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) In 1539, it was believed that hiccups resulted from a simple imbalance of the humours. "To treat one without the others will only put the balance further out." Liz Shaw was accused of being a witch for supposedly trying to further that imbalance by suggesting treating King Henry VIII's indigestion. (PROSE: Hiccup in Time)

On the planet Vulpana, certain humours of the blood resulted in the condition of lycanthropy. During the Golden Millennium, the Vulpanan doctor Barton successfully isolated the humours that caused it. She introduced them into her own body in an attempt to become one of the werewolves, who were the planet's elite, but only succeeded in inducing a mild head cold. (AUDIO: The Moons of Vulpana)

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.