Professor Lazarus-Barlow calls attention to the fact that it is precisely those tubercular persons who tan easily who are said to derive the greatest benefit from a sojourn at high altitude. Very remarkable is a recently adopted machine which “pours ultra-violet light through a funnel down the throat of a patient.” The new apparatus, first used in London, is employed for treatment of various mouth and throat diseases, “thus making it possible for patients to take internal baths of artificial sunlight” (_Science_, February 26, 1926). In England, where the sky is so often overclouded, it is natural that much attention has been given to ultra-violet ray therapy. A recent press dispatch tells us: “London recently had 23 consecutive days on which no beam of the sun could force its way through the mantle of cloud and fog which spread over that section of England. Now the Britons are making artificial suns that may be available for both indoor and outdoor illumination. Arc lights throwing powerful ultra-violet rays are being installed in beauty shops and hotels, and patrons are given opportunity to bathe their bodies in this brilliance. These rays are being billed as more potent than sun baths, and citizens who have small chance to see the orb of day get their sunshine and their medicine at one swoop.” Two Indian scientists, S. S. Bhatnagar and R. B. Lal, of the University of the Punjab, Lahore, discovered in 1925 that germs grow faster when exposed to “polarized” light than to ordinary light. (Ordinary light—according to the undulatory theory—is due to vibrations transverse to the direction of the ray, but varying so rapidly as to show no particular direction of their own, the fronts of the light-waves crisscrossing at all angles. When, by any means, these vibrations are given a definite direction, the light is said to be _polarized_, the fronts of the waves being all arranged in the same direction, though the path of the rays may be plane, elliptical, circular, or rotary, according to the method of polarization employed.) The Indian experimenters took cultures of the germs of typhoid fever and cholera, and exposed one set to ordinary light, and another to a beam of polarized light. The latter multiplied much faster than did the germs under ordinary light. It was demonstrated in 1925 by Dr. Elizabeth S. Semmens, of Bedford College, London, that the digestion of starch takes place more readily under polarized light than in ordinary light. Prolonged exposure to the ultra-violet rays will destroy any germs known to science. (Cathode rays—which are shorter than ultra-violet rays—will kill not only germs, but insects as well, by means of a device developed by Prof. W. D. Coolidge.)