“The doctor of the future will give no medicine, but will instruct his patient in the care of the human frame, in diet and in the cause and prevention of disease.”
This has been reprinted many times with slight variations on the wording; it is part of a much larger quote directly from Edison published in 1903:
:Nineteen hundred and three will bring great advances in surgery, in the study of bacteria, in the knowledge of the cause and prevention of disease. Medicine is played out. Every new discovery of bacteria shows us all the more convincingly that we have been wrong and that the million tons of stuff we have taken was all useless.
The doctor of the future will give no medicine, but will instruct his patient in the care of the human frame, in diet and in the cause and prevention of disease.
They may even discover the germ of old age. I don't predict it, but it might be by the sacrifice of animal life human life could be prolonged.
Surgery, diet, antiseptics — these three are the vital things of the future in preserving the health of humanity. There were never so many able, active minds at work on the problems of diseases as now, and all their discoveries are tending to the simple truth — that you can't improve on nature.
:* As quoted in "Wizard Edison" in The Newark Advocate (2 January 1903), p. 1 according to research by Barbara and David P. Mikkelson at snopes.com http://www.snopes.com/quotes/edison.asp.
1900s
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Thomas Edison 57
American inventor and businessman 1847–1931Related quotes
Y así, enfermos, ojo alerta
y ningún médico admitan;
mueran de gorra sin dar
un real a la medicina.
Diente del Parnaso ('Parnassus' Tooth') (1689), 'Prólogo al que leyere este tratado’.
Quoted in Chambers Dictionary of Quotations (1997), p. 1038.

“The art of medicine consists of amusing the patient while nature cures the disease.”
According to The Veterinarian (Monthly Journal of Veterinary Science) for 1851, edited by Mr. Percivall, this is Ben Jonson's "satirical definition of physic".
Misattributed

Les médecins administrent des médicaments dont ils savent très peu, à des malades dont ils savent moins, pour guérir des maladies dont ils ne savent rien.
This attribution to Voltaire appears in Strauss' Familiar Medical Quotations (1968), p. 394, and in publications as early as 1956 http://books.google.pt/books?id=lCtCAQAAIAAJ&q=%22Doctors+are+men+who+prescribe+medicine+of%22&dq=%22Doctors+are+men+who+prescribe+medicine+of%22&hl=pt-PT&sa=X&ei=mbnWUsvDIfTB7Aaw_YD4Dw&redir_esc=y; the quotation in French does not, however, appear to be original, and is probably a relatively modern invention, only quoted in recent (21st century) published works, which attribute it to "Voltaire" without citing any source.
Attributed

This attribution to Voltaire appears in Strauss' Familiar Medical Quotations (1968), p. 394, and in publications as early as 1956 http://books.google.pt/books?id=lCtCAQAAIAAJ&q=%22Doctors+are+men+who+prescribe+medicine+of%22&dq=%22Doctors+are+men+who+prescribe+medicine+of%22&hl=pt-PT&sa=X&ei=mbnWUsvDIfTB7Aaw_YD4Dw&redir_esc=y; the quotation in French does not, however, appear to be original, and is probably a relatively modern invention, only quoted in recent (21st century) published works, which attribute it to "Voltaire" without citing any source.
Original: (fr) Les médecins administrent des médicaments dont ils savent très peu, à des malades dont ils savent moins, pour guérir des maladies dont ils ne savent rien.

On doctors who ask patients to avoid Ayurveda, as quoted in " Doctors prescribing non-ayurvedic medicines are anti-national http://m.timesofindia.com/city/kolhapur/Doctors-prescribing-non-ayurvedic-medicines-are-anti-national/articleshow/52058067.cms", The Times of India (30 April 2016)

http://www.youtube.com/watch?v=4XWTHoMBJvk