A second outbreak of phage infection with complete cessation of acid production in experimental vats is described. Although occasional positive indications were obtained from the milk supply itself, the original source of the phage was not definitely demonstrated.

The results obtained in testing for phage appeared to be influenced by the size of milk sample examined, and by refrigerated storage for 7–16 hr. before testing.

Trouble with slow working vats in two factories which had continued over a period of 6 weeks was shown to be due to lysis of the dominant strains of the mixed culture of starter organisms by phage.

Attention is called to the need for substitution of a starter of entirely different bacterial strains when such trouble is encountered.