The Ultraviolet Rays of the Sun

The essential importance of ultraviolet rays in medicine has just begun to be appreciated. The action of these rays, as distinct from the visible radiations of the sun, has been known for many years, but physiologists have only recently become fully alive to their significance in relation to the normal and pathologic conditions of man. This is all the more surprising in view of the fact that plant physiologists have laid great stress on the role of the invisible or chemical rays of the sun in the biologic processes of the vegetable world. Some twenty years ago, the physiologist Hertel carried out striking experiments in this field, which demonstrated the marked abiotic power of ultraviolet rays—their ability to destroy bacteria within a period of sixty seconds. About the same time, Finsen showed that the improvement or cure of lupus could be brought about by means of irradiations from the carbon