infested by disease is the resort of evil spirits. This is a mere delusion, for the real "evil spirits" in such cases are the foul air inside the house. A change of residence ensures a change of air, and with it the cure of the diseases brought on by it. Indeed, so vital is the relation between health and air that the good or evil effects of even a slight change are instantaneously felt. For a change of air the rich can afford to go to distant places, but even the poor can go from one village to another, or at least from one house to another. Even a change of room in the same house often brings great relief to a sick man. But, of course, care should be taken to see that the change of air is really for the better. Thus, for instance, a disease that has been brought on by damp air cannot be cured by a change to a damper locality. It is because sufficient attention is not paid to simple precautions like this that a change of air is often so ineffectual.
This chapter has been devoted to some simple instances of the application of air to the treatment of disease, while the chapter on Air in Part I of this book contains a general consideration of the value of pure air to health. Hence I would request my readers to read these two chapters side by side.
