Abstract
The general aspects of immunological specificity have been discussed before this society in a masterly manner by authorities like Hektoen and Wells, on former similar occasions. If the following review concerns itself again with related matters, this may be justified by the broadening of the subject of serological specificity which has branched off from medical immunology as a somewhat independent line of research.
The interest in the particular topic of blood antigens has been revived of late by investigations centering round several distinct issues, such as the principles of species specificity, the chemical nature of cell antigens and the human blood groups. Beginning with the blood groups, one of the questions which has arisen is whether the differences of human blood are limited to the four groups or whether there are other variations.
