In your own words, write a short summary for this passage.
Bloodletting and the four humors.

Bloodletting represents the folly of the past, the sorcery and the misguided physiology that we now proudly say marked the dark ages of medicine - or did it (1)? In fact, bloodletting has a place in medicine today and a history that is worthy of review.
The Four Humors
The traditionally held "Father of Medicine" was the Greek physician Hippocrates (460-370 BC), who taught medicine on the island of Cos. One of his major precepts was the rule of harmony, the theory that all body systems were in balance and that disease resulted from an imbalance. Galen (130-201 AD) was the physician to Marcus Aurelius and became the heir to Hippocrates and one of the most influential physicians of all times. He taught the importance of maintaining balance between the four bodily fluids, or "humors" (2): blood, phlegm, yellow bile, and black bile. Each fluid was associated with a specific personality characteristic. Blood was associated with a sanguine personality, that is laughter, music, and a passionate disposition. Someone with a phlegmatic personality was sluggish and dull, while yellow bile represented an individual quick to anger or choleric (cholera meaning yellow as in yellow fever). Lastly, black bile represented a melancholic or depressed personality, melan meaning black. It was the job of the physician to restore harmony in those four humors by the use of emetics, cathartics, purgatives, and by bloodletting. Bleeding was used to reduce excess circulation, to slow the pulse, and to "reduce irritation", all felt to be the cause of inflammation. Dr. Benjamin Rush, a signer of the Declaration of Independence, was a major figure in colonial American medicine and was an important proponent of bleeding, though unfortunately he mistakenly thought that the body held 12 instead of 6 quarts. Shortly before his death, George Washington was bled 4 ‡ quarts in 24 hours for an infected throat and died not long after (3).
Early transfusion was based on the notion that giving blood would help balance the humors (4). On June 15, 1667, Jean Davis replaced part of a patient's blood with sheep's blood though the patient died and Dr. Davis was subsequently accused of murder. Transfusion was set back until the 19th century, well before blood typing was understood.
A doctor cuts open a patient's arm and blood from the cut flows into a bowl. A series of 4 images. A man plays guitar and a woman sings. A man and woman dancing. A man hitting a woman. A man sleeping in a bed. An old man resting in a bed while a doctor looks over him.
A sitting man has a cut in his right arm that is bleeding into a bowl, while blood from a bottle connected to a tube in the man's left arm enters his body.