When I first learned about the four humors in class. It didn't make much sense to me, especially the two humors- black bile and yellow bile.
Apparently, yellow bile means bilirubin. When components of red blood cells break down, they create bilirubin which is yellow in color. And black bile is a blackish component of platelets which are cell fragments.
When I think about these humors in this sense, humoral theory makes a lot more sense to me. I know that with metabolic and genetic illnesses, a lot of it has to do with how cells function or dysfunction.