AMONG PEOPLE who like to philosophize about such hard-to-pin-down notions as "the power of the press," there is a debate going on these days as to whether the media's power to shape (or misshape) public opinion is at its greatest right now, or whether it peaked during the Watergate era. In fact, though, one of the most stunning demonstrations of the potency of the American newspaper occurred 35 years ago today, Sept. 2, 1944, when a single headline triggered a textbook case of mass hysteria. The incident, which can indeed be found in most texts on Collective Behavior, has come to known as the case of The Mad Gasser of Mattoon.

The Mad Gasser first came to notice on the night of Sept. 1, 1944, when an elderly woman, who prefers anonymity and whom I'll call Mrs. Jones, reported to her local police station in Mattoon, Ill., that someone had pumped into her bedroom a sweet-smalling gas that made her ill and temporarily paralyzed her legs; Mrs. Jones' daughter was also in the house, but reported no symptoms.

A nocturnal gas attack was hot news in a town like Mattoon, a generally placid downstate rail depot, and the daily newspaper, the Mattoon Journal Gazette, pounced on the story with full force. "Anesthetic Prowler on Loose," the paper reported in a front-page headline on Sept. 2, "Mrs. [Jones] and Daughter First Victims." (First Victims? Did the headline writer forsee a wave of similar attacks?)

The story received universal attention in Mattoon, a town of 17,000, partly because it was such an intriguing story and partly because the Journal Gazette literally blanketed the town -- according to a survey by a marketing firm in Chicago, it reached 97 percent of Mattoon's families. This figure seems astounding today, but it was not so unlikely in 1944, when television was still mainly a laboratory animal and radio stations did not bother much with local news. Of course, the Mad Gasser did not remain local news for long.

Over the next few days, Mrs. Jones' neighbors began to report similar attacks on their homes [just as the initial headline had suggested]. "Mad Anesthetist Strikes Again," the Journal Gazette headlined, and even on Sept. 7, when there were no reported attacks, the gasser made news. "Mattoon's 'mad anesthetist' apparently took a respite from his maniacal forays Thursday night," the paper reported, adding that "terrified citizens" are "inclined to hold their breath and wonder when and where he might strike next."

The Chicago papers, which circulated fairly widely in Mattoon, soon picked up the scent, and within a few days a Mattoon newspaper buff could read three or four times each day about the nightly danger stalking his town. Over the ensuing two-week period, 25 residents reported waking up in the middle of the night to a heavy smell of gas that caused choking, vomiting and temporary paralysis. Now the gasser became a national figure, challenging the war news and the Dewey-Roosevelt election for front-page space in newspapers around the country. Time magazine waxed -- by Time's standards, at least -- poetic; "He moves through the night as nimbly and secretly as a cat, squirting a sweetish gas through bedroom windows." Hundreds of people wrote and wired the town's city hall suggesting what should be done.

Meanwhile, back in Mattoon, the police chief put his entire 10-man force on the case, but not one of them could find any trace of the prowler. The state police were called in ["State Hunts Gas Madman"], the Army's Chemical Warfare Service tried to determine what the mysterious gas might be, and armed bands of vigilantes took to the city's streets by night to apprehend the gasser.

The prowler, however, was never found -- and for a good reason. The Mad Gasser never existed. A detailed investigation by the Illinois Crime Bureau and Prof. D. M. Johnson, a psychologist at the University of Illinois, determined that the physical symptoms of the "victims" were quite real -- they were, in fact, the classic symptoms of hysteria as reported by Janet, the pioneer student of the disease, 50 years before -- but that there was never any real gas, and there was no evidence of any prowler.

"The case of the phantom anesthetist was entirely psychogenic," Prof. Johnson wrote in his report of the investigation. It began, he said, with Mrs. Jones' imagination. "An exciting, uncritical story appeared in the evening paper. As the news spread, other people reported similar symptoms, more exciting stories were written, and so the affair snowballed."

The whole incident, according to Johnson, was testament to the power of a newspaper to influence not just public opinion, but even public health. Without the press coverage, he concluded, the epidemic of hysteria would not have broken out, because the only other medium of mass communication for such local news, word of mouth, was too slow to create a mass outbreak, and was considered, in those benighted times, far less reliable than the daily paper.

With the diagnosis of hysteria, Mattoon returned to its normal obscurity, although local boosters there still boast about the Mad Gasser, in the same way people in other towns might brag about their George Washington statue or a local boy who went off and became a rock star. Mrs. Jones returned to her previously uneventful life and today chooses not discuss what sparked her initial report of the sweet-smelling gas.

A little literary detective work, however, may provide the answer to that mystery as well. Let us suppose that, in that pre-television age, Mrs. Jones passed her evenings reading, and that on the night of the attack she had been reading one of the popular books of the era, James Thurber's "My Life and Hard Times." In that volume she would have met one of Thurber's most manic characters, Sarah Shoaf.

Miss Shoaf, as described by Thurber in a vaguely autobiographical essay entitled "The Night the Bed Fell," was a woman "who never went to bed at night without the fear that a burglar was going to get in and blow chloroform under her door through a tube.

"To avert this calamity -- for she was in greater dread of anesthetics than of losing her household goods -- she always piled her money, silverware and other valuables in a neat stack just outside her bedroom, with a note reading: 'This is all I have. Please take it and do not use your chloroform, as this is all I have.'"

Surely it is not too far-fetched to suggest that a reader could have spun the author's invention into a nightmare so arrestingly real that it moved her to hysteria, with the attendant physical symptoms. And surely one cannot be too critical of the Journal Gazette reporter, assigned to the tedious job of checking the nightly police blotter, who discovered this delicious incident the next morning and spun it into a story that sent a whole town into hysterics.

In any case, the events in Mattoon 35 years ago this week should offer a nice perspective to those who either boast of or bemoan the "power of the press" in our day. Powerful as the media may be, it is hard to conceive of a newspaper today that could convince itself, its readers and eventually the entire nation that a Thurber fantasy had come true.