With regard to the interior of these houses, they must contain a room for each girl; on no account are two prostitutes allowed to occupy the same room, much less the same bed. Each room must, moreover, be amply provided with utensils, soap, and water, for ablution. No house of prostitution can have back or side doors, or in any way communicate with the adjoining buildings. No house can contain dark closets, or dark passages, or concealed hiding-places. In none of them can any trade or traffic be carried on. With regard to the class of houses called _maisons de passe_ (assignation houses), the police authorities require that in every such house two regular prostitutes, inscribed on the police rolls, shall live permanently. The object of this rule is to obtain a control and supervision over these houses. Before it was adopted the police was often embarrassed by denials of its authority to invade them. It is found that the prostitutes, being naturally hostile to the mistresses of the houses, will act as agents of the police in the event of any scandalous proceedings. The windows of houses of prostitution must be roughed, as also must those of rooms where individual prostitutes live. They can only be partially opened. These regulations were made in consequence of the shocking scenes that were witnessed at the windows of brothels after the Revolution, naked women being the least of the scandals that used to be exposed. No one can keep a house of prostitution in Paris without an authorization from the police. Men are never permitted to keep establishments of the kind. A woman who desires to open a house must apply in writing to the Prefect of Police. On receipt of her application, reference is made to the Commissary of Police of the ward to ascertain her character. If she has been condemned for crime or misdemeanor, her request is rarely granted. If she stands in the police books as a woman requiring supervision, she can not succeed. Nor can she obtain a license, under ordinary circumstances, _unless she has been a prostitute herself_. The reason of this regulation is obvious; no one but a prostitute understands the business thoroughly; and as the position of brothel-keeper is found to be the most demoralizing station in the world, it has been the policy of the Paris police to throw impediments in the way of persons not wholly depraved devoting themselves to so dangerous a calling. Furthermore, the applicant must have reached a certain age. She must also be of sober habits, and apparently possessed of sufficient force of character to be able to command a house full of prostitutes. She must possess a sum of money sufficient to guarantee her against immediate failure, and she must own the furniture in the house she wishes to keep.