The germ theory, beriberi, and the deficiency theory of disease.

BY THE BEGINNING of the twentieth century, many diseases could be causally explained by the germ theory. However, other important diseases defied every attempted explanation. One such disease was beriberi which, in some groups, was responsible for more deaths than were all the infectious illnesses combined.' To explain how beriberi was caused, a new theory of disease was developed, the deficiency theory. Historical accounts consistently treat the germ theory as an obstacle that delayed progress on the deficiency theory of disease. Ihde and Becker claim that "the germ concept proved a major barrier to the recognition and study of deficiency diseases."2 C. P. Stewart writes, "one factor which undoubtedly held up the development of the concept of deficiency diseases was the discovery of bacteria in the nineteenth century [sic] and the consequent preoccupation of scientists and doctors with positive infecting agents in disease."3 Numerous writers assert that the deficiency concept was difficult to accept because the germ theory suggested that only a positive agent (such as a micro-organism or a toxin) could cause something.4 In his excellent history of nutrition, E. V. McCollum notes that "improved microscopes and the staining and other