These are among the most common diseases of this organ and moreover lead
to many of the changes in structure to be hereafter noticed so that it
is convenient to treat of them here. According to their relative
frequency they may be ranged:—1st. Inflammation of the external covering
of the heart—pericarditis; 2d. Inflammation of the internal lining
membrane of the heart—endocarditis; and 3d. Inflammation of the muscular
substance of the heart—carditis.