This paper is the third in a series of studies of antiseptics. The first was a study of the bactericidal effect of mercurochrome-220 soluble1 on Bacillus pyocyaneus, while the second2 was an investigation of some of the properties of the antiseptic known as S. T. 37, described in 1927 by Leonard and Feirer.3 The present article is the direct outgrowth of the first two papers, and has for its object a comparative study, in vitro, of the bactericidal effect of twenty-one commonly used antiseptics on four different organisms growing on agar slants.
The organisms used were a freshly isolated strain of Staphylococcus aureus, a similar strain of Bacillus pyocyaneus, and laboratory stock cultures of Bacillus subtilis and Bacillus typhosus. Preliminary to the actual experimental work, each culture was transplanted for five successive days on agar slants. Immediately preceding experimentation, two fresh transplants were made from the fifth