In general, this study shows that no compounds are effective in vivo unless also effective in vitro, whereas 8 compounds were shown to have in vitro activity, but to be ineffective in the animal. This is in agreement with similar studies with regard to streptococci, as noted, and seems to indicate that preliminary in vitro studies are of value for the elimination of inactive compounds. Three compounds which were effective in animals but not in the test tube were all capable of being broken down in the body to compounds active in vitro.