Notwithstanding the fact that substances supposed to affect the flow of the bile have been administered to man for more than 2000 years, there is still very great uncertainty as to what does and what does not augment the biliary excretion. The indefinite state of knowledge regarding this point is due to the circumstance that variations in the flow of bile from the human liver are estimated by simply observing the colour of the dejections,—a method that is of necessity exceedingly rough, for it is impossible thus to detect slight variations in the excretion of bile, especially when, as in the case of rhubarb, the substance gives to the dejections a colour similar to that of the bile, and where, as in the case of sodium sulphate, the substance gives rise to copious dejections of a watery character, whereby the colour is diluted.