Complex sentence: His interests were widespread and he wrote articles on subjects as varied as leprosy, cholera, gravity, and plant diseases.His main interest, however, was yellow fever, and he was the author of 40 articles on this disease.
Split into simpler sentences: His interests were widespread and he wrote articles on subjects as varied as leprosy, cholera, gravity, and plant diseases. But his main interest was yellow fever, and he was the author of 40 articles on this disease.