The anatomic, physiologic and pathologic relations between the gastrointestinal tract and the liver are discussed frequently, but many problems arising from these relations remain unexplored. It is my purpose to present some of these problems with the view of emphasizing their probable importance rather than supplying an answer to them.
The liver can rightly be considered as one of the organs of digestion because it produces a secretion which is passed into the intestine and which is important in the maintenance of normal digestion. However, the liver is of much more significance in relation to the digestive tract than being merely one of the organs producing a digestive secretion. It is in addition the organ through which most of the products of digestion pass before reaching other tissues of the body. In this capacity it can be considered as a filter of the blood that has passed through the organs