Marks, David F., Murray, Michael, Evans, Brian, Estacio, Emee Vida (13 mei 2015). Health Psychology. SAGE, p. 406. ISBN 978-1-4739-2759-9 "four bodily humours, blood, phlegm, black bile and yellow bile. Little scope was left for psychological causation and this theory only really lost its hold on Western thinking in the 1850s. [...] The humoral theory was eventually abandoned following [...] Rudolf Virchow in the 1850s."
