2024 Reprint of the 1910 Edition. Full facsimile of the original edition and not reproduced with Optical Recognition software. The scientific use of light to heal the body in modern times was predominantly an invention of nineteenth-century health reformers; and while the religion of the ancient Egyptians was far from most of the minds of practitioners of light therapy, they were nevertheless participating in an ancient practice of looking to the sun for health. In his 1910 work, Light Therapeutics, Kellogg summed up the short history of light therapy (also called phototherapy or heliotherapy) yet also recognized its ancient roots: "Heliotherapy, or the use of sunlight as a curative means, is one of the oldest of natural healing agents....It is only within the last twenty years, however, that the physiological and therapeutic effects of light derived from natural and artificial sources have been made the subject of careful scientific study. Within this period numerous investigators have devoted themselves to the study of this subject, and the extended researches [sic] that have been made have resulted in the development of a new class of therapeutic methods, principles and measures which constitute the science of phototherapy." Quoted from: https://link.springer.com/article/10.1057/s42738-022-00092-7 This book describes in detail Kellogg's philosophy and practice of curing ailments with the use of light. Profusely illustrated.