This micrograph of brain tissue reveals the cytoarchitectural histopathologic changes found in bovine spongiform encephalopathy. Vacuoles, the microscopic holes in the brain's grey matter, give the brain of BSE-affected cows a sponge-like appearance when tissue sections are examined in the lab. BSE has been linked to the fatal human condition vCJD (new variant Creutzfeldt-Jakob disease). Both these diseases are caused by abnormal virus-like forms of the prion protein PrP, gradually destroying the brain.