chap, x.] THE HEART AND 



vessels, and small branches of nerV^fib'res are met 

 with everywhere. The subpericardial and subeiido- 

 cardial tissues consist of loosely connected trabeculse of 

 fibrous connective tissue, forming a continuity with 

 the intermuscular connective tissue of the muscular 

 part of the heart. 

 The former contains 

 in many places 

 groups of fat cells. 



96. On the free 

 surface of the papil- 

 lary muscles, in some 

 parts of the surface 

 of the trabecul?e car- 

 neae, and at the inser- 

 tion of the valves, 

 the endocardium is 

 thickened by ten- 

 dinous connective 

 tissue. The valves 

 themselves are folds 

 of the endocardium, 

 and contain in their 



essential parts fibrous Fig. 44. Transverse Section through the 



connective tissue, to Auricle of the Heart of a Child - 



which, especially in 



the semilunar valves, 



numerous elastic 



fibres are added. The muscular tissue of the wall 



of the auricle penetrates a short way into the auriculo- 



ventricular valves. 



All the cordse tendinese and the valves are of course 

 covered on their free surfaces with endothelium. 



Special tracts of muscle fibres occur in the sub- 

 endocardial tissue. 



The fibres of Purkinje are peculiar fibres occurring 

 in the subendocardial tissue in some mammals and 



a, Endothelium lining the endocardium ; J, en- 

 docardium ; c, muscular bundles cut trans- 

 versely ; d, muscular bundles cut longitu- 

 dinally ; , pericardia! covering. 



