Simplified Fluorescence Microscopy of Tubercle Bacilli

SUMMARY: The fluorescence of tubercle bacilli stained with auramine and rhodamine does not require ultra-violet light. It can be caused by blue light up to 496 mμ. A copper sulphate ammonia liquid filter, suitably diluted, will transmit this waveband. A gelatin screen filter, absorbing all light below 510 mμ. is used in the eyepiece. Normal, high intensity projection filament lamps, combined with lamp condensers of large aperture, provide suitable light sources. The numerical aperture of the microscope condenser must be fully used by immersion in glycerol. The fluorescence is very bright with the usual biological, and certain binocular, microscopes. The simplicity of the equipment enables fluorescence microscopy of tubercle bacilli to be used at low cost in any laboratory.