Inflammation of the pericardium, be it an acute or a chronic process, represents one of the pathologic lesions of the body which the clinician rarely diagnoses and which is discovered only at necropsy. The explanation of this observation lies not so much in the want of clinical data that may have a bearing on the diagnosis, but rather on the failure of the physician to make use of all the available facts disclosed by complete and thorough examination of the patient. The so-called pathognomonic signs are looked for, and, if not observed, the case is dismissed as one without pericardial involvement. Conclusive signs are rare. In this condition, as "in most other inner disease, we have to regard the case as a whole, comparing all the symptoms and signs and giving to each its due perspective."1 There is another factor that may be responsible for the inability of the