7i8 HUMAN ANATOMY. 



closer to the ear, with fewer intervening structures than elsewhere ; {b) preceded or 

 accompanied by pain {vide supra) ; (r) usually increased by pressure with the stetho- 

 scope, which brings the two roughened pericardial layers into closer apposition ; (^) 

 accompanied by an extension of the area of cardiac dulness {znde infra); (e) is 

 double, — that is, corresponding, although not altogether synchronously, to both 

 systole and diastole ; and (/) may disappear when effusion occurs, — separating the 

 two layers, — or may persist over a small area near either the diaphragmatic attach- 

 ment or the pericardial reflection at the base. 



2. As the pericardium is markedly elastic, when effusion takes place the parietal 

 layer may stretch so that the pericardial cavity may hold ten or twelve ounces instead 

 of a few grammes, or in chronic cases may contain several pints. As its cavity is in the 

 shape of that of a hollow cone or pear, the apex corresponding to the fixed portion of 

 the heart — held in place by the great vessels — and the base — enlarged to permit the 

 considerable degree of motion of the heart's apex — to the upper surface of the dia- 

 phragm, pericardial effusions also take this general shape, and the area oi peraission- 

 dulncss will be found to have its base — about on a level with the fifth or sixth 

 interspace — inferior, and its apex — about on a level with the second interspace — 

 directed upward towards the first segment of the sternum. It is more marked to the 

 left of the sternum on account of the larger area of heart and pericardium on that 

 side, but may be found to the right of the sternum, especially about the fifth intercostal 

 space (Rotch), because on the right side (owing to the presence of the right lobe of 

 the liver) the lower border of the distended sac is somewhat higher than on the left. 



3. As such enlargement must affect the contiguous organs and the overlying 

 parietes, there will be found in full distention : («) prominence of the intercostal 

 spaces, especially on the left side, or of the left antero-lateral thoracic walls, of the 

 epigastrium (from depression of the diaphragm and left lobe of the liver), of the 

 lower two-thirds of the sternum, or, in children with yielding thoracic walls, of the 

 whole precordia ; i^b) compression of the left lung, sometimes causing a tympanitic 

 percussion-note in the left axillary region ; {c) compression, between the relatively 

 unyielding sternum and the dorsal spine, of the trachea and left bronchus (irritative 

 cough), the oesophagus (dysphagia), and the aorta (affecting the systemic blood- 

 supply); (^) a backward curve of the dorsal spine has been described (Sibson) as 

 resulting from the necessity of limiting pressure on these important structures ; (^) 

 compression or irritation of the recurrent laryngeal nerve (aphonia) and the superior 

 vena cava (venous engorgement of neck and face) have been noted {vide supra). 



4. The upward displacement of the heart itself, due to {a) its attachments to 

 the great vessels fixing its upper portion ; and {b) the effect of gravity upon the 

 effusion which distends the lower part of the sac, separates to an extent the chest- 

 walls and the inferior portion of the right ventricle, and occupying the space between 

 the lower surface of the heart and the tendinous centre of the diaphragm, forces the 

 former organ into the upper part of the pericardial sac, causes a corresponding 

 alteration in the cardiac imp2ilse, which is diminished or obliterated, and a change in 

 the position of the apex beat, which may be found at the third or fourth interspace 

 instead of at the fifth ; as the upper portion of the chest is the narrower, and as the 

 left lung has been pushed aside by the distended sac, the apex beat may also be 

 found much nearer a vertical line drawn through the nipple than is normally the case. 



Either paracentesis pericardii or incision of the pericardium for the purpose of 

 tapping or of draining the sac in cases of purulent efjusion may be done in the fifth 

 or sixth intercostal space on the left side about one inch from the sternum. The 

 internal mammary artery descends vertically about a half inch from the margin of 

 the sternum. The pleura is often pushed by the distended sac beyond the point 

 mentioned. If not, the trocar would penetrate its two layers if inserted one inch from 

 the sternal border. In the sixth interspace there is somewhat less danger of wound- 

 ing the heart. Incision close to the edge of the sternum will usually avoid both of 

 these risks. Incision or puncture in the fifth space on the right side has been ad- 

 vised as minimizing the danger to the heart. Deguy (quoted by Treves) advises sub- 

 periosteal resection of the xiphoid cartilage by a median incision, downward detach- 

 ment of the diaphragmatic muscle-fibres, and dissection through the loose cellular 

 tissue to the pericardium, which is seized, drawn down and forward, and incised. 



