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Page:Popular Science Monthly Volume 90.djvu/59

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Popular Science Monthly

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��Dr. Klein and Dr. Pascini of New York's Central Testing Labora- tory — a seven-story building filled with the latest scien- tific paraphernalia, equip ped to test anything from steel girders to fly- specks. No weapons or clues were to be found. A bundle of papers held together by a leather strap had been opened, but whether by the mining engineer or his mur- derer, could not be determined. The end of the strap had been broken off. The piece was missing. Follow- ing the instructions of Inspector Faurot, the chemists took that piece of strap into their possession.

The inspector observed that someone had spat upon the floor. The two chemists took a sample of this sputum. The inspector further observed that there was what appeared to be a blood-stain on the door-knob. He examined this for finger- prints. There was none, because the murderer had so moved his hand that a clear finger-print was not obtainable. Nevertheless, the door-knob was removed and taken to the labo- ratory.

Once in the labora- tory with the evidence thus collected, the chem- ists began their work.

���Inspector Faurot discovers what may be a trace of blood on the door-knob

��Under the microscope, tubercle bacilli were immediately identi- fied. At once the search was narrowed down to a man who had consumption, who spat freely and who probably coughed. Next, the stain found on the door-knob was tested. Was it or was it not human blood? A delicate test was made with a rabbit which had been injected with human serum. The serum obtained from a rabbit thus treated is a sensitive reagent which at once reveals the presence of human blood in a solu- tion. The chemists found that the stain on the door-knob was indeed that of human blood. But of what human being? An- other test was made for malarial parasitic and other organisms. So delicate are blood tests that it is sometimes pos- sible to state with certainty that a given sample of blood has been taken

��At right: A photograph of the blood as it appeared under the microscope

���Above: Inspector Faurot holding the door knob while Dr. Klein tests the blood print. Dr. Pascini is examining under the microscope scrapings from the victim's finger-nails. The rabbit will be used in the blood tests. At left: The central hair was found in the nail-scrapings

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