Silk threads, impregnated with anthrax spores, were placed in bottles containing carbolic acid of various strengths, and at stated periods threads were removed and placed in nutrient media, and development or otherwise observed. But, as Professor Crookshank[103] has pointed out, this method is fallacious, the thread being still wet with the solution when transferred to the medium, and thus modified in culture, possibly even inhibited altogether. It is unnecessary for us here to discuss every mode adopted by investigators in similar researches. We may just mention that the most approved methods at the present time are based upon two simple plans of exposure. In one we use a known volume of recent broth culture of an organism grown under specified conditions. To this is added a measured quantity of the antiseptic. At stated periods loopfuls of the broth and antiseptic mixture are sub-cultured in fresh-sterilised broth, and resulting development or otherwise closely observed. The other method is practicable when we are dealing with volatile bodies. In such cases a standard culture is made of the organism in broth at a standard temperature. Into this are dipped small strips of sterilised linen. When thoroughly impregnated these are removed from the broth and subsequently dried over sulphuric acid in a vacuum at 38° C. These may now be exposed for a longer or shorter period to the fumes of the antiseptic in question, and broth cultures made at the end of the exposure. It is obvious that a very large number of modifications are possible of these two simple devices for testing the bactericidal power of chemical substances. It should be remembered that here, perhaps, more than anywhere else in bacteriological research, careful control experiments are absolutely necessary. _Mineral acids_ (nitric, hydrochloric, sulphuric), especially concentrated, are all germicides. The _halogens_--chlorine, bromine, iodine, and fluorine--are, all four, disinfectants, but not used in practice. They are named in their order of power as such. A number of separate bodies, such as _chloroform_ and _iodoform_, have been much advocated as antiseptics. The cost of the former and odour of the latter have, however, greatly militated against their general adoption. _Chloride of lime_ is a powerful disinfectant. Professor Sheridan Delépine and Dr. Arthur Ransome have demonstrated its germicidal effect as a solution applied directly to the walls of rooms inhabited by tuberculous patients.[104] It may also be used in solid form for dusting decomposing matter.