THE PERICARDIUM. 451 



cava, it gives prolongations along the vessels, the strongest of which 

 is on the aorta. 



Below the pericardium is united to the central tendon of the Attach- 

 diaphragm, and extends a little over the muscular tissue, especially diaphragm ; 

 on the left side. For the most part it can be readily separated 

 from the diaphragm, but in the median part of the central tendon 

 it is firmly adherent, and the intimate association of the diaphragm, 

 the back part of the pericardium and the roots of the lungs through 

 the ligamentum latum pulmonis should be noticed. The inferior 

 vena cava pierces the pericardia! attachment below, and, imme- 

 diately entering the lower part of the right auricle, does not 

 receive a sheath from the pericardium. In front, the pericardium 

 is loosely connected to the back of the sternum in the superior to sternum ; 

 mediastinum through the sterno-pericardial ligaments already 

 noticed. The extent of its investments of the vessels entering or 

 leaving the heart will be better seen when it is opened. It can 

 now be seen that it is thickest at the upper part, and is formed 

 of fibres crossing in different directions, many being longitudinal, to fascia of 

 and it can be traced up on to the large vessels at the opening of th 

 the thorax, and by pulling upon it, it will be seen that it is 

 connected with the fascia at the root of the neck. 



Dissection. The pericardium should now be opened by a 

 longitudinal incision running its whole length from the front of the 

 aorta, and by a cross cut passing from the front of the root of one 

 lung to that of the other. 



The serous sac consists of parietal and visceral parts, which are Serous 

 continuous with one another along the great vessels. The parietal 

 part lines the fibrous membrane, with which it is inseparably 

 united, and the included portion of the diaphragm ; while the 

 visceral part covers the heart. It is reflected around the and covers 

 pulmonary artery and aorta, enclosing them in one sheath, but rt; 

 not passing between them. The passage, through which the finger disposition 

 should be passed from side to side behind the aorta and pulmonary vessels; 

 artery within the sac, is called the transverse sinus of the pericardium, transverse 

 The superior vena cava and the four pulmonary veins are only covered sn 

 by the serous membrane on the front and sides, and are in contact with 

 the fibrous layer behind. If the apex of the heart be lifted upwards to 

 the right, at the back of the left auricle the serous membrane will be 

 seen to form a blind pouch between the pulmonary veins of the two 

 sides. This pouch is known as the oblique sinus of the pericardium, oblique 



In front of the root of the left lung the serous layer forms a smus 

 small triangular fold, the vestigial fold of the pericardium (Marshall), vestigial 

 between the pulmonary artery and the upper pulmonary vein. fold> 

 This includes the remains of a left superior cava which existed in 

 the fcetus, and, like the oblique sinus, can be seen by lifting the 

 heart over to the right side. 



The vessels of the pericardium are derived from the aorta, the internal Vessels. 

 mammary, the bronchial, the ossophageal and the phrenic arteries. 



* See a paper by Keith on " The Nature of the Mammalian Diaphiagm and 

 Pleural Cavities." Journal of Anat. and Phys., vol. xxxix., 1905. 



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