The importance of Lactobacilli in maintaining normal microbial balance in the crop.

1. The effect of lactobacilli on Escherichia coli has been examined in vitro and in chicken crop in vivo. 2. Inhibition of E. coli was dependent on the presence of sufficient numbers of lactobacilli. 3. In a standard test some lactobacilli were bacteriostatic and one was bactericidal. The bacteriostasis was due to the low pH produced by these strains but bactericidal activity could not be accounted for by pH alone. 4. In gnotobiotic animals the bactericidal strain was no more inhibitory for E. coli than was a bacteriostatic strain.