e skin can stand a great
deal of sunlight without harm, but light-skinned persons, while needing
a certain amount of sunlight, should not expose themselves for too long
a time to the midday sun in summer, or at least not until they have
gradually become sufficiently tanned to do so. Everyone knows the
painful character of a sunburn. This only illustrates the powerful
chemical effect of the sun's rays. In taking sun baths one should
very gradually accustom himself to the sunshine until he is so tanned
that the pigment in his skin will protect him. The short or chemical
rays of the sun are actually destructive to white men in the tropics.
In May, June and July they have a pronounced chemical effect even in
our own latitude. They are stimulating up to a certain point, but
beyond that point one should be careful. I may say, therefore, that
brunettes in summer may take sun baths even at noon, but blondes
should take them preferably before nine or ten o'clock in the morning or
after three o'clock in the afternoon. In winter, however, when the
sun's rays are more slanting, the sun baths can be taken even by the
blondes at any time. And because of the more limited amount of
sunlight in winter, special attention should be given to sun bathing
during that season.

Everyone needs a certain amount of sunlight, and if you cannot take a
sun bath regularly every day you should at least wear clothing of
a character that will permit the light-rays of the sun to penetrate. I
will refer to this again, however, in the chapter on the subject
of clothing.

After all that we can say in regard to these various methods of
stimulating the skin there is really nothing so effective as active
exercise for those who are strong enough to take a sufficient amount of
it. Exercise, so far as function of the skin is concerned, is valuable
because of the copious perspiration which is induced when one gets
enough of it. In these days great numbers of people no longer "earn
their bread by the sweat of their brow," and their health suffers in
consequence. If you do not have to perform such an amount of physical
labor as will promote free perspiration, then for the sake of
acquiring the very purest quality of blood your special exercise should
be sufficiently active and continuous to bring about free perspiration.
There is really nothing so effective as a good old-fashioned "sweat" for
rapidly purifying the blood.