Although the status of blood grouping and its value in preventing harmful reactions have been definitely established, more or less severe reactions following blood transfusions are still reported in the literature. Attempts have been made by many men to explain the phenomena observed. Unger1 has urged the advisability of grouping the donor's blood directly against the blood of the recipient. Lately, several cases have been reported which demonstrate that our previous conceptions of hemolysis and agglutination may need some revision. Astrowe2 has pointed out the necessity of repeated tests of donor's versus recipient's blood before each transfusion. West,3 in a later note, cites a case in which hemolysis of the donor's cells took place without preliminary agglutination.
In January, 1922, Eden4 advanced the theory that the agglutinins present in the blood could be changed or altered in various degrees. This change from one group to another