PERICARDIUM, ENDOCARDIUM, VALVES. 



71 



Only the general arrangement of the ventricular muscular fibres has been 

 indicated here (Lower, Gasp. Wolff, 1780-92). C. Ludwig (1849), and more 

 recently Pettigrew (1864) have made the subject a special study, and followed out 

 its complications. According to the last observer, there are seven layers in the 

 ventricle, viz., three external, a fourth or central layer, and three internal. These 

 internal layers are continuous with the corresponding external layers at the apex, 

 thus one and seven, two and six. 



46. Pericardium, Endocardium, Valves. 



The PERICARDIUM encloses within its two layers [visceral and parietal] a lymph 

 space the pericardial space which contains a small ^quantity of lymph the 

 pericardial fluid. It has the structure of a serous membrane, i.e., it consists of 

 connective tissue mixed with fine elastic fibres arranged in the form of a thin delicate 

 membrane, and covered on its free surfaces with a single layer of epithelium or 

 endothelium, composed of irregular, polygonal, flat cells. 



A rich lymphatic network lies under the pericardium (fig. 20) and endocardium 

 and also in the deeper layers of the visceral pericardium next the heart, but stomata 

 have not been found leading from 

 the pericardial cavity into these 

 lymphatics, nor do these open- 

 ings exist on the parietal layer. 

 [Salvioli has shown that lym- 

 phatic spaces also He between 

 the muscular bundles.] Around 

 the coronary arteries of the heart 

 exist deposits of fat and lymph- 

 vessels (Wedl), which lie in the 

 furrows and grooves in the sub- 

 serosa of the epicardium (visceral 

 layer). 



TheENDOCARDiUM (accordingto 

 Luschka) does not represent the 

 intima alone, but the entire wall 

 of a blood-vessel. Next the cavity . Fi S- 2(X 



of the heart, it consists of a L y m P hatlc of the pericardium epithelium stained 

 single layer of polygonal, flat, with nitrate of silver, 



nucleated endothelial cells. [Under this there is a nearly homogeneous hyaline 

 layer (fig. 21, a), slightly thicker on the left side, which gives the endocardium its 

 polished appearance.] Then 

 follows, as the basis of the 

 membrane, a layer of fine elastic 

 fibres stronger in the auricles, 

 and in some places thereof as- 

 suming the characters of a 

 fenestrated membrane. Be- 

 tween these fibres a small 

 quantity of connective tissue 

 exists, which is in larger 

 amount and more areolar in its 

 characters next the myocar- 

 dium. Bundles of non-striped 

 muscular fibres (few in the 

 auricles) are scattered and 

 arranged for the most part 

 longitudinally between the 



Fig. 21. 



Section of the endocardium a, hyaline layer ; b, 

 network of fine elastic fibres ; c, network of 

 stronger elastic fibres; d, myocardium with 

 blood-vessels, which do not pass into the. endo- 

 cardium. 



