THE PERICARDIUM. 



457 



of the Diaphragm to the ribs ; this is more marked behind than in front, so that 

 only a narrow space is left between it and the Avail of the thorax. 



THE PERICARDIUM. 



The Pericardium (Figs. 273, 274) is a conical membranous sac in which the 

 heart and the commencement of the great vessels are contained. It is placed 

 behind the sternum and the cartilages of the third, fourth, fifth, sixth, and seventh 

 ribs of the left side, in the interval between the pleurae. 



Riyht common 

 carotid artery. 

 Inferior thyroid 

 vein. 



Left innomi- 

 nate vein. 

 Right innomi- 

 nate rein. 



Right sab- 

 art. 



Left common 

 carotid art. 



ulmo- 

 nary reins. 



Left sub- 

 el avion 

 artery. 



FK;. 273. Pericardium', from in front. The sac has been distended with plaster. (From a preparation in 

 the Museum of the Royal College of Surgeons of England.) 



Its apex is directed upward, and surrounds the great vessels about two inches 

 above their origin from the base of the heart. Its base is attached to the central 

 tendon and to the left part of the adjoining muscular structure of the Diaphragm. 

 In front it is separated from the sternum by the remains of the thymus gland 

 above and a little loose areolar tissue below, and is covered by the margins of the 

 lungs, especially the left. Behind, it rests upon the bronchi, the oesophagus, and 

 the descending aorta. Laterally, it is covered by the pleurae, and is in relation to 

 the inner surface of the lungs ; the phrenic nerve with its accompanying vessels 

 descends between the pericardium and pleura on either side. 



