432 



THE CIRCULATORY SYSTEM. 



ing, or may be a simple dilatation of part of the ventricle. The wall of 

 such an aneurism becomes thinner as the sac increases in size. It is com- 

 posed of the endocardium, new fibrous tissue, visceral pericardium, and 

 sometimes the adherent parietal pericardium. The walls may calcify, or 

 rarely they become so thin as to rupture externally or into the right ven- 

 tricle. The sacs may contain fluid blood or be filled with fibrin. 



Such aneurisms are usually situated in the wall of the left ventricle ; 

 rarely in that of the left auricle. If they are in the septum they may 

 project into the right ventricle or auricle (Fig. 227). They are usually 

 single, but sometimes two or three are found in the same heart. 



2. Fatty degeneration of the heart wall may reach such a degree that 

 the wall yields and is pouched out into an aneurismal sac. 



3. Endocarditis and myocarditis, or fatty degeneration, may so soften 

 a portion of the heart wall that the endocardium and part of the muscu- 

 lar tissue are ruptured and a ragged cavity is formed. This form of an- 

 eurism usually does not attain a large size, but soon ruptures externally 

 and causes the death of the patient. 



Small aneurisms of the sinus of Valsalva are of occasional occurrence. 



THROMBOSIS OF THE HEART. 



It is common to find after death, in the heart cavities, yellow, succu- 

 lent, semi -translucent masses. They are most common and of firmest 

 texture in persons who die of acute inflammatory diseases. They may 



adhere quite firmly to the 

 walls of the heart, and may 

 extend in long, branching 

 cords into the vessels. They 

 are formed in the last hours 

 of life and just after death. 

 They have no clinical or pa- 

 thological importance. 



Coagula of the fibrin of the 

 blood in the heart do, how- 

 ever, form during life, and 

 may exist for years. If the 

 fibrin adheres to the valves in 

 small masses these are called 

 vegetations; if it coagulates 

 in the heart cavities in larger 

 bodies they are called thrombi 

 or heart polypi. 



Such thrombi are found 

 in all the heart cavities. 

 They form flattened masses 



FIG. 338.-POLYPOID THROMBUS^ THE LEFT AURICLE OP firmly adherent fa the endo . 



The thrombus was dark red in color, with smooth surface. Cardilim ; Or rounded bodies 



