Dr. Cyril Clarke, a British physician and professor of medicine whose fascination with butterfly wings led him to pursue research that helped end infant deaths from a blood disease caused by incompatible Rh factors, died on Nov. 21 in Hoylake, Cheshire, England. He was 93.

As a geneticist, he found parallels between the inheritance of wing patterns in butterflies and the inheritance of blood types in people. That insight led to discoveries by him and others that eventually enabled women with Rh-negative blood who produce antibodies to the blood of their Rh-positive babies to have them safely.

He investigated a broad variety of topics, including the coloration of swallowtailed butterflies and the longevity secrets of centenarians. He was an emeritus professor of medicine at the University of Liverpool and a past president of the Royal College of Physicians.

But Dr. Clarke was known in the United States chiefly as a figure in the battle to thwart Rh disease of newborns, short for rhesus hemolytic disease. That feat ranked among the triumphs of modern preventive medicine.