Studies of normal and malignant tissue antigens.

The problem of the replacement of blood in the event of blood loss or in blood disease has captivat ed the minds of men for centuries. As the source of fresh blood, animal blood was used, but severe transfusion reactions followed these initial at tempts. Agglutination and hemolysis of the red blood cells were observed. Later, transfusion was successfully performed by the use of blood from the same species. Dog blood can be taken by dogs, rabbit blood by rabbits, and so forth. The transfusion of human blood into hu mans, however, caused severe transfusion reac tions in some instances, similar to those observed when blood of a different species was used for transfusion. Landsteiner (10) discovered the exist ence of groups within the human race, referred to as blood groups. In addition to Landsteiner's four