The first successful and officially registered human-to-human blood transfusion was performed on 09/25/1818. It was carried out by British obstetrician James Blundell and thus saved the life of a woman in labor.
Before that, Blundell studied the features of hemotransfusion, proved the incompatibility of human and animal blood. And unlike his predecessors, who tried to do transfusion with arterial blood, Blundell justified the choice in favor of venous blood.
Patients often died from transfusion due to the mismatch of blood groups, but this was not known until the beginning of the 20th century
Mass hemotransfusion was used already during the First World War.
Image: The science museum group and Wikipedia