One great benefit to health comes from sleeping in huts and cottages situated entirely in the open, and which at all times offer free access to light and air.

We call them light-and-air huts and light-and-air cottages, but there is nothing about them in the way of appointments that would make of them special hygiene apparatuses and institutions.

They are huts with a roof to keep the rain from coming through, but without walls, or only lattice walls. For protection against stormy weather they are provided with curtains. For winter (for they may be used also at this season) they can be kept warm and made to keep out the snow by means of straw and partition walls penetrable by the air.

It is still better to erect more perfect cottages with thicker walls, adapted to real dwelling purposes. But they must be sufficiently provided with windows, blinds, ventilators, etc, to permit the ingress, when open, of plenty of fresh air. The ceiling must be provided with ventilators which may be opened when windows and doors are closed.

Pure fresh air is required by the body, especially in the night, when it is chiefly engaged in the work of digestion. Therefore sleeping in such a hut is very important.

The rooms of houses, even if they are in the woods, are apt to be penetrated with odours from the cellar, the kitchen, closets, garbage heaps, etc. The air is vitiated, moreover, by the circumstance that several, often many persons live in a house side by side, and below and above one another, and that stone walls retain foul odours for a long time. They are therefore never filled with entirely pure, unvitiated air. But this is the case in light-and-air huts.