Obstruction of vehicle-drivers' vision by spectacle frames.

and to remove such reservoirs. The majority of disinfectants tested at the chosen concentration appeared to be highly effective in this respect. The tests were carried out by using one concentration of disinfectant on terrazzo flooring in one ward, and it is possible that different results might be obtained under other conditions. In the selection of a disinfectant for floor treatment its activity against the range of pathogens in the reservoir, its safety, acceptability in use, aesthetic results, and cost must be considered; the type of flooring is also relevant, because materials used for flooring may be damaged by some compounds. Some disinfectants which were highly active against Staph. aureus but less active against Ps. aeruginosa in laboratory tests were effective in field tests, and our experiments suggest that Ps. aeruginosa could be successfully removed from surfaces by cleaning with these agents; as a result of their high death rate on drying, these organisms, when present in floor dust, are very scanty and are probably further depleted by the evaporation of solutions used for disinfecting the floor. Chlorine compounds, though better than soap and water, were less effective than the best of the disinfectants. Phenolic compounds varied in their effectiveness ; the best of these, however, showed highly satisfactory results both in laboratory and in field tests. Toxicity will also affect the choice of a disinfectant; many phenolic compounds-for example, Lysol and to a less extent Sudol-and tri-n-butyltin compounds may be corrosive, particularly in high concentration, and should be handled with care. In testing the effectiveness of a new method of disinfection it is perhaps reasonable to require that it shall reduce the total floor bacteria on areas protected from recontamination by about 95-99%, or to fewer than 15 bacterial colonies and less than one colony of Staph. aureus per impression plate.