STRUCTURAL CHANGES DUE TO DAMAGE. 303 



regarded as constituting the destructive phase of acute inflamma- 

 tion. 



2. The Fixed Elements of the Tissues. It is evident that the 

 cause of damage itself, or the disturbances of nutrition resulting 

 from the changes in the circulation, must either cause rapid death, 

 necrosis, or that slower form of death entailed by a relatively in- 

 sufficient supply of nourishment, which has been described in the 

 chapter on the degenerations. The cells are either killed at once, or 

 are starved within a certain radius of the point at which the cause 

 of the inflammation was applied. Beyond this radius these changes 

 give place to those that bring about repair. But the susceptibility 

 of the different tissue-elements varies : an injury that would kill 

 some might hardly affect others ; a given degree of innutrition 

 might cause degeneration in some and not in others, so that the 

 depth to which those changes are felt will depend upon the nature 

 of the tissues present. In general, it may be stated that those tis- 

 sues which are highly specialized and those which carry on functions 

 requiring active intracellular metabolism are the ones most deeply 

 affected by damaging influences. 



Repair. The view was at one time strongly upheld that emi- 

 grated leucocytes were active in the formation of the new tissues 

 that developed during inflammation. These corpuscles were re- 

 garded as of indifferent character, capable of differentiation into 

 the various forms of connective tissue. This view has not been 

 supported by the results of experimental study, and is now aban- 

 doned, giving place to a revival of the earlier belief that the cells 

 of the fixed tissues are the active elements in the reparative process 

 which results in the formation of new tissues. 



Since the significance of the mitotic figures during karyokinesis 

 has been learned, it has become possible to ascertain positively that 

 the fixed cells multiply beyond the zone of destruction in acute 

 inflammations. The cells \vhich have suffered neither destruction 

 nor degeneration beyond their powers of recuperation undergo a 

 species of rejuvenescence, returning to a comparatively undiffer- 

 entiated condition, in which their powers of reproduction and tissue- 

 formation are revived. It is as though they reverted, under the 

 influence of strong irritation, to the condition in which their pro- 

 genitors existed at an earlier stage of tissue-development. The 

 process of repair depends upon this capacity for rejuvenescence on 

 the part of the cells of the tissues, but that power varies greatly in 



