Abstract
Summary
The action of ultra-violet light when projected through thin walled small test tubes containing mixtures of Spirochæta pallida and various bacteria may be summarized as follows: With an exposure of 75 seconds at close range, Colon bacilli were killed and treponemata showed good growth. This growth diminished as the time of exposure was increased. Upon re-inoculating on to the fresh media, the spirochxtes exhibited good procreative and normal morphological properties, with no evidence of bacterial contamination. A five to ten cm. projection distance was lethal to the spirochztes within 45 to 60 minutes. One hour's radiation at a distance of 10 cm. did not prove bactericidal, but with the lamp placed five cm. away from the tubes and allowed to act but 45 minutes, the Colon bacillus was effectively destroyed.
When a definite interval of exposure to ultra-violet rays was selected, it was observed that the lighter suspensions of bacteria were more readily killed than heavier ones. In other words, this germicidal phenomena is quantitative. It was also noted that the further the source of the rays was from the organisms, all other things being equal, the less the bactericidal action. The longer the time of action, the greater the danger to both the bacteria and spirocliztes. A period of exposure of 90 to 120 seconds at close range consistently proved detrimental or lethal to the pallida. Up to an interval of one minute, they were little affected.
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