This paper describes the microscopic studies of human and experimental cancers made by Henry Wade during the years 1904-9. William Ford Robertson, his mentor, and Wade claimed to have discovered a microbial cause of human cancer. The claim was at once fiercely disputed. Wade turned to the investigation of a transmissible sarcoma of the dog, during which he demonstrated an early form of immune transplant rejection. He also undertook studies of Hodgkin's disease. Later in life, Wade established urological surgery at the Royal Infirmary of Edinburgh and became President of the Royal College of Surgeons of Edinburgh.