Of the imagination, as a cause and as a cure of disorders of the body; exemplified by fictitious tractors, and epidemical convulsions. Read to the Literary and Philosophical Society of Bath

Royal College of Physicians of Edinburgh Bndg: Bound in pamphlet volume Copy: Lacks all after page 40 Note: In the 1790s the American physician Elisha Perkins developed a theory of "magnetic healing" using metal tractors which were claimed to relieve the symptoms of rheumatism. To test this John Haygarth conducted a single blind experiment using a placebo device. He treated five patients with painted wooden tractors. Four said they felt relief. He then used Perkins' metal tractors on the same patients and obtained the same results. Haygarth concluded that this placebo effect revealed "a wonderful and powerful influence of the passions of the mind upon the state and disorder of the body" This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh