"Light is as indispensable to life as air itself. Hence it is that Hell is represented as completely dark. Where light cannot penetrate, the air can never be pure. ... Those who thus deprive themselves of air and light are always weak and haggard. ... Now-a-days, there are many doctors in Europe who cure their patients by means of air-bath and sun-bath alone. Thousands of diseased persons have been cured by mere exposure to the air and to the sunlight. ... Dwellers in towns are, as a rule, more delicate than those in the country, for they get less air and light than the latter. (Chapter III, Air)"