Humoral is a term that refers to the body fluids, especially the immune responses that are mediated by antibodies that are carried by the body fluids (as opposed to being carried in the cells). Historically this terms harks back to the medieval philosophy of humorism that held that bodily health was controlled by four humors; blood, black bile, yellow bile, and phlegm. Originating in ancient times this humoral system was used in Western medicine until the 1800s. To be healthy, these humors need to be in balance - when imbalanced, the result was poor health. Medical practices believed to balance the humors included bleeding the patient in which blood was drained from the patient.