Walter J. Kilner MRCP (1847-1920) was a British medical electrician and physician active in the late nineteenth and early twentieth centuries. He served at St. Thomas' Hospital, London, where he was responsible for the administration and oversight of electrotherapy treatments, and he also maintained a private medical practice in Ladbroke Grove, London.Kilner's professional career unfolded during a period when electricity was an established therapeutic modality within mainstream medicine, and when physiological research increasingly explored the effects of electrical, optical, and energetic phenomena on the human body.He is best known for his experimental investigations into human vitality and perception, including the use of early optical technologies to observe radiance associated with physiological processes. His writings reflect a transitional phase in medical and scientific history, marked by active inquiry at the intersection of medicine, physics, and perception.While some aspects of his work fall outside modern biomedical frameworks, Kilner's contributions remain of historical interest to readers studying the development of electrotherapy, early biophysical research, and the evolution of medical thought at the turn of the twentieth century.