Every care was taken during these experiments to avoid any vitiation of such experiments by the actual swallowing of lead dust by the animals exposed to breathing. Moreover, all the animals were carefully controlled, in that an animal of somewhat similar weight at the same time was subjected to the ingestion of the same lead compound, but in much bigger quantities, via the mouth. It will be seen immediately, on comparing Tables XI. and XII. with Table XIII., that the rate of poisoning by means of dust is greatly in excess of the rate of poisoning by feeding, even where poisoning by feeding actually occurred. Also that the amount of dust present in the air inhaled shows a marked correlation with the date of appearance of the first symptoms of poisoning, and that where the quantity of dust is very much reduced the poisoning was delayed longer than might have been expected, and that when poisoning did appear the symptoms were much less pronounced than with the more dusty atmospheres; and this although the quantity of lead obtained would be relatively the same over the range of time the animals were exposed. The knowledge gained in dealing with industrial poisoning clinically receives very strong corroboration from these inhalation experiments, for it is a well-known fact that many persons engaged in dusty trades exhibit a species of immunity to lead poisoning. It is true that some susceptible persons, as has already been pointed out, very rapidly show signs of poisoning, even with a dosage producing no effect in other persons working under similar conditions; and it is highly probable that these persons have arrived at a species of equilibrium by which they are able to excrete the lead ingested, and so prevent any accumulation and general damage to their tissues. Directly, however, the dosage is increased, signs of poisoning come on, as in the case of animals Nos. 10 and 11. For some seventy to eighty days little or no sign of poisoning was seen with the small dosage commenced with. At the end of this time, as no symptoms appeared, the quantity of lead in the air was increased, with the result that poisoning rapidly became manifest. We have also in these inhalation experiments, in Cases 21 and 22, definite evidence that a low-solubility glaze--that is to say, glaze containing fritted lead--is capable of setting up lead poisoning when taken via the lung, as when such glaze is inoculated, although it produces no such symptoms when given via the mouth, except, perhaps, when it is complicated by excessive alcohol. =Symptoms exhibited by Experimental Animals.=--The cat is peculiarly susceptible to lead poisoning. In lead works it is impossible to keep a cat any length of time, as it rapidly dies of poisoning. All the animals subjected to lead absorption, and definitely suffering from symptoms of lead poisoning, exhibited the following symptoms: 1. Slight increase of weight over the first period of poisoning, lasting from one to three weeks.