Our knowledge of diseases of the heart is of comparatively recent date. It is true that Vesalius did much to make known the anatomy of the organ and that Harvey demonstrated its purpose or function. This much was learned in the sixteenth century, and during the following centuries contributions were made slowly to a knowledge of its pathology; but methods of physical diagnosis by which its pathologic states could be recognized during life were not discovered until the end of the eighteenth and first quarter of the nineteenth centuries.
The opinions of former generations of medical men have not yet been outgrown by laymen, and many of the latter think that a permanent anatomic defect in the heart means sudden death, death which is especially apt to be caused by physical exertion. The fact that overexertion, either mental or physical, can cause dilatation, and, perhaps, fatal weakness, of the