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XXV] the conditions found in the tropics; and it may be that when such conditions are reproduced elsewhere, even in temperate climates, the result will be just the same. Although for a long time something had been known about the conditions predisposing to beriberi, it is only lately that anything like approximately accurate knowledge as to the causa causans of the disease has been attained. Many hypotheses had been advanced on the subject, some plausible enough if judged of in the light of the times, others manifestly absurd. It is unnecessary to refer at length to these exploded theories. Suffice it to say that their authors appear for the most part to have been dominated by the idea that for the production of a disease something in the nature of a germ or of a poison has to be introduced into the body; they overlooked the possibility of disease being brought about, not by the introduction of something foreign or abnormal to the body, but by the deprivation of something essential for its healthy nutrition. We now know that it is to the latter circumstance we have to look for the cause, or at least a principal part of the cause, of beriberi. Beriberi is a disease of "deficiency," to use the expression of Funk. It is desirable, in view of the possibility of further discovery, somewhat to qualify this statement. It is just possible that the condition brought about by this deficiency merely predisposes to, or is necessary for the operation of, something else, perhaps an unknown germ which in the absence of this deficiency would remain inoperative even if introduced. Further, it may be that there are two or more diseases included under the term " beriberi," each of them acknowledging a different specific cause. Indeed there are not a few facts suggestive of such a possibility.

However this may be, thanks to the pioneer work of Eijkman, Braddon, Fraser and Stanton,* we now