Another solution is possible--namely, that the particles seen in the intestinal wall are particles of lead in process of excretion into the intestine itself, and that the pigmentation of the vessel walls and cells is caused by the staining of the particles of lead passing from the blood into the lumen of the tube, which have been converted into a sulphide during their passage. The localization of the staining in the large intestine, especially in the region of the appendix in animals (cats), tends to support this theory. The large bowel near the ileo-cæcal valve, the appendix, and even the glands in the immediate neighbourhood, are found to be discoloured, and to contain lead in larger quantities than any other portion of the intestine. In extreme cases the whole of the large intestine may be stained a greyish-blue. The bloodvessels in the mesentery in this region are also engorged. When, however, a salt of lead, such as lead carbonate or lead oxide, gains access to the stomach, it may be easily converted into chloride by the free hydrochloric acid present in the stomach; and, in addition, should there be any chronic acid-dyspepsia (hyperchlorhydria), particularly of the fermentative type, in which free lactic acid and other organic acids are to be found within the viscus, small quantities of lead swallowed as dust undergo solution and conversion into chloride or lactate. The pouring out of acid gastric juice from the stomach glands does not take place immediately after the first bolus of food is swallowed, and it may be twenty minutes or half an hour before the gastric contents have an acid reaction. During this time any lead salts previously swallowed may become incorporated with the bolus of food and escape absorption. Lead in solution or suspension in the stomach which becomes mixed up with the food, and at the same time subjected to the action of various albuminous constituents of the food in addition to acids, causes an albuminate or peptonate of lead to be easily formed, _and as such can never be absorbed from the stomach direct_; practically no absorption takes place in the stomach, and the presence of food containing albuminate precipitates any lead in solution as an organic insoluble salt. The bolus of food impregnated with small quantities of lead passes onwards to the intestine, where further digestion takes place. As the mass passes through the intestine the action gradually results in the reappearance of acidity, but at the same time a certain quantity of sulphuretted hydrogen is produced, some of it from the degradation of the sulphur-containing moiety of the protein molecule by ordinary hydrolytic process and intestinal ferments, quite apart from any bacterial action. A portion of the lead present in the chyme may be set free again for absorption. The bile is said to assist in the solution of lead _in vitro_.