Rikli seems to have been the apostle of air-baths and sun-baths regarded as a systematic method. He established light-and air-baths over half a century ago at Trieste and elsewhere in Austria. His motto was: "Light, Truth, and Freedom are the motive forces towards the highest development of physical and moral health." Man is not a fish, he declared; light and air are the first conditions of a highly organized life. Solaria for the treatment of a number of different disordered conditions are now commonly established, and most systems of natural therapeutics attach prime importance to light and air, while in medicine generally it is beginning to be recognized that such influences can by no means be neglected. Dr. Fernand Sandoz, in his _Introduction à la Thérapeutique Naturiste par les agents Physiques et Dietétiques_ (1907) sets forth such methods comprehensively. In Germany sun-baths have become widely common; thus Lenkei (in a paper summarized in _British Medical Journal_, Oct. 31, 1908) prescribes them with much benefit in tuberculosis, rheumatic conditions, obesity, anæmia, neurasthenia, etc. He considers that their peculiar value lies in the action of light. Professor J.N. Hyde, of Chicago, even believes ("Light-Hunger in the Production of Psoriasis," _British Medical Journal_, Oct. 6, 1906), that psoriasis is caused by deficiency of sunlight, and is best cured by the application of light. This belief, which has not, however, been generally accepted in its unqualified form, he ingeniously supports by the fact that psoriasis tends to appear on the most exposed parts of the body, which may be held to naturally receive and require the maximum of light, and by the absence of the disease in hot countries and among negroes. The hygienic value of nakedness is indicated by the robust health of the savages throughout the world who go naked. The vigor of the Irish, also, has been connected with the fact that (as Fynes Moryson's _Itinerary_ shows) both sexes, even among persons of high social class, were accustomed to go naked except for a mantle, especially in more remote parts of the country, as late as the seventeenth century. Where-ever primitive races abandon nakedness for clothing, at once the tendency to disease, mortality, and degeneracy notably increases, though it must be remembered that the use of clothing is commonly accompanied by the introduction of other bad habits. "Nakedness is the only condition universal among vigorous and healthy savages; at every other point perhaps they differ," remarks Frederick Boyle in a paper ("Savages and Clothes," _Monthly Review_, Sept., 1905) in which he brings together much evidence concerning the hygienic advantages of the natural human state in which man is "all face."