Reappraisal of the historic 1959 cat experiment in Minamata by the Chisso factory

Autopsy specimens from the historic cat experiment were recently discovered in a storage area at the Kumamoto University School of Medicine. The speci mens were from an experiment prompted by physicians in the Chisso Minamata Plant following the announcement made by the Study Group for Minamata disea se. On July 14, 1959 the Group announced that the disease was most likely c aused by a kind of organic mercury. In order to prove or disprove that indu strial waste from the Chisso Factory was the culprit in Minamata disease, a total of ten cats were fed food mixed with industrial waste produced in th e acetaldehyde-producing plant. One of the ten cats, No. 717, was subsequen tly autopsied but the autopsy findings have never been published or recorde d in the literature despite their historic significance. The rediscovered s pecimens were studied pathologically and biochemically, and were analyzed c hemically with currently available techniques. Characteristic lesions of me thylmercury poisoning were observed in the central nervous system, and the mercury levels in the cerebrum, cerebellum, liver and kidney were found to be markedly elevated in this animal.