Not all blood is the same

In 1900, the Austrian chemist, botanist and medical researcher Karl Landsteiner realized that not all human blood is alike, that some people's blood contains substances that are toxic to other people's blood.

That began to solve the mystery of why some people who received blood transfusions were fine, while others became ill and often died.

Karl Landsteiner
Karl Landsteiner

Landsteiner subsequently discovered three of the four genetically determined blood groups or types, O, A and B. A couple of years later, Alfred von Decastello and Adriano Sturli, Landsteiner's colleagues in Vienna, identified a fourth blood group, AB. While about 30 blood types have been discovered, the original four essentially cover everyone.

In 1910, at the Heidelberg Institute for Experimental Cancer Research in Germany, Ludwig Hirszfeld and Emil von Dungern demonstrated that blood type is an inherited trait.

In the speech he made when he accepted the Nobel Prize in 1930 for his work, Landsteiner described the mystery blood presented, and how he and his fellow researchers unraveled its secrets.

In 1922, Landsteiner moved to the Rockefeller Institute of Medical Research in New York, where he discovered an extremely powerful blood antigen he called "the Rh factor."

Today, hospital personnel make sure they know a mother's blood type in case she needs a transfusion. She will also be tested for her Rh factor because it can pose a danger to her baby's well being.

William Harvey

In the early 17th century, before the scientific method began its ascendancy in the Western world, the Englishman William Harvey described how the blood circulates through the human body, solving a mystery that had stumped scientists for centuries.

Some other scientists — Galen, the ancient Greek; Ibn al-Nafis, who worked in Egypt in the 13th century; and Michael Servetus, a 16th-century Spaniard — had got a chunk of the story right.

William Harvey

William Harvey

Only Harvey, who assiduously tested his theories on living animals, figured out that blood circulates throughout the entire body.

He published his thesis in 1628, as On the Motion of the Heart and Blood in Animals. His discovery is considered one of the most important achievements in medical history.

Harvey introduced the "experimental and observational approach" to scientific inquiry, the British medical historian P.M. Dunn writes in an article for the Archives of Disease in Childhood.

In addition to his revolutionary work on blood, Harvey also advanced our understanding of human reproduction. His practice extended to obstetrics, and he was interested in and knowledgeable about birth.

Harvey's 1651 book On the Generation of Animals, published with the stunning essay "On Parturition," debunked the idea that embryos were fully formed at conception, and advanced the theory of epigenesis, which held correctly that a chick, for example, grew all its various parts from a single cell.

Harvey also addressed labor, advising birth attendants to let nature take its course rather than to intervene unnecessarily. Harvey's tract was the first original work on obstetrics written by an Englishman. Aside from these famous works, the rest of his prodigious writing has been lost.

What remains is "truly remarkable when judged against the ignorance of the times and the prevalent reliance on ancient authority," Dunn writes of Harvey.