A doctor’s wife had fluid in her chest. She was seen by another doctor in the same town, who aspirated her chest and did not notice whether the fluid contained albumen. Fearing that it was a tuberculous case, he sent her away for six months. She was not benefited. She passed through London on her way back – and I was asked to see her. I put a needle into the chest and aspirated fluid containing no albumen. She was operated on, and hydatids were evacuated from the chest. Unfortunately, just after the operation, a yellow fog set in over London, lasting three or four days, and that killed her. Nevertheless, if we had known six months earlier that the fluid was hydatid, and not tuberculous, it is quite likely that the woman’s life would have been saved.