294 CIRCULATORY APRARATUS. 



shallow bulging, or of a rounded, saccular appendage to the 

 heart's apex, communicating with the interior of the ventricle 

 by a somcAAdiat narrow opening. The size of the aneurism varies 

 within wide limits, from that of a cherry to that of a hen's egg. 

 Coagulation not unfrequently occurs in its interior ; the pro- 

 bability of such a complication being proportionate to the degree 

 in which the aneurism approaches the saccular or pedunculated 

 type. In marked contrast to the aneurismal dilatations of the 

 larger arteries, this form occasionally undergoes spontaneous 

 obliteration ; a phenomenon which depends, according to Boki- 

 tcmskij not so much on the presence of a clot, as on the develop- 

 ment of veo-etations of connective tissue from the inner surface 

 of the sac. Rupture seldom occurs, and only when the walls 

 of the sac are extremely thinned ; in striking contrast to its 

 frequency in cases of acute aneurism of the heart due to sup- 

 purative myocarditis. 



G. Thromhosis of the Heart. — Polypi of the Heart. 



§ 258. If wo glance at the usual causes of thrombosis, 

 (^roughening of the inner wall of vessels, and retardation of the 

 blood-current) we shall be led a priori to the conclusion, that 

 diseases of the" heart must afford excellent opportunities for the 

 occurrence of this phenomenon. Attention has already been 

 called to the flict that the recent efflorescences of endocarditis 

 are usually coated with fibrinous deposits of variable thickness ; 

 such deposits are very rarely to be seen on the surface of in- 

 durated valve-flaps, even when these exhibit projections and 

 irregularities of every sort. We must nevertheless remember 

 that every irregularity of the endocardial surface may serve as 

 a nucleus for the precipitation of fibrin. True, the thrombi so 

 produced are usually of moderate dimensions, and are never con- 

 verted into those great, globular coagula which are briefly termed 

 ^^ polypi of the heart," or, with Laennec, '^vegetations globu- 

 leuses." These are always due to a relative retardation or 

 absolute stoppage of the movement of the blood in certain 

 regions of the heart. The most usual case is that of incomplete 

 expulsion of the blood contained in one or other of the heart's 

 cavities owing to stenosis of an orifice, or to imperfect con- 

 traction of the organ. That portion of the contained blood 



