PURULENT CYSTS IN THE HEART. 337 



sel. At other times, certainly, phlebitis, properly so 

 called (and in like manner arteritis and endocarditis), is 

 the cause of thrombosis, in consequence of the formation 

 of inequalities, elevations, depressions, and even ulcera- 

 tions upon the inner wall which favour the production of 

 the thrombus. Still, wherever phlebitis, in the usual 

 sense of the word, takes place, the alteration in the coat 

 of the vessel is almost always a secondary one, and in- 

 deed occurs at a comparatively late period. 



The process runs its course in such a way that the most 

 recent parts of the thrombus always consist of the blood 

 which has most lately coagulated. The softening, the 

 partial liquefaction, generally commences in the centre, 

 in the oldest layers, so that, when the thrombus has 

 attained a certain size, there exists in the midst of it a 

 cavity of larger or smaller dimensions, which gradually 

 enlarges and keeps approaching more and more closely 

 to the wall of the vessel. But in general this cavity is 

 shut off in an upward and downward direction by means 

 of a more recent and tougher portion of the clot which, 

 after the manner of a cap, takes care that, as Cruveilhier 

 expresses himself, the ' ' pus " remains sequestered, 

 and all contact between the debris and the circulating 

 blood is prevented. Only sideways does the softening 

 extend until it at last reaches the wall of the vessel itself ; 

 this becomes altered, it begins to grow thicker and at 

 the same time cloudy, and ultimately even suppuration 

 takes place within the walls. 



The same thing which we have hitherto considered in 

 the veins occurs also in the heart. In the right ventricle 

 especially we not unfrequently see what are called puru- 

 lent cysts between the trabeculse of its wall. They pro- 

 ject into the cavity like small rounded knobs, and form 

 little pouches which, when cut open, contain a soft pulp 

 that may present a completely pus-like appearance. 



