Basic article on the four humors, the four elements, and the connection between these four-part divisions and Hippocratic medicine.
HISTNEUR-L: The History of Neuroscience Internet Forum
Explains what Black bile (kole melaina), phlegm, melancholy and yellow bile mean in a modern context.
"Some Presuppositions of Greek Philosophy," by George Boas. The Classical Weekly, Vol. 19, No. 11 (Jan. 11, 1926), pp. 84-90.
"Galen's Platonism," by Phillip De Lacy. The American Journal of Philology, Vol. 93, No. 1, Studies in Honor of Henry T. Rowell (Jan., 1972), pp. 27-39.
"Philosophy and Medicine in Ancient Greece," by # Harold W. Miller. The Classical Journal, Vol. 44, No. 5 (Feb., 1949), pp. 309-318.