All free governments, whatever their name, are in reality governments by public opinion, and it is on the quality of this public opinion that their prosperity depends. It is, therefore, their first duty to purify the element from which they draw the breath of life. With the growth of democracy grows also the fear, if not the danger, that this atmosphere may be corrupted with poisonous exhalations from lower and more malarious levels, and the question of sanitation becomes more instant and pressing. Democracy in its best sense is merely the letting in of light and air.