NECROSIS 309 



that the intracellular proteases bring about the subsequent 

 nuclear and cytoplasmic alterations, but that the eventual 

 digestion of the area is accomplished by the invading leucocytes 

 working slowly inward from the periphery. Apparently when 

 the supply of materials from outside ceases, and when the oxi- 

 dation processes of the cells no longer accomplish necessary 

 steps of synthetic reactions or destroy products of proteid catab- 

 olism, the proteases continue to split proteids without the balan- 

 cing by the above-mentioned factors, with a resulting disintegra- 

 tion of the cells. 



Karyolysis and karyorrhexis are, then, the result of an auto- 

 lytic process, which is perhaps due to intracellular proteases that 

 act specifically on nucleoproteids, and which may be designated as 

 nudeases. 1 Nuclear staining by the usual methods depends 

 upon an affinity of the acid nucleoproteids (in which the 

 nucleic acid is not completely saturated by proteids) for basic 

 dyes. Presumably in karyolysis the first step consists in a 

 splitting of the nucleoproteid of the chromatin into nucleic 

 acid and proteid ; this can be accomplished, according to Sachs, 

 by the ordinary trypsin, and presumably, therefore, by the tryp- 

 sin-like enzymes of the cell. Corresponding with this change 

 we should expect the free nucleic acid to give an intense stain- 

 ing with basic stains, and this has frequently been described by 

 those who have studied the cytological changes in anemic 

 necrosis, 2 and called pycnosis. As supporting this view still 

 further may be quoted Arnheim's 3 observation that in alkaline 

 solutions the nucleus soon stains diffusely and weakly, and not 

 at all after twelve to eighteen hours ; this is to be explained by 

 the fact that nucleic acid is both dissolved and neutralized by 

 alkaline solutions. After the nucleic acid has been freed from 

 the proteid by the autolytic enzymes, it is still further decom- 

 posed by the " nuclease " or similar intracellular enzymes that 

 have the property of splitting nucleic acid into the purin bases 

 that compose it corresponding with this change the hyper- 

 chromatic nucleus loses its affinity for stains, and karyolysis is 

 complete. 



It may be observed that autolysis of aseptically preserved 

 tissues outside the body is much more rapid than is the autol- 

 ysis of infarcts and similar aseptic necrotic areas within the 



1 Jones, Araer. Jour. Physiol., 1903 (10), p. xxiv ; Zeit. physiol. Chem., 1903 

 (41), 101 ; ibid., 1906 (48), 110. Sachs, Zeit. physiol. Chem., 1905 (46), 337. 



2 Schmaus and Albrecht, Virchow's Arch., 1895 (138), supp., p. 1 ; Ergeb. 

 allg. Pathol., 1896 (3), 486 (literature). 



3 Virchow's Arch., 1890 (120), 367. 



