Abstract
Mice infected with Stapholo-coccies aureus, Pseudomonoz aeruginosa or Escherichia coli could be cured by a single simultaneous treatment; repeated treatment did not alter the effect. In infections with P avicida, Klebsiella pneumoniae, Salmonella typhimurium, Dyslococcies pneumoniae, Listeria monocy-togenes and Streptococcus pyogenes this is not always true, for in many cases multiple treatment resulted in better cure at a lower dosage. Nevertheless single treatment together with a shorter observation time (5 instead of 10 days) is the generally preferred method because it is more economical and because experiments of this type are much less distrubed by non-specific factors.