The humoral theory
The humoral theory consists in the idea that four basic fluids (humors) flow in the human body: blood, phlegm (mucus), yellow bile and black bile. Normally, these fluids are in balance, but an excess of one or more of them causes almost all internal diseases. Accordingly, treatment consists of removing excess fluid, usually by bleeding, emetics, and laxatives. Each liquid corresponded to a natural element and two "states of matter" (dry / wet; warm / cold), and the prevailing value of one or another liquid determined the temperament, that is, the character of a person.
Humor Element State Temperature Temperament
Blood Air moist hot sanguine
Phlegm Water moist cold phlegmatic
Yellow bile Fire dry hot choleric
Black bile Earth dry cold melancholic
Formulated by Hippocrates, the humoral theory developed and supplemented in the Middle Ages and Modern Times, firmly entering European medicine for more than two thousand years. Only at the end of the 19th - beginning of the 20th centuries, bloodletting ceased to be considered as a universal remedy, restoring the "balance of fluids."
It's very simple. Bloodletting instantly lowers blood and vascular pressure. And this has a very beneficial effect on many diseases and in general on the entire body as a whole. I don’t think that bloodletting could heal anything, but it was definitely possible to alleviate the patient's condition.
Ancient thinkers were not empiricists. Experience was not considered by them as a source of reliable knowledge, only reason. The theory that explains reality was supposed to be harmonious, elegant, consistent with the philosophical ideals of those times, but the experience was completely secondary. This is clearly seen from Aristotle's "Physics", in which the movement is rectilinear and the thrown object flies straight until it hits an obstacle. The obvious parabolicity of the trajectories of the abandoned bodies was discovered only by Galileo.
Bloodletting was a consequence of the theory of humoral fluids of Hippocrates, who believed that a person's condition depends on the balance in the body of bile, blood, mucus and black bile, respectively, it was supposed to regulate the balance by release prevailing liquids. In the time of Hippocrates, no one opened the human body, it was difficult to get a more or less adequate idea of the true state of affairs.
I don’t know if I’m reasoning sanely, but I have my own theory on this issue. I think this practice was of some use, because even religion does not arise from scratch. Logically, the main "positive" effect of bloodletting is a decrease in excess blood pressure (well, not to mention the renewal of the pool of formed elements). And since it was at that time that stress was the norm of life (not because "there is no Internet!" - woe, damn it, but because tomorrow at the stake), this essentially gave its effect. Garbage, of course, not a theory, but it turned out cool)
In those days, the so-called. humoral theory of pathology. That is, diseases arise from an abnormal ratio of body fluids: blood, mucus, bile and black bile. A "normal" ratio is a guarantee of health. It was believed that in case of illness, this or that fluid flows out of the body. Bloodletting tried to restore the balance of these environments.
By the way. In the middle of the 20th century, there was about the same bias - the neural theory of pathology. From there the saying went that "all diseases are from nerves, one syphilis is from pleasure." The bias towards the nervous side was associated with an overly broad attempt to interpret Pavlov's work.
In general, the bloodletting was not done by doctors, but by barbers (as well as the thing that was later called "surgery"). But this is so, a lyrical digression.
This is not the point. The Middle Ages are dark times, when the Church burned everyone who thought wrong and, accordingly, could not come up with anything new (or invented, but very secretly and tried not to make it public), and they were engaged in bloodletting far before our era. What is the essence of bloodletting? In fact, it just lowered blood pressure. No matter how trite it may sound. With headaches - it could help, with tuberculosis - well, you understand. And since it was possible to push everything to the will of God, then the inefficiency was not confirmed.
That's the way it is)
I hope I answered the question) I will gladly accept criticism)