Phrenology, and more specifically head readings, constituted one of the most significant medical and scientific fads of the nineteenth century. Although much has been written about popular phrenology in Britain, how it spread and eventually lost its luster in the United States has drawn less attention. The battles waged over phrenology and its purveyors did not just occur in medical books and journals for specialists. They also involved educating the public about the head readers and their doctrine. Samuel Clemens, writing as Mark Twain, and before him, Dr. Oliver Wendell Holmes, were involved in this mission. Both used wit and humor to convey their serious messages in broad public venues. The present book shows how Clemens and Holmes were exposed to phrenology throughout their lives, as well as why and how they lampooned the head readers. It further reveals how much Clemens was influenced by Holmes, whom he knew and read, and that neither man rejected everything the phrenologists were claiming when they targeted phrenology’s craniological methods and the head readers preying on the gullible public.