Not even the doctors of today would equate a temperament, that is, a certain kind of emotional state or excitability, directly with the constitution of the blood or lymph… The ‘humours’ of present-day medicine are no longer the old body-secretions, but the more subtle hormones, which influence ‘temperament’ to an outstanding degree
Jung redefines temperament as the sum-total of emotional reactions while tracing its genealogy from humoral medicine to endocrinology, insisting the psyche-body unity underpinning it remains scientifically unresolved.
, Psychological Types, 1921thesis