Because the fashionable nineteenth-century top per required the use of mercury for stiffening its felt so it would stand up straight, factory workers would come into frequent contact with the metal. They would often suffer from a damaged central nervous system, loss of speech control, impaired vision and the ability to move. These hatters were not suffering from any disease; they had been poisoned by mercury.
十九世紀流行於西方男士間的高禮帽，毛氈燻製過程中，必需加入水銀，才能使之挺直，制帽廠內工人長期與水銀接觸，中樞神經受損，因此失去控制語言、視覺、動作的能力﹘﹘制帽人並非發瘋，而是水銀中毒。