Blood letting was practiced from ancient times through the late 19th century, and likely began as a result of the belief that the disease resided within the body, and often along with the evil or bad spirits that caused disease. Blood letting was a means of relieving the disease and/or spirit from the confines of the body.
Other beliefs that influenced this practice included the belief that blood did not circulate, and that the blood could become stagnant in the body. Also, there were those who asserted that we could have excess blood in our systems, which could be a cause of illness. (It's likely this belief was in response to symptoms of hypertension, and a resulting drop in blood pressure when a patient was bled out.)
Other beliefs that influenced this practice included the belief that blood did not circulate, and that the blood could become stagnant in the body. Also, there were those who asserted that we could have excess blood in our systems, which could be a cause of illness. (It's likely this belief was in response to symptoms of hypertension, and a resulting drop in blood pressure when a patient was bled out.)
