Bile, a product of liver action, has a dual nature: (1) a secretion, a digestive fluid, produced in largest quantities and required most abundantly during the periods of digestive activity; (2) an excretion formed from the disintegration of hemoglobin in the destruction of red blood corpuscles, a continuous process in the body economy. The physiologically periodic outflow into the small intestine of a fluid continuously produced is maintained supposedly by a reflex mechanism between the alimentary canal and the gallbladder, the latter a diverticulum, so to speak, of the extrahepatic passages in which the bile is supposedly stored between the intervals of gastric activity.
In the gallbladder certain changes occur in the composition of this storage bile. There is a loss of water by concentration, a change in color and an increase in the specific gravity owing to the addition of certain mucins and nucleo-albumins. Whether these changes are essential
JACOBSON C, GYDESEN C. THE FUNCTION OF THE GALLBLADDER IN BILIARY FLOW. Arch Surg. 1922;5(2):374–394. doi:10.1001/archsurg.1922.01110140162009