Let's Reminisce: A short history of blood
By Jerry Lincecum
Jan 29, 2019
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One of my early memories from childhood is how frightened I felt the first time I suffered a nosebleed.  That memory came to mind as I read a recent article about the history of blood. In reviewing a new book entitled Nine Pints (which is approximately the amount of blood in a typical human), Jerome Groopman discusses some interesting facts about the evolution of human attitudes toward blood.

Ancient peoples were certain of blood’s importance and fascinated by its mystery. For them, blood was something hidden—visible only when flowing from a wound, or during childbirth—so it became a symbol both of life and of death. To control blood was to master life itself, so it is unsurprising that blood features prominently in religious traditions. The wall between medicine and myth is thinner than we suppose, and blood is continually moving back and forth across it.

Observant Jews follow dietary laws that forbid the consumption of blood. Yet, despite the firm taboo against ingesting blood, one breakaway Jewish sect of the first century AD made the idea of doing so central to its rituals. Its leader, Jesus of Nazareth, told his disciples that the bread and wine at the Last Supper were his body and blood, and should be consumed thereafter in memory of him. The ritual of the Eucharist became a cornerstone of early Christianity.

For many centuries, the human body was understood as a vessel for a quartet of liquids: yellow bile, black bile, white phlegm, and red blood. Each corresponded to one of the four classical elements—fire, earth, water, and air—from which it was thought everything in the cosmos was made. The key to good health was thought to be an ideal balance among the four humors. Danger arose if one predominated, so periodic voiding was crucial. From ancient times until well into the modern era, bloodletting was a cornerstone of medical practice.

Leeches were an essential tool for physicians to use in bloodletting. One of the earliest evidences of the human use of leeches is a painting on the wall of a 3000-year-old Egyptian tomb.  The leech can be compared to an oil tanker--the bulk of it is storage, and when feeding, a leech can increase its body weight fivefold.  Its bite causes far less trauma to the skin than a scalpel would, and it injects its prey with anesthetic, making its feeding painless for the host.

Only in the 17th century did the study of blood begin to acquire a truly scientific basis. In 1628, William Harvey’s revolutionary insight—that blood circulated from the left side of the heart through arteries and returned to the right side through veins--was published and today it is often cited as the greatest single-handed discovery in medicine.

Even more remarkable is the fact that he arrived at his discovery by empirical observation and inductive reasoning—the core of the modern scientific method. Armed with that knowledge, physicians began to consider the possibility of blood transfusions.  Because all the early attempts were failures, for 150 years the procedure was banned from orthodox medicine. It didn’t start to become viable as a treatment until 1900, with the discovery of blood types. Now blood could be more safely administered to patients, making it in effect a medicine.

More discoveries followed. In 1914, it was found that sodium citrate prevented blood from clotting, allowing it to be taken from a donor and stored until needed by a recipient. In WWI, this discovery saved the lives of countless wounded soldiers.

Using terms like bloodlines, blood brothers and blood feud, we still think of blood as what makes tribal identity.  Blood is also figurative and emotional: our blood “boils” when we’re angry, “chills” when we’re afraid, “curdles” when we’re threatened. Such primitive associations appear to be immune to advances in our scientific understanding of the nature of blood.

Jerry Lincecum is a retired English professor who now teaches classes for older adults who want to write their life stories.  A new class begins at Grayson College on Feb. 6 as part of the TEAMS program for senior citizens: