Chap. X] 



BLOOD VASCULAR SYSTEM 



163 



parts, nerves and ganglia. There is also a considerable amount 

 of fat, collected chiefly at the base of the heart, beneath the 

 pericardium. 



Pericardium. — The heart is covered by a membranous sac 

 called the pericardium (around the heart.) It consists of two 



BRONCMlAL 

 TUBES 



Fig. 99. — The Pulmonary Arterv and Aorta. The front part of the right 

 lung has been removed, and the pulmonary vessels and the bronchial tubes are 

 thus exposed. (Gerrish.) 



parts : (1) an external fibrous portion, and (2) an internal, serous 

 portion. 



(1) The external fibrous pericardium is composed of white 

 fibrous tissue, and is attached by its upper surface to the large 

 blood-vessels which emerge from the heart. It covers these vessels 

 for about an inch and a half (38 mm.) and blends with their 

 sheaths. The lower border is firmly adherent to the diaphragm, 

 and the front surface is attached to the sternum by means of 

 fibrous bands. 



