It has been recognized for many years that the wall of the gastrointestinal tract forms one of the numerous paths of excretion of foreign substances which have entered the blood. One of the earliest proofs of this vital phenomenon consisted in the injection of antimony subcutaneously, and, after a short interval the demonstration of the presence of this drug in the stomach. Various other drugs and poisons, such as morphin, atropin, strychnin and snake-venom have similarly been proved to pass from the blood through the gastric or intestinal wall, following intravenous or subcutaneous inoculation. In fact this mode of excretion is so well established and so thoroughly accepted that it has led to the routine employment of repeated washing of the stomach and colon in the treatment of poisoning by these drugs. Various other chemical substances, for example, strontium,1 barium,2 lithium,3 manganese4