Popular Science Monthly 



43 



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 tvvo 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 



