When the eye is exposed to light, vibrations are carried to the brain through the afferent nerve fibers and Innate Intelligence becomes aware of the light. If it is intense and is allowed to remain in contact with the retina the delicate nerve tissue will be injured. To compensate for this Innate Intelligence sends motor impulses to the circular fibers in the iris, causing them to contract and decrease the size of the pupil and thus shut out a part of the light rays. In a less intense light or in the darkness the muscular fibers are relaxed, enlarging the pupil and admitting more light. In all of this adaptative action there must be sufficient time, although the action does take place almost instantly. This action is not automatic as some would have us believe, but is intelligent and under the direct control of Innate Intelligence. If we were living in the natural state of man’s existence there would be no need for a consideration of these natural laws governing the working of the human body and the intelligence which controls these manifestations; but as man has increased his knowledge and has made for himself a more or less artificial environment, it becomes necessary for him to understand the natural laws that he may adapt his artificial environment to them. If man lived in the open outdoors there would be no need for the artificial lighting of buildings; but since he has created buildings it becomes necessary for him to study the laws of nature that he may produce a condition in this environment conducive to the expression of life. In providing artificial light for our buildings the laws of the physical organ of sight must be considered. However, the question of lighting is not alone one of artificial production of light in our buildings, but also deals with proper admission of natural light from natural sources. Value of Sunlight The value of the sunlight in respect to health has been recognized from time immemorial. Direct rays of the sun are essential in the development and expression of animal and plant life. The sun’s rays are Nature’s greatest germicide. They destroy almost all forms of germ life. Most of the chemical reactions are hastened or induced by the action of light. Light prevents or retards the development of the lower forms of life but promotes the growth of the higher forms. Natural Light in Buildings From the foregoing statement it is quite obvious that a proper amount of light, and if possible the direct rays of the sun, must be admitted to the home if it is to afford an environment at all conducive to the expression of life. It is therefore necessary to make special provision for the admission of light. The amount of light admitted to a building will be determined by its location and aspect, the source of the light, whether direct or reflected, the location and size of the openings, and the kind of glass used. The character of the walls and other inside surfaces will determine the light diffusion.