The ancients supposed disease of the heart to be incompatible with life, the heart being the center of life. Galen, in the second century after Christ, observed pericarditis in the lower animals and inferred its occurrence in man. Before this knowledge had been gleaned, all peculiarities of the structure or appearance of the heart were supposed to denote attributes of character. Thus, Haller speaks of the "hairy hearts" of Leonidas, Lysander and Aristomenes, as indicative of great bravery, those "hairy hearts" undoubtedly being viscera covered with stringy fibrin. ETIOLOGY. The disease is now known to be of frequent occurrence. It is most common in adolescence and early adult life, between the ages of 15 and 30. It occurs in childhood and in infancy, and rarely in the fetus. It also occurs in late adult lif and sometimes in senility. Knopf saw pericarditis 10 times among 459 cases of diseases of