THE TESTS FOR BLOOD 



113 



base of malachite green and of phenolphthalein. The last-named 

 body is stated to be extremely sensitive. 



CRYSTALS, x 1,500. 



Biological. The biological test depends upon the fact that the 

 serum of an animal injected with foreign corpuscles develops the power 

 of precipitating, agglutinating, and dissolving corpuscles similar to 

 those injected, but not those of other species of animals. A rabbit is 

 injected with 2 to 3 c.c. of human serum at intervals during four 

 days, until 10 to 15 c.c. have been injected. After one to two weeks 

 the animal is bled, the serum collected and placed in sterile tubes, and 

 used as needed. This serum is mixed with the suspected blood, which 

 is dissolved or suspended in isotonic salt solution in the proportion of 

 1 : 100; the mixture is placed at 37 C. If the blood be human, a 

 turbidity is produced, changing within three hoars to a flocculent 

 precipitate. The blood of closely allied species, such as the other 

 Primates e.g., chimpanzee may give a slight precipitate. The test 

 has been used to detect human blood in medico-legal cases, and to con- 

 firm the supposed consanguinity of different species of animals. It shows 

 the near relation of man tolsh^e gorilla, the ourang, and the chimpanzee. 



8 



