ABSTRACT
By the beginning of the twentieth century, many diseases had been explained as infestations of microscopic parasites or of filterable viruses. However, other important diseases defied such explanations. One such disease was beriberi which, in some populations, was responsible for more deaths than all known parasitic diseases combined (Carter, 1977, p. 1191). Identifying the cause of beriberi required a new theory of disease: a deficiency theory.
