Space will not permit any detailed description of the symptoms and signs of endo- or pericarditis: these will be found in their proper places in this work, but a few observations are needed upon myocarditis, which occasionally occurs in combination with rheumatic pericarditis, and is a source of much more danger than the latter is, per se. Dr. Maclagan[63] is almost the only authority who recognizes the occurrence of rheumatic myocarditis independently of inflammation of the membranes of the heart. He maintains that the rheumatic poison probably and not infrequently acts directly on the cardiac muscle; in which case the resulting inflammation is apt to be diffused over the left ventricle and to produce grave symptoms, while in other instances the inflammatory process begins in the fibrous rings which surround the orifices of the heart (especially the mitral), extends to the substance at the base of the heart, and is there localized. As in this latter form the inflammation usually extends also to the valves, "any symptoms to which the myocarditis gives rise are lost in the more obvious indications of the valvulitis." However, this limited inflammation of the myocardium is not dangerous. Dr. Maclagan asserts that the more diffused and dangerous inflammation of the walls of the left ventricle, while always difficult, and sometimes impossible, of diagnosis, can be determined with tolerable certainty in some cases. In this view, however, he has been preceded by Dr. Hayden,[64] who states that the diagnosis of myocarditis is quite practicable irrespective of the accompanying inflammation of the membranes of the heart. [Footnote 63: _Rheumatism: its Nature, Pathology, and Successful Treatment_, 1881.] [Footnote 64: _Diseases of the Heart and Aorta_, 1875, 746.]