The flow and composition of bile have been objects of serious, if sporadic, investigation in many species for more than a century. An impressive variety of techniques have been employed to permit collection of bile from living subjects and to facilitate the chemical analysis of this complex fluid. Much of this work has been descriptive, and a great deal of effort has been devoted to the identification and characterization of the many pigments, lipids, and bile acids which are so abundant in bile. However, the accumulated knowledge on this subject can be integrated to provide a good general picture of the physiology of bile formation which may serve as a rational basis for the direction of future research.
Certain well-known characteristics of the biliary tract are worthy of reiteration in an appraisal of this kind. It is important to recognize, for example, the extraordinary differences in bile flow and composition