I’ll have to expand a bit since you are still reading into the text that somehow Leviticus 17:11 is speaking to the medical practice of blood letting. But first, let’s look at a few quick things about blood:
Blood essentially functions as a delivery system between cells for oxygen and nutrients and a transport network for the immune response to name a few things. Blood of far from the ‘source of life.’ Cells, for example, can survive perfectly fine in the absence of blood provided there are nutrients nearby. And in general, vertebrates need a lot of things to live! Take away oxygen and poof, we’re all dead. Take away nutrients, and again, we die. Is oxygen the source of life? Are nutrients the source of life? Blood is more analogous to a delivery truck bringing essential supplies to regions that need them but in no way shape or form is the life-force or essence of life.
Furthermore, the majority of living things do not actually have blood! Most insects for example don’t have blood, but instead have a fluid called hemolymph. Plants also lack blood but yet are clearly ‘living.’ Single celled organisms or jelly fish, or sponges, or fungi and all bacteria are also clearly alive, yet also do not have any blood.
Back to the Scripture though… I don’t see how anyone can argue that this Scripture clearly is speaking about the medical practice of blood letting. Ultimately, I must disagree with you Edward in that this Scripture does appear to be ‘ancient out-dated knowledge.’ It doesn’t take a genius to figure out that blood is important to animals that have blood. The vast majority of living things don’t have blood however. Out of those that do, even ‘non-sentient’ animals tend to react negatively to their blood gushing out so it doesn’t take a divine revelation to see that it is important.
To the credit of the writers of the text, they did the best they could have given limited knowledge. Was what they said wrong? Well certainly not! But in the same sense that Aristotle was not wrong in how he explained why certain things float and rise and others sink and fall. He explained the world in the best way he could and really was on to something!