Have you ever seen an angel? Dr. S. W. Mitchell thought he had. Dr. Mitchell was a well-known neurologist in Philadelphia. After one very tiring day he retired early, but he was awakened by a persistent knocking at the door. It was a little girl, poorly dressed and deeply upset. She told him that her mother was very sick and needed his help. Even though it was a bitterly told, snowy night and he was bone tired, Mitchell dressed and followed the girl. He found the mother desperately ill with pneumonia. After treating her, Dr. Mitchell complimented the sick woman on her daugh…