visible Rays Physiological Effects of
These little consideration has been given from the hygienic or therapeutic standpoint, and there seems to be an accord of opinion as to the neutrality of their relation to physiology and health. Yet it is common knowledge among farmers and stock-raisers that animals thrive better in well-lighted build¬ings than in dark ones. In tenements and other places where daylight is deficient, children thrive poorly and develop seri¬ous physical disorders. The lack of sufficient ultra-violet rays may be a factor in these developments, but since the visible rays are associated in nature with the invisible rays, one would expect them to have some favorable influence upon health and growth.