Delusions of the Imagination
How the “Tractor”—an Early 19th Century Medical Quack Device—Was Debunked by One of the Earliest Single Blind Placebo Studies
BY TERENCE HINES
In 1783 King Louis XVI of France organized a royal commission to investigate whether mesmerism was a real phenomenon or a sham. It is well known that Benjamin Franklin and Antoine Lavoisier were authors of the Commission’s report. The report was translated into English and published in a 1996 issue of Skeptic magazine with a commentary by Michael Shermer, who noted:
Franklin and Lavoisier devised a test whereby some subjects would be deceived into thinking they were receiving the experimental treatment (magnetism) when they really were not, while others did receive the treatment and were told that they had not. The results were clear: the effects were due to the power of suggestion only.1
The Franklin and Lavoisier study represents the first known example of the use of what would now be termed a single blind placebo study to determine whether a treatment is effective or not.
While reading James J. Walsh’s 1923 book Cures: The Story of Cures that Fail,2 I discovered what is probably the second known case of the use of a single blind placebo design to evaluate a medical claim. In the late 18th century a Connecticut physician named Elisha Perkins (1741-1799) invented devices he called “tractors” that he claimed could treat all sorts of medical afflictions. The tractors were pairs of metal rods, each made of a different metal. With vague references to galvanism and “animal electricity” Perkins said the rods drew out noxious fluids, or some such, from the body and thus could effect a cure.3 Walsh says that Perkins:
Invented his metallic tractors and proceeded to cure nearly all the chronic diseases with them. He created a great sensation not only here but across the water. His tractors may still be seen in our American museums. Almost needless to say there is nothing in them, they are just inert pieces of metal, but hundreds of thousands of cures were made by them; the enthusiastic son of the inventor thinks that the cures were up in the millions.4