CIRCULAR l)ISTURl!Ai\XKS. 127 



established. The endothelium and the vasa vasorum of the 

 contacting vessel proliferate and extend into the thrombus soon 

 after the fibrin contracts, the vasa vasorum usually being of 

 sufficient extent to produce complete vascularization of the 

 thrombus. The proliferated endothelial cells become fibrous 

 connective tissue cells and prtiduce fibrous connective tissue 

 which later contracts and thus reduces the size of the throm- 

 bus. The dead and disintegrated tissue in the thrombus is car- 

 ried awajr by leucocytes, thus reducing the size of the throm- 

 bus still more. The contraction of the fibers usually continues 

 until there is a mere cicatrix where there once existed an oc- 

 cluding thrombus. (This is a favorable termination.) The or- 

 ganization may result in the formation of an excessive amount 

 of fibrous tissue which mav practically occlude the vessel, and 

 the vessel itself become a fibrous cord. 



4. Calcification of the tliroiiihi in the human is quite C(jni- 

 mon, the calcified thrombi being called jjhleboliths and arteri- 

 oliths, according to the vessel in which they occur. The same 

 changes occur in thrombi of lower animals. 



Effects — The effects of thrombi de]3end upon the vessel 

 in which it occurs and the nature of the thrombus. If it 

 ©ccurs in a terminal vessel the outcome will be different 

 than if it occurs in a vessel having collateral branches. If the 

 thrombus is occluding the outcome will be dift'erent than if it 

 is parietal. A thrombus that is lirittle or is easily detached will 

 produce different results than one that is not easily broken 

 and is adherent to the vessel wall. The general condition of 

 the vessel wall is also a determining factor on the subsequent 

 changes of a thrombus. The principle results are as follows: 



1. Obstructed circulation, which may be either partial or 

 complete, depending upon the nature of the thrombus and of 

 the vessel and the rapidity with which collateral circulation is 

 established. Continued partial obstruction in veins favors 

 hvperemia with its consecjuent oedema. Degeneration in ar- 

 teries favors anemia and atrophy. Complete obstruction re- 

 sults in necrosis with or without formation of infarcts. 



2. Proditctiov. of ciiihoUsm by fragments becoming de- 

 tached and occluding smaller vessels. 



3. Forination of nc7V blood tcsscIs. 



