330 



HISTOLOGY OF THE MORBID PROCESSES. 



the vascular wall, which eventually reaches the intima. Here a 

 fibrinous inflammation, analogous to that of a serous membrane 

 (p. 313), is induced. The roughness of the intima so occasioned 

 induces the formation of a thrombus (Fig. 291). Meanwhile the 



Thrombophlebitis, incident to erysipelas of the arm. (Kaufmami.) The thrombus occupies 

 about two-thirds of the lumen of the vein, which is surrounded by areolar tissue infil- 

 trated with serum and leucocytes. 



septic process in the wall of the vessel progresses and extends into 

 the thrombus, which is softened. The rate of softening may now 

 exceed that of thrombus-formation, in which case the thrombus is 

 broken up, and particles containing some of the bacteria occasion- 

 ing the inflammation gain access to the venous circulation (see 

 Embolism). 



Embolism. The obstruction of a vessel by a foreign body 

 brought from a distance by the circulating blood is called embolism. 

 The foreign body, or embolus, is usually a small mass of fibrin ; 

 but it may be air, fat (derived, for example, from the medulla of a 

 fractured bone), a calcareous fragment, or a particle of tissue. 



With the exception of the branches of the portal vein, the vessels 

 obstructed by an embolus are arterial. The results of embolism 

 will depend, first, upon the anatomical distribution of the vessel 

 plugged, whether there are anastomotic branches of considerable 

 calibre beyond the site of the obstruction ; second, upon the nature 



