The ideal clinical disinfectant and antiseptic is still sought after by clinicians and surgeons in general. In recent years a gradual appraisal has been made of the unusual disinfecting and antiseptic properties possessed by a mercurial compound commercially called metaphen. In order to evaluate the claims made for metaphen as a germicide, more powerful than mercuric chloride when tested on cultures ofStaphylococcus aureusandBacillus typhosus,1the present extensive and entirely detached comparative study of commonly used disinfectants and antiseptics was undertaken. I. A COMPARATIVE STUDY OF COMMONLY USED DISINFECTANTS AND ANTISEPTICS Metaphen. —In 1919 Schamberg, Kolmer and Raiziss2discovered that the introduction of a nitro group attached to benzene in conjunction with organic compounds of mercury markedly increased the bactericidal properties of mercurial compounds. One such compound was sodium-hydroxymercuri-ortho-nitro-phenolate, commercially called mercurophen. This preparation was found to possess useful local antiseptic properties and was recommended by