The activity of the gastric juice on lead is directly caused by the quantity of organic acids present in addition to the hydrochloric acid, and by the presence of foodstuffs--(1) in the undigested and (2) in the semidigested condition. In considering the absorption of lead products from the gastro-intestinal canal, the normal digestive processes should not be lost sight of--that is, the sequence of events which occur during digestion of food. On swallowing food, no definite acidity is present in the stomach for fifteen to twenty minutes, and even after that time the hydrochloric acid is only commencing to be secreted. As digestion proceeds, and the whole mass becomes partially dissolved, such portions as are in a soluble condition are passed through the pyloric opening at intervals, and the whole contents of the stomach do not pass straight through the pyloric opening as through an ordinary straight drain-pipe. As each mass of food passes onwards through the pylorus, it comes into contact in the duodenum with pancreatic juice, and with the bile, these alkaline fluids rapidly change the reaction, and allow the other ferments, trypsin, etc., to become active. As the mass proceeds onwards through the intestine, the succus entericus also exerts its function. Finally the fluid contents of the intestine are passed onwards through the ileo-cæcal valve. During the passage from the pylorus to the ileo-cæcal valve, the reaction of the intestinal contents undergoes variations, from an alkaline in the duodenum or upper parts of the jejunum, to acid at the ileo-cæcal valve. Practically no absorption takes place from the stomach itself; a small quantity of water and such highly volatile fluids as alcohol may be absorbed, but the main absorption is not commenced until the food has left the stomach; in fact, the stomach contains no mechanism for food absorption. The work of absorption of the products of digestion is carried on actively through the small intestine until finally the materials have reached the large intestine through the ileo-cæcal valve; water is then mainly absorbed, and albuminous fluids and substances in solution to some extent, but the amount of absorption which takes place is infinitesimal as compared with that of the small intestine. These points in the physiology of digestion require to be taken into account when discussing the absorption of lead salts in the gastro-intestinal canal.