Serologic methods were applied in forensic medicine shortly after the discovery of immunologic species characteristics. The specific precipitin reaction made it possible to differentiate human from animal blood even in minute stains, a task beyond the reach of ordinary chemical methods. To go still further and attempt to distinguish bloods of various human individuals from one another seemed almost hopeless at that time. In part this problem was solved by the observation that there exist several types of human blood which can be identified by a very simple reaction, normal human serums being used as reagents.
I presume that the properties of the human blood groups are known well enough to make a repetition unnecessary. Because of the regularity of the blood group scheme it was obvious from the outset that the underlying blood properties are constitutional and, following the rediscovery of Mendel's laws by de Vries, Correns and Tschermak,