MIRACLES OF SCIENCE 



and transmitted it to the Cambridge Laboratory. 

 There the discolored piece of paper was soaked in 

 water to produce a clear solution of blood serum. 

 A portion of this solution was placed in a test-tube, 

 and this test-tube put in a rack along with scores of 

 other specimens, each bearing only a number. 



Into each test-tube a small drop of a certain liquid 

 was placed. If the solution in the test-tube became 

 cloudy, the experimenter was able to pronounce 

 definitely that the blood was that of an animal of a 

 certain tribe. It might, for example, be the blood 

 of a tiger or a leopard or a panther or a cheetah; 

 but it could not be the blood of a hyena or a wolf 

 or a dog. 



Again the test might be applied to a blood stain 

 on a handkerchief or knife, or on a fragment of wood 

 from a floor or window sill, or scraped from the sur- 

 face of a boot or a coin. In this case the proof as 

 to whether the stain was caused by human blood or 

 by that of some animal might be the deciding testi- 

 mony in a murder trial. 



Here the method of procedure would be the same 

 as before. A solution being made from the blood 

 stain and placed in a test-tube, the trial fluid would 

 determine whether the stain was due to human blood. 

 If the test proved negative, other tests might deter- 

 mine what particular animal supplied the blood. In 

 a case reported by Professor Uhlenroth, for example, 

 a blood spot in the road, suspected to be of human 

 origin, was found to be from the blood of a pig. In 

 another case blood stains on a garment were reported 

 as being partly human and partly due to the blood 



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