As each head reached the end of the table, a worker would insert a metal hose into the foramen magnum, the opening that the spinal cord passes through. High-pressure blasts of compressed air then turned the brain into a slurry that squirted out through the same hole in the skull, often spraying brain tissue around and splattering the hose operator in the process.

The brains were pooled, poured into 10-pound containers and shipped to be sold as food — mostly in China and Korea, where cooks stir-fry them, but also in some parts of the American South, where people like them scrambled up with eggs.

The person blowing brains was separated from the other workers by a plexiglass shield that had enough space under it to allow the heads to ride through on a conveyor belt. There was also enough space for brain tissue to splatter nearby employees.

“You could see aerosolization of brain tissue,” Dr. Lynfield said.

The workers wore hard hats, gloves, lab coats and safety glasses, but many had bare arms, and none had masks or face shields to prevent swallowing or inhaling the mist of brain tissue.

Dr. Lynfield asked Mr. Wadding, “Kelly, what do you think is going on?”

The plant owner watched for a while and said, “Let’s stop harvesting brains.”

Quality Pork halted the procedure that day and ordered face shields for workers at the head table.

Epidemiologists contacted 25 swine slaughterhouses in the United States, and found that only two others used compressed air to extract brains. One, a plant in Nebraska owned by Hormel, has reported no cases. But the other, Indiana Packers in Delphi, Ind., has several possible cases that are being investigated. Both of the other plants, like Quality Pork, have stopped using compressed air. full story