CIRCULAR llISTURnANCES. 131 



Obstructed circulation. —Obstructed circulation when produce.! 

 by non-infcctive emboli will have the same effects an<l terminations 

 as the non-infective obstructive thrombi. 



/n/flrc/w;/.— Infarction is the process of obstructing a 

 vessel with an embolus. The area supplied by the obstructed 

 vessel IS called an infarct. The area of infarction is determined 

 by the region supplied by the occluded vessel and is usually 

 wedge-shaped. An area supplied by an artery that has been in- 

 farcted does not become bloodless at once because some of the 

 blood remains in the vessels of the infarcted area and some 

 may enter the periphery of the infarct through anastamosing 

 capillaries and venules of adjacent regions. 



Infarcts may be anemic or hemorrhagic. 



An anemic infarct is one in which there is limited anasta- 

 moses of venules and capillaries of contiguous areas. The blood 

 remaining in the vessels of an anemic infarct soon becomes de- 

 colorized and the area appears pale in color. Anemic infarcts 

 usually undergo necrosis early because of the lack of nutrition. 

 The type of necrosis is largely dependent upon the nature of 

 the embolus. Infarcts produced by infectious emboli usually 

 suppurate or putrefy and infarcts produced by non-infective em- 

 boli may become liquified, absorbed and replaced with fibrous 

 tissue or it may become caseated or calcified and surrounded by 

 a fibrous capsule and persist for a long time. 



A hemorrhagic infarct is one in which there are anastamoses 

 of the vessels of the infarct and the \-enules and capillaries 

 of contiguous areas through which blood passes and becomes 

 stagnated in the aft'ected area. Hemorrhagic infarcts may be- 

 come decolorized, there mav be inflammation established around 

 their periphery, or the blood and the involved tissue may be dis- 

 integrated and al)sorl)ed. 



Infarcts may become cystic, caseous, calcareous, absorbed 

 and substituted with fibrous tissue, or they may become infected 

 and there may be abscess formation or gangrene. 



Infarction occurs most frequenth- in the kidne}', spleen, Ijrain, 

 lung and less frec|uently in the heart, liver, retina, etc. 



Typical terminal arteries are common in the kidney and spleen 

 and hence infarction frequentlv occurs in these organs. In 

 the kidney anemic infarcts are most common, hemorrhagic and 

 anemic infarcts occur in the spleen. Cardiac infarction is not 

 common and is usually caused by thrombosis of the coronary 

 vessels. Cerebral anemic infarction occurs occasionally and the 

 infarct usuallv undergoes simple softening, hemorrhagic cere- 

 bral infarction is rare. 



