The brain succumbs to mercury's ravages more readily than other tissues. Borne by the bloodsteram, methyl mercury penetrates brain membranes that bar most other poisons. First it damages the organ without appreciable loss of cells (top), then erodes whole pockets of tissue (middle). Worst hit are the brain's visual, hearing, and equilibrium centers, thus explaining the effects of mercury poisoning — blindness, deafness, and loss of balance.

Seeking an antidote, Dr. Thomas Clarkson of the University of Rochester's Medical Center tests the ability of various synthetic resins to inactivate methyl mercury (below). Given orally, the resins trap the poison, enabling the body to excrete it instead of retaining it, as usually occurs.