318 RETROGRESSIVE CHANGES 



Extreme changes in osmotic pressure may lead to cell 

 death, either by causing structural alteration in the cell (e. g., 

 the bursting of plant-cells in water), or concentration of the 

 electrolytes may become so great that the colloids are thrown 

 out of solution, as in the ordinary salting-out processes of the 

 laboratory. It is doubtful, however, if osmotic changes per se 

 ever become so abnormal within the animal body (except in 

 experimental conditions) as of themselves to cause cell necrosis. 



VARIETIES OF NECROSIS 



Coagulation Necrosis.' This name is applied to ne- 

 crotic areas that are firm, dry, usually pale yellowish in color, 

 and observed principally in areas of total anemia or tubercu- 

 losis. The question has been long disputed as to whether a 

 true coagulation occurs in such tissues or not. Necrosis pro- 

 duced by heat, carbolic acid, corrosive sublimate, etc., is natur- 

 ally a coagulation necrosis, the cells of the aifected area having 

 undergone true coagulation ; i. e., the conversion of their solu- 

 ble colloids (sols) into the insoluble "pectous" modification. 

 Whether the same change occurs in areas of anemic necrosis is 

 not so well established. If the part contains a fair amount of 

 plasma the liberation of the tissue coagulins from the dead 

 cells will cause a conversion of the fibriuogen into fibrin this 

 can usually be demonstrated microscopically, but the presence 

 of fibrin is not constant, and its quantity is usually insufficient 

 to explain satisfactorily the condition of coagulation necrosis in 

 infarcts, etc., as Weigert maintained. 2 Schmaus and Albrecht 

 believe that a true coagulation of the cell proteids does occur 

 in anemic infarcts, etc., for they found that the cells of kidneys 

 with ligated vessels contain at first granules soluble in water 

 and salt solution ; after forty -eight hours the granules cannot 

 be dissolved in these solvents or in weak acetic acid, but are 

 soluble in 2 per cent. KOH ; after five to six days the granules 

 are insoluble even in KOH. Beyond these experiments, we seem 

 to have no proof of the occurrence of intracelmlar coagulation 

 within areas of coagulation necrosis due to anemia ; exact chemical 

 studies on this point are much needed. Since tissue-cells contain 



1 Literature by Jores, Ergebnisse der PathoL, 1898 (5), 16. 



2 Weigert believed that the dead area becomes permeated by plasma contain- 

 ing fibrinogen, which is coagulated in and between the cells. He put much 

 weight on an increase in size of the necrotic area, which is by no means con- 

 stant, as he intimated ; necrotic areas are inelastic, and when death occurs, they 

 do not shrink with the fall of blood pressure as the surrounding tissues do, and 

 hence they may appear to project from the surface of the dead organ when 

 they did not do so during life. 



