In one of his “Proverbs of Hell,” the poet William Blake wrote, “The lust of the goat is the bounty of God.” The unbridled randiness of the billy goat was an ancient commonplace: The Greeks gave Pan, their goatherd god, horns and hooves; he was not only the lord of panic but epitomized the rutting instinct. But neither the ancient Greeks nor Blake, even in his wildest imaginings, could have foreseen quite how bountiful — or how lucrative — that goatish libido could be. It took an American con man, a quack of genius, to show that the road to riches wound through the gonads of goats.

In “Charlatan: America’s Most Dangerous Huckster, the Man Who Pursued Him, and the Age of Flimflam” (Crown, 324 pages, $24.95), the journalist and historian Pope Brock tells the sordid and comical story of John R. Brinkley, “M.D.” (the scare quotes have become part of his moniker), and of his nemesis Dr. Morris Fishbein of the American Medical Association. For more than 20 years, Fishbein, the most celebrated “quackbuster” of his day, dogged Brinkley’s every step; not since Inspector Javert tracked Jean Valjean through the sewers of Paris, in Victor Hugo’s “Les Misérables,” has a pursuit been more relentless than the one Fishbein mounted against Brinkley. The crucial difference, of course, is that unlike Valjean, Brinkley was a scoundrel of the greatest magnitude.

John R. Brinkley (1885-1942) had tried his hand at various swindles in his youth, but it was only in 1917, when he was in his early 30s, that he hit upon an idea which would make him both rich and world-famous. This involved transplanting goat testicles into men whose virility was flagging. He set up the Brinkley Institute of Health in Milford, Kan., a dreary farming town swallowed up in cornfields but the only place he could find with a vacant practice which would have him, no questions asked.

It was a lucky move for Brinkley. Kansas farmers may have been gullible, but they knew their goats. Soon, if the testimonials Brinkley garnered from his patients are to believed, the drooping men who flocked to the clinic emerged, a day or two later, capering like freshly weaned kids, and just as frisky.

As a young man, Brinkley had dabbled in “medicine man tours,” peddling such nostrums as “Aunt Fanny’s Worm Candy” with brassy fanfare. His showmanship, combined with his increasingly grandiose self-image — he compared himself to Christ, as a persecuted savior of mankind — led both to his greatest success and to his downfall. At the same time, there was something frugal in his fraudulence. He began implanting goat glands in men, as well as goat ovaries in women, as cure-alls for prostate cancer, infertility, and even congenital idiocy. It was patent medicine with a rusty scalpel. Many of his operations resulted in mutilation or death, which he concealed. Mr. Brock calls him “the worst serial killer in American history,” estimating that he was responsible for at least 42 deaths — and probably many more — over his lethal career.

Brinkley’s genius, like Barnum’s, lay in promotion. He took to the radio waves, mixing sermons and homespun anecdotes with country Western music — he made the Carter Family famous — to reinforce his shilling messages. When his station was shut down in Kansas, he moved it across the Mexican border, building the largest transmitter in the world to peddle his remedies and his overpriced — and worthless — pharmaceuticals. He became a multimillionaire. When his bogus medical license was revoked in 1930, he retaliated by running for governor of Kansas, on two weeks’ notice, and almost won. He electrified voters by swooping down on cornfields in his private plane, the first time a politician had used the stunt.

Mr. Brock tells this saga of quackery wonderfully well. The crackpots and swindlers may steal the show, but their opponents — not only the obsessive and fast-talking Fishbein but his friends and cronies, from bibulous Sinclair Lewis to growling H.L. Mencken — come alive in all their period flamboyance as well. As a social historian, Mr. Brock delights, too, in the outlandish contraptions that quacks foisted on a gullible public, from the oscilloclast to the Recto Rotor (don’t ask), some of which, like the Thermocap, or “electric fez,” are shown in hilarious period photographs.

But even con men can be conned. After years of sparring, Fishbein cunningly provoked his quarry into filing a libel suit, and Brinkley took the bait. Forced to testify, Brinkley was demolished on cross-examination and utterly discredited. He died a few years later, bankrupt. Fishbein, who would survive him for another 30 years, pronounced his own wry version of Brinkley’s epitaph when he said, “The centuries to come may never produce again such blatancy, such fertility of imagination, such ego.”