactivated.

4. Attempts to extract phage precursor from activated staphylococci by exposing the cells to sonic vibrations were unsuccessful.

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