598 



HEART. 



bag surrounding the heart and origin of the 

 large bloodvessels, but without any direct 

 attachment to the heart itself, having its inner 

 surface lined by a serous membrane. It is 

 from this latter circumstance that it is generally 

 termed a fibre-serous membrane. It is placed 

 behind the cartilages of the second, third, fourth, 

 and fifth ribs of the left side and middle part 

 of the sternum. Posteriorly it rests upon the 

 parts contained in the posterior mediastinum ; 

 anteriorly it corresponds to the anterior medias- 

 tinum, and may be reached by perforating the 

 left side of the sternum, as has been proposed 

 in some cases of hydrops pericardii. The 

 pleura; adhere to its lateral and part of its 

 anterior surface by pretty close cellular tissue, 

 when the interposed fat is small in quantity. 

 The phrenic nerves with their small accom- 

 panying arteries pass down the thorax between 

 the pleurae and lateral surfaces of the pericar- 

 dium. Below, the fibrous part of the pericar- 

 dium adheres intimately to the upper surface 

 of the cordifonm tendon of the diaphragm, and 

 is also connected by pretty dense cellular tissue 

 to the upper surface of the muscular fibres 

 running into the anterior part of the left lobe 

 of the tendon. It adheres more firmly to the 

 cordiform tendon at the edges, particularly 

 anteriorly, than at the centre. It is broader 

 below where it adheres to the upper surface of 

 the diaphragm, narrower above where it is 

 attached to the large vessels that pass in and 

 out from the heart. Upon these large vessels 

 the fibrous part of the pericardium is prolonged, 

 forming a kind of sheath, which gradually be- 

 comes thinner until it is confounded with the 

 cellular coat of the vessels. From the manner, 

 however, in which the vena cava inferior enters 

 the heart, it can have no fibrous sheath of this 

 kind. At the different points where the fibrous 

 coat becomes applied upon these vessels, and 

 where the cava inferior passes through the 

 cordiform tendon, the serous coat is reflected 

 upon the outer surface of the vessels, and 

 accompanies them back to the heart to cover 

 the outer surface of that organ. In this man- 

 ner the serous part of the pericardium is a shut 

 sac, the outer surface of which adheres to the 

 inner surface of the fibrous portion, and to the 

 outer surface of the heart. The inner surface, 

 like that of all the other serous membranes, is 

 unadherent, smooth, and shining, and is every- 

 where in contact with itself, and only contains 

 the small quantity of fluid which serves to 

 lubricate its interior. The serous portion of 

 the pericardium adheres intimately to the inner 

 surface of the fibrous. At that part, however, 

 where the serous leaves the fibrous to pass 

 back upon the surface of the large vessels, 

 there is a small triangular space left between 

 them. The serous membrane is reflected upon 

 and covers the outer surface of the aorta rather 

 more than two inches above its origin; upon 

 the pulmonary artery about the same distance 

 and immediately before its bifurcation ; upon 

 the cava superior about an inch above its 

 entrance into the right auricle; upon the cava 

 inferior shortly before it reaches the heart ; upon 

 the two right pulmonary veins soon after they 



have emerged from the right lung ; and upon 

 the left pulmonary veins shortly before they 

 enter the auricle. This serous membrane, in 

 passing upon the aorta and pulmonary arteries, 

 covers the anterior surfaces of both before it 

 passes round upon their posterior ; it then en- 

 velopes both arteries in the same sheath, so 

 that their opposed surfaces are only separated 

 from each other by a little cellular tissue. It 

 leaves part of the posterior surface of the cavae 

 and pulmonary veins uncovered, occasionally, 

 however, enveloping the whole or nearly the 

 whole, of the left pulmonary veins. It adheres 

 but loosely to the large bloodvessels, and firmly 

 to the outer surface of the auricles and ven- 

 tricles. The attachment of the fibrous part to 

 the cordiform tendon is very firm at the edges 

 and blended with the tendon, but becomes 

 looser towards the centre. Cloquet* describes 

 the serous membrane as lying in contact with 

 the upper surface of the cordiform tendon ; or, 

 in other words, he appears to consider the 

 fibrous part not to be prolonged over the upper 

 surface of the tendon, but to stop at its attached 

 margin. In most cases I have been able to 

 trace the fibrous part of the pericardium over 

 the upper surface of the cordiform tendon, but 

 almost always more or less diminished in thick- 

 ness. In some cases I was unable to detect 

 anything like a fibrous layer at this part. The 

 fibrous part of the pericardium is comparatively 

 thin, and is composed of tendinous fibres 

 interwoven together. It is not much larger 

 than sufficient to contain the heart when its 

 cavities are distended. This fact taken along 

 with the physical properties of the membrane, 

 not admitting of sudden dilatation, explains 

 how the sudden escape of a small quantity of 

 blood (8 oz. or sometimes less) into the interior 

 of the pericardium is sufficient to arrest the 

 heart's action. 



The arteries of the pericardium are small and 

 come from various sources, from the bronchial, 

 oesophageal, phrenic, from the arteries of the 

 thymus gland, internal mammary, coronary 

 arteries, and the aorta itself. Its veins partly 

 terminate in the azygos, and partly accompany 

 the corresponding arteries to terminate in the 

 veins of the same name. Its lymphatics pass 

 to the glands placed around the cava superior. 

 The nerves can be traced into its texture. 



Uses of the pericardium. The pericardium 

 restrains within certain limits the irregular 

 movements of the heart. The inner serous 

 surface of the pericardium must also facilitate 

 its ordinary and healthy movements. 



Relative position of the vessels within the 

 pericardium. The pulmonary artery at its origin 

 overlaps the anterior surface of the aorta as it 

 springs from the left ventricle. (See fig. 276, s, 

 for the lelative position of these vessels at their 



* Traite d'Anatomic Descriptive, p. 633, trans- 

 lated by Knox. Cloquet does not state distinctly 

 that the fibrous part of the pericardium is not con- 

 tinued over the cordiform tendon, but this may be 

 inferred from the statement that the serous mem- 

 brane " is applied below, directly and in a very 

 close manner upon the aponeuroses of the dia- 

 phragm/' 



