Jones fell unconscious on the job and it was suspected that he had swallowed a certain chemical
he was rushed to the local hospital' s emergency room. In making her diagnosis, the emergency-room physician knew that if Jones had swallowed the chemical, a deficiency in the content of a mineral in his blood would result. She also knew that deficiency in the mineral causes inflammation of the skin. Since Jones' s skin was not inflamed when he was admitted to the emergency room, the physician concluded that Jones had not swallowed the chemical.
Jones had suffered inflammation of the skin in the past.