15. Holding a Corpse’s Fingers Over a Candle to Look for Blood
While 18th-century medical practitioners didn’t truly understand the nature of the human body or the circulatory system, they did recognize that blood circulation was a required element for life. Checking pulses was not yet widespread or standardized, but there were ways of testing for blood circulation that were widely practiced, even by barber-surgeons of minimal education. The most common method of checking for blood circulation in presumed dead bodies was to hold a finger of the deceased over a candle. Not only would the heat of the flame possibly produced a reaction, but the light shining through the finger would show if blood were circulating or pooling.
In a genuinely dead body, blood pools in the extremities. Since the heart is no longer beating and circulating blood, it pools in extremities and low lying areas. If a dead body’s finger were examined over a candle and no pain response was produced from the flame, and blood appeared to be pooling in the fingertips making them darker than normal, an 18th-century doctor could be relatively sure that the person was dead. Of course, we know now that some diseases and conditions can cause blood to pool while still alive, but the medical arts of the period wouldn’t have saved someone in that condition anyway.