Abstract
The precipitin reaction has been used extensively in medico-legal work for almost 30 years. Nuttall 1 used the precipitin tests in zoological relationships and Boyden 2 confirmed the work of Nuttall and stressed the principle of reciprocal relationships. The methods used in medico-legal work have been entirely of the “trial and error” type and no satisfactory method is known for identification of the individual bloods of a mixture, often an important item in criminal trials. Zoological relationships based on serological evidence can give a basis for a less cumbersome technique in medico-legal work.
In verifying the principle of reciprocal relationships and the per cent values of relationships the methods of Boyden were used. Two per cent antigen solutions of human, horse, sheep, beef, pig, cat and rat sera were made and the protein percentage determined. Antisera of all but the cat and rat sera were used. Two and often 3 readings, were made of each reaction and they agreed very well within themselves. A comparison of some of the relationships obtained with those of Boyden and of Nuttall showed a good agreement. The general correspondence of these results demonstrates the value of this biological method for the study of relationships.
The reciprocal values of the antisera employed in the preceding experiments are shown in Table I. Of the 18 reciprocal values shown, 13 are within the range of the error of the test (100% possible error). Three of the remaining 5 which show a greater divergence are anti-horse sera reactions, which have been consistently irregular in previous tests.
The work shows that in all cases the heterologous reactions were weaker that the homologous ones by definite per cents of the homologous titers. Hence in the identification of an unknown stain, if the protein content is determined, the first test can give a clue as to the possible origin of the blood by the percentage of the reaction.
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