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Show ClSZIlIZZZZZZI During theso hot summer days occur phenomena which n very few of us rigidly "Cyi.-. understand. "What is sunstroke? Why arc 6omo persons affected by tho sun and not SlIIl'S others? Why do negroes bear tropical heat U better than whito men? Why are southern KtiyS races dark, and how did they becomo so? Prncfrflfp after a w"to man ia8 cn cx" posed to tho sun's rays for several hours, i ' does ho first burn,- then peel and finally Dy 0. ELLIOT FLINT, tan? AB"r7r0":Ex1AV.,ThroB!, To begin with, heat, while it is a con- 1 1 tributing cause, is not tho chief cause of sunstroke. Solar light is mado up of different dif-ferent rays of varying wave lengths, and it is tho wave length that produces pro-duces the particular eircct. Thus tho red and infra-red rays havo tho greatest wave length and produce tho greatest nmount of heat; tho yellow nnd orange, with shorter wave length, give most light; tho green, with still shorter wave length, are least irritating; thoso of shortest wavo length are the actinic rays tho violet, indigo blue and-ultra-violet. Theso last named rays are the least heating but tho most dangerous. According to Von SchamacdcJ, tho uctinic rays of intenso sunlight destroy tissuo by 86ttiug up very rapid molecular, or atomic, movements which dissociate it, tho protoplasm of tissues being a very unstable substance. It will seem strange to somo that the heat rays should be less harmful harm-ful than nro tho comparatively cool actinic rays. It is a matter of penetration, pene-tration, tho long heat waves having little, whilo tho short, actinic rays havo great penetrative power. ' During tho cxposuro tho heat rays penctrato but littlo, whilo the ictinic rays penctrato considerably below tho superficial layers. (Neither tho heat roys nor the actinic rays affect appreciably tho epidermis, its constituent molecules being comparatively stable, and, therefore, not susceptible.) The resulting Bunburn is an inflammation of tho tissues pro- duccd by the terrific bombardment of their molecules by tho corpuscles of tho aclinic rays, which, recollect, havo a prodigious velocity. Moreover, corpuscular vibrations, by setting up equal vibrations in tho molecules and atoms of tho affected substance, tear to pieces, just as when a certain note is greatly prolonged on a violin it will shatter a glnss resonator that it causes, to vibrato in unison with it. Tho peeling of tho skni that follows . is a natural result of the partial destruction and breaking up of the lowei layers. Now, nature, stimulated by tho effect of tho irritant, pours blood mf joloring matter, and even red blood cells themselves, into tho intercel- lular spaces, and a .yollowish-brown pigmentation (tan) results, which thereafter protects tho body from tho rays that onco damaged it. Every one knows that a man well tanned will neither burn nor peel, however much ho exposes himself to tho sun. Besides the theory thut execssivo exposure to tho actinic rays causo unstroke, other contributing causes aro recognized. Plafn heat-stroke may occur in hot fire-rooms or kitchens, in which all tho rays are tht longer iufractcd. This comes on from an inability on tho part of the body to get rid of its superfluous heat, which, if continuing, will of itself injure und finally parulyzo protolasm, causing coma. Moreover, auto-Intoxication auto-Intoxication (self-poisoning) will help cause a collapse, thus: If nol enough water bo drunk during exposure to intenso heat, perspiration being be-ing excessive, fluids are drained from the body, until there is not sufficient loft for the uso of tho kidneys to dissolvo tho wasto products, which, be-s be-s ing poisonous, causo various nervous symptoms. Then tho kidneys and bladder rwomo inflamed, and often tho kidnoys refuse to act at nil. It therefore, a physiological necessity jgmm to drinlt much water under such conditions both fLflJk to carry off tho poisonous waste products, and tf? to supply copious perspiration to reduce tho body VW&J temperature by evaporation. American officers and jjflPL soldiers in the Philippines suffered greatly from 'jffKy it1 sunstroke becauso of tho impossibility of carry- fWW s w ' injr sufficient water for their needs. y" |