I am on the search for scientifically founded information (if possible in the WWW) over the transportation function of the intestine wall in both directions in particular the elimination of material/molecules already absorbed and processed. I heard, a large portion of the Faekalien contained in the intestine would not come on direct way, i.e. as during digesting not absorbed remnants, into the intestine, but over the intestine wall. About any referring to relevant scientific sources I would be pleased.