A good deal of experimental work has also been performed in one way or another--mainly by feeding with, or inoculation of, considerable quantities of soluble lead salts--but, with one or two notable exceptions, such experiments have not carried the knowledge of the true pathology of lead poisoning very much farther. The statement is not uncommonly made that no definite correlation exists between the symptoms observed in animals and those observed in man, the reason being that the massive doses given to animals cannot be similar to, nor can they produce results comparable with, the slow intoxication taking place in man; although the after-history of the majority of cases of acute poisoning shows that the symptoms suffered are generally identical with the severer symptoms seen in cases of chronic poisoning of industrial origin. One of the chief reasons explaining this remarkable point of view arises from the fact that the tissues which come into the hands of the pathologist for post-mortem and histological examination are as a rule derived from cases of chronic poisoning, cases in which the acute symptoms have drifted into the subacute or chronic stage, when any minute changes existing in the initial stages of the poisoning have long since disappeared, or their significance has been so far obscured by secondary changes that the primary lesions are lost sight of. A critical examination of the very large amount of literature published on lead poisoning negatives the idea that acute and chronic poisoning differ fundamentally in their pathology, and observers are found describing identical pathological lesions resulting from acute or chronic industrial poisoning. It is impossible to review the whole of the existing literature. Kobert[1], in summing up the general effect of lead upon the animal body, makes the following general statement: “Lead affects especially the striped and unstriped muscles, the epithelium of the excretory glands, the neuroglia of the central nervous system, and is essentially a protoplasmic poison.” We base our knowledge on definite experiments, so arranged that the method of exposure was in every way similar to that in lead industries. The only point of difference that can be urged against them is one of degree; but as the train of symptoms produced was in every way comparable with those suffered by man, this objection cannot be sustained. The fact that the symptoms develop in a shorter time than they do in industrial processes is merely a function of the intensity of the poisoning. An attempt will be made first to summarize the literature on the pathology of lead poisoning, and, as such literature covers an immense amount of ground, to group the pathological findings of various observers, as far as possible, under four main headings--namely: Gastro-intestinal system. Nervous system. Excretory system. Circulatory system.