92 



ATROPHY, DEGENERATION, PIGMENTATION, AND NECROSIS. 



FIG. 29. AN AREA OF CHEESY DEGEXERA- 

 IN A MILIARY TCBERCLE 



become shiny, the nuclei disappear, and the shape of the cells is changed 

 by the coagulation necrosis, so that a 

 number of them together often look 

 like a network of coagulated fibrin. 



Cheesy Degeneration (Caseation). 

 As commonly used this term embraces 

 the changes in the tissues which we 

 have just considered under the more 

 appropriate name of coagulation ne- 

 crosis. But it is also applied to that 

 form of degeneration in which, under 

 a variety of conditions, the dead tissue 

 elements lose their normal structural 

 features and become converted into an 

 irregularly granular albuminous and 

 fatty material (Fig. 29) which some- 



times tends to disintegrate and soften, sometimes dries and becomes 

 dense and firm, or may become infiltrated with salts of calcium. Thus 

 cheesy degeneration may, and very often does, occur in tissues which 

 are in the condition of coagulation necrosis ; but it also occurs in tissues 

 which are not the seat of coagulation necrosis, but which, for a variety 

 of reasons and in a variety of ways, have lost their vitality. 



The terms coagulation necrosis and cheesy degeneration, as com- 

 monly used, in part actually cover the same degenerative conditions in 

 the tissues. Both are indefinite, and will no doubt remain so until we 

 gain a more precise knowledge of the conditions under which they occur. 



FAT NECROSIS. This is a degenerative process most frequent near 

 the pancreas, and especially associated with lesion of that organ. We 

 refer for details to the special section, page 578. 



Fragments of dead tissues in the living body are in part disposed of 

 by leucocytes or other mesoblastic cells which are attracted to them, and 

 may cause their solution by a ferment substance 1 which they set free or 

 by the incorporation of particles of the dead tissue into their bodies. 

 Thus through chemotaxis, phagocytosis, and autolysis (see pages 111 and 

 116) considerable masses of necrotic tissue may be finally disposed of 

 (see Fig. 45). 



Eecent studies relating to the adaptation of the body to various alien 

 substances have led to new conceptions of the nature of the processes by 

 which the body frees itself of useless or harmful material either devel- 

 oped within it or introduced from without. For a fuller consideration 

 of these processes see cytolysis, page 182. 



1 For a consideration of autolysis and the significance of ferments in pathology with 

 bibliography aee'Jacoby, Centralb. f. Path., Bd. xiii., p. 2, 1902. 



