Early classifications emphasized bile and phlegm, and although 'sufferers from melancholy' are mentioned, black bile is not considered a specific humour, but rather a depraved form of (yellow) bile. Only with On the Nature of Man, the text which Galen and subsequent generations believed was quitessentially Hippocratic, does black bile become an essential humour. By contrast, with beneficient blood, black bile was regarded as mainly harmful - it was visible in vomit and excreta, and later authors described how it hissed and bubbled on reaching the ground, burning up whatever it touched. Modern scholars disagree on what black bile actually was (perhaps some form of dried blood), but once proposed as a humour, it fitted neatly into a rational scheme made even more credible to the ease with which it could be extended to cover a whole range of circumstances (pp 24-25).
|Black Bile in the Humoral System of Medicine|