Humours
When Lynley died mysteriously in 1599, the Tenth Doctor told the public a lie and claimed the death a result of a "sudden imbalance of the humours". (TV: The Shakespeare Code)
Behind the scenes
Though not defined in The Shakespeare Code, "the humours" were the four vital liquids that ancient physicians believed existed within the body: blood, phlegm, black bile and yellow bile. The latter two "biles" aren't precise liquids, and do not correlate precisely to bile as we understand it today. Rather, they were suppositions about the human body made before internal medicine was at an advanced stage of development. It was believed that the four liquids must be "in balance" for the human body to function correctly, though the nature of this balance was never defined with precision. Nowadays, the expression is used with some irony, or as a way to avoid giving details about blood chemistry or other medical workups.
