Bleeding bowlsThe beauty of this bleeding bowl belies its dark history. Now, of course, we know removing blood from a patient is almost never a great idea. But both ancient and not so ancient societies practiced blood-letting as a way to balance the humors. Humans were thought to have four humors: phlegm, yellow bile, black bile, and blood.
Robin Fåhræus has suggested that the four humors were based on the observation of blood sedimentation layers. When blood is drawn in a glass container and left undisturbed it separates into four different layers: A dark clot at the bottom (black bile); a layer of red blood cells (blood); a whitish layer of white blood cells (phlegm); and a top layer of clear yellow serum (yellow bile).
Bloodletting was popular for a variety of treatments at least until the 1850s, when Pierre Louis began to advocate for doctors to rely on statistical evidence over anecdotal “recoveries.” Louis’s work, along with John Hughes Bennett, helped usher in the age of epidemiological evidence for medicine.
The stamping out of bloodletting is a story of medical progress. It should be noted, however, that despite the strong evidence against bloodletting from Hughes Bennett and Louis, physicians (and barbers) were slow to change. Bloodletting for pneumonia, for example, continued sporadically in Western medicine until the 1940s with the arrival of antibiotics.