Oliver Wendell Holmes's sharp, witty medical essays and lectures turn skepticism into a craft, taking aim at superstition, professional vanity, and the easy credulity that lets pseudoscience flourish. Opening with a warm salute to students, teachers, and the shared labor of medical education, he frames science as a disciplined advance into darkness: knowledge is limited, ignorance immense, and wisdom begins with knowing where certainty ends. From that foundation, Holmes attacks homeopathy, royal cures, sympathetic remedies, tar-water, metallic tractors, and the bizarre Weapon Ointment, showing how anecdote, imagination, and wishful thinking can masquerade as proof. He also revisits his famous critique of overmedication, arguing that even false systems can expose the excesses of conventional drugging. Blending irony, conviction, and moral seriousness, Holmes defends practical observation and honest inquiry, and gives grave attention to puerperal fever, a deadly contagion whose study helped save lives. This edition has been fully restored with modern typesetting, custom cover design.