The first reported blood transfusion occurred in 1492. The transfusion was done on Pope Innocent VII in Rome. His doctors advised to transfuse blood from three healthy individuals as a therapeutic measure for his illness. However the outcome of this blood transfusion was not successful and the Pope died soon after.

In 1628, William Harvey, an English physician discovered how blood circulated around the body, with the heart pumping blood into the body through the arteries, and the blood returning back to the heart through the veins.

In the year 1665 the first successful blood transfusion was recorded. Experiments were done by an English physician, Richard Lower, who transfused blood from one dog to another. Most of the dogs survived the transfusion. By the year 1667 Richard Lower and Jean-Baptiste Denis reported successful transfusions from animals to humans. Animals used included sheep and lamb. However, due to the deaths that were reported, within ten years this practice became illegal and for the next 150 years no studies in blood transfusion were recorded.

Syng Physick did the first successful blood transfusion from one human to another human in America. The year was 1795; however he never published his studies. In 1818 the first successful transfusion was recorded. It was performed by James Blundell, a British obstetrician, on a mother that suffered post-partum haemorrhage (sever bleeding after delivery). Blood from her husband was taken with a syringe and successfully injected into the patient. Between 1825 and 1830 he performed ten of these transfusions, with five of the patients showing clinical benefits.

During the transfusions that were performed in the following years, two problems were being encountered. The first was that frequently, blood clotted during the procedure, as no anticoagulants (a solution that inhibits blood to clot) were being used until the year 1914. The second problem was that about half of the transfused patients had severe reactions, some of which led to death. The breakthrough came in 1900 when Karl Landsteiner, an Austrian scientist, discovered three human blood groups. These were the A, B and O blood groups. For this discovery he was awarded the Nobel Prize for medicine in 1930. In 1902, two students who worked with Karl Landsteiner discovered the fourth human blood group, the AB. These two were A. van Decastello and A. Sturli. These four blood groups together are what we today know as the ABO blood group system. In 1925, while Karl Landsteiner was working in New York he discovered two more blood group systems, the MN and the P blood group systems.

In 1912, Roger Lee defined the terms ‘Universal donor’ and ‘Universal recipient’. He demonstrated that group O blood could be transfused in patients having anyone of the four blood groups, while group AB patients could receive blood having anyone of the four blood groups.

As mentioned earlier in 1914 several anticoagulants were being introduced. In 1916, Francis Rous and J.R. Turner introduced a citrate-glucose solution, which was added to the collected blood. This allowed blood to be stored in containers and refrigerated for several days before being transfused. In the years to follow establishments where blood was collected and stored were being introduced. Later, these were to be known as 'Blood Banks', the first being introduced in a Leningrad Hospital in 1932. However the term 'Blood Bank' originated in 1937, by Bernard Fantus, who established the first Blood Bank at the Cook County Hospital in Chicago. In the following years Blood Banks spread throughout the United States.

Although the discovery of the ABO blood group system reduced dramatically the number of deaths following blood transfusion, several other transfusion reactions (such as fever) were being observed. These were caused by other blood group systems, which yet had to be discovered. The most important of these systems was the Rhesus (RH) system. This discovery was made by Philip Levine and R.E. Stetson in 1939. They observed that after a mother gave birth to a stillborn child and subsequently transfused with her husband's blood, she suffered a severe reaction to the blood. Both the mother and the husband were group O. The two scientists explained the presence of a new factor as being the cause; however no name was given to it. The name was given by Karl Landsteiner and Alex Weiner in 1940. They conducted a study in which they injected blood from the monkey ‘Maccacus rhesus’ into rabbits and guinea pigs. The blood from the rabbits and the guinea pigs was then collected, and the serum (the liquid in which red blood cells flow), which contained the anti-Rh factor (a protein that binds to the rhesus antigen), was mixed with red blood cells from a number of samples from individuals of a population of New York City. Red blood cells from 85% of this population agglutinated (clumped together) with this serum. This population was called Rhesus Positive (Rh Positive). The remaining 15% that did not have any agglutination were called Rhesus Negative (Rh Negative).

Other important blood group systems were discovered during the following years. The introduction of the anti-human globulin reagent (Coombs reagent) as part of the pre-transfusion testing was an important step for the detection and identification of incomplete antibodies that were causing transfusion reactions. The reagent was described in 1908 by Moreschi, and was rediscovered in 1945 by Dr. R. Coombs, Mourant and Race. The use of this reagent and the principles behind it are still an important tool today.

By the year 1950, the number of blood banks was increasing around the world. In the United States alone the number of hospital blood banks reached 1500. During this year one of the most important technical developments in blood banking was introduced by Carl Walter and W.P. Murphy Jr. They introduced the plastic bags for the collection of blood, which replaced the breakable glass bottles that were in use.

The scientific research that was done in the next fifty years revolutionized blood banking. New concepts and important techniques were developing, all of which moved blood banks towards a system that took into consideration the safety of both blood donors and patients receiving their blood. In 1970 blood banks started collecting blood from volunteers. Testing of blood for transfusion-transmitted diseases was being introduced. The first testing started in 1971 when blood collected for transfusion was being tested for Hepatitis B. In 1985 the first test to detect HIV was quickly implemented by all blood banks to protect the patients from infections of this virus. Testing for Hepatitis C was introduced in 1987. In the years to follow other testing was implemented and the techniques by which the testing was done improved, minimizing the risks of diseases transmitted through blood transfusions.

Other important developments that occurred in these last thirty years were related to the storage of blood. Due to the fact that blood banks were collecting blood from volunteers and to the increasing demand of blood, several blood banks were starting to suffer shortage in their blood supply and were not coping with the demand. Although this problem still exists today the discovery that was made in 1979 reduced the problem. This was the development of a new anticoagulant preservative, CPDA-1, that extended the preservation of blood to 35 days. Subsequently the shelf life of red blood cells increased to 42 days in 1983 when a new additive, SAG-M was introduced.
Today, the experiments and methods that were used in the past may seem to be crude; however it is thanks to these researchers, that we have reached the safe standards that we have today. The only thing that never changed throughout the years is the importance of blood.