On December 22, 1902, in the basement of the Agriculture Department's chemistry building in Washington, six young men sat down to the first dosed meal of a trial that would involve twelve volunteers in all; the other six continued their ordinary lives until a second group began its own dosed meals the next month. Harvey W. Wiley, chief of the Bureau of Chemistry, screened all twelve for health, habits, and reputation for honesty; most were connected with the department, many in scientific work. Each man's meals came from the Bureau's own kitchen, weighed to the gram, and every volunteer had signed a pledge to eat nothing else during his own observation period and to keep his usual hours of work and sleep, with one further clause: that he would not hold the department responsible for any illness the meals produced.
The substance in that first dosed meal was boric acid, a preservative stirred into butter and meat to slow spoilage in an age before reliable refrigeration. The preservative trade argued that the amounts anyone actually ate were too small to matter. Researchers elsewhere had already tried testing such chemicals in isolated digestive fluids or in laboratory animals, but neither method could show how one behaved in an ordinary stomach eating an ordinary diet for weeks on end; only a trial on human volunteers, under real working conditions, could settle that. Reporters following the story began calling the volunteers the Poison Squad, a name that outlasted the Bureau's own official one, the hygienic table.
Four to five grams of boric acid a day, continued for some time, left most of the men without appetite and unable to work at all; four grams, the Bureau concluded, was about as far as a healthy man could go. At three grams a day, many felt the same symptoms, though most still worked. Even half a gram a day, sustained for fifty days in one trial series, still proved too much for the normal man to receive regularly. The finished 1904 report took up the preservative trade's standing defense, that the doses involved were too small to regulate, and rejected it on its own terms: the law does not excuse the use of injurious substances because they may be present in small quantities. Whatever held for boric acid, the Bureau argued, would have to hold for every other preservative sold on the same shelf.
The findings made national news starting in 1904, as papers followed the Poison Squad's reports. A shopper who had shrugged at a label listing a trace of preservative could now picture a clerk losing his appetite on that same chemical, measured and watched by a federal physician. That attention, with Upton Sinclair's exposure of the meatpacking industry and decades of failed bills in Congress, carried the Pure Food and Drug Act to Roosevelt's desk. He signed it on June 30, 1906, and put its enforcement in Wiley's own Bureau of Chemistry, which kept testing other preservatives the same way, publishing further bulletins through 1908.
The Poison Squad never proved that borax would kill anyone eating an ordinary meal. It proved something narrower: that an unmeasured dose is not a known one. Twelve men ate the question for breakfast, every morning, until the government knew it, not just the industry selling it.