In London in 1873, Mark Twain saw an advertisement for the services of a fellow American who had hung out a shingle on Fleet Street. At once inspired and skeptical, Twain made his way to the offices of Lorenzo N. Fowler, "practical phrenologist."

"I found Fowler on duty," Twain wrote, "amidst the impressive symbols of his trade. On brackets, on tables . . . all about the room, stood marble-white busts, hairless, every inch of the skull occupied by a shallow bump, and every bump labeled with its imposing name, in black letters."

During the 19th century, thousands of busts like those Twain described were manufactured and sold by Fowler and others. One of them — its surfaces inked with lines showing the location of such traits as "Conjugality" and "Combativeness" — is on display at the American History Museum's "Science in American Life" exhibit, surrounded by other measures of human intellect and personality.

According to the "science" of phrenology, an individual's character and abilities could be deduced from the size and shape of various bumps on the head. By the time Twain visited Fowler, phrenology had developed an enormous following, especially in America. Characteristics such as verbal memory, "Amativeness" and "Secretiveness" were supposed to be controlled by corresponding areas, or "organs," of the brain. The more developed the trait, the larger the organ, and the larger a protrusion it formed in the skull.

Phrenologists also believed that such traits — and their respective organs — could be modified through the practice of restraint or by the conscious "exercise" of a positive quality.

In the 20th century, phrenological busts have become comic conversation pieces, their images often used to patronize the past. Phrenology's failings are indeed obvious, but in our modern dismissal of it, its tremendous impact on 19th century society can easily be forgotten. And despite its shaky scientific foundations, phrenology is enjoying a measure of respect from those who study the brain today.

Like another theory of mind that later permeated American culture, phrenology was the brainchild of a Viennese physician fascinated by the human psyche. Even as a schoolboy in the late 1700s, Franz Joseph Gall noticed that classmates who could memorize long passages with ease all seemed to have prominent eyes and large foreheads. From this he inferred that an organ of verbal memory must lie behind the eyes. He speculated that if one ability was "indicated by an external feature," others might be also.

His expanded theory brought Gall renown, but also the disapproval of church authorities, who considered such ideas heretical. In 1802, the state prohibited him from promoting his theory in Austria. Not surprisingly, this only increased public interest. Gall began lecturing throughout Europe and in 1805, with his protégé and former student, Johann Kaspar Spurzheim, he left Austria for good.

In the early years of the 19th century, Gall's ideas spread across Europe. But it was in America, a country starved for a "scientific" insight into the human mind (and one that offered the hope of individual perfectibility — read "self-help"), that phrenology would find its most devoted and enduring audience. And it was Spurzheim, having further expanded Gall's theory and adopted the name "phrenology," who would bring it to our shores.

Spurzheim arrived in 1832 for a whirlwind lecture tour — one that literally killed him after just six months. But in that short time, he converted thousands, lecturing at Harvard and Yale, and across the American heartland. Ralph Waldo Emerson described him as one of the world's greatest minds. After Spurzheim's death, John James Audubon sketched his remains for posterity; Harvard president Josiah Quincy handled his funeral arrangements. "The prophet is gone," the American Journal of Medical Sciences declared, "but his mantle is upon us."

The mantle fell, in large part, to a ministry student named Orson Fowler, who suddenly found his true calling in Spurzheim's theory and polemical practice. Fowler began to lecture on the topic to his classmates at Amherst College in Massachusetts, and to offer "readings" for 2 cents apiece. In one friend, the future Rev. Henry Ward Beecher, Fowler reported finding evidence of a "strong social brain" with "very large Benevolence."

Orson's enthusiasm infected his younger brother, Lorenzo, along with the rest of the family. The two Fowler brothers — frustrated evangelists both — began touring the country, carrying "the truth of phrenology" from town to town, lecturing and offering readings, analyzing the character and pro-pensities of utter strangers from the bumps and valleys on their skulls. (In one of his early sessions, Lorenzo Fowler studied the head of a shy 15-year-old named Clara Barton. Years later, in her memoirs, the founder of the American Red Cross recalled Fowler's comments: "She will never assert herself for herself — she will suffer wrong first — but for others she will be fearless.")

America quickly became cranium-conscious. Employers advertised for workers with particular phrenological profiles — even asking for a reading by the Fowlers as a reference. Women began changing their hairstyles to show off their more flattering phrenological features. Everyone, from small-town folk to the rich and famous, sat for readings, including such notables as Horace Greeley and Brigham Young. (Predictably, P.T. Barnum scored high in all traits but "Cautiousness.")

By the 1840s, the Fowlers' New York office, known as the Phrenological Cabinet, had become one of the most visited attractions in town, serving as a bizarre museum that included phrenological portraits of hundreds of famous people's heads. (At least one of them was specially commissioned, post-mortem. After the 1836 death of Aaron Burr, the Fowlers ordered a cast of the deceased's head, and found, upon examination, that Burr's organs of "Secretiveness" and "Destructiveness" were- — not surprisingly — far larger than those of the average person.)

As publishers, the Fowlers churned out the American Phrenological Journal and Miscellany (which remained in print until 1911), along with countless volumes on phrenology and its applications to health and happiness, including guides to phrenological parenting and the proper choice of a mate. They also printed the first volume by a young writer named Walt Whitman.

When Emerson, after reading a manuscript of Leaves of Grass, famously wrote to its author, "I greet you at the beginning of a great career," the letter was addressed in care of the Fowlers. In the book itself, the Fowlers' influence is clear: "Who are you indeed who would talk or sing of America?" Whitman wrote. "Have you . . . learn'd the . . . phrenology . . . of the land?" So pleased was Whitman with his own phrenological reading ("large hope and comparison . . . and causality") that he would quote it time and time again in his writings.

Edgar Allan Poe also regularly wove phrenological concepts into his work, even employing cranial descriptions in an 1850 series of sketches of New York literary figures. (Of William Cullen Bryant, he wrote, the "forehead is broad, with prominent organs of Ideality.") Charlotte Brontë's work is also laced with phrenological analyses. Herman Melville's Moby Dick even offers a lengthy (albeit mocking) phrenological description of the great whale.

Because phrenological theory espoused the idea of perfectibility, social reformers quickly latched onto it. Horace Mann regarded phrenology as the greatest discovery of the age. The Fowlers themselves became vocal advocates of reform and self-improvement, sometimes through advice on the proper phrenological choice of a career, but also with regard to education, temperance, even prison reform.

Of course, there were always skeptics--not least of them, Mark Twain, who recounted with horror that Fowler had found on his skull "a cavity" where humor ought to be. John Quincy Adams is said to have wondered how two phrenologists could look each other in the eye without laughing. But phrenology sailed on, pretty much unscathed, and until the turn of the century, continued to have an enormous impact on the public's ideas about the mind.

So pervasive was it that as late as 1888, the editors of the Encyclopaedia Britannica, wanting to debunk it in the name of reason (not to mention common sense), felt compelled to publish a detailed, seven-page refutation of it.

Gall's "so called organs," the Britannica declared, "were for the most part identified on slender grounds . . . made by an induction from very limited data." In some cases, the exponents of phrenology "have discovered coincidences of a surprising nature." But more often than not, such coincidences did not occur, and, the Britannica complained, when they did not, the phrenologists were apt to simply rationalize away the inconsistencies.

By the 20th century, phrenology had lost any shred of scientific authority, except among a few diehards. But the Britannica had included in its lengthy attack a perceptive prediction: "Based, like many other artificial philosophies, on an admixture of assumption and truth, certain parts will survive and become incorporated into scientific psychology, while the rest will in due course come to be relegated to the limbo of effete heresies."

And so it proved. Though phrenology fell into deserved disrepute, modern scientists note that in some ways it was remarkably prescient. As early as 1929, in his History of Experimental Psychology, Harvard psychologist Edwin G. Boring wrote that "it is almost correct to say that scientific psychology was born of phrenology, out of wedlock with science."

It had, after all, an understanding that physiological characteristics of the brain influence behavior and — conversely — that behavior can alter our very physiology. (Of course, today scientists look at changes in neurochemistry and synaptic connections rather than "brain organs," but the principle is the same.) Phrenologists also reckoned that the mind is not unitary but composed of independent faculties. Their ideas — in other guises — have since given birth to the field of cognitive psychology, which breaks down mental functions (such as reading) into separate faculties (letter recognition, sentence comprehension and so forth).

Perhaps most interesting is the idea that different mental functions are localized in the brain. One of the first scientists to provide evidence of this localization of function was a contemporary of the Fowlers. In 1861, Paul Broca, a French surgeon and anthropologist, showed that damage to a particular region of the brain — only about four square centimeters in size — can make a person unable to speak coherently, without affecting his or her comprehension of others' speech.

"The phrenologists were definitely on the right track in that regard," says Marcus Raichle, a neuroscientist at Washington University in St. Louis. "The problem is where they took it."

According to Antonio Damasio, a neuroscientist at the University of Iowa College of Medicine, the phrenologists were, in many ways, "quite astounding" for their time. "However, they did not understand that even the areas we have identified — quite different from their 'organs' — are interdependent parts of larger 'brain systems.'" Damasio, who studies the effects of lesions in the brain, believes he has located an area in the prefrontal cortex that is part of a system crucial to controlling inappropriate behavior and considering the emotional repercussions of one's actions. One of the most dramatic cases he has studied provides a suggestive link between 19th-century phrenology and modern neuroscience.

It involves a New England railroad worker named Phineas Gage who, in 1848, suffered an amazing accident: an iron bar, more than an inch in diameter, was thrust by an explosion through his brain, entering his head under his cheekbone and exiting at the top of his skull. That he lived was astounding; even more remarkable, his reasoning and language were left entirely intact. What changed, however, was his temperament. Previously a responsible, gentle man, Gage was now argumentative, irresponsible and prone to cursing so vilely that women were warned not to remain in his presence.

Using Gage's actual skull as a guide, Damasio and his wife, Hanna, a fellow neuroscientist, recently created a 3-D computer image of Gage's injury. The bar's trajectory, they found, had damaged the same region of the brain as had been injured in patients of theirs who exhibited similar behavior.

Back in 1848, the diagnosis was only somewhat different. Along with all the doctors and journalists who came to observe him, Gage was visited by Nelson Sizer, a phrenology expert and associate of the Fowlers.

The meeting provides further evidence that faulty logic can sometimes lead to correct conclusions. After comparing Gage's exit wound with his phrenological charts, Sizer determined — and accurately, no doubt- that Gage's change in demeanor, his violence and rudeness, were due not to damage in the prefrontal cortex but to an injury "in the neighborhood of Benevolence and the front part of Veneration."

By Minna Morse