Alexander Wiener was a physician who, along with fellow scientist Karl Landsteiner, discovered the Rh factor in blood. He also discovered a number of other antigens (substances in the blood that cause the development of antibodies). The Rh factor is an antigen named after the rhesus monkey, the animal in which it was first discovered. Blood that contains the factor is called Rh-positive, whereas blood that lacks it is labeled Rh-negative. The discovery of the Rh factor led to an understanding of adverse reactions to blood transfusions that occurred inexplicably in some patients even though compatibility of blood type (A, B, AB, and O) in donor and recipient had been observed. The discovery of the Rh factor also brought about an understanding of the possible adverse reactions when an Rh-negative mother carried an Rh-positive fetus. Wiener developed a life-saving method of replacing the damaged blood of new-born infants...