THE EXPLORATION of the liver and its excretory bile ducts by means of contrast roentgenography has developed into an exact science. Just as urograms have transformed urology from a suppositional to a precision specialty, so cholangiograms have displaced the haphazard methods which have been employed in recognizing pathologic dysfunctions of the biliary system. The importance of cholangiography cannot be overemphasized. HISTORICAL OBSERVATIONS The early literature on cholangiography contains sporadic reports from various parts of the world. Reich1 in 1918 introduced a mixture of "petrolatum and barium paste" into an external biliary fistula and obtained an accurate roentgenographic pattern of the bile ducts. In January of 1922 Tenney and Patterson2 visualized an incarcerated ampullary stone by introducing bismuth paste into a persistent external biliary fistula. Unfortunately the thick paste plugged the bile ducts, and the resulting cholangitis and cholemia did much to discourage further development of this procedure in