We now proceed to the investigation of a class of diseases exceedingly common in our variable and ever-changing climate, and which, neglected, often lead to. serious consequences. In the chapters on Anatomy and Physiology I have shown the important part which the organs connected with respiration perform in the economy of life, the beauty and regularity with which they perform their functions in health, and the necessity of their being well developed, vigorous and active, unclog-ged in their movements, to secure beauty of form and maintain a healthy and harmonious equilibrium in the system.

A slight irritation of a certain portion of the windpipe may destroy the music of the sweetest voice, and the seeds of that wasting consumption, which has saddened so many a hearth and blighted so many sweet buds of promise, may be sown by a slight cold, at the time easily removed, but neglected, planting its roots so deep and strong as to sap the fountains of life, and lay its victim in the grave.

Serious disturbances of the chest of course require the aid of the careful and skilful physician, but many of the incipient symptoms are so plain, that not unfre-quently a few doses of medicine, properly selected by the patient, may remove the whole difficulty, and prevent the development of what might have been a serious disease.

For the sake of convenience, we shall divide the diseases treated in this chapter into two classes.

* For a description of the organs included under this head, see plate 2, fig. 4, and plate 5. Also Anatomy.

1. Affections of the Windpipe and Lungs.

2. Affections of the Heart.