<P> It was not until 1901 , when the Austrian Karl Landsteiner discovered three human blood groups ( O , A , and B ) , that blood transfusion was put onto a scientific basis and became safer . </P>
<P> It was not until 1901 , when the Austrian Karl Landsteiner discovered three human blood groups ( O , A , and B ) , that blood transfusion was put onto a scientific basis and became safer . </P>
when did blood transfusions become safer and why
when did blood transfusions become safer and why
1901
1901