“Spectro-Chrome,” an alternative healing method based on the application of colored visible light to the body, was practiced by more than ten thousand Americans over the half-century following its introduction in 1920. It was the invention of Dinshah Ghadiali, a charismatic inventor and popular science lecturer, who used the rhetoric and tactics of contemporary popularizers to discredit orthodox medicine’s claim to scientific authority, and to advance his own on behalf of his followers of the “Science of Automatic Precision.” Practitioners, who mostly treated themselves and their immediate families, were encouraged to think of themselves as scientific researchers. Dinshah’s students presented their findings at local and national meetings, engaged in continuing education, critiqued one another’s work, and articulated an ethos of science that repudiated the obscurantism and greed that they believed had infected scientific medicine. Beyond its perceived value as a healing practice, Spectro-Chrome’s inclusive, pragmatic, and straightforward nature appealed to Americans excluded from a scientific establishment that had begun to seem remote and arcane, and from a medical culture they perceived as oriented more toward commercial ends and professional consolidation than traditional patient care.

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