The development of keratoses on the chest of a 27 year old patient after exposures to ultraviolet rays over a period of eighteen months was reported by Colquhoun.1Findlay2exposed rats to ultraviolet rays and produced keratoses in these animals. He attributed the results to the ultraviolet rays and not to heat, as from an electric bulb. This work was confirmed by Roffo.3Findlay stated that in Queensland, Australia, farmers have abandoned the raising of white cattle because of their susceptibility to the development of cancer of the skin. Roffo4reported an increase in the cholesterol content of the skin in exposed areas of the body in contrast to the protected areas. He suggested that these variations in the cholesterol content are referable to heliotropism and expressed the belief that cholesterol is fixed in the skin as a result of its heliotropism. He concluded as a