140 PATHOLOGY 



sons, anemia, cachexia, etc., normal tissue cells are con- 

 verted into fatty tissue. This occurs most frequently 

 in the heart muscle, the tissues of the kidney, liver, 

 blood-vessels, and nervous system. Other degenerations 

 are amyloid, mucoid, hyaline. 



Necrosis is the term used to define the condition of 

 local tissue death. 



The causes of necrosis are trauma or chemical injury, 

 as in crushing injuries and acid burns; thermal injuries, 

 as in freezing or burning; nutritional or circulatory dis- 

 turbances, as thrombosis, embolism, atheroma, cachexia, 

 senility, and diabetes. 



Coagulation Necrosis. This is a form of tissue death 

 in which there occurs a coagulation of the dead tissue 

 similar to the coagulation of blood. It is more often 

 the result of bacterial poisons, though it occurs as a re- 

 sult of chemical irritants and thermal injuries. 



Liquefaction Necrosis. In this form pf tissue death 

 the dead tissues become liquefied. In coagulation ne- 

 crosis the dead tissues become firmer and stiffer, while 

 in liquefaction necrosis they become fluid or semifluid. 

 It occurs most frequently in the brain, less often in the 

 skin and heart muscle. 



Caseation. This is the term applied to the form of 

 necrosis in which the dead tissue is transformed into a 

 cheese-like substance. It is exemplified in the cheese- 

 like degeneration which takes place in the tubercle of 

 tuberculosis. 



