Howard, one of the few regular physicians who did not share the prevailing enthusiasm for calomel, went on to point out that patients who asked why they had to take the stuff did so at their peril. Their doctors, he wrote, “in the plenitude of their wisdom and power, are determined to inflict summary vengeance on them for their temerity and doubt, by a ten times more frequent and greater use of the article in question, than they otherwise would have done.”

While most physicians were satisfied that bleedine. blistering, and purging were good for their patients, they did not agree on just why this should be so. Some believed, with the celebrated Dr. Benjamin Rush of Philadelphia, that virtually all disease was caused by an overstimulation of the blood vessels, and that this, in turn, was the result of too much blood in the system, a condition that the physician was in a position to correct with his lancet. (In cases of serious illness Rush advised tapping as much as four-fifths of the patient’s blood supply—not all at once, to be sure, but in fairly short order.)

Other doctors had other theories, equally bizarre. Only a few were inclined to agree with Thomas Jefferson, who scoffed at all contemporary theory-spinners and put forward the radical notion that in many cases the physician’s proper office was to stand aside and let nature do the healing.

Thomson, too, was a theory-spinner. Like Rush, he held that all disease stemmed from a single cause. In Thomson’s view, that cause was a lack of bodily heat, brought about by the body’s failure to digest food properly. Consequently the first step in a course of Thomsonian therapy was usually to steam the patient thoroughly.

“When the sweat rolls off as thick as your finger,” a Maryland man noted in 1837, in a letter to his son, “the body is washed with cold water and the patient is straightway put to bed with hot bricks to bring back his heat. Then a powerful vomitive is administered, composed of bay berry , of cayenne (red pepper) and lobelia, which suffer naught impure to remain in the stomach, and all these herbs are mixed in 40 proof brandy, after which warm water is drunk until there has ensued the most extraordinary vomiting. Next, the patient rises and takes a second bath, like the first. He takes again to his bed, after having been laved with cold water and is surrounded with hot bricks and remains in bed for an hour. At the end of this time he takes two injections [ i.e. , enemas] of penny royal, cayenne pepper and lobelia and the treatment is over for the day.” Thomson also recommended various mild tonics, such as tincture of myrrh, “to give tone to the stomach and bowels, and prevent mortification.”

All this was no more likely to cure a patient than bleeding or purging him. But Thomson’s system had several advantages over conventional therapies. One was that a family owning a copy of the New Guide to Health , which even gave detailed instructions for building a home steam bath, did not need to call in a doctor when someone was sick. Another advantage was that Thomsonian remedies were relatively easy on the patient. There were practitioners, it is true, who tended to pour on the lobelia. Thomson sternly chided one such enthusiast who gave a patient nineteen treatments of Thomsonian medicine in a six-week period “and then left her in a very weak and low condition (no wonder).” But in the dosages recommended by Thomson, lobelia was not nearly as hard on the system as calomel.

Thomson’s do-it-yourself treatise was not the first book of its kind to come on the market. But it differed from earlier guides to botanic healing in that it included a lengthy autobiographical sketch, titled “Narrative of the Life and Medical Discoveries of the Author.” And the book’s popularity no doubt stemmed in part from the pleasure many Americans got from Thomson’s account of how a poor and uneducated farm boy, forced to rely on his native wit and powers of observation, nevertheless grew up to expose the greed and wrongheadedness of the medical profession.

Thomson was born in Alstead, New Hampshire, in February, 1769. As he tells it in the “Narrative,” he attached himself in very early childhood to a local herb doctor, an old woman named Benton. When she went out to collect roots and herbs, Thomson writes, “she would take me with her, and learn me their names, with what they were good for; and I used to be very curious in my inquiries, and in tasting every thing that I found.”