Hans Von Gersdorff Bloodletting

Hans von Gersdorff: Feldbuch der Wundarzney (Field book of surgery) (Page 16V), 1517
The above diagram is from a medicine book published in 1517 by a German surgeon Hans von Gersdorff, showing the points of bloodletting, we can see that there are nearly 50 points of bloodletting distributed in all parts of the body. The diagram also shows a dissection of a male human body with most of the organs shown, it seems that people at time or before that time already did a lot of experiments and dissections on human body trying to understand their own body and how to treat different illness by bloodletting. It can also be conclude that bloodletting is a very scientific way to treat illness at that time as it appears in a published medicine book, the diagram shows a quite accurate human dissection and there are so many points of bloodletting for treating illnesses.
This idea come from the menstruation of female as people at that time though that menstruation is a process of removing bad humours. The idea of bloodletting is reinforced by the humoral theory and research of Galen. Galen states that blood is produced in the live and is consumed in body parts, blood is not circulating and so will stagnate in different body parts. And the humoral theory of Galen state that the healthiness of our body is maintained by the humoral balance. So if there is excessive humours, we should remove them in order to maintain health. If blood is the excessive humour, bloodletting should be performed. These two idea combined together and contributed to the development of