Thrombosis. 



m 



case the substance is broken up into a tinely granular falty material 

 this may be taken up by the blood current and washed away and 

 the lumen of the vessel may thus be 

 again established, or through the soft- 

 ened clot the blood stream may some- 

 times force one or more passageways 

 (canalization of the thrombus). 

 Should, however, larger fragments, 

 as a result of the degenerative 

 changes, bd loosened from the coagu- 

 lum and swept onward by the current 

 of blood they may find lodgment in 

 some other part of the circulator}' ap- 

 paratus and give rise to embolism. 



A thrombus acts as a foreign 

 body u])on the living vessel walls 

 with which it is in contact ; and its 

 characteristic properties excite an in- 

 vasion by leucocytes and phagocytic 

 activity. The latter may, as is uni- 

 formly true in case of small traumatic 

 thrombi, bring about complete ab- 

 sorption of the clot, Coincidently 

 there is established an inflammation 

 of the vessel wall w'ith fibroplastic 

 and angioplastic proliferation, result- 

 ing in the formation of embryonic 

 connective tissue and vascular buds 

 from the endothelium and vasa vaso- 

 rum and their penetration into the 

 thrombus. These proliferating ele- 

 ments replace in time more or less 

 completely the clot substance. In 

 case the thrombus were a parietal 

 one, occupying onl\- one side of the 

 vessel wall, as after venesection, after 

 removal of the clot the connective 

 tissue contracts and shrinks into a 

 flat scar or mere thickening of the 

 wall. \Micre the thrombus occupies the whole lumen the 

 embryonic tissue develops about it, and in its growth pene- 



a 



r^ 



Fig. 6. 



Schematic section of a throm- 

 bosed vein; somewhat en- 

 larged. (After Thoma. I 



