The biological action of light.—I. The influence of temperature

Abstract

In a series of experiments carried out by one of us at Montana-Vermala with the co-operation of Dr. B. Hudson, who afforded facilities for the work at the English Sanatorium, the biological action of Alpine winter sunlight was studied under varying temperature conditions. While the treatment of weakly or tubercular children by sunlight and open air has gained high repute, e. g ., by Rollier at Leysin, or Gauvain at the Treloar Hospital, the sun treatment of phthisis is generally regarded unfavourably. The children, more or less nude, according to weather, are exposed on open galleries to sun together with a high cooling power of air, a cooling power which, measured by the kata-thermometer, is two, two and a half and even three times that of an ordinary cool room. On the other hand, phthisical adults, e. g ., in Switzerland, are exposed clothed in sun-boxes facing south where they are more or less over-heated by combination of sun, warm enclosure and absence of cooling wind. Personal experience shows that Alpine winter sun, plus cooling air, have an exhilarating effect on the nude body, and that, while the body-heat production is put up by the cold, 'with general advantage to health, no sunburn results. On the other hand, warm sun in a warm shelter produces sunburn and is oppressive and disadvantageous. The advice of an old sea captain was, “expose yourself to the sun in the prow if you want to get nicely browned, you will get sunburnt if sheltered from wind in the waist of the ship.” Bayliss writes “The great effect of ultra-violet light on the skin is familiar to everyone in the inflammation (erythema solare) called sunburn, which results in a brown coloration. It may be pointed out that this is not an effect of heat, in fact, it is more liable to occur in cold surroundings, probably owing in part to the fact that the heat of the sun’s rays is not noticed and no means taken to protect the skin from their action.” The Arctic sun with low air temperature can produce severe sun burns. The following statement is made by M. de Laroquette :—“ The calorific rays by provoking hypersemia and sweating render the epidermis more resistant to the action of the chemical rays. The skin is most fragile when it is dry and made bloodless by cold (Coup de soleil des glaciers).”