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446 amœbæ. Prof. Alessandrini of Berne first (1910) ascribed the disease to a filaria, the eggs of which he stated he had found in the skin of pellagrins, but later (1914), together with Scala, asserted that the primary cause of the disease is a deficiency of alkaline salts in water. Without these, silica, which is normally present in water, cannot be neutralized, and its presence gives rise to pellagra. In examining the numerous observations that have been made, there is one fact which stands out very prominently, and that is that each investigator claims to have reproduced true pellagra, either in animals or man, sometimes in himself, by inoculating beneath the skin, injecting into the veins, or administering per os the special organism or toxic product which he happens to have isolated. But the peculiar symptoms and anatomical lesions of pellagra, together with its epidemiology, seasonal habit, and geographical distribution, show very clearly that the disease must have one specific cause and cannot be brought about by each, or all, or any of the numerous aforementioned nematodes, protozoa, fungi, bacteria, and chemical products. It would be unwise, therefore, to place much reliance on these experiments. The interpretation of experiments is often as fallacious as the interpretation of ordinary natural facts. The history of the investigation of almost every disease furnishes examples in plenty. The maize theory of pellagra is based chiefly on the belief that the disease appeared soon after the introduction of maize into Europe, and that it everywhere followed the extension of maize cultivation, and increased with the more general adoption of the new cereal as an article of food. This opinion has been repeated by almost every writer on pellagra. Neither the statement nor the argument is indisputable. Maize was introduced into Europe by the Spaniards from South America soon after the discovery of the western world, and the history of its cultivation in Spain, France, and Italy begins about the middle of the sixteenth century. Italian pellagrologists, eager to establish a relationship of cause and effect between the introduction of the new cereal into Italy and the first appearance of pellagra, which