Light and Radiant Heat
THE health-giving virtues of light and warmth have always been recognized. It is but lately, however, that these generalities have been analysed and their elem'ents separately examined. The discovery that the Solar spectrum includes rays other than the visible ones; and that some of these are capable of provoking violent chemical reactions, naturally stirred the scientific as *ell as the commercial imagination, with results such' as always follow such excitation. Few scientific novelties have provoked greater popular interest or greater expectations of benefits to follow than that of the ultra-violet rays and their influence on human physiology. Here seemed to lie the explanation of the spirit-reviving influence of the sun, and of the health- destroying effects of a gloomy and sunless environment. Not unnaturally, -the therapeutic possibilities of this newly ...isolate(L.Ageat. %assumed. ,fabulous.. -proportion& ; and, when the healing power of ultra-violet radiation -over-suela--bitherto-resistant---lesions its tubercular joints and rickets became manifest, hopes were entertained that it might prove equally effective in dealing with all,sorts of other ailments before which medical science stood impotent. Exaggerated beliefs grew up ; credulity and commercial acumen each contributing. There is hardly n human ill over Which the curative influence of ultra-violet rays has not been claimed by doctors • of repute.
Time, however, acts as an effective sieve ; and, one after another, these claims have dwindled—so. much so, indeed, that sceptics are to-day inclined to consign the new agent to a Limbo already densely populated with rejected panaceas and exploded superstitions. Again, as is usual, the scepticism, like the hyperbolic optimism that provoked it, has overstepped reason. Ultra-violet rays cannot be dismissed as of the bread-pill or coloured water class. That they are not chemically and physio- logically inert is obvious from the evidence of the photographic plate and of the tanning of the exposed skin. Their curative and preventive influence on the once common disease, rickets, is proved beyond question ; so, also, is their healing effect on tubercular lesions of skin and bone. Moreover, careful experiment has shOwn the effectiveness of these rays in bringing about changes in the composition of the blood ; changes which add, not only to its bactericidal and disease-preventing potency, but also to its quality as a nourisher of brain and nerve, and so as a maker of energy and lightness of heart. To mention one or two outstanding facts, exposure to ultra- violet radiation, whether as afforded by the Alpine sun or by special lamps now available for the purpose, increases the calcium and phosphorus, content of the blood, and provokes, such reaction in the human body as to speed up its Metabolic activity. We may dismiss as unproven its alleged curative effect on most of the diseases in respect of which over-optimistic claims have been made, though further experience may modify this judicial hesitation. On the other hand, we have plenty of evidence that in ultra-violet rays the town dweller has at his disposal a serviceable instrument which, if properly used and combined with other elements of a sensible regimen of health, may contribute generously to the attainment of a higher level of physical and psychic fitness.
Within the last few years attention has been drawn to certain rays near the other end of the visible spectrum —rays of greater wave-length and lower frequency of vibration than those which provoke in us the sensation of redness. Just as the power of electro-magnetic rays to penetrate our tissues is diminished as we ascend the scale front red to violet, and from violet onwards through the several degrees of ultra-violet radiation, so, contrari- wise, does the power of penetration increase as we descend to rays of increasing wave-length—the very long " wire- less " waves apparently passing through us without appre- ciable resistance. Red has more penetrating power than blue or violet, and the invisible rays just below the red have greater penetrating power still. This is convincingly demonstrated in the splendid long-distance " infra-red photographs " recently reproduced in The Times. Herein, presumably, lies the explanation of the alleged physio- logical effects of these rays when they fall on the skin. Before they are obstructed or absorbed, they reach a .deeper layer of our tissues than do other rays commonly employed for heating our rooms and ourselves. There- fore, seeing that heat is generated only at the point of obstruction, the warmth they . yield. has a quality of its • OWIler-Pripia latie evidence:- of _ -their beneficence Is afforded by the agreeableness of the sensation they prOyoke as compared with that yielded by :lull red heat of the ordinary type-, But we now have a good deal of supplemental proof of the useful possibilitieS of these rays. Interesting experiments conducted by Dr. Eidinow and Sir}Leonard Hill have shown, for example, that resisting pOWer 'to hOstile germs is appreciably raised by exposure of the skin to Suitable'doles Of infra-red radiation. Further obrvations made at the Zoological Gardens by Sir Lecinard Hill have demonstrated to how great an extent health and vitality may in Many animals be promoted by the discriminating- application of the shorter infra-red rays yielded by appropriate lamps. In a letter to-The 'Tin es few years ago he -pointed out how much niore pleasant is the sensation caused by exposure to the visible and shorter infra-red rays than- that -caused-by exposure to dark heat-rays. A feeling of dryness and diseOrrifort, he !said,• is often felt When the face is exposed to any source of dull red or dark heat, . " whether if be .stedin stove, gas-fire, or electric heater." ." The oppressive feeling; so induced • is commonly, though erroneously,. put - down to supposed escape of fumes or to excessive dryness' of the air." He went on to contend that " much of the good resulting from sun treatment in the ease of wounds and surgical tuberculosis can justly be ascribed to short infra-red and visible rays. These, as well as the ultra- violet rays, have a curative effect." To sum up,. we may say that already we have con- vincing evidence of the therapeutic and hygienic rele- vance of light ; and that to the several rays of the electro- magnetic spectrum our bodies react in diverse ways. Beyond this, dogmatism, positive or negative, is inex- cusable. Further study is essential ; the field is a pro- mising one ; and great results may ultimately- be looked for.
Previous page
